Merge tag 'uml-for-linus-6.13-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/uml/linux

Pull UML updates from Richard Weinberger: - Lots of cleanups, mostly from Benjamin Berg and Tiwei Bie - Removal of unused code - Fix for sparse warnings - Cleanup around stub_exe() * tag 'uml-for-linus-6.13-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/uml/linux: (68 commits) hostfs: Fix the NULL vs IS_ERR() bug for __filemap_get_folio() um: move thread info into task um: Always dump trace for specified task in show_stack um: vector: Do not use drvdata in release um: net: Do not use drvdata in release um: ubd: Do not use drvdata in release um: ubd: Initialize ubd's disk pointer in ubd_add um: virtio_uml: query the number of vqs if supported um: virtio_uml: fix call_fd IRQ allocation um: virtio_uml: send SET_MEM_TABLE message with the exact size um: remove broken double fault detection um: remove duplicate UM_NSEC_PER_SEC definition um: remove file sync for stub data um: always include kconfig.h and compiler-version.h um: set DONTDUMP and DONTFORK flags on KASAN shadow memory um: fix sparse warnings in signal code um: fix sparse warnings from regset refactor um: Remove double zero check um: fix stub exe build with CONFIG_GCOV um: Use os_set_pdeathsig helper in winch thread/process ...
author: Linus Torvalds <torvalds@linux-foundation.org> 2024-11-30 10:34:54 -0800
committer: Linus Torvalds <torvalds@linux-foundation.org> 2024-11-30 10:34:54 -0800
commit: 831c1926ee728c3e747255f7c0f434762e8e863d (patch)
tree: 92d1c73842c3f95b362810aba2080b7582c12c11
parent: 04b43ea325d21c4c98e831383a1b7d540721898a (diff)
parent: bed2cc482600296fe04edbc38005ba2851449c10 (diff)
83 files changed, 1227 insertions, 1394 deletions
diff --git a/arch/um/Kconfig b/arch/um/Kconfig
index c89575d05021..18051b1cfce0 100644
--- a/arch/um/Kconfig
+++ b/arch/um/Kconfig
@@ -5,6 +5,7 @@ menu "UML-specific options"
 config UML
 	bool
 	default y
+	select ARCH_WANTS_DYNAMIC_TASK_STRUCT
 	select ARCH_HAS_CPU_FINALIZE_INIT
 	select ARCH_HAS_FORTIFY_SOURCE
 	select ARCH_HAS_GCOV_PROFILE_ALL
@@ -32,6 +33,8 @@ config UML
 	select HAVE_ARCH_VMAP_STACK
 	select HAVE_RUST
 	select ARCH_HAS_UBSAN
+	select HAVE_ARCH_TRACEHOOK
+	select THREAD_INFO_IN_TASK
 
 config MMU
 	bool
@@ -94,7 +97,7 @@ config MAY_HAVE_RUNTIME_DEPS
 
 config STATIC_LINK
 	bool "Force a static link"
-	depends on CC_CAN_LINK_STATIC_NO_RUNTIME_DEPS || !MAY_HAVE_RUNTIME_DEPS
+	depends on !MAY_HAVE_RUNTIME_DEPS
 	help
 	  This option gives you the ability to force a static link of UML.
 	  Normally, UML is linked as a shared binary.  This is inconvenient for
@@ -209,8 +212,8 @@ config MMAPPER
 
 config PGTABLE_LEVELS
 	int
-	default 3 if 3_LEVEL_PGTABLES
-	default 2
+	default 4 if 64BIT
+	default 2 if !64BIT
 
 config UML_TIME_TRAVEL_SUPPORT
 	bool
@@ -227,6 +230,21 @@ config UML_TIME_TRAVEL_SUPPORT
 
 	  It is safe to say Y, but you probably don't need this.
 
+config UML_MAX_USERSPACE_ITERATIONS
+	int
+	prompt "Maximum number of unscheduled userspace iterations"
+	default 10000
+	depends on UML_TIME_TRAVEL_SUPPORT
+	help
+	  In UML inf-cpu and ext time-travel mode userspace can run without being
+	  interrupted. This will eventually overwhelm the kernel and create OOM
+	  situations (mainly RCU not running). This setting specifies the number
+	  of kernel/userspace switches (minor/major page fault, signal or syscall)
+	  for the same userspace thread before the sched_clock is advanced by a
+	  jiffie to trigger scheduling.
+
+	  Setting it to zero disables the feature.
+
 config KASAN_SHADOW_OFFSET
 	hex
 	depends on KASAN
diff --git a/arch/um/Makefile b/arch/um/Makefile
index 00b63bac5eff..1d36a613aad8 100644
--- a/arch/um/Makefile
+++ b/arch/um/Makefile
@@ -61,7 +61,8 @@ KBUILD_CFLAGS += $(CFLAGS) $(CFLAGS-y) -D__arch_um__ \
 	$(ARCH_INCLUDE) $(MODE_INCLUDE) -Dvmap=kernel_vmap	\
 	-Dlongjmp=kernel_longjmp -Dsetjmp=kernel_setjmp \
 	-Din6addr_loopback=kernel_in6addr_loopback \
-	-Din6addr_any=kernel_in6addr_any -Dstrrchr=kernel_strrchr
+	-Din6addr_any=kernel_in6addr_any -Dstrrchr=kernel_strrchr \
+	-D__close_range=kernel__close_range
 
 KBUILD_RUSTFLAGS += -Crelocation-model=pie
 
@@ -70,7 +71,9 @@ KBUILD_AFLAGS += $(ARCH_INCLUDE)
 USER_CFLAGS = $(patsubst $(KERNEL_DEFINES),,$(patsubst -I%,,$(KBUILD_CFLAGS))) \
 		$(ARCH_INCLUDE) $(MODE_INCLUDE) $(filter -I%,$(CFLAGS)) \
 		-D_FILE_OFFSET_BITS=64 -idirafter $(srctree)/include \
-		-idirafter $(objtree)/include -D__KERNEL__ -D__UM_HOST__
+		-idirafter $(objtree)/include -D__KERNEL__ -D__UM_HOST__ \
+		-include $(srctree)/include/linux/compiler-version.h \
+		-include $(srctree)/include/linux/kconfig.h
 
 #This will adjust *FLAGS accordingly to the platform.
 include $(srctree)/$(ARCH_DIR)/Makefile-os-Linux
diff --git a/arch/um/Makefile-skas b/arch/um/Makefile-skas
index 67323b028999..1a27e65bcb9c 100644
--- a/arch/um/Makefile-skas
+++ b/arch/um/Makefile-skas
@@ -3,15 +3,15 @@
 # Licensed under the GPL
 #
 
-GPROF_OPT += -pg
+export UM_GPROF_OPT += -pg
 
 ifdef CONFIG_CC_IS_CLANG
-GCOV_OPT += -fprofile-instr-generate -fcoverage-mapping
+export UM_GCOV_OPT += -fprofile-instr-generate -fcoverage-mapping
 else
-GCOV_OPT += -fprofile-arcs -ftest-coverage
+export UM_GCOV_OPT += -fprofile-arcs -ftest-coverage
 endif
 
-CFLAGS-$(CONFIG_GCOV) += $(GCOV_OPT)
-CFLAGS-$(CONFIG_GPROF) += $(GPROF_OPT)
-LINK-$(CONFIG_GCOV) += $(GCOV_OPT)
-LINK-$(CONFIG_GPROF) += $(GPROF_OPT)
+CFLAGS-$(CONFIG_GCOV) += $(UM_GCOV_OPT)
+CFLAGS-$(CONFIG_GPROF) += $(UM_GPROF_OPT)
+LINK-$(CONFIG_GCOV) += $(UM_GCOV_OPT)
+LINK-$(CONFIG_GPROF) += $(UM_GPROF_OPT)
diff --git a/arch/um/configs/i386_defconfig b/arch/um/configs/i386_defconfig
index 9c9c77f1255a..1ffa088739f4 100644
--- a/arch/um/configs/i386_defconfig
+++ b/arch/um/configs/i386_defconfig
@@ -1,4 +1,3 @@
-CONFIG_3_LEVEL_PGTABLES=y
 # CONFIG_COMPACTION is not set
 CONFIG_BINFMT_MISC=m
 CONFIG_HOSTFS=y
diff --git a/arch/um/drivers/chan_user.c b/arch/um/drivers/chan_user.c
index a66e556012c4..35f9beeb19b3 100644
--- a/arch/um/drivers/chan_user.c
+++ b/arch/um/drivers/chan_user.c
@@ -161,6 +161,8 @@ static __noreturn int winch_thread(void *arg)
 	int count;
 	char c = 1;
 
+	os_set_pdeathsig();
+
 	pty_fd = data->pty_fd;
 	pipe_fd = data->pipe_fd;
 	count = write(pipe_fd, &c, sizeof(c));
diff --git a/arch/um/drivers/hostaudio_kern.c b/arch/um/drivers/hostaudio_kern.c
index 9d228878cea2..0ac149de1ac0 100644
--- a/arch/um/drivers/hostaudio_kern.c
+++ b/arch/um/drivers/hostaudio_kern.c
@@ -48,6 +48,7 @@ MODULE_PARM_DESC(mixer, MIXER_HELP);
 #ifndef MODULE
 static int set_dsp(char *name, int *add)
 {
+	*add = 0;
 	dsp = name;
 	return 0;
 }
@@ -56,6 +57,7 @@ __uml_setup("dsp=", set_dsp, "dsp=<dsp device>\n" DSP_HELP);
 
 static int set_mixer(char *name, int *add)
 {
+	*add = 0;
 	mixer = name;
 	return 0;
 }
diff --git a/arch/um/drivers/net_kern.c b/arch/um/drivers/net_kern.c
index 77c4afb8ab90..75d04fb4994a 100644
--- a/arch/um/drivers/net_kern.c
+++ b/arch/um/drivers/net_kern.c
@@ -336,7 +336,7 @@ static struct platform_driver uml_net_driver = {
 
 static void net_device_release(struct device *dev)
 {
-	struct uml_net *device = dev_get_drvdata(dev);
+	struct uml_net *device = container_of(dev, struct uml_net, pdev.dev);
 	struct net_device *netdev = device->dev;
 	struct uml_net_private *lp = netdev_priv(netdev);
 
diff --git a/arch/um/drivers/ubd_kern.c b/arch/um/drivers/ubd_kern.c
index 7f28ec1929dc..66c1a8835e36 100644
--- a/arch/um/drivers/ubd_kern.c
+++ b/arch/um/drivers/ubd_kern.c
@@ -779,7 +779,7 @@ static int ubd_open_dev(struct ubd *ubd_dev)
 
 static void ubd_device_release(struct device *dev)
 {
-	struct ubd *ubd_dev = dev_get_drvdata(dev);
+	struct ubd *ubd_dev = container_of(dev, struct ubd, pdev.dev);
 
 	blk_mq_free_tag_set(&ubd_dev->tag_set);
 	*ubd_dev = ((struct ubd) DEFAULT_UBD);
@@ -898,6 +898,8 @@ static int ubd_add(int n, char **error_out)
 	if (err)
 		goto out_cleanup_disk;
 
+	ubd_dev->disk = disk;
+
 	return 0;
 
 out_cleanup_disk:
@@ -1499,6 +1501,7 @@ int io_thread(void *arg)
 {
 	int n, count, written, res;
 
+	os_set_pdeathsig();
 	os_fix_helper_signals();
 
 	while(1){
diff --git a/arch/um/drivers/vector_kern.c b/arch/um/drivers/vector_kern.c
index c992da83268d..64c09db392c1 100644
--- a/arch/um/drivers/vector_kern.c
+++ b/arch/um/drivers/vector_kern.c
@@ -815,7 +815,8 @@ static struct platform_driver uml_net_driver = {
 
 static void vector_device_release(struct device *dev)
 {
-	struct vector_device *device = dev_get_drvdata(dev);
+	struct vector_device *device =
+		container_of(dev, struct vector_device, pdev.dev);
 	struct net_device *netdev = device->dev;
 
 	list_del(&device->list);
diff --git a/arch/um/drivers/vhost_user.h b/arch/um/drivers/vhost_user.h
index 6f147cd3c9f7..fcfa3b7e021b 100644
--- a/arch/um/drivers/vhost_user.h
+++ b/arch/um/drivers/vhost_user.h
@@ -10,6 +10,7 @@
 /* Feature bits */
 #define VHOST_USER_F_PROTOCOL_FEATURES	30
 /* Protocol feature bits */
+#define VHOST_USER_PROTOCOL_F_MQ			0
 #define VHOST_USER_PROTOCOL_F_REPLY_ACK			3
 #define VHOST_USER_PROTOCOL_F_SLAVE_REQ			5
 #define VHOST_USER_PROTOCOL_F_CONFIG			9
@@ -23,7 +24,8 @@
 /* Supported transport features */
 #define VHOST_USER_SUPPORTED_F		BIT_ULL(VHOST_USER_F_PROTOCOL_FEATURES)
 /* Supported protocol features */
-#define VHOST_USER_SUPPORTED_PROTOCOL_F	(BIT_ULL(VHOST_USER_PROTOCOL_F_REPLY_ACK) | \
+#define VHOST_USER_SUPPORTED_PROTOCOL_F	(BIT_ULL(VHOST_USER_PROTOCOL_F_MQ) | \
+					 BIT_ULL(VHOST_USER_PROTOCOL_F_REPLY_ACK) | \
 					 BIT_ULL(VHOST_USER_PROTOCOL_F_SLAVE_REQ) | \
 					 BIT_ULL(VHOST_USER_PROTOCOL_F_CONFIG) | \
 					 BIT_ULL(VHOST_USER_PROTOCOL_F_INBAND_NOTIFICATIONS))
diff --git a/arch/um/drivers/virtio_uml.c b/arch/um/drivers/virtio_uml.c
index 2b6e701776b6..cc3be48a9d6e 100644
--- a/arch/um/drivers/virtio_uml.c
+++ b/arch/um/drivers/virtio_uml.c
@@ -56,6 +56,7 @@ struct virtio_uml_device {
 	int sock, req_fd, irq;
 	u64 features;
 	u64 protocol_features;
+	u64 max_vqs;
 	u8 status;
 	u8 registered:1;
 	u8 suspended:1;
@@ -72,8 +73,6 @@ struct virtio_uml_vq_info {
 	bool suspended;
 };
 
-extern unsigned long long physmem_size, highmem;
-
 #define vu_err(vu_dev, ...)	dev_err(&(vu_dev)->pdev->dev, ##__VA_ARGS__)
 
 /* Vhost-user protocol */
@@ -343,6 +342,17 @@ static int vhost_user_set_protocol_features(struct virtio_uml_device *vu_dev,
 				   protocol_features);
 }
 
+static int vhost_user_get_queue_num(struct virtio_uml_device *vu_dev,
+				    u64 *queue_num)
+{
+	int rc = vhost_user_send_no_payload(vu_dev, true,
+			VHOST_USER_GET_QUEUE_NUM);
+
+	if (rc)
+		return rc;
+	return vhost_user_recv_u64(vu_dev, queue_num);
+}
+
 static void vhost_user_reply(struct virtio_uml_device *vu_dev,
 			     struct vhost_user_msg *msg, int response)
 {
@@ -516,6 +526,15 @@ static int vhost_user_init(struct virtio_uml_device *vu_dev)
 			return rc;
 	}
 
+	if (vu_dev->protocol_features &
+			BIT_ULL(VHOST_USER_PROTOCOL_F_MQ)) {
+		rc = vhost_user_get_queue_num(vu_dev, &vu_dev->max_vqs);
+		if (rc)
+			return rc;
+	} else {
+		vu_dev->max_vqs = U64_MAX;
+	}
+
 	return 0;
 }
 
@@ -625,7 +644,7 @@ static int vhost_user_set_mem_table(struct virtio_uml_device *vu_dev)
 {
 	struct vhost_user_msg msg = {
 		.header.request = VHOST_USER_SET_MEM_TABLE,
-		.header.size = sizeof(msg.payload.mem_regions),
+		.header.size = offsetof(typeof(msg.payload.mem_regions), regions[1]),
 		.payload.mem_regions.num = 1,
 	};
 	unsigned long reserved = uml_reserved - uml_physmem;
@@ -673,13 +692,6 @@ static int vhost_user_set_mem_table(struct virtio_uml_device *vu_dev)
 
 	if (rc < 0)
 		return rc;
-	if (highmem) {
-		msg.payload.mem_regions.num++;
-		rc = vhost_user_init_mem_region(__pa(end_iomem), highmem,
-				&fds[1], &msg.payload.mem_regions.regions[1]);
-		if (rc < 0)
-			return rc;
-	}
 
 	return vhost_user_send(vu_dev, false, &msg, fds,
 			       msg.payload.mem_regions.num);
@@ -897,7 +909,7 @@ static int vu_setup_vq_call_fd(struct virtio_uml_device *vu_dev,
 {
 	struct virtio_uml_vq_info *info = vq->priv;
 	int call_fds[2];
-	int rc;
+	int rc, irq;
 
 	/* no call FD needed/desired in this case */
 	if (vu_dev->protocol_features &
@@ -914,19 +926,23 @@ static int vu_setup_vq_call_fd(struct virtio_uml_device *vu_dev,
 		return rc;
 
 	info->call_fd = call_fds[0];
-	rc = um_request_irq(vu_dev->irq, info->call_fd, IRQ_READ,
-			    vu_interrupt, IRQF_SHARED, info->name, vq);
-	if (rc < 0)
+	irq = um_request_irq(vu_dev->irq, info->call_fd, IRQ_READ,
+			     vu_interrupt, IRQF_SHARED, info->name, vq);
+	if (irq < 0) {
+		rc = irq;
 		goto close_both;
+	}
 
 	rc = vhost_user_set_vring_call(vu_dev, vq->index, call_fds[1]);
 	if (rc)
 		goto release_irq;
 
+	vu_dev->irq = irq;
+
 	goto out;
 
 release_irq:
-	um_free_irq(vu_dev->irq, vq);
+	um_free_irq(irq, vq);
 close_both:
 	os_close_file(call_fds[0]);
 out:
@@ -1023,7 +1039,9 @@ static int vu_find_vqs(struct virtio_device *vdev, unsigned nvqs,
 	struct virtqueue *vq;
 
 	/* not supported for now */
-	if (WARN_ON(nvqs > 64))
+	if (WARN(nvqs > 64 || nvqs > vu_dev->max_vqs,
+		 "%d VQs requested, only up to 64 or %lld supported\n",
+		 nvqs, vu_dev->max_vqs))
 		return -EINVAL;
 
 	rc = vhost_user_set_mem_table(vu_dev);
@@ -1210,6 +1228,7 @@ static int virtio_uml_probe(struct platform_device *pdev)
 	vu_dev->vdev.id.vendor = VIRTIO_DEV_ANY_ID;
 	vu_dev->pdev = pdev;
 	vu_dev->req_fd = -1;
+	vu_dev->irq = UM_IRQ_ALLOC;
 
 	time_travel_propagate_time();
 
diff --git a/arch/um/include/asm/Kbuild b/arch/um/include/asm/Kbuild
index 18f902da8e99..428f2c5158c2 100644
--- a/arch/um/include/asm/Kbuild
+++ b/arch/um/include/asm/Kbuild
@@ -1,7 +1,6 @@
 # SPDX-License-Identifier: GPL-2.0
 generic-y += bug.h
 generic-y += compat.h
-generic-y += current.h
 generic-y += device.h
 generic-y += dma-mapping.h
 generic-y += emergency-restart.h
diff --git a/arch/um/include/asm/current.h b/arch/um/include/asm/current.h
new file mode 100644
index 000000000000..de64e032d66c
--- /dev/null
+++ b/arch/um/include/asm/current.h
@@ -0,0 +1,23 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __ASM_CURRENT_H
+#define __ASM_CURRENT_H
+
+#include <linux/compiler.h>
+#include <linux/threads.h>
+
+#ifndef __ASSEMBLY__
+
+struct task_struct;
+extern struct task_struct *cpu_tasks[NR_CPUS];
+
+static __always_inline struct task_struct *get_current(void)
+{
+	return cpu_tasks[0];
+}
+
+
+#define current get_current()
+
+#endif /* __ASSEMBLY__ */
+
+#endif /* __ASM_CURRENT_H */
diff --git a/arch/um/include/asm/page.h b/arch/um/include/asm/page.h
index 834313ecd3d6..3d516f3ca9c7 100644
--- a/arch/um/include/asm/page.h
+++ b/arch/um/include/asm/page.h
@@ -29,51 +29,35 @@ struct page;
 #define clear_user_page(page, vaddr, pg)	clear_page(page)
 #define copy_user_page(to, from, vaddr, pg)	copy_page(to, from)
 
-#if defined(CONFIG_3_LEVEL_PGTABLES) && !defined(CONFIG_64BIT)
-
 typedef struct { unsigned long pte; } pte_t;
-typedef struct { unsigned long pmd; } pmd_t;
 typedef struct { unsigned long pgd; } pgd_t;
-#define pte_val(p) ((p).pte)
 
-#define pte_get_bits(p, bits) ((p).pte & (bits))
-#define pte_set_bits(p, bits) ((p).pte |= (bits))
-#define pte_clear_bits(p, bits) ((p).pte &= ~(bits))
-#define pte_copy(to, from) ({ (to).pte = (from).pte; })
-#define pte_is_zero(p) (!((p).pte & ~_PAGE_NEWPAGE))
-#define pte_set_val(p, phys, prot) \
-	({ (p).pte = (phys) | pgprot_val(prot); })
+#if CONFIG_PGTABLE_LEVELS > 2
 
+typedef struct { unsigned long pmd; } pmd_t;
 #define pmd_val(x)	((x).pmd)
 #define __pmd(x) ((pmd_t) { (x) } )
 
-typedef unsigned long long phys_t;
+#if CONFIG_PGTABLE_LEVELS > 3
 
-#else
-
-typedef struct { unsigned long pte; } pte_t;
-typedef struct { unsigned long pgd; } pgd_t;
+typedef struct { unsigned long pud; } pud_t;
+#define pud_val(x)	((x).pud)
+#define __pud(x) ((pud_t) { (x) } )
 
-#ifdef CONFIG_3_LEVEL_PGTABLES
-typedef struct { unsigned long pmd; } pmd_t;
-#define pmd_val(x)	((x).pmd)
-#define __pmd(x) ((pmd_t) { (x) } )
-#endif
+#endif /* CONFIG_PGTABLE_LEVELS > 3 */
+#endif /* CONFIG_PGTABLE_LEVELS > 2 */
 
 #define pte_val(x)	((x).pte)
 
-
 #define pte_get_bits(p, bits) ((p).pte & (bits))
 #define pte_set_bits(p, bits) ((p).pte |= (bits))
 #define pte_clear_bits(p, bits) ((p).pte &= ~(bits))
 #define pte_copy(to, from) ((to).pte = (from).pte)
-#define pte_is_zero(p) (!((p).pte & ~_PAGE_NEWPAGE))
+#define pte_is_zero(p) (!((p).pte & ~_PAGE_NEEDSYNC))
 #define pte_set_val(p, phys, prot) (p).pte = (phys | pgprot_val(prot))
 
 typedef unsigned long phys_t;
 
-#endif
-
 typedef struct { unsigned long pgprot; } pgprot_t;
 
 typedef struct page *pgtable_t;
diff --git a/arch/um/include/asm/pgalloc.h b/arch/um/include/asm/pgalloc.h
index de5e31c64793..04fb4e6969a4 100644
--- a/arch/um/include/asm/pgalloc.h
+++ b/arch/um/include/asm/pgalloc.h
@@ -31,7 +31,7 @@ do {								\
 	tlb_remove_page_ptdesc((tlb), (page_ptdesc(pte)));	\
 } while (0)
 
-#ifdef CONFIG_3_LEVEL_PGTABLES
+#if CONFIG_PGTABLE_LEVELS > 2
 
 #define __pmd_free_tlb(tlb, pmd, address)			\
 do {								\
@@ -39,6 +39,15 @@ do {								\
 	tlb_remove_page_ptdesc((tlb), virt_to_ptdesc(pmd));	\
 } while (0)
 
+#if CONFIG_PGTABLE_LEVELS > 3
+
+#define __pud_free_tlb(tlb, pud, address)			\
+do {								\
+	pagetable_pud_dtor(virt_to_ptdesc(pud));		\
+	tlb_remove_page_ptdesc((tlb), virt_to_ptdesc(pud));	\
+} while (0)
+
+#endif
 #endif
 
 #endif
diff --git a/arch/um/include/asm/pgtable-2level.h b/arch/um/include/asm/pgtable-2level.h
index 8256ecc5b919..ab0c8dd86564 100644
--- a/arch/um/include/asm/pgtable-2level.h
+++ b/arch/um/include/asm/pgtable-2level.h
@@ -31,7 +31,7 @@
         printk("%s:%d: bad pgd %p(%08lx).\n", __FILE__, __LINE__, &(e), \
 	       pgd_val(e))
 
-static inline int pgd_newpage(pgd_t pgd)	{ return 0; }
+static inline int pgd_needsync(pgd_t pgd)	{ return 0; }
 static inline void pgd_mkuptodate(pgd_t pgd)	{ }
 
 #define set_pmd(pmdptr, pmdval) (*(pmdptr) = (pmdval))
diff --git a/arch/um/include/asm/pgtable-3level.h b/arch/um/include/asm/pgtable-4level.h
index 8a5032ec231f..0d279caee93c 100644
--- a/arch/um/include/asm/pgtable-3level.h
+++ b/arch/um/include/asm/pgtable-4level.h
@@ -4,21 +4,25 @@
  * Derived from include/asm-i386/pgtable.h
  */
 
-#ifndef __UM_PGTABLE_3LEVEL_H
-#define __UM_PGTABLE_3LEVEL_H
+#ifndef __UM_PGTABLE_4LEVEL_H
+#define __UM_PGTABLE_4LEVEL_H
 
-#include <asm-generic/pgtable-nopud.h>
+#include <asm-generic/pgtable-nop4d.h>
 
-/* PGDIR_SHIFT determines what a third-level page table entry can map */
+/* PGDIR_SHIFT determines what a fourth-level page table entry can map */
 
-#ifdef CONFIG_64BIT
-#define PGDIR_SHIFT	30
-#else
-#define PGDIR_SHIFT	31
-#endif
+#define PGDIR_SHIFT	39
 #define PGDIR_SIZE	(1UL << PGDIR_SHIFT)
 #define PGDIR_MASK	(~(PGDIR_SIZE-1))
 
+/* PUD_SHIFT determines the size of the area a third-level page table can
+ * map
+ */
+
+#define PUD_SHIFT	30
+#define PUD_SIZE	(1UL << PUD_SHIFT)
+#define PUD_MASK	(~(PUD_SIZE-1))
+
 /* PMD_SHIFT determines the size of the area a second-level page table can
  * map
  */
@@ -32,13 +36,9 @@
  */
 
 #define PTRS_PER_PTE 512
-#ifdef CONFIG_64BIT
 #define PTRS_PER_PMD 512
+#define PTRS_PER_PUD 512
 #define PTRS_PER_PGD 512
-#else
-#define PTRS_PER_PMD 1024
-#define PTRS_PER_PGD 1024
-#endif
 
 #define USER_PTRS_PER_PGD ((TASK_SIZE + (PGDIR_SIZE - 1)) / PGDIR_SIZE)
 
@@ -48,11 +48,14 @@
 #define pmd_ERROR(e) \
         printk("%s:%d: bad pmd %p(%016lx).\n", __FILE__, __LINE__, &(e), \
 	       pmd_val(e))
+#define pud_ERROR(e) \
+        printk("%s:%d: bad pud %p(%016lx).\n", __FILE__, __LINE__, &(e), \
+	       pud_val(e))
 #define pgd_ERROR(e) \
         printk("%s:%d: bad pgd %p(%016lx).\n", __FILE__, __LINE__, &(e), \
 	       pgd_val(e))
 
-#define pud_none(x)	(!(pud_val(x) & ~_PAGE_NEWPAGE))
+#define pud_none(x)	(!(pud_val(x) & ~_PAGE_NEEDSYNC))
 #define	pud_bad(x)	((pud_val(x) & (~PAGE_MASK & ~_PAGE_USER)) != _KERNPG_TABLE)
 #define pud_present(x)	(pud_val(x) & _PAGE_PRESENT)
 #define pud_populate(mm, pud, pmd) \
@@ -60,23 +63,40 @@
 
 #define set_pud(pudptr, pudval) (*(pudptr) = (pudval))
 
-static inline int pgd_newpage(pgd_t pgd)
+#define p4d_none(x)	(!(p4d_val(x) & ~_PAGE_NEEDSYNC))
+#define	p4d_bad(x)	((p4d_val(x) & (~PAGE_MASK & ~_PAGE_USER)) != _KERNPG_TABLE)
+#define p4d_present(x)	(p4d_val(x) & _PAGE_PRESENT)
+#define p4d_populate(mm, p4d, pud) \
+	set_p4d(p4d, __p4d(_PAGE_TABLE + __pa(pud)))
+
+#define set_p4d(p4dptr, p4dval) (*(p4dptr) = (p4dval))
+
+
+static inline int pgd_needsync(pgd_t pgd)
 {
-	return(pgd_val(pgd) & _PAGE_NEWPAGE);
+	return pgd_val(pgd) & _PAGE_NEEDSYNC;
 }
 
-static inline void pgd_mkuptodate(pgd_t pgd) { pgd_val(pgd) &= ~_PAGE_NEWPAGE; }
+static inline void pgd_mkuptodate(pgd_t pgd) { pgd_val(pgd) &= ~_PAGE_NEEDSYNC; }
 
 #define set_pmd(pmdptr, pmdval) (*(pmdptr) = (pmdval))
 
 static inline void pud_clear (pud_t *pud)
 {
-	set_pud(pud, __pud(_PAGE_NEWPAGE));
+	set_pud(pud, __pud(_PAGE_NEEDSYNC));
+}
+
+static inline void p4d_clear (p4d_t *p4d)
+{
+	set_p4d(p4d, __p4d(_PAGE_NEEDSYNC));
 }
 
 #define pud_page(pud) phys_to_page(pud_val(pud) & PAGE_MASK)
 #define pud_pgtable(pud) ((pmd_t *) __va(pud_val(pud) & PAGE_MASK))
 
+#define p4d_page(p4d) phys_to_page(p4d_val(p4d) & PAGE_MASK)
+#define p4d_pgtable(p4d) ((pud_t *) __va(p4d_val(p4d) & PAGE_MASK))
+
 static inline unsigned long pte_pfn(pte_t pte)
 {
 	return phys_to_pfn(pte_val(pte));
@@ -97,4 +117,3 @@ static inline pmd_t pfn_pmd(unsigned long page_nr, pgprot_t pgprot)
 }
 
 #endif
-
diff --git a/arch/um/include/asm/pgtable.h b/arch/um/include/asm/pgtable.h
index faab5a2a4b06..0bd60afcc37d 100644
--- a/arch/um/include/asm/pgtable.h
+++ b/arch/um/include/asm/pgtable.h
@@ -11,8 +11,7 @@
 #include <asm/fixmap.h>
 
 #define _PAGE_PRESENT	0x001
-#define _PAGE_NEWPAGE	0x002
-#define _PAGE_NEWPROT	0x004
+#define _PAGE_NEEDSYNC	0x002
 #define _PAGE_RW	0x020
 #define _PAGE_USER	0x040
 #define _PAGE_ACCESSED	0x080
@@ -24,10 +23,12 @@
 /* We borrow bit 10 to store the exclusive marker in swap PTEs. */
 #define _PAGE_SWP_EXCLUSIVE	0x400
 
-#ifdef CONFIG_3_LEVEL_PGTABLES
-#include <asm/pgtable-3level.h>
-#else
+#if CONFIG_PGTABLE_LEVELS == 4
+#include <asm/pgtable-4level.h>
+#elif CONFIG_PGTABLE_LEVELS == 2
 #include <asm/pgtable-2level.h>
+#else
+#error "Unsupported number of page table levels"
 #endif
 
 extern pgd_t swapper_pg_dir[PTRS_PER_PGD];
@@ -78,22 +79,22 @@ extern unsigned long end_iomem;
  */
 #define ZERO_PAGE(vaddr) virt_to_page(empty_zero_page)
 
-#define pte_clear(mm,addr,xp) pte_set_val(*(xp), (phys_t) 0, __pgprot(_PAGE_NEWPAGE))
+#define pte_clear(mm, addr, xp) pte_set_val(*(xp), (phys_t) 0, __pgprot(_PAGE_NEEDSYNC))
 
-#define pmd_none(x)	(!((unsigned long)pmd_val(x) & ~_PAGE_NEWPAGE))
+#define pmd_none(x)	(!((unsigned long)pmd_val(x) & ~_PAGE_NEEDSYNC))
 #define	pmd_bad(x)	((pmd_val(x) & (~PAGE_MASK & ~_PAGE_USER)) != _KERNPG_TABLE)
 
 #define pmd_present(x)	(pmd_val(x) & _PAGE_PRESENT)
-#define pmd_clear(xp)	do { pmd_val(*(xp)) = _PAGE_NEWPAGE; } while (0)
+#define pmd_clear(xp)	do { pmd_val(*(xp)) = _PAGE_NEEDSYNC; } while (0)
 
-#define pmd_newpage(x)  (pmd_val(x) & _PAGE_NEWPAGE)
-#define pmd_mkuptodate(x) (pmd_val(x) &= ~_PAGE_NEWPAGE)
+#define pmd_needsync(x)   (pmd_val(x) & _PAGE_NEEDSYNC)
+#define pmd_mkuptodate(x) (pmd_val(x) &= ~_PAGE_NEEDSYNC)
 
-#define pud_newpage(x)  (pud_val(x) & _PAGE_NEWPAGE)
-#define pud_mkuptodate(x) (pud_val(x) &= ~_PAGE_NEWPAGE)
+#define pud_needsync(x)   (pud_val(x) & _PAGE_NEEDSYNC)
+#define pud_mkuptodate(x) (pud_val(x) &= ~_PAGE_NEEDSYNC)
 
-#define p4d_newpage(x)  (p4d_val(x) & _PAGE_NEWPAGE)
-#define p4d_mkuptodate(x) (p4d_val(x) &= ~_PAGE_NEWPAGE)
+#define p4d_needsync(x)   (p4d_val(x) & _PAGE_NEEDSYNC)
+#define p4d_mkuptodate(x) (p4d_val(x) &= ~_PAGE_NEEDSYNC)
 
 #define pmd_pfn(pmd) (pmd_val(pmd) >> PAGE_SHIFT)
 #define pmd_page(pmd) phys_to_page(pmd_val(pmd) & PAGE_MASK)
@@ -144,14 +145,9 @@ static inline int pte_young(pte_t pte)
 	return pte_get_bits(pte, _PAGE_ACCESSED);
 }
 
-static inline int pte_newpage(pte_t pte)
+static inline int pte_needsync(pte_t pte)
 {
-	return pte_get_bits(pte, _PAGE_NEWPAGE);
-}
-
-static inline int pte_newprot(pte_t pte)
-{
-	return(pte_present(pte) && (pte_get_bits(pte, _PAGE_NEWPROT)));
+	return pte_get_bits(pte, _PAGE_NEEDSYNC);
 }
 
 /*
@@ -160,12 +156,6 @@ static inline int pte_newprot(pte_t pte)
  * =================================
  */
 
-static inline pte_t pte_mknewprot(pte_t pte)
-{
-	pte_set_bits(pte, _PAGE_NEWPROT);
-	return(pte);
-}
-
 static inline pte_t pte_mkclean(pte_t pte)
 {
 	pte_clear_bits(pte, _PAGE_DIRTY);
@@ -180,19 +170,14 @@ static inline pte_t pte_mkold(pte_t pte)
 
 static inline pte_t pte_wrprotect(pte_t pte)
 {
-	if (likely(pte_get_bits(pte, _PAGE_RW)))
-		pte_clear_bits(pte, _PAGE_RW);
-	else
-		return pte;
-	return(pte_mknewprot(pte));
+	pte_clear_bits(pte, _PAGE_RW);
+	return pte;
 }
 
 static inline pte_t pte_mkread(pte_t pte)
 {
-	if (unlikely(pte_get_bits(pte, _PAGE_USER)))
-		return pte;
 	pte_set_bits(pte, _PAGE_USER);
-	return(pte_mknewprot(pte));
+	return pte;
 }
 
 static inline pte_t pte_mkdirty(pte_t pte)
@@ -209,23 +194,19 @@ static inline pte_t pte_mkyoung(pte_t pte)
 
 static inline pte_t pte_mkwrite_novma(pte_t pte)
 {
-	if (unlikely(pte_get_bits(pte,  _PAGE_RW)))
-		return pte;
 	pte_set_bits(pte, _PAGE_RW);
-	return(pte_mknewprot(pte));
+	return pte;
 }
 
 static inline pte_t pte_mkuptodate(pte_t pte)
 {
-	pte_clear_bits(pte, _PAGE_NEWPAGE);
-	if(pte_present(pte))
-		pte_clear_bits(pte, _PAGE_NEWPROT);
-	return(pte);
+	pte_clear_bits(pte, _PAGE_NEEDSYNC);
+	return pte;
 }
 
-static inline pte_t pte_mknewpage(pte_t pte)
+static inline pte_t pte_mkneedsync(pte_t pte)
 {
-	pte_set_bits(pte, _PAGE_NEWPAGE);
+	pte_set_bits(pte, _PAGE_NEEDSYNC);
 	return(pte);
 }
 
@@ -233,13 +214,11 @@ static inline void set_pte(pte_t *pteptr, pte_t pteval)
 {
 	pte_copy(*pteptr, pteval);
 
-	/* If it's a swap entry, it needs to be marked _PAGE_NEWPAGE so
-	 * fix_range knows to unmap it.  _PAGE_NEWPROT is specific to
-	 * mapped pages.
+	/* If it's a swap entry, it needs to be marked _PAGE_NEEDSYNC so
+	 * update_pte_range knows to unmap it.
 	 */
 
-	*pteptr = pte_mknewpage(*pteptr);
-	if(pte_present(*pteptr)) *pteptr = pte_mknewprot(*pteptr);
+	*pteptr = pte_mkneedsync(*pteptr);
 }
 
 #define PFN_PTE_SHIFT		PAGE_SHIFT
@@ -279,7 +258,7 @@ static inline void set_ptes(struct mm_struct *mm, unsigned long addr,
 #define __HAVE_ARCH_PTE_SAME
 static inline int pte_same(pte_t pte_a, pte_t pte_b)
 {
-	return !((pte_val(pte_a) ^ pte_val(pte_b)) & ~_PAGE_NEWPAGE);
+	return !((pte_val(pte_a) ^ pte_val(pte_b)) & ~_PAGE_NEEDSYNC);
 }
 
 /*
@@ -294,8 +273,6 @@ static inline int pte_same(pte_t pte_a, pte_t pte_b)
 	({ pte_t pte;					\
 							\
 	pte_set_val(pte, page_to_phys(page), (pgprot));	\
-	if (pte_present(pte))				\
-		pte_mknewprot(pte_mknewpage(pte));	\
 	pte;})
 
 static inline pte_t pte_modify(pte_t pte, pgprot_t newprot)
@@ -329,7 +306,7 @@ extern pte_t *virt_to_pte(struct mm_struct *mm, unsigned long addr);
  *   <--------------- offset ----------------> E < type -> 0 0 0 1 0
  *
  *   E is the exclusive marker that is not stored in swap entries.
- *   _PAGE_NEWPAGE (bit 1) is always set to 1 in set_pte().
+ *   _PAGE_NEEDSYNC (bit 1) is always set to 1 in set_pte().
  */
 #define __swp_type(x)			(((x).val >> 5) & 0x1f)
 #define __swp_offset(x)			((x).val >> 11)
diff --git a/arch/um/include/asm/processor-generic.h b/arch/um/include/asm/processor-generic.h
index bce4595798da..5d6356eafffe 100644
--- a/arch/um/include/asm/processor-generic.h
+++ b/arch/um/include/asm/processor-generic.h
@@ -20,10 +20,7 @@ struct task_struct;
 struct mm_struct;
 
 struct thread_struct {
-	struct pt_regs regs;
 	struct pt_regs *segv_regs;
-	void *fault_addr;
-	jmp_buf *fault_catcher;
 	struct task_struct *prev_sched;
 	struct arch_thread arch;
 	jmp_buf switch_buf;
@@ -33,12 +30,14 @@ struct thread_struct {
 			void *arg;
 		} thread;
 	} request;
+
+	/* Contains variable sized FP registers */
+	struct pt_regs regs;
 };
 
 #define INIT_THREAD \
 { \
 	.regs		   	= EMPTY_REGS,	\
-	.fault_addr		= NULL, \
 	.prev_sched		= NULL, \
 	.arch			= INIT_ARCH_THREAD, \
 	.request		= { } \
diff --git a/arch/um/include/asm/thread_info.h b/arch/um/include/asm/thread_info.h
index c7b4b49826a2..f9ad06fcc991 100644
--- a/arch/um/include/asm/thread_info.h
+++ b/arch/um/include/asm/thread_info.h
@@ -17,35 +17,17 @@
 #include <sysdep/ptrace_user.h>
 
 struct thread_info {
-	struct task_struct	*task;		/* main task structure */
 	unsigned long		flags;		/* low level flags */
 	__u32			cpu;		/* current CPU */
 	int			preempt_count;  /* 0 => preemptable,
 						   <0 => BUG */
-	struct thread_info	*real_thread;    /* Points to non-IRQ stack */
-	unsigned long aux_fp_regs[FP_SIZE];	/* auxiliary fp_regs to save/restore
-						   them out-of-band */
 };
 
 #define INIT_THREAD_INFO(tsk)			\
 {						\
-	.task =		&tsk,			\
 	.flags =		0,		\
 	.cpu =		0,			\
 	.preempt_count = INIT_PREEMPT_COUNT,	\
-	.real_thread = NULL,			\
-}
-
-/* how to get the thread information struct from C */
-static inline struct thread_info *current_thread_info(void)
-{
-	struct thread_info *ti;
-	unsigned long mask = THREAD_SIZE - 1;
-	void *p;
-
-	asm volatile ("" : "=r" (p) : "0" (&ti));
-	ti = (struct thread_info *) (((unsigned long)p) & ~mask);
-	return ti;
 }
 
 #endif
diff --git a/arch/um/include/asm/tlbflush.h b/arch/um/include/asm/tlbflush.h
index db997976b6ea..13a3009942be 100644
--- a/arch/um/include/asm/tlbflush.h
+++ b/arch/um/include/asm/tlbflush.h
@@ -9,8 +9,8 @@
 #include <linux/mm.h>
 
 /*
- * In UML, we need to sync the TLB over by using mmap/munmap/mprotect syscalls
- * from the process handling the MM (which can be the kernel itself).
+ * In UML, we need to sync the TLB over by using mmap/munmap syscalls from
+ * the process handling the MM (which can be the kernel itself).
  *
  * To track updates, we can hook into set_ptes and flush_tlb_*. With set_ptes
  * we catch all PTE transitions where memory that was unusable becomes usable.
diff --git a/arch/um/include/shared/as-layout.h b/arch/um/include/shared/as-layout.h
index 06292fca5a4d..ea65f151bf48 100644
--- a/arch/um/include/shared/as-layout.h
+++ b/arch/um/include/shared/as-layout.h
@@ -30,25 +30,23 @@
 
 #include <sysdep/ptrace.h>
 
-struct cpu_task {
-	void *task;
-};
+struct task_struct;
+extern struct task_struct *cpu_tasks[];
 
-extern struct cpu_task cpu_tasks[];
+extern unsigned long long physmem_size;
 
 extern unsigned long high_physmem;
 extern unsigned long uml_physmem;
 extern unsigned long uml_reserved;
 extern unsigned long end_vm;
 extern unsigned long start_vm;
-extern unsigned long long highmem;
 
 extern unsigned long brk_start;
 
 extern unsigned long host_task_size;
 extern unsigned long stub_start;
 
-extern int linux_main(int argc, char **argv);
+extern int linux_main(int argc, char **argv, char **envp);
 extern void uml_finishsetup(void);
 
 struct siginfo;
diff --git a/arch/um/include/shared/common-offsets.h b/arch/um/include/shared/common-offsets.h
index 579ed946a3a9..73f3a4792ed8 100644
--- a/arch/um/include/shared/common-offsets.h
+++ b/arch/um/include/shared/common-offsets.h
@@ -6,7 +6,6 @@ DEFINE(KERNEL_MADV_REMOVE, MADV_REMOVE);
 DEFINE(UM_KERN_PAGE_SIZE, PAGE_SIZE);
 DEFINE(UM_KERN_PAGE_MASK, PAGE_MASK);
 DEFINE(UM_KERN_PAGE_SHIFT, PAGE_SHIFT);
-DEFINE(UM_NSEC_PER_SEC, NSEC_PER_SEC);
 
 DEFINE(UM_GFP_KERNEL, GFP_KERNEL);
 DEFINE(UM_GFP_ATOMIC, GFP_ATOMIC);
@@ -15,17 +14,3 @@ DEFINE(UM_THREAD_SIZE, THREAD_SIZE);
 
 DEFINE(UM_NSEC_PER_SEC, NSEC_PER_SEC);
 DEFINE(UM_NSEC_PER_USEC, NSEC_PER_USEC);
-
-#ifdef CONFIG_PRINTK
-DEFINE(UML_CONFIG_PRINTK, CONFIG_PRINTK);
-#endif
-#ifdef CONFIG_UML_X86
-DEFINE(UML_CONFIG_UML_X86, CONFIG_UML_X86);
-#endif
-#ifdef CONFIG_64BIT
-DEFINE(UML_CONFIG_64BIT, CONFIG_64BIT);
-#endif
-#ifdef CONFIG_UML_TIME_TRAVEL_SUPPORT
-DEFINE(UML_CONFIG_UML_TIME_TRAVEL_SUPPORT, CONFIG_UML_TIME_TRAVEL_SUPPORT);
-#endif
-
diff --git a/arch/um/include/shared/kern_util.h b/arch/um/include/shared/kern_util.h
index d8ffd2db168e..f21dc8517538 100644
--- a/arch/um/include/shared/kern_util.h
+++ b/arch/um/include/shared/kern_util.h
@@ -60,7 +60,6 @@ extern unsigned long from_irq_stack(int nested);
 extern int singlestepping(void);
 
 extern void segv_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs);
-extern void bus_handler(int sig, struct siginfo *si, struct uml_pt_regs *regs);
 extern void winch(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs);
 extern void fatal_sigsegv(void) __attribute__ ((noreturn));
 
diff --git a/arch/um/include/shared/mem_user.h b/arch/um/include/shared/mem_user.h
index 11a723a58545..adfa08062f88 100644
--- a/arch/um/include/shared/mem_user.h
+++ b/arch/um/include/shared/mem_user.h
@@ -47,10 +47,9 @@ extern int iomem_size;
 #define ROUND_4M(n) ((((unsigned long) (n)) + (1 << 22)) & ~((1 << 22) - 1))
 
 extern unsigned long find_iomem(char *driver, unsigned long *len_out);
-extern void mem_total_pages(unsigned long physmem, unsigned long iomem,
-		     unsigned long highmem);
+extern void mem_total_pages(unsigned long physmem, unsigned long iomem);
 extern void setup_physmem(unsigned long start, unsigned long usable,
-			  unsigned long len, unsigned long long highmem);
+			  unsigned long len);
 extern void map_memory(unsigned long virt, unsigned long phys,
 		       unsigned long len, int r, int w, int x);
 
diff --git a/arch/um/include/shared/os.h b/arch/um/include/shared/os.h
index 9a039d6f1f74..5babad8c5f75 100644
--- a/arch/um/include/shared/os.h
+++ b/arch/um/include/shared/os.h
@@ -145,7 +145,6 @@ extern int os_ioctl_generic(int fd, unsigned int cmd, unsigned long arg);
 extern int os_get_ifname(int fd, char *namebuf);
 extern int os_set_slip(int fd);
 extern int os_mode_fd(int fd, int mode);
-extern int os_fsync_file(int fd);
 
 extern int os_seek_file(int fd, unsigned long long offset);
 extern int os_open_file(const char *file, struct openflags flags, int mode);
@@ -199,15 +198,11 @@ extern int create_mem_file(unsigned long long len);
 extern void report_enomem(void);
 
 /* process.c */
-extern unsigned long os_process_pc(int pid);
-extern int os_process_parent(int pid);
 extern void os_alarm_process(int pid);
-extern void os_stop_process(int pid);
 extern void os_kill_process(int pid, int reap_child);
 extern void os_kill_ptraced_process(int pid, int reap_child);
 
 extern int os_getpid(void);
-extern int os_getpgrp(void);
 
 extern void init_new_thread_signals(void);
 
@@ -220,6 +215,8 @@ extern int os_drop_memory(void *addr, int length);
 extern int can_drop_memory(void);
 extern int os_mincore(void *addr, unsigned long len);
 
+void os_set_pdeathsig(void);
+
 /* execvp.c */
 extern int execvp_noalloc(char *buf, const char *file, char *const argv[]);
 /* helper.c */
@@ -244,7 +241,6 @@ extern void block_signals(void);
 extern void unblock_signals(void);
 extern int um_set_signals(int enable);
 extern int um_set_signals_trace(int enable);
-extern int os_is_signal_stack(void);
 extern void deliver_alarm(void);
 extern void register_pm_wake_signal(void);
 extern void block_signals_hard(void);
@@ -283,13 +279,11 @@ int map(struct mm_id *mm_idp, unsigned long virt,
 	unsigned long len, int prot, int phys_fd,
 	unsigned long long offset);
 int unmap(struct mm_id *mm_idp, unsigned long addr, unsigned long len);
-int protect(struct mm_id *mm_idp, unsigned long addr,
-	    unsigned long len, unsigned int prot);
 
 /* skas/process.c */
 extern int is_skas_winch(int pid, int fd, void *data);
 extern int start_userspace(unsigned long stub_stack);
-extern void userspace(struct uml_pt_regs *regs, unsigned long *aux_fp_regs);
+extern void userspace(struct uml_pt_regs *regs);
 extern void new_thread(void *stack, jmp_buf *buf, void (*handler)(void));
 extern void switch_threads(jmp_buf *me, jmp_buf *you);
 extern int start_idle_thread(void *stack, jmp_buf *switch_buf);
@@ -329,9 +323,6 @@ extern int __ignore_sigio_fd(int fd);
 /* tty.c */
 extern int get_pty(void);
 
-/* sys-$ARCH/task_size.c */
-extern unsigned long os_get_top_address(void);
-
 long syscall(long number, ...);
 
 /* irqflags tracing */
diff --git a/arch/um/include/shared/registers.h b/arch/um/include/shared/registers.h
index a0450326521c..7d81b2339a48 100644
--- a/arch/um/include/shared/registers.h
+++ b/arch/um/include/shared/registers.h
@@ -8,12 +8,6 @@
 
 #include <sysdep/ptrace.h>
 
-extern int save_i387_registers(int pid, unsigned long *fp_regs);
-extern int restore_i387_registers(int pid, unsigned long *fp_regs);
-extern int save_fp_registers(int pid, unsigned long *fp_regs);
-extern int restore_fp_registers(int pid, unsigned long *fp_regs);
-extern int save_fpx_registers(int pid, unsigned long *fp_regs);
-extern int restore_fpx_registers(int pid, unsigned long *fp_regs);
 extern int init_pid_registers(int pid);
 extern void get_safe_registers(unsigned long *regs, unsigned long *fp_regs);
 extern int get_fp_registers(int pid, unsigned long *regs);
diff --git a/arch/um/include/shared/skas/stub-data.h b/arch/um/include/shared/skas/stub-data.h
index 2b6b44759dfa..81a4cace032c 100644
--- a/arch/um/include/shared/skas/stub-data.h
+++ b/arch/um/include/shared/skas/stub-data.h
@@ -12,6 +12,17 @@
 #include <as-layout.h>
 #include <sysdep/tls.h>
 
+struct stub_init_data {
+	unsigned long stub_start;
+
+	int stub_code_fd;
+	unsigned long stub_code_offset;
+	int stub_data_fd;
+	unsigned long stub_data_offset;
+
+	unsigned long segv_handler;
+};
+
 #define STUB_NEXT_SYSCALL(s) \
 	((struct stub_syscall *) (((unsigned long) s) + (s)->cmd_len))
 
@@ -19,7 +30,6 @@ enum stub_syscall_type {
 	STUB_SYSCALL_UNSET = 0,
 	STUB_SYSCALL_MMAP,
 	STUB_SYSCALL_MUNMAP,
-	STUB_SYSCALL_MPROTECT,
 };
 
 struct stub_syscall {
diff --git a/arch/um/include/shared/timetravel.h b/arch/um/include/shared/timetravel.h
index c8db2f213dba..7c2b277b7eb0 100644
--- a/arch/um/include/shared/timetravel.h
+++ b/arch/um/include/shared/timetravel.h
@@ -12,14 +12,13 @@ enum time_travel_mode {
 	TT_MODE_EXTERNAL,
 };
 
-#if defined(UML_CONFIG_UML_TIME_TRAVEL_SUPPORT) || \
-    defined(CONFIG_UML_TIME_TRAVEL_SUPPORT)
+#if IS_ENABLED(CONFIG_UML_TIME_TRAVEL_SUPPORT)
 extern enum time_travel_mode time_travel_mode;
 extern int time_travel_should_print_bc_msg;
 #else
 #define time_travel_mode TT_MODE_OFF
 #define time_travel_should_print_bc_msg 0
-#endif /* (UML_)CONFIG_UML_TIME_TRAVEL_SUPPORT */
+#endif /* CONFIG_UML_TIME_TRAVEL_SUPPORT */
 
 void _time_travel_print_bc_msg(void);
 static inline void time_travel_print_bc_msg(void)
diff --git a/arch/um/include/shared/user.h b/arch/um/include/shared/user.h
index bbab79c0c074..139eb78a4767 100644
--- a/arch/um/include/shared/user.h
+++ b/arch/um/include/shared/user.h
@@ -38,7 +38,7 @@ extern void panic(const char *fmt, ...)
 #define UM_KERN_DEBUG	KERN_DEBUG
 #define UM_KERN_CONT	KERN_CONT
 
-#ifdef UML_CONFIG_PRINTK
+#if IS_ENABLED(CONFIG_PRINTK)
 #define printk(...) _printk(__VA_ARGS__)
 extern int _printk(const char *fmt, ...)
 	__attribute__ ((format (printf, 1, 2)));
diff --git a/arch/um/kernel/dtb.c b/arch/um/kernel/dtb.c
index 8d78ced9e08f..15c342426489 100644
--- a/arch/um/kernel/dtb.c
+++ b/arch/um/kernel/dtb.c
@@ -31,6 +31,7 @@ void uml_dtb_init(void)
 
 static int __init uml_dtb_setup(char *line, int *add)
 {
+	*add = 0;
 	dtb = line;
 	return 0;
 }
diff --git a/arch/um/kernel/dyn.lds.S b/arch/um/kernel/dyn.lds.S
index 3385d653ebd0..a36b7918a011 100644
--- a/arch/um/kernel/dyn.lds.S
+++ b/arch/um/kernel/dyn.lds.S
@@ -116,8 +116,6 @@ SECTIONS
   .fini_array     : { *(.fini_array) }
   .data           : {
     INIT_TASK_DATA(KERNEL_STACK_SIZE)
-    . = ALIGN(KERNEL_STACK_SIZE);
-    *(.data..init_irqstack)
     DATA_DATA
     *(.data.* .gnu.linkonce.d.*)
     SORT(CONSTRUCTORS)
@@ -178,3 +176,6 @@ SECTIONS
 
   DISCARDS
 }
+
+ASSERT(__syscall_stub_end - __syscall_stub_start <= PAGE_SIZE,
+       "STUB code must not be larger than one page");
diff --git a/arch/um/kernel/initrd.c b/arch/um/kernel/initrd.c
index 47b8cb1a1156..99dba827461c 100644
--- a/arch/um/kernel/initrd.c
+++ b/arch/um/kernel/initrd.c
@@ -34,6 +34,7 @@ int __init read_initrd(void)
 
 static int __init uml_initrd_setup(char *line, int *add)
 {
+	*add = 0;
 	initrd = line;
 	return 0;
 }
diff --git a/arch/um/kernel/irq.c b/arch/um/kernel/irq.c
index 534e91797f89..338450741aac 100644
--- a/arch/um/kernel/irq.c
+++ b/arch/um/kernel/irq.c
@@ -674,115 +674,3 @@ void __init init_IRQ(void)
 	/* Initialize EPOLL Loop */
 	os_setup_epoll();
 }
-
-/*
- * IRQ stack entry and exit:
- *
- * Unlike i386, UML doesn't receive IRQs on the normal kernel stack
- * and switch over to the IRQ stack after some preparation.  We use
- * sigaltstack to receive signals on a separate stack from the start.
- * These two functions make sure the rest of the kernel won't be too
- * upset by being on a different stack.  The IRQ stack has a
- * thread_info structure at the bottom so that current et al continue
- * to work.
- *
- * to_irq_stack copies the current task's thread_info to the IRQ stack
- * thread_info and sets the tasks's stack to point to the IRQ stack.
- *
- * from_irq_stack copies the thread_info struct back (flags may have
- * been modified) and resets the task's stack pointer.
- *
- * Tricky bits -
- *
- * What happens when two signals race each other?  UML doesn't block
- * signals with sigprocmask, SA_DEFER, or sa_mask, so a second signal
- * could arrive while a previous one is still setting up the
- * thread_info.
- *
- * There are three cases -
- *     The first interrupt on the stack - sets up the thread_info and
- * handles the interrupt
- *     A nested interrupt interrupting the copying of the thread_info -
- * can't handle the interrupt, as the stack is in an unknown state
- *     A nested interrupt not interrupting the copying of the
- * thread_info - doesn't do any setup, just handles the interrupt
- *
- * The first job is to figure out whether we interrupted stack setup.
- * This is done by xchging the signal mask with thread_info->pending.
- * If the value that comes back is zero, then there is no setup in
- * progress, and the interrupt can be handled.  If the value is
- * non-zero, then there is stack setup in progress.  In order to have
- * the interrupt handled, we leave our signal in the mask, and it will
- * be handled by the upper handler after it has set up the stack.
- *
- * Next is to figure out whether we are the outer handler or a nested
- * one.  As part of setting up the stack, thread_info->real_thread is
- * set to non-NULL (and is reset to NULL on exit).  This is the
- * nesting indicator.  If it is non-NULL, then the stack is already
- * set up and the handler can run.
- */
-
-static unsigned long pending_mask;
-
-unsigned long to_irq_stack(unsigned long *mask_out)
-{
-	struct thread_info *ti;
-	unsigned long mask, old;
-	int nested;
-
-	mask = xchg(&pending_mask, *mask_out);
-	if (mask != 0) {
-		/*
-		 * If any interrupts come in at this point, we want to
-		 * make sure that their bits aren't lost by our
-		 * putting our bit in.  So, this loop accumulates bits
-		 * until xchg returns the same value that we put in.
-		 * When that happens, there were no new interrupts,
-		 * and pending_mask contains a bit for each interrupt
-		 * that came in.
-		 */
-		old = *mask_out;
-		do {
-			old |= mask;
-			mask = xchg(&pending_mask, old);
-		} while (mask != old);
-		return 1;
-	}
-
-	ti = current_thread_info();
-	nested = (ti->real_thread != NULL);
-	if (!nested) {
-		struct task_struct *task;
-		struct thread_info *tti;
-
-		task = cpu_tasks[ti->cpu].task;
-		tti = task_thread_info(task);
-
-		*ti = *tti;
-		ti->real_thread = tti;
-		task->stack = ti;
-	}
-
-	mask = xchg(&pending_mask, 0);
-	*mask_out |= mask | nested;
-	return 0;
-}
-
-unsigned long from_irq_stack(int nested)
-{
-	struct thread_info *ti, *to;
-	unsigned long mask;
-
-	ti = current_thread_info();
-
-	pending_mask = 1;
-
-	to = ti->real_thread;
-	current->stack = to;
-	ti->real_thread = NULL;
-	*to = *ti;
-
-	mask = xchg(&pending_mask, 0);
-	return mask & ~1;
-}
-
diff --git a/arch/um/kernel/mem.c b/arch/um/kernel/mem.c
index a5b4fe2ad931..53248ed04771 100644
--- a/arch/um/kernel/mem.c
+++ b/arch/um/kernel/mem.c
@@ -6,7 +6,6 @@
 #include <linux/stddef.h>
 #include <linux/module.h>
 #include <linux/memblock.h>
-#include <linux/highmem.h>
 #include <linux/mm.h>
 #include <linux/swap.h>
 #include <linux/slab.h>
@@ -51,8 +50,6 @@ EXPORT_SYMBOL(empty_zero_page);
 pgd_t swapper_pg_dir[PTRS_PER_PGD];
 
 /* Initialized at boot time, and readonly after that */
-unsigned long long highmem;
-EXPORT_SYMBOL(highmem);
 int kmalloc_ok = 0;
 
 /* Used during early boot */
@@ -98,7 +95,7 @@ static void __init one_page_table_init(pmd_t *pmd)
 
 static void __init one_md_table_init(pud_t *pud)
 {
-#ifdef CONFIG_3_LEVEL_PGTABLES
+#if CONFIG_PGTABLE_LEVELS > 2
 	pmd_t *pmd_table = (pmd_t *) memblock_alloc_low(PAGE_SIZE, PAGE_SIZE);
 	if (!pmd_table)
 		panic("%s: Failed to allocate %lu bytes align=%lx\n",
@@ -109,6 +106,19 @@ static void __init one_md_table_init(pud_t *pud)
 #endif
 }
 
+static void __init one_ud_table_init(p4d_t *p4d)
+{
+#if CONFIG_PGTABLE_LEVELS > 3
+	pud_t *pud_table = (pud_t *) memblock_alloc_low(PAGE_SIZE, PAGE_SIZE);
+	if (!pud_table)
+		panic("%s: Failed to allocate %lu bytes align=%lx\n",
+		      __func__, PAGE_SIZE, PAGE_SIZE);
+
+	set_p4d(p4d, __p4d(_KERNPG_TABLE + (unsigned long) __pa(pud_table)));
+	BUG_ON(pud_table != pud_offset(p4d, 0));
+#endif
+}
+
 static void __init fixrange_init(unsigned long start, unsigned long end,
 				 pgd_t *pgd_base)
 {
@@ -126,6 +136,8 @@ static void __init fixrange_init(unsigned long start, unsigned long end,
 
 	for ( ; (i < PTRS_PER_PGD) && (vaddr < end); pgd++, i++) {
 		p4d = p4d_offset(pgd, vaddr);
+		if (p4d_none(*p4d))
+			one_ud_table_init(p4d);
 		pud = pud_offset(p4d, vaddr);
 		if (pud_none(*pud))
 			one_md_table_init(pud);
diff --git a/arch/um/kernel/physmem.c b/arch/um/kernel/physmem.c
index fb2adfb49945..a74f17b033c4 100644
--- a/arch/um/kernel/physmem.c
+++ b/arch/um/kernel/physmem.c
@@ -22,19 +22,14 @@ static int physmem_fd = -1;
 unsigned long high_physmem;
 EXPORT_SYMBOL(high_physmem);
 
-extern unsigned long long physmem_size;
-
-void __init mem_total_pages(unsigned long physmem, unsigned long iomem,
-		     unsigned long highmem)
+void __init mem_total_pages(unsigned long physmem, unsigned long iomem)
 {
-	unsigned long phys_pages, highmem_pages;
-	unsigned long iomem_pages, total_pages;
+	unsigned long phys_pages, iomem_pages, total_pages;
 
-	phys_pages    = physmem >> PAGE_SHIFT;
-	iomem_pages   = iomem   >> PAGE_SHIFT;
-	highmem_pages = highmem >> PAGE_SHIFT;
+	phys_pages  = physmem >> PAGE_SHIFT;
+	iomem_pages = iomem   >> PAGE_SHIFT;
 
-	total_pages   = phys_pages + iomem_pages + highmem_pages;
+	total_pages = phys_pages + iomem_pages;
 
 	max_mapnr = total_pages;
 }
@@ -64,13 +59,12 @@ void map_memory(unsigned long virt, unsigned long phys, unsigned long len,
  * @reserve_end:	end address of the physical kernel memory.
  * @len:	Length of total physical memory that should be mapped/made
  *		available, in bytes.
- * @highmem:	Number of highmem bytes that should be mapped/made available.
  *
- * Creates an unlinked temporary file of size (len + highmem) and memory maps
+ * Creates an unlinked temporary file of size (len) and memory maps
  * it on the last executable image address (uml_reserved).
  *
  * The offset is needed as the length of the total physical memory
- * (len + highmem) includes the size of the memory used be the executable image,
+ * (len) includes the size of the memory used be the executable image,
  * but the mapped-to address is the last address of the executable image
  * (uml_reserved == end address of executable image).
  *
@@ -78,24 +72,24 @@ void map_memory(unsigned long virt, unsigned long phys, unsigned long len,
  * of all user space processes/kernel tasks.
  */
 void __init setup_physmem(unsigned long start, unsigned long reserve_end,
-			  unsigned long len, unsigned long long highmem)
+			  unsigned long len)
 {
 	unsigned long reserve = reserve_end - start;
-	long map_size = len - reserve;
+	unsigned long map_size = len - reserve;
 	int err;
 
-	if(map_size <= 0) {
+	if (len <= reserve) {
 		os_warn("Too few physical memory! Needed=%lu, given=%lu\n",
 			reserve, len);
 		exit(1);
 	}
 
-	physmem_fd = create_mem_file(len + highmem);
+	physmem_fd = create_mem_file(len);
 
 	err = os_map_memory((void *) reserve_end, physmem_fd, reserve,
 			    map_size, 1, 1, 1);
 	if (err < 0) {
-		os_warn("setup_physmem - mapping %ld bytes of memory at 0x%p "
+		os_warn("setup_physmem - mapping %lu bytes of memory at 0x%p "
 			"failed - errno = %d\n", map_size,
 			(void *) reserve_end, err);
 		exit(1);
@@ -107,9 +101,8 @@ void __init setup_physmem(unsigned long start, unsigned long reserve_end,
 	 */
 	os_seek_file(physmem_fd, __pa(__syscall_stub_start));
 	os_write_file(physmem_fd, __syscall_stub_start, PAGE_SIZE);
-	os_fsync_file(physmem_fd);
 
-	memblock_add(__pa(start), len + highmem);
+	memblock_add(__pa(start), len);
 	memblock_reserve(__pa(start), reserve);
 
 	min_low_pfn = PFN_UP(__pa(reserve_end));
@@ -137,10 +130,6 @@ int phys_mapping(unsigned long phys, unsigned long long *offset_out)
 			region = region->next;
 		}
 	}
-	else if (phys < __pa(end_iomem) + highmem) {
-		fd = physmem_fd;
-		*offset_out = phys - iomem_size;
-	}
 
 	return fd;
 }
@@ -149,6 +138,8 @@ EXPORT_SYMBOL(phys_mapping);
 static int __init uml_mem_setup(char *line, int *add)
 {
 	char *retptr;
+
+	*add = 0;
 	physmem_size = memparse(line,&retptr);
 	return 0;
 }
diff --git a/arch/um/kernel/process.c b/arch/um/kernel/process.c
index be2856af6d4c..30bdc0a87dc8 100644
--- a/arch/um/kernel/process.c
+++ b/arch/um/kernel/process.c
@@ -43,7 +43,8 @@
  * cares about its entry, so it's OK if another processor is modifying its
  * entry.
  */
-struct cpu_task cpu_tasks[NR_CPUS] = { [0 ... NR_CPUS - 1] = { NULL } };
+struct task_struct *cpu_tasks[NR_CPUS];
+EXPORT_SYMBOL(cpu_tasks);
 
 void free_stack(unsigned long stack, int order)
 {
@@ -64,7 +65,7 @@ unsigned long alloc_stack(int order, int atomic)
 
 static inline void set_current(struct task_struct *task)
 {
-	cpu_tasks[task_thread_info(task)->cpu] = ((struct cpu_task) { task });
+	cpu_tasks[task_thread_info(task)->cpu] = task;
 }
 
 struct task_struct *__switch_to(struct task_struct *from, struct task_struct *to)
@@ -116,7 +117,7 @@ void new_thread_handler(void)
 	 * callback returns only if the kernel thread execs a process
 	 */
 	fn(arg);
-	userspace(&current->thread.regs.regs, current_thread_info()->aux_fp_regs);
+	userspace(&current->thread.regs.regs);
 }
 
 /* Called magically, see new_thread_handler above */
@@ -133,7 +134,7 @@ static void fork_handler(void)
 
 	current->thread.prev_sched = NULL;
 
-	userspace(&current->thread.regs.regs, current_thread_info()->aux_fp_regs);
+	userspace(&current->thread.regs.regs);
 }
 
 int copy_thread(struct task_struct * p, const struct kernel_clone_args *args)
@@ -187,6 +188,13 @@ void initial_thread_cb(void (*proc)(void *), void *arg)
 	kmalloc_ok = save_kmalloc_ok;
 }
 
+int arch_dup_task_struct(struct task_struct *dst,
+			 struct task_struct *src)
+{
+	memcpy(dst, src, arch_task_struct_size);
+	return 0;
+}
+
 void um_idle_sleep(void)
 {
 	if (time_travel_mode != TT_MODE_OFF)
@@ -287,11 +295,3 @@ unsigned long __get_wchan(struct task_struct *p)
 
 	return 0;
 }
-
-int elf_core_copy_task_fpregs(struct task_struct *t, elf_fpregset_t *fpu)
-{
-	int cpu = current_thread_info()->cpu;
-
-	return save_i387_registers(userspace_pid[cpu], (unsigned long *) fpu);
-}
-
diff --git a/arch/um/kernel/skas/.gitignore b/arch/um/kernel/skas/.gitignore
new file mode 100644
index 000000000000..c3409ced0f38
--- /dev/null
+++ b/arch/um/kernel/skas/.gitignore
@@ -0,0 +1,2 @@
+stub_exe
+stub_exe.dbg
diff --git a/arch/um/kernel/skas/Makefile b/arch/um/kernel/skas/Makefile
index 6f86d53e3d69..3384be42691f 100644
--- a/arch/um/kernel/skas/Makefile
+++ b/arch/um/kernel/skas/Makefile
@@ -3,14 +3,48 @@
 # Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
 #
 
-obj-y := stub.o mmu.o process.o syscall.o uaccess.o
+obj-y := stub.o mmu.o process.o syscall.o uaccess.o \
+	 stub_exe_embed.o
+
+# Stub executable
+
+stub_exe_objs-y := stub_exe.o
+
+stub_exe_objs := $(foreach F,$(stub_exe_objs-y),$(obj)/$F)
+
+# Object file containing the ELF executable
+$(obj)/stub_exe_embed.o: $(src)/stub_exe_embed.S $(obj)/stub_exe
+
+$(obj)/stub_exe.dbg: $(stub_exe_objs) FORCE
+	$(call if_changed,stub_exe)
+
+$(obj)/stub_exe: OBJCOPYFLAGS := -S
+$(obj)/stub_exe: $(obj)/stub_exe.dbg FORCE
+	$(call if_changed,objcopy)
+
+quiet_cmd_stub_exe = STUB_EXE $@
+      cmd_stub_exe = $(CC) -nostdlib -o $@ \
+			   $(filter-out $(UM_GPROF_OPT) $(UM_GCOV_OPT),$(KBUILD_CFLAGS)) $(STUB_EXE_LDFLAGS) \
+			   $(filter %.o,$^)
+
+STUB_EXE_LDFLAGS = -Wl,-n -static
+
+targets += stub_exe.dbg stub_exe $(stub_exe_objs-y)
+
+# end
 
 # stub.o is in the stub, so it can't be built with profiling
 # GCC hardened also auto-enables -fpic, but we need %ebx so it can't work ->
 # disable it
 
 CFLAGS_stub.o := $(CFLAGS_NO_HARDENING)
-UNPROFILE_OBJS := stub.o
+CFLAGS_stub_exe.o := $(CFLAGS_NO_HARDENING)
+
+# Clang will call memset() from __builtin_alloca() when stack variable
+# initialization is enabled, which is used in stub_exe.c.
+CFLAGS_stub_exe.o += $(call cc-option, -ftrivial-auto-var-init=uninitialized)
+
+UNPROFILE_OBJS := stub.o stub_exe.o
 KCOV_INSTRUMENT := n
 
 include $(srctree)/arch/um/scripts/Makefile.rules
diff --git a/arch/um/kernel/skas/mmu.c b/arch/um/kernel/skas/mmu.c
index 886ed5e65674..0eb5a1d3ba70 100644
--- a/arch/um/kernel/skas/mmu.c
+++ b/arch/um/kernel/skas/mmu.c
@@ -40,35 +40,13 @@ int init_new_context(struct task_struct *task, struct mm_struct *mm)
 		goto out_free;
 	}
 
-	/*
-	 * Ensure the new MM is clean and nothing unwanted is mapped.
-	 *
-	 * TODO: We should clear the memory up to STUB_START to ensure there is
-	 * nothing mapped there, i.e. we (currently) have:
-	 *
-	 * |- user memory -|- unused        -|- stub        -|- unused    -|
-	 *                 ^ TASK_SIZE      ^ STUB_START
-	 *
-	 * Meaning we have two unused areas where we may still have valid
-	 * mappings from our internal clone(). That isn't really a problem as
-	 * userspace is not going to access them, but it is definitely not
-	 * correct.
-	 *
-	 * However, we are "lucky" and if rseq is configured, then on 32 bit
-	 * it will fall into the first empty range while on 64 bit it is going
-	 * to use an anonymous mapping in the second range. As such, things
-	 * continue to work for now as long as we don't start unmapping these
-	 * areas.
-	 *
-	 * Change this to STUB_START once we have a clean userspace.
-	 */
-	unmap(new_id, 0, TASK_SIZE);
+	/* Ensure the new MM is clean and nothing unwanted is mapped */
+	unmap(new_id, 0, STUB_START);
 
 	return 0;
 
  out_free:
-	if (new_id->stack != 0)
-		free_pages(new_id->stack, ilog2(STUB_DATA_PAGES));
+	free_pages(new_id->stack, ilog2(STUB_DATA_PAGES));
  out:
 	return ret;
 }
diff --git a/arch/um/kernel/skas/process.c b/arch/um/kernel/skas/process.c
index 68657988c8d1..05dcdc057af9 100644
--- a/arch/um/kernel/skas/process.c
+++ b/arch/um/kernel/skas/process.c
@@ -22,15 +22,13 @@ static int __init start_kernel_proc(void *unused)
 {
 	block_signals_trace();
 
-	cpu_tasks[0].task = current;
-
 	start_kernel();
 	return 0;
 }
 
 extern int userspace_pid[];
 
-extern char cpu0_irqstack[];
+static char cpu0_irqstack[THREAD_SIZE] __aligned(THREAD_SIZE);
 
 int __init start_uml(void)
 {
diff --git a/arch/um/kernel/skas/stub.c b/arch/um/kernel/skas/stub.c
index 5d52ffa682dc..796fc266d3bb 100644
--- a/arch/um/kernel/skas/stub.c
+++ b/arch/um/kernel/skas/stub.c
@@ -35,16 +35,6 @@ static __always_inline int syscall_handler(struct stub_data *d)
 				return -1;
 			}
 			break;
-		case STUB_SYSCALL_MPROTECT:
-			res = stub_syscall3(__NR_mprotect,
-					    sc->mem.addr, sc->mem.length,
-					    sc->mem.prot);
-			if (res) {
-				d->err = res;
-				d->syscall_data_len = i;
-				return -1;
-			}
-			break;
 		default:
 			d->err = -95; /* EOPNOTSUPP */
 			d->syscall_data_len = i;
diff --git a/arch/um/kernel/skas/stub_exe.c b/arch/um/kernel/skas/stub_exe.c
new file mode 100644
index 000000000000..23c99b285e82
--- /dev/null
+++ b/arch/um/kernel/skas/stub_exe.c
@@ -0,0 +1,95 @@
+#include <sys/ptrace.h>
+#include <sys/prctl.h>
+#include <asm/unistd.h>
+#include <sysdep/stub.h>
+#include <stub-data.h>
+
+void _start(void);
+
+noinline static void real_init(void)
+{
+	struct stub_init_data init_data;
+	unsigned long res;
+	struct {
+		void  *ss_sp;
+		int    ss_flags;
+		size_t ss_size;
+	} stack = {
+		.ss_size = STUB_DATA_PAGES * UM_KERN_PAGE_SIZE,
+	};
+	struct {
+		void *sa_handler_;
+		unsigned long sa_flags;
+		void *sa_restorer;
+		unsigned long long sa_mask;
+	} sa = {
+		/* Need to set SA_RESTORER (but the handler never returns) */
+		.sa_flags = SA_ONSTACK | SA_NODEFER | SA_SIGINFO | 0x04000000,
+		/* no need to mask any signals */
+		.sa_mask = 0,
+	};
+
+	/* set a nice name */
+	stub_syscall2(__NR_prctl, PR_SET_NAME, (unsigned long)"uml-userspace");
+
+	/* Make sure this process dies if the kernel dies */
+	stub_syscall2(__NR_prctl, PR_SET_PDEATHSIG, SIGKILL);
+
+	/* read information from STDIN and close it */
+	res = stub_syscall3(__NR_read, 0,
+			    (unsigned long)&init_data, sizeof(init_data));
+	if (res != sizeof(init_data))
+		stub_syscall1(__NR_exit, 10);
+
+	stub_syscall1(__NR_close, 0);
+
+	/* map stub code + data */
+	res = stub_syscall6(STUB_MMAP_NR,
+			    init_data.stub_start, UM_KERN_PAGE_SIZE,
+			    PROT_READ | PROT_EXEC, MAP_FIXED | MAP_SHARED,
+			    init_data.stub_code_fd, init_data.stub_code_offset);
+	if (res != init_data.stub_start)
+		stub_syscall1(__NR_exit, 11);
+
+	res = stub_syscall6(STUB_MMAP_NR,
+			    init_data.stub_start + UM_KERN_PAGE_SIZE,
+			    STUB_DATA_PAGES * UM_KERN_PAGE_SIZE,
+			    PROT_READ | PROT_WRITE, MAP_FIXED | MAP_SHARED,
+			    init_data.stub_data_fd, init_data.stub_data_offset);
+	if (res != init_data.stub_start + UM_KERN_PAGE_SIZE)
+		stub_syscall1(__NR_exit, 12);
+
+	/* setup signal stack inside stub data */
+	stack.ss_sp = (void *)init_data.stub_start + UM_KERN_PAGE_SIZE;
+	stub_syscall2(__NR_sigaltstack, (unsigned long)&stack, 0);
+
+	/* register SIGSEGV handler */
+	sa.sa_handler_ = (void *) init_data.segv_handler;
+	res = stub_syscall4(__NR_rt_sigaction, SIGSEGV, (unsigned long)&sa, 0,
+			    sizeof(sa.sa_mask));
+	if (res != 0)
+		stub_syscall1(__NR_exit, 13);
+
+	stub_syscall4(__NR_ptrace, PTRACE_TRACEME, 0, 0, 0);
+
+	stub_syscall2(__NR_kill, stub_syscall0(__NR_getpid), SIGSTOP);
+
+	stub_syscall1(__NR_exit, 14);
+
+	__builtin_unreachable();
+}
+
+__attribute__((naked)) void _start(void)
+{
+	/*
+	 * Since the stack after exec() starts at the top-most address,
+	 * but that's exactly where we also want to map the stub data
+	 * and code, this must:
+	 *  - push the stack by 1 code and STUB_DATA_PAGES data pages
+	 *  - call real_init()
+	 * This way, real_init() can use the stack normally, while the
+	 * original stack further down (higher address) will become
+	 * inaccessible after the mmap() calls above.
+	 */
+	stub_start(real_init);
+}
diff --git a/arch/um/kernel/skas/stub_exe_embed.S b/arch/um/kernel/skas/stub_exe_embed.S
new file mode 100644
index 000000000000..6d8914fbe8f1
--- /dev/null
+++ b/arch/um/kernel/skas/stub_exe_embed.S
@@ -0,0 +1,11 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#include <linux/init.h>
+#include <linux/linkage.h>
+
+__INITDATA
+
+SYM_DATA_START(stub_exe_start)
+	.incbin "arch/um/kernel/skas/stub_exe"
+SYM_DATA_END_LABEL(stub_exe_start, SYM_L_GLOBAL, stub_exe_end)
+
+__FINIT
diff --git a/arch/um/kernel/sysrq.c b/arch/um/kernel/sysrq.c
index 4bb8622dc512..13ee5666668d 100644
--- a/arch/um/kernel/sysrq.c
+++ b/arch/um/kernel/sysrq.c
@@ -32,12 +32,6 @@ void show_stack(struct task_struct *task, unsigned long *stack,
 	struct pt_regs *segv_regs = current->thread.segv_regs;
 	int i;
 
-	if (!segv_regs && os_is_signal_stack()) {
-		pr_err("Received SIGSEGV in SIGSEGV handler,"
-				" aborting stack trace!\n");
-		return;
-	}
-
 	if (!stack)
 		stack = get_stack_pointer(task, segv_regs);
 
@@ -52,5 +46,5 @@ void show_stack(struct task_struct *task, unsigned long *stack,
 	}
 
 	printk("%sCall Trace:\n", loglvl);
-	dump_trace(current, &stackops, (void *)loglvl);
+	dump_trace(task ?: current, &stackops, (void *)loglvl);
 }
diff --git a/arch/um/kernel/time.c b/arch/um/kernel/time.c
index 29b27b90581f..1394568c0210 100644
--- a/arch/um/kernel/time.c
+++ b/arch/um/kernel/time.c
@@ -25,6 +25,8 @@
 #include <shared/init.h>
 
 #ifdef CONFIG_UML_TIME_TRAVEL_SUPPORT
+#include <linux/sched/clock.h>
+
 enum time_travel_mode time_travel_mode;
 EXPORT_SYMBOL_GPL(time_travel_mode);
 
@@ -47,6 +49,15 @@ static u16 time_travel_shm_id;
 static struct um_timetravel_schedshm *time_travel_shm;
 static union um_timetravel_schedshm_client *time_travel_shm_client;
 
+unsigned long tt_extra_sched_jiffies;
+
+notrace unsigned long long sched_clock(void)
+{
+	return (unsigned long long)(jiffies - INITIAL_JIFFIES +
+				    tt_extra_sched_jiffies)
+					* (NSEC_PER_SEC / HZ);
+}
+
 static void time_travel_set_time(unsigned long long ns)
 {
 	if (unlikely(ns < time_travel_time))
@@ -443,6 +454,11 @@ static void time_travel_periodic_timer(struct time_travel_event *e)
 {
 	time_travel_add_event(&time_travel_timer_event,
 			      time_travel_time + time_travel_timer_interval);
+
+	/* clock tick; decrease extra jiffies by keeping sched_clock constant */
+	if (tt_extra_sched_jiffies > 0)
+		tt_extra_sched_jiffies -= 1;
+
 	deliver_alarm();
 }
 
@@ -594,6 +610,10 @@ EXPORT_SYMBOL_GPL(time_travel_add_irq_event);
 
 static void time_travel_oneshot_timer(struct time_travel_event *e)
 {
+	/* clock tick; decrease extra jiffies by keeping sched_clock constant */
+	if (tt_extra_sched_jiffies > 0)
+		tt_extra_sched_jiffies -= 1;
+
 	deliver_alarm();
 }
 
diff --git a/arch/um/kernel/tlb.c b/arch/um/kernel/tlb.c
index 548af31d4111..cf7e0d4407f2 100644
--- a/arch/um/kernel/tlb.c
+++ b/arch/um/kernel/tlb.c
@@ -23,9 +23,6 @@ struct vm_ops {
 		    int phys_fd, unsigned long long offset);
 	int (*unmap)(struct mm_id *mm_idp,
 		     unsigned long virt, unsigned long len);
-	int (*mprotect)(struct mm_id *mm_idp,
-			unsigned long virt, unsigned long len,
-			unsigned int prot);
 };
 
 static int kern_map(struct mm_id *mm_idp,
@@ -44,15 +41,6 @@ static int kern_unmap(struct mm_id *mm_idp,
 	return os_unmap_memory((void *)virt, len);
 }
 
-static int kern_mprotect(struct mm_id *mm_idp,
-			 unsigned long virt, unsigned long len,
-			 unsigned int prot)
-{
-	return os_protect_memory((void *)virt, len,
-				 prot & UM_PROT_READ, prot & UM_PROT_WRITE,
-				 1);
-}
-
 void report_enomem(void)
 {
 	printk(KERN_ERR "UML ran out of memory on the host side! "
@@ -65,33 +53,37 @@ static inline int update_pte_range(pmd_t *pmd, unsigned long addr,
 				   struct vm_ops *ops)
 {
 	pte_t *pte;
-	int r, w, x, prot, ret = 0;
+	int ret = 0;
 
 	pte = pte_offset_kernel(pmd, addr);
 	do {
-		r = pte_read(*pte);
-		w = pte_write(*pte);
-		x = pte_exec(*pte);
-		if (!pte_young(*pte)) {
-			r = 0;
-			w = 0;
-		} else if (!pte_dirty(*pte))
-			w = 0;
-
-		prot = ((r ? UM_PROT_READ : 0) | (w ? UM_PROT_WRITE : 0) |
-			(x ? UM_PROT_EXEC : 0));
-		if (pte_newpage(*pte)) {
-			if (pte_present(*pte)) {
-				__u64 offset;
-				unsigned long phys = pte_val(*pte) & PAGE_MASK;
-				int fd = phys_mapping(phys, &offset);
-
-				ret = ops->mmap(ops->mm_idp, addr, PAGE_SIZE,
-						prot, fd, offset);
-			} else
-				ret = ops->unmap(ops->mm_idp, addr, PAGE_SIZE);
-		} else if (pte_newprot(*pte))
-			ret = ops->mprotect(ops->mm_idp, addr, PAGE_SIZE, prot);
+		if (!pte_needsync(*pte))
+			continue;
+
+		if (pte_present(*pte)) {
+			__u64 offset;
+			unsigned long phys = pte_val(*pte) & PAGE_MASK;
+			int fd = phys_mapping(phys, &offset);
+			int r, w, x, prot;
+
+			r = pte_read(*pte);
+			w = pte_write(*pte);
+			x = pte_exec(*pte);
+			if (!pte_young(*pte)) {
+				r = 0;
+				w = 0;
+			} else if (!pte_dirty(*pte))
+				w = 0;
+
+			prot = (r ? UM_PROT_READ : 0) |
+			       (w ? UM_PROT_WRITE : 0) |
+			       (x ? UM_PROT_EXEC : 0);
+
+			ret = ops->mmap(ops->mm_idp, addr, PAGE_SIZE,
+					prot, fd, offset);
+		} else
+			ret = ops->unmap(ops->mm_idp, addr, PAGE_SIZE);
+
 		*pte = pte_mkuptodate(*pte);
 	} while (pte++, addr += PAGE_SIZE, ((addr < end) && !ret));
 	return ret;
@@ -109,7 +101,7 @@ static inline int update_pmd_range(pud_t *pud, unsigned long addr,
 	do {
 		next = pmd_addr_end(addr, end);
 		if (!pmd_present(*pmd)) {
-			if (pmd_newpage(*pmd)) {
+			if (pmd_needsync(*pmd)) {
 				ret = ops->unmap(ops->mm_idp, addr,
 						 next - addr);
 				pmd_mkuptodate(*pmd);
@@ -132,7 +124,7 @@ static inline int update_pud_range(p4d_t *p4d, unsigned long addr,
 	do {
 		next = pud_addr_end(addr, end);
 		if (!pud_present(*pud)) {
-			if (pud_newpage(*pud)) {
+			if (pud_needsync(*pud)) {
 				ret = ops->unmap(ops->mm_idp, addr,
 						 next - addr);
 				pud_mkuptodate(*pud);
@@ -155,7 +147,7 @@ static inline int update_p4d_range(pgd_t *pgd, unsigned long addr,
 	do {
 		next = p4d_addr_end(addr, end);
 		if (!p4d_present(*p4d)) {
-			if (p4d_newpage(*p4d)) {
+			if (p4d_needsync(*p4d)) {
 				ret = ops->unmap(ops->mm_idp, addr,
 						 next - addr);
 				p4d_mkuptodate(*p4d);
@@ -180,18 +172,16 @@ int um_tlb_sync(struct mm_struct *mm)
 	if (mm == &init_mm) {
 		ops.mmap = kern_map;
 		ops.unmap = kern_unmap;
-		ops.mprotect = kern_mprotect;
 	} else {
 		ops.mmap = map;
 		ops.unmap = unmap;
-		ops.mprotect = protect;
 	}
 
 	pgd = pgd_offset(mm, addr);
 	do {
 		next = pgd_addr_end(addr, mm->context.sync_tlb_range_to);
 		if (!pgd_present(*pgd)) {
-			if (pgd_newpage(*pgd)) {
+			if (pgd_needsync(*pgd)) {
 				ret = ops.unmap(ops.mm_idp, addr,
 						next - addr);
 				pgd_mkuptodate(*pgd);
diff --git a/arch/um/kernel/trap.c b/arch/um/kernel/trap.c
index 97c8df9c4401..cdaee3e94273 100644
--- a/arch/um/kernel/trap.c
+++ b/arch/um/kernel/trap.c
@@ -201,7 +201,6 @@ void segv_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs)
 unsigned long segv(struct faultinfo fi, unsigned long ip, int is_user,
 		   struct uml_pt_regs *regs)
 {
-	jmp_buf *catcher;
 	int si_code;
 	int err;
 	int is_write = FAULT_WRITE(fi);
@@ -246,15 +245,8 @@ unsigned long segv(struct faultinfo fi, unsigned long ip, int is_user,
 		address = 0;
 	}
 
-	catcher = current->thread.fault_catcher;
 	if (!err)
 		goto out;
-	else if (catcher != NULL) {
-		current->thread.fault_addr = (void *) address;
-		UML_LONGJMP(catcher, 1);
-	}
-	else if (current->thread.fault_addr != NULL)
-		panic("fault_addr set but no fault catcher");
 	else if (!is_user && arch_fixup(ip, regs))
 		goto out;
 
@@ -310,14 +302,6 @@ void relay_signal(int sig, struct siginfo *si, struct uml_pt_regs *regs)
 	}
 }
 
-void bus_handler(int sig, struct siginfo *si, struct uml_pt_regs *regs)
-{
-	if (current->thread.fault_catcher != NULL)
-		UML_LONGJMP(current->thread.fault_catcher, 1);
-	else
-		relay_signal(sig, si, regs);
-}
-
 void winch(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs)
 {
 	do_IRQ(WINCH_IRQ, regs);
diff --git a/arch/um/kernel/um_arch.c b/arch/um/kernel/um_arch.c
index e8e8b54b3037..8037a967225d 100644
--- a/arch/um/kernel/um_arch.c
+++ b/arch/um/kernel/um_arch.c
@@ -65,9 +65,6 @@ struct cpuinfo_um boot_cpu_data = {
 
 EXPORT_SYMBOL(boot_cpu_data);
 
-union thread_union cpu0_irqstack
-	__section(".data..init_irqstack") =
-		{ .thread_info = INIT_THREAD_INFO(init_task) };
 
 /* Changed in setup_arch, which is called in early boot */
 static char host_info[(__NEW_UTS_LEN + 1) * 5];
@@ -131,7 +128,7 @@ static int have_root __initdata;
 static int have_console __initdata;
 
 /* Set in uml_mem_setup and modified in linux_main */
-long long physmem_size = 64 * 1024 * 1024;
+unsigned long long physmem_size = 64 * 1024 * 1024;
 EXPORT_SYMBOL(physmem_size);
 
 static const char *usage_string =
@@ -167,19 +164,6 @@ __uml_setup("root=", uml_root_setup,
 "        root=/dev/ubd5\n\n"
 );
 
-static int __init no_skas_debug_setup(char *line, int *add)
-{
-	os_warn("'debug' is not necessary to gdb UML in skas mode - run\n");
-	os_warn("'gdb linux'\n");
-
-	return 0;
-}
-
-__uml_setup("debug", no_skas_debug_setup,
-"debug\n"
-"    this flag is not needed to run gdb on UML in skas mode\n\n"
-);
-
 static int __init uml_console_setup(char *line, int *add)
 {
 	have_console = 1;
@@ -257,6 +241,8 @@ static struct notifier_block panic_exit_notifier = {
 
 void uml_finishsetup(void)
 {
+	cpu_tasks[0] = &init_task;
+
 	atomic_notifier_chain_register(&panic_notifier_list,
 				       &panic_exit_notifier);
 
@@ -302,7 +288,24 @@ static void parse_cache_line(char *line)
 	}
 }
 
-int __init linux_main(int argc, char **argv)
+static unsigned long get_top_address(char **envp)
+{
+	unsigned long top_addr = (unsigned long) &top_addr;
+	int i;
+
+	/* The earliest variable should be after the program name in ELF */
+	for (i = 0; envp[i]; i++) {
+		if ((unsigned long) envp[i] > top_addr)
+			top_addr = (unsigned long) envp[i];
+	}
+
+	top_addr &= ~(UM_KERN_PAGE_SIZE - 1);
+	top_addr += UM_KERN_PAGE_SIZE;
+
+	return top_addr;
+}
+
+int __init linux_main(int argc, char **argv, char **envp)
 {
 	unsigned long avail, diff;
 	unsigned long virtmem_size, max_physmem;
@@ -324,20 +327,23 @@ int __init linux_main(int argc, char **argv)
 	if (have_console == 0)
 		add_arg(DEFAULT_COMMAND_LINE_CONSOLE);
 
-	host_task_size = os_get_top_address();
-	/* reserve a few pages for the stubs (taking care of data alignment) */
-	/* align the data portion */
-	BUILD_BUG_ON(!is_power_of_2(STUB_DATA_PAGES));
-	stub_start = (host_task_size - 1) & ~(STUB_DATA_PAGES * PAGE_SIZE - 1);
+	host_task_size = get_top_address(envp);
+	/* reserve a few pages for the stubs */
+	stub_start = host_task_size - STUB_DATA_PAGES * PAGE_SIZE;
 	/* another page for the code portion */
 	stub_start -= PAGE_SIZE;
 	host_task_size = stub_start;
 
+	/* Limit TASK_SIZE to what is addressable by the page table */
+	task_size = host_task_size;
+	if (task_size > (unsigned long long) PTRS_PER_PGD * PGDIR_SIZE)
+		task_size = PTRS_PER_PGD * PGDIR_SIZE;
+
 	/*
 	 * TASK_SIZE needs to be PGDIR_SIZE aligned or else exit_mmap craps
 	 * out
 	 */
-	task_size = host_task_size & PGDIR_MASK;
+	task_size = task_size & PGDIR_MASK;
 
 	/* OS sanity checks that need to happen before the kernel runs */
 	os_early_checks();
@@ -366,18 +372,15 @@ int __init linux_main(int argc, char **argv)
 
 	setup_machinename(init_utsname()->machine);
 
-	highmem = 0;
+	physmem_size = (physmem_size + PAGE_SIZE - 1) & PAGE_MASK;
 	iomem_size = (iomem_size + PAGE_SIZE - 1) & PAGE_MASK;
+
 	max_physmem = TASK_SIZE - uml_physmem - iomem_size - MIN_VMALLOC;
 
-	/*
-	 * Zones have to begin on a 1 << MAX_PAGE_ORDER page boundary,
-	 * so this makes sure that's true for highmem
-	 */
-	max_physmem &= ~((1 << (PAGE_SHIFT + MAX_PAGE_ORDER)) - 1);
 	if (physmem_size + iomem_size > max_physmem) {
-		highmem = physmem_size + iomem_size - max_physmem;
-		physmem_size -= highmem;
+		physmem_size = max_physmem - iomem_size;
+		os_info("Physical memory size shrunk to %llu bytes\n",
+			physmem_size);
 	}
 
 	high_physmem = uml_physmem + physmem_size;
@@ -398,6 +401,8 @@ int __init linux_main(int argc, char **argv)
 		os_info("Kernel virtual memory size shrunk to %lu bytes\n",
 			virtmem_size);
 
+	arch_task_struct_size = sizeof(struct task_struct) + host_fp_size;
+
 	os_flush_stdout();
 
 	return start_uml();
@@ -412,9 +417,9 @@ void __init setup_arch(char **cmdline_p)
 {
 	u8 rng_seed[32];
 
-	stack_protections((unsigned long) &init_thread_info);
-	setup_physmem(uml_physmem, uml_reserved, physmem_size, highmem);
-	mem_total_pages(physmem_size, iomem_size, highmem);
+	stack_protections((unsigned long) init_task.stack);
+	setup_physmem(uml_physmem, uml_reserved, physmem_size);
+	mem_total_pages(physmem_size, iomem_size);
 	uml_dtb_init();
 	read_initrd();
 
diff --git a/arch/um/kernel/uml.lds.S b/arch/um/kernel/uml.lds.S
index 5c92d58a78e8..a409d4b66114 100644
--- a/arch/um/kernel/uml.lds.S
+++ b/arch/um/kernel/uml.lds.S
@@ -77,8 +77,6 @@ SECTIONS
   .data    :
   {
     INIT_TASK_DATA(KERNEL_STACK_SIZE)
-    . = ALIGN(KERNEL_STACK_SIZE);
-    *(.data..init_irqstack)
     DATA_DATA
     *(.gnu.linkonce.d*)
     CONSTRUCTORS
diff --git a/arch/um/os-Linux/Makefile b/arch/um/os-Linux/Makefile
index 544e0b344c75..049dfa5bc9c6 100644
--- a/arch/um/os-Linux/Makefile
+++ b/arch/um/os-Linux/Makefile
@@ -12,6 +12,8 @@ obj-y = execvp.o file.o helper.o irq.o main.o mem.o process.o \
 
 CFLAGS_signal.o += -Wframe-larger-than=4096
 
+CFLAGS_main.o += -Wno-frame-larger-than
+
 obj-$(CONFIG_ARCH_REUSE_HOST_VSYSCALL_AREA) += elf_aux.o
 
 USER_OBJS := $(user-objs-y) elf_aux.o execvp.o file.o helper.o irq.o \
diff --git a/arch/um/os-Linux/file.c b/arch/um/os-Linux/file.c
index f1d03cf3957f..a0d01c68ce3e 100644
--- a/arch/um/os-Linux/file.c
+++ b/arch/um/os-Linux/file.c
@@ -255,12 +255,6 @@ void os_close_file(int fd)
 {
 	close(fd);
 }
-int os_fsync_file(int fd)
-{
-	if (fsync(fd) < 0)
-	    return -errno;
-	return 0;
-}
 
 int os_seek_file(int fd, unsigned long long offset)
 {
diff --git a/arch/um/os-Linux/main.c b/arch/um/os-Linux/main.c
index f98ff79cdbf7..0afcdeb8995b 100644
--- a/arch/um/os-Linux/main.c
+++ b/arch/um/os-Linux/main.c
@@ -11,6 +11,7 @@
 #include <signal.h>
 #include <string.h>
 #include <sys/resource.h>
+#include <sys/personality.h>
 #include <as-layout.h>
 #include <init.h>
 #include <kern_util.h>
@@ -108,6 +109,21 @@ int __init main(int argc, char **argv, char **envp)
 	char **new_argv;
 	int ret, i, err;
 
+	/* Disable randomization and re-exec if it was changed successfully */
+	ret = personality(PER_LINUX | ADDR_NO_RANDOMIZE);
+	if (ret >= 0 && (ret & (PER_LINUX | ADDR_NO_RANDOMIZE)) !=
+			 (PER_LINUX | ADDR_NO_RANDOMIZE)) {
+		char buf[4096] = {};
+		ssize_t ret;
+
+		ret = readlink("/proc/self/exe", buf, sizeof(buf));
+		if (ret < 0 || ret >= sizeof(buf)) {
+			perror("readlink failure");
+			exit(1);
+		}
+		execve(buf, argv, envp);
+	}
+
 	set_stklim();
 
 	setup_env_path();
@@ -140,7 +156,7 @@ int __init main(int argc, char **argv, char **envp)
 #endif
 
 	change_sig(SIGPIPE, 0);
-	ret = linux_main(argc, argv);
+	ret = linux_main(argc, argv, envp);
 
 	/*
 	 * Disable SIGPROF - I have no idea why libc doesn't do this or turn
@@ -182,6 +198,7 @@ int __init main(int argc, char **argv, char **envp)
 }
 
 extern void *__real_malloc(int);
+extern void __real_free(void *);
 
 /* workaround for -Wmissing-prototypes warnings */
 void *__wrap_malloc(int size);
@@ -219,10 +236,6 @@ void *__wrap_calloc(int n, int size)
 	return ptr;
 }
 
-extern void __real_free(void *);
-
-extern unsigned long high_physmem;
-
 void __wrap_free(void *ptr)
 {
 	unsigned long addr = (unsigned long) ptr;
diff --git a/arch/um/os-Linux/mem.c b/arch/um/os-Linux/mem.c
index cf44d386f23c..72f302f4d197 100644
--- a/arch/um/os-Linux/mem.c
+++ b/arch/um/os-Linux/mem.c
@@ -39,10 +39,22 @@ void kasan_map_memory(void *start, size_t len)
 			strerror(errno));
 		exit(1);
 	}
+
+	if (madvise(start, len, MADV_DONTDUMP)) {
+		os_info("Couldn't set MAD_DONTDUMP on shadow memory: %s\n.",
+			strerror(errno));
+		exit(1);
+	}
+
+	if (madvise(start, len, MADV_DONTFORK)) {
+		os_info("Couldn't set MADV_DONTFORK on shadow memory: %s\n.",
+			strerror(errno));
+		exit(1);
+	}
 }
 
 /* Set by make_tempfile() during early boot. */
-static char *tempdir = NULL;
+char *tempdir = NULL;
 
 /* Check if dir is on tmpfs. Return 0 if yes, -1 if no or error. */
 static int __init check_tmpfs(const char *dir)
diff --git a/arch/um/os-Linux/process.c b/arch/um/os-Linux/process.c
index e52dd37ddadc..9f086f939420 100644
--- a/arch/um/os-Linux/process.c
+++ b/arch/um/os-Linux/process.c
@@ -12,94 +12,18 @@
 #include <fcntl.h>
 #include <sys/mman.h>
 #include <sys/ptrace.h>
+#include <sys/prctl.h>
 #include <sys/wait.h>
 #include <asm/unistd.h>
 #include <init.h>
 #include <longjmp.h>
 #include <os.h>
 
-#define ARBITRARY_ADDR -1
-#define FAILURE_PID    -1
-
-#define STAT_PATH_LEN sizeof("/proc/#######/stat\0")
-#define COMM_SCANF "%*[^)])"
-
-unsigned long os_process_pc(int pid)
-{
-	char proc_stat[STAT_PATH_LEN], buf[256];
-	unsigned long pc = ARBITRARY_ADDR;
-	int fd, err;
-
-	sprintf(proc_stat, "/proc/%d/stat", pid);
-	fd = open(proc_stat, O_RDONLY, 0);
-	if (fd < 0) {
-		printk(UM_KERN_ERR "os_process_pc - couldn't open '%s', "
-		       "errno = %d\n", proc_stat, errno);
-		goto out;
-	}
-	CATCH_EINTR(err = read(fd, buf, sizeof(buf)));
-	if (err < 0) {
-		printk(UM_KERN_ERR "os_process_pc - couldn't read '%s', "
-		       "err = %d\n", proc_stat, errno);
-		goto out_close;
-	}
-	os_close_file(fd);
-	pc = ARBITRARY_ADDR;
-	if (sscanf(buf, "%*d " COMM_SCANF " %*c %*d %*d %*d %*d %*d %*d %*d "
-		   "%*d %*d %*d %*d %*d %*d %*d %*d %*d %*d %*d %*d %*d %*d "
-		   "%*d %*d %*d %*d %*d %lu", &pc) != 1)
-		printk(UM_KERN_ERR "os_process_pc - couldn't find pc in '%s'\n",
-		       buf);
- out_close:
-	close(fd);
- out:
-	return pc;
-}
-
-int os_process_parent(int pid)
-{
-	char stat[STAT_PATH_LEN];
-	char data[256];
-	int parent = FAILURE_PID, n, fd;
-
-	if (pid == -1)
-		return parent;
-
-	snprintf(stat, sizeof(stat), "/proc/%d/stat", pid);
-	fd = open(stat, O_RDONLY, 0);
-	if (fd < 0) {
-		printk(UM_KERN_ERR "Couldn't open '%s', errno = %d\n", stat,
-		       errno);
-		return parent;
-	}
-
-	CATCH_EINTR(n = read(fd, data, sizeof(data)));
-	close(fd);
-
-	if (n < 0) {
-		printk(UM_KERN_ERR "Couldn't read '%s', errno = %d\n", stat,
-		       errno);
-		return parent;
-	}
-
-	parent = FAILURE_PID;
-	n = sscanf(data, "%*d " COMM_SCANF " %*c %d", &parent);
-	if (n != 1)
-		printk(UM_KERN_ERR "Failed to scan '%s'\n", data);
-
-	return parent;
-}
-
 void os_alarm_process(int pid)
 {
 	kill(pid, SIGALRM);
 }
 
-void os_stop_process(int pid)
-{
-	kill(pid, SIGSTOP);
-}
-
 void os_kill_process(int pid, int reap_child)
 {
 	kill(pid, SIGKILL);
@@ -130,11 +54,6 @@ int os_getpid(void)
 	return syscall(__NR_getpid);
 }
 
-int os_getpgrp(void)
-{
-	return getpgrp();
-}
-
 int os_map_memory(void *virt, int fd, unsigned long long off, unsigned long len,
 		  int r, int w, int x)
 {
@@ -285,3 +204,8 @@ void init_new_thread_signals(void)
 	set_handler(SIGIO);
 	signal(SIGWINCH, SIG_IGN);
 }
+
+void os_set_pdeathsig(void)
+{
+	prctl(PR_SET_PDEATHSIG, SIGKILL);
+}
diff --git a/arch/um/os-Linux/registers.c b/arch/um/os-Linux/registers.c
index bd80b921add0..d7ca148807b2 100644
--- a/arch/um/os-Linux/registers.c
+++ b/arch/um/os-Linux/registers.c
@@ -10,11 +10,12 @@
 #include <sysdep/ptrace.h>
 #include <sysdep/ptrace_user.h>
 #include <registers.h>
+#include <stdlib.h>
 
 /* This is set once at boot time and not changed thereafter */
 
 static unsigned long exec_regs[MAX_REG_NR];
-static unsigned long exec_fp_regs[FP_SIZE];
+static unsigned long *exec_fp_regs;
 
 int init_pid_registers(int pid)
 {
@@ -24,7 +25,11 @@ int init_pid_registers(int pid)
 	if (err < 0)
 		return -errno;
 
-	arch_init_registers(pid);
+	err = arch_init_registers(pid);
+	if (err < 0)
+		return err;
+
+	exec_fp_regs = malloc(host_fp_size);
 	get_fp_registers(pid, exec_fp_regs);
 	return 0;
 }
@@ -34,5 +39,5 @@ void get_safe_registers(unsigned long *regs, unsigned long *fp_regs)
 	memcpy(regs, exec_regs, sizeof(exec_regs));
 
 	if (fp_regs)
-		memcpy(fp_regs, exec_fp_regs, sizeof(exec_fp_regs));
+		memcpy(fp_regs, exec_fp_regs, host_fp_size);
 }
diff --git a/arch/um/os-Linux/sigio.c b/arch/um/os-Linux/sigio.c
index 9e71794839e8..9aac8def4d63 100644
--- a/arch/um/os-Linux/sigio.c
+++ b/arch/um/os-Linux/sigio.c
@@ -55,6 +55,7 @@ static int write_sigio_thread(void *unused)
 	int i, n, respond_fd;
 	char c;
 
+	os_set_pdeathsig();
 	os_fix_helper_signals();
 	fds = &current_poll;
 	while (1) {
diff --git a/arch/um/os-Linux/signal.c b/arch/um/os-Linux/signal.c
index b11ed66c8bb0..9ea7269ffb77 100644
--- a/arch/um/os-Linux/signal.c
+++ b/arch/um/os-Linux/signal.c
@@ -26,7 +26,7 @@ void (*sig_info[NSIG])(int, struct siginfo *, struct uml_pt_regs *) = {
 	[SIGFPE]	= relay_signal,
 	[SIGILL]	= relay_signal,
 	[SIGWINCH]	= winch,
-	[SIGBUS]	= bus_handler,
+	[SIGBUS]	= relay_signal,
 	[SIGSEGV]	= segv_handler,
 	[SIGIO]		= sigio_handler,
 };
@@ -65,7 +65,7 @@ static void sig_handler_common(int sig, struct siginfo *si, mcontext_t *mc)
 #define SIGALRM_MASK (1 << SIGALRM_BIT)
 
 int signals_enabled;
-#ifdef UML_CONFIG_UML_TIME_TRAVEL_SUPPORT
+#if IS_ENABLED(CONFIG_UML_TIME_TRAVEL_SUPPORT)
 static int signals_blocked, signals_blocked_pending;
 #endif
 static unsigned int signals_pending;
@@ -75,7 +75,7 @@ static void sig_handler(int sig, struct siginfo *si, mcontext_t *mc)
 {
 	int enabled = signals_enabled;
 
-#ifdef UML_CONFIG_UML_TIME_TRAVEL_SUPPORT
+#if IS_ENABLED(CONFIG_UML_TIME_TRAVEL_SUPPORT)
 	if ((signals_blocked ||
 	     __atomic_load_n(&signals_blocked_pending, __ATOMIC_SEQ_CST)) &&
 	    (sig == SIGIO)) {
@@ -190,43 +190,8 @@ static void hard_handler(int sig, siginfo_t *si, void *p)
 {
 	ucontext_t *uc = p;
 	mcontext_t *mc = &uc->uc_mcontext;
-	unsigned long pending = 1UL << sig;
 
-	do {
-		int nested, bail;
-
-		/*
-		 * pending comes back with one bit set for each
-		 * interrupt that arrived while setting up the stack,
-		 * plus a bit for this interrupt, plus the zero bit is
-		 * set if this is a nested interrupt.
-		 * If bail is true, then we interrupted another
-		 * handler setting up the stack.  In this case, we
-		 * have to return, and the upper handler will deal
-		 * with this interrupt.
-		 */
-		bail = to_irq_stack(&pending);
-		if (bail)
-			return;
-
-		nested = pending & 1;
-		pending &= ~1;
-
-		while ((sig = ffs(pending)) != 0){
-			sig--;
-			pending &= ~(1 << sig);
-			(*handlers[sig])(sig, (struct siginfo *)si, mc);
-		}
-
-		/*
-		 * Again, pending comes back with a mask of signals
-		 * that arrived while tearing down the stack.  If this
-		 * is non-zero, we just go back, set up the stack
-		 * again, and handle the new interrupts.
-		 */
-		if (!nested)
-			pending = from_irq_stack(nested);
-	} while (pending);
+	(*handlers[sig])(sig, (struct siginfo *)si, mc);
 }
 
 void set_handler(int sig)
@@ -297,7 +262,7 @@ void unblock_signals(void)
 		return;
 
 	signals_enabled = 1;
-#ifdef UML_CONFIG_UML_TIME_TRAVEL_SUPPORT
+#if IS_ENABLED(CONFIG_UML_TIME_TRAVEL_SUPPORT)
 	deliver_time_travel_irqs();
 #endif
 
@@ -389,7 +354,7 @@ int um_set_signals_trace(int enable)
 	return ret;
 }
 
-#ifdef UML_CONFIG_UML_TIME_TRAVEL_SUPPORT
+#if IS_ENABLED(CONFIG_UML_TIME_TRAVEL_SUPPORT)
 void mark_sigio_pending(void)
 {
 	/*
@@ -487,11 +452,3 @@ void unblock_signals_hard(void)
 	unblocking = false;
 }
 #endif
-
-int os_is_signal_stack(void)
-{
-	stack_t ss;
-	sigaltstack(NULL, &ss);
-
-	return ss.ss_flags & SS_ONSTACK;
-}
diff --git a/arch/um/os-Linux/skas/mem.c b/arch/um/os-Linux/skas/mem.c
index 9a13ac23c606..d7f1814b0e5a 100644
--- a/arch/um/os-Linux/skas/mem.c
+++ b/arch/um/os-Linux/skas/mem.c
@@ -217,24 +217,3 @@ int unmap(struct mm_id *mm_idp, unsigned long addr, unsigned long len)
 
 	return 0;
 }
-
-int protect(struct mm_id *mm_idp, unsigned long addr, unsigned long len,
-	    unsigned int prot)
-{
-	struct stub_syscall *sc;
-
-	/* Compress with previous syscall if that is possible */
-	sc = syscall_stub_get_previous(mm_idp, STUB_SYSCALL_MPROTECT, addr);
-	if (sc && sc->mem.prot == prot) {
-		sc->mem.length += len;
-		return 0;
-	}
-
-	sc = syscall_stub_alloc(mm_idp);
-	sc->syscall = STUB_SYSCALL_MPROTECT;
-	sc->mem.addr = addr;
-	sc->mem.length = len;
-	sc->mem.prot = prot;
-
-	return 0;
-}
diff --git a/arch/um/os-Linux/skas/process.c b/arch/um/os-Linux/skas/process.c
index b6f656bcffb1..f683cfc9e51a 100644
--- a/arch/um/os-Linux/skas/process.c
+++ b/arch/um/os-Linux/skas/process.c
@@ -10,8 +10,11 @@
 #include <sched.h>
 #include <errno.h>
 #include <string.h>
+#include <fcntl.h>
+#include <mem_user.h>
 #include <sys/mman.h>
 #include <sys/wait.h>
+#include <sys/stat.h>
 #include <asm/unistd.h>
 #include <as-layout.h>
 #include <init.h>
@@ -141,16 +144,10 @@ bad_wait:
 
 extern unsigned long current_stub_stack(void);
 
-static void get_skas_faultinfo(int pid, struct faultinfo *fi, unsigned long *aux_fp_regs)
+static void get_skas_faultinfo(int pid, struct faultinfo *fi)
 {
 	int err;
 
-	err = get_fp_registers(pid, aux_fp_regs);
-	if (err < 0) {
-		printk(UM_KERN_ERR "save_fp_registers returned %d\n",
-		       err);
-		fatal_sigsegv();
-	}
 	err = ptrace(PTRACE_CONT, pid, 0, SIGSEGV);
 	if (err) {
 		printk(UM_KERN_ERR "Failed to continue stub, pid = %d, "
@@ -164,18 +161,11 @@ static void get_skas_faultinfo(int pid, struct faultinfo *fi, unsigned long *aux
 	 * the stub stack page. We just have to copy it.
 	 */
 	memcpy(fi, (void *)current_stub_stack(), sizeof(*fi));
-
-	err = put_fp_registers(pid, aux_fp_regs);
-	if (err < 0) {
-		printk(UM_KERN_ERR "put_fp_registers returned %d\n",
-		       err);
-		fatal_sigsegv();
-	}
 }
 
-static void handle_segv(int pid, struct uml_pt_regs *regs, unsigned long *aux_fp_regs)
+static void handle_segv(int pid, struct uml_pt_regs *regs)
 {
-	get_skas_faultinfo(pid, &regs->faultinfo, aux_fp_regs);
+	get_skas_faultinfo(pid, &regs->faultinfo);
 	segv(regs->faultinfo, 0, 1, NULL);
 }
 
@@ -189,69 +179,131 @@ static void handle_trap(int pid, struct uml_pt_regs *regs)
 
 extern char __syscall_stub_start[];
 
-/**
- * userspace_tramp() - userspace trampoline
- * @stack:	pointer to the new userspace stack page
- *
- * The userspace trampoline is used to setup a new userspace process in start_userspace() after it was clone()'ed.
- * This function will run on a temporary stack page.
- * It ptrace()'es itself, then
- * Two pages are mapped into the userspace address space:
- * - STUB_CODE (with EXEC), which contains the skas stub code
- * - STUB_DATA (with R/W), which contains a data page that is used to transfer certain data between the UML userspace process and the UML kernel.
- * Also for the userspace process a SIGSEGV handler is installed to catch pagefaults in the userspace process.
- * And last the process stops itself to give control to the UML kernel for this userspace process.
- *
- * Return: Always zero, otherwise the current userspace process is ended with non null exit() call
- */
+static int stub_exe_fd;
+
 static int userspace_tramp(void *stack)
 {
-	struct sigaction sa;
-	void *addr;
-	int fd;
+	char *const argv[] = { "uml-userspace", NULL };
+	int pipe_fds[2];
 	unsigned long long offset;
-	unsigned long segv_handler = STUB_CODE +
-				     (unsigned long) stub_segv_handler -
-				     (unsigned long) __syscall_stub_start;
-
-	ptrace(PTRACE_TRACEME, 0, 0, 0);
-
-	signal(SIGTERM, SIG_DFL);
-	signal(SIGWINCH, SIG_IGN);
-
-	fd = phys_mapping(uml_to_phys(__syscall_stub_start), &offset);
-	addr = mmap64((void *) STUB_CODE, UM_KERN_PAGE_SIZE,
-		      PROT_EXEC, MAP_FIXED | MAP_PRIVATE, fd, offset);
-	if (addr == MAP_FAILED) {
-		os_info("mapping mmap stub at 0x%lx failed, errno = %d\n",
-			STUB_CODE, errno);
-		exit(1);
+	struct stub_init_data init_data = {
+		.stub_start = STUB_START,
+		.segv_handler = STUB_CODE +
+				(unsigned long) stub_segv_handler -
+				(unsigned long) __syscall_stub_start,
+	};
+	struct iomem_region *iomem;
+	int ret;
+
+	init_data.stub_code_fd = phys_mapping(uml_to_phys(__syscall_stub_start),
+					      &offset);
+	init_data.stub_code_offset = MMAP_OFFSET(offset);
+
+	init_data.stub_data_fd = phys_mapping(uml_to_phys(stack), &offset);
+	init_data.stub_data_offset = MMAP_OFFSET(offset);
+
+	/* Set CLOEXEC on all FDs and then unset on all memory related FDs */
+	close_range(0, ~0U, CLOSE_RANGE_CLOEXEC);
+
+	fcntl(init_data.stub_data_fd, F_SETFD, 0);
+	for (iomem = iomem_regions; iomem; iomem = iomem->next)
+		fcntl(iomem->fd, F_SETFD, 0);
+
+	/* Create a pipe for init_data (no CLOEXEC) and dup2 to STDIN */
+	if (pipe(pipe_fds))
+		exit(2);
+
+	if (dup2(pipe_fds[0], 0) < 0)
+		exit(3);
+	close(pipe_fds[0]);
+
+	/* Write init_data and close write side */
+	ret = write(pipe_fds[1], &init_data, sizeof(init_data));
+	close(pipe_fds[1]);
+
+	if (ret != sizeof(init_data))
+		exit(4);
+
+	execveat(stub_exe_fd, "", argv, NULL, AT_EMPTY_PATH);
+
+	exit(5);
+}
+
+extern char stub_exe_start[];
+extern char stub_exe_end[];
+
+extern char *tempdir;
+
+#define STUB_EXE_NAME_TEMPLATE "/uml-userspace-XXXXXX"
+
+#ifndef MFD_EXEC
+#define MFD_EXEC 0x0010U
+#endif
+
+static int __init init_stub_exe_fd(void)
+{
+	size_t written = 0;
+	char *tmpfile = NULL;
+
+	stub_exe_fd = memfd_create("uml-userspace",
+				   MFD_EXEC | MFD_CLOEXEC | MFD_ALLOW_SEALING);
+
+	if (stub_exe_fd < 0) {
+		printk(UM_KERN_INFO "Could not create executable memfd, using temporary file!");
+
+		tmpfile = malloc(strlen(tempdir) +
+				  strlen(STUB_EXE_NAME_TEMPLATE) + 1);
+		if (tmpfile == NULL)
+			panic("Failed to allocate memory for stub binary name");
+
+		strcpy(tmpfile, tempdir);
+		strcat(tmpfile, STUB_EXE_NAME_TEMPLATE);
+
+		stub_exe_fd = mkstemp(tmpfile);
+		if (stub_exe_fd < 0)
+			panic("Could not create temporary file for stub binary: %d",
+			      -errno);
 	}
 
-	fd = phys_mapping(uml_to_phys(stack), &offset);
-	addr = mmap((void *) STUB_DATA,
-		    STUB_DATA_PAGES * UM_KERN_PAGE_SIZE, PROT_READ | PROT_WRITE,
-		    MAP_FIXED | MAP_SHARED, fd, offset);
-	if (addr == MAP_FAILED) {
-		os_info("mapping segfault stack at 0x%lx failed, errno = %d\n",
-			STUB_DATA, errno);
-		exit(1);
+	while (written < stub_exe_end - stub_exe_start) {
+		ssize_t res = write(stub_exe_fd, stub_exe_start + written,
+				    stub_exe_end - stub_exe_start - written);
+		if (res < 0) {
+			if (errno == EINTR)
+				continue;
+
+			if (tmpfile)
+				unlink(tmpfile);
+			panic("Failed write stub binary: %d", -errno);
+		}
+
+		written += res;
 	}
 
-	set_sigstack((void *) STUB_DATA, STUB_DATA_PAGES * UM_KERN_PAGE_SIZE);
-	sigemptyset(&sa.sa_mask);
-	sa.sa_flags = SA_ONSTACK | SA_NODEFER | SA_SIGINFO;
-	sa.sa_sigaction = (void *) segv_handler;
-	sa.sa_restorer = NULL;
-	if (sigaction(SIGSEGV, &sa, NULL) < 0) {
-		os_info("%s - setting SIGSEGV handler failed - errno = %d\n",
-			__func__, errno);
-		exit(1);
+	if (!tmpfile) {
+		fcntl(stub_exe_fd, F_ADD_SEALS,
+		      F_SEAL_WRITE | F_SEAL_SHRINK | F_SEAL_GROW | F_SEAL_SEAL);
+	} else {
+		if (fchmod(stub_exe_fd, 00500) < 0) {
+			unlink(tmpfile);
+			panic("Could not make stub binary executable: %d",
+			      -errno);
+		}
+
+		close(stub_exe_fd);
+		stub_exe_fd = open(tmpfile, O_RDONLY | O_CLOEXEC | O_NOFOLLOW);
+		if (stub_exe_fd < 0) {
+			unlink(tmpfile);
+			panic("Could not reopen stub binary: %d", -errno);
+		}
+
+		unlink(tmpfile);
+		free(tmpfile);
 	}
 
-	kill(os_getpid(), SIGSTOP);
 	return 0;
 }
+__initcall(init_stub_exe_fd);
 
 int userspace_pid[NR_CPUS];
 
@@ -270,7 +322,7 @@ int start_userspace(unsigned long stub_stack)
 {
 	void *stack;
 	unsigned long sp;
-	int pid, status, n, flags, err;
+	int pid, status, n, err;
 
 	/* setup a temporary stack page */
 	stack = mmap(NULL, UM_KERN_PAGE_SIZE,
@@ -286,10 +338,10 @@ int start_userspace(unsigned long stub_stack)
 	/* set stack pointer to the end of the stack page, so it can grow downwards */
 	sp = (unsigned long)stack + UM_KERN_PAGE_SIZE;
 
-	flags = CLONE_FILES | SIGCHLD;
-
 	/* clone into new userspace process */
-	pid = clone(userspace_tramp, (void *) sp, flags, (void *) stub_stack);
+	pid = clone(userspace_tramp, (void *) sp,
+		    CLONE_VFORK | CLONE_VM | SIGCHLD,
+		    (void *)stub_stack);
 	if (pid < 0) {
 		err = -errno;
 		printk(UM_KERN_ERR "%s : clone failed, errno = %d\n",
@@ -336,7 +388,10 @@ int start_userspace(unsigned long stub_stack)
 	return err;
 }
 
-void userspace(struct uml_pt_regs *regs, unsigned long *aux_fp_regs)
+int unscheduled_userspace_iterations;
+extern unsigned long tt_extra_sched_jiffies;
+
+void userspace(struct uml_pt_regs *regs)
 {
 	int err, status, op, pid = userspace_pid[0];
 	siginfo_t si;
@@ -345,6 +400,29 @@ void userspace(struct uml_pt_regs *regs, unsigned long *aux_fp_regs)
 	interrupt_end();
 
 	while (1) {
+		/*
+		 * When we are in time-travel mode, userspace can theoretically
+		 * do a *lot* of work without being scheduled. The problem with
+		 * this is that it will prevent kernel bookkeeping (primarily
+		 * the RCU) from running and this can for example cause OOM
+		 * situations.
+		 *
+		 * This code accounts a jiffie against the scheduling clock
+		 * after the defined userspace iterations in the same thread.
+		 * By doing so the situation is effectively prevented.
+		 */
+		if (time_travel_mode == TT_MODE_INFCPU ||
+		    time_travel_mode == TT_MODE_EXTERNAL) {
+#ifdef CONFIG_UML_MAX_USERSPACE_ITERATIONS
+			if (CONFIG_UML_MAX_USERSPACE_ITERATIONS &&
+			    unscheduled_userspace_iterations++ >
+			    CONFIG_UML_MAX_USERSPACE_ITERATIONS) {
+				tt_extra_sched_jiffies += 1;
+				unscheduled_userspace_iterations = 0;
+			}
+#endif
+		}
+
 		time_travel_print_bc_msg();
 
 		current_mm_sync();
@@ -435,11 +513,11 @@ void userspace(struct uml_pt_regs *regs, unsigned long *aux_fp_regs)
 			case SIGSEGV:
 				if (PTRACE_FULL_FAULTINFO) {
 					get_skas_faultinfo(pid,
-							   &regs->faultinfo, aux_fp_regs);
+							   &regs->faultinfo);
 					(*sig_info[SIGSEGV])(SIGSEGV, (struct siginfo *)&si,
 							     regs);
 				}
-				else handle_segv(pid, regs, aux_fp_regs);
+				else handle_segv(pid, regs);
 				break;
 			case SIGTRAP + 0x80:
 				handle_trap(pid, regs);
@@ -487,6 +565,8 @@ void new_thread(void *stack, jmp_buf *buf, void (*handler)(void))
 
 void switch_threads(jmp_buf *me, jmp_buf *you)
 {
+	unscheduled_userspace_iterations = 0;
+
 	if (UML_SETJMP(me) == 0)
 		UML_LONGJMP(you, 1);
 }
@@ -570,6 +650,7 @@ static bool noreboot;
 
 static int __init noreboot_cmd_param(char *str, int *add)
 {
+	*add = 0;
 	noreboot = true;
 	return 0;
 }
diff --git a/arch/um/os-Linux/umid.c b/arch/um/os-Linux/umid.c
index e09d65b05d1c..eb523ab1e218 100644
--- a/arch/um/os-Linux/umid.c
+++ b/arch/um/os-Linux/umid.c
@@ -358,6 +358,8 @@ char *get_umid(void)
 
 static int __init set_uml_dir(char *name, int *add)
 {
+	*add = 0;
+
 	if (*name == '\0') {
 		os_warn("uml_dir can't be an empty string\n");
 		return 0;
diff --git a/arch/um/os-Linux/util.c b/arch/um/os-Linux/util.c
index 1dca4ffbd572..4193e04d7e4a 100644
--- a/arch/um/os-Linux/util.c
+++ b/arch/um/os-Linux/util.c
@@ -52,8 +52,8 @@ void setup_machinename(char *machine_out)
 	struct utsname host;
 
 	uname(&host);
-#ifdef UML_CONFIG_UML_X86
-# ifndef UML_CONFIG_64BIT
+#if IS_ENABLED(CONFIG_UML_X86)
+# if !IS_ENABLED(CONFIG_64BIT)
 	if (!strcmp(host.machine, "x86_64")) {
 		strcpy(machine_out, "i686");
 		return;
diff --git a/arch/x86/um/Kconfig b/arch/x86/um/Kconfig
index 186f13268401..986045d5e638 100644
--- a/arch/x86/um/Kconfig
+++ b/arch/x86/um/Kconfig
@@ -10,6 +10,7 @@ config UML_X86
 	def_bool y
 	select ARCH_BINFMT_ELF_EXTRA_PHDRS if X86_32
 	select DCACHE_WORD_ACCESS
+	select HAVE_EFFICIENT_UNALIGNED_ACCESS
 
 config 64BIT
 	bool "64-bit kernel" if "$(SUBARCH)" = "x86"
@@ -28,17 +29,6 @@ config X86_64
 	def_bool 64BIT
 	select MODULES_USE_ELF_RELA
 
-config 3_LEVEL_PGTABLES
-	bool "Three-level pagetables" if !64BIT
-	default 64BIT
-	help
-	  Three-level pagetables will let UML have more than 4G of physical
-	  memory.  All the memory that can't be mapped directly will be treated
-	  as high memory.
-
-	  However, this it experimental on 32-bit architectures, so if unsure say
-	  N (on x86-64 it's automatically enabled, instead, as it's safe there).
-
 config ARCH_HAS_SC_SIGNALS
 	def_bool !64BIT
 
diff --git a/arch/x86/um/Makefile b/arch/x86/um/Makefile
index 36e67fc97c22..b42c31cd2390 100644
--- a/arch/x86/um/Makefile
+++ b/arch/x86/um/Makefile
@@ -10,7 +10,7 @@ else
 endif
 
 obj-y = bugs_$(BITS).o delay.o fault.o \
-	ptrace_$(BITS).o ptrace_user.o setjmp_$(BITS).o signal.o \
+	ptrace.o ptrace_$(BITS).o ptrace_user.o setjmp_$(BITS).o signal.o \
 	stub_segv.o \
 	sys_call_table_$(BITS).o sysrq_$(BITS).o tls_$(BITS).o \
 	mem_$(BITS).o subarch.o os-Linux/
diff --git a/arch/x86/um/asm/elf.h b/arch/x86/um/asm/elf.h
index 6052200fe925..62ed5d68a978 100644
--- a/arch/x86/um/asm/elf.h
+++ b/arch/x86/um/asm/elf.h
@@ -8,6 +8,8 @@
 #include <asm/user.h>
 #include <skas.h>
 
+#define CORE_DUMP_USE_REGSET
+
 #ifdef CONFIG_X86_32
 
 #define R_386_NONE	0
diff --git a/arch/x86/um/asm/ptrace.h b/arch/x86/um/asm/ptrace.h
index 2fef3da55533..2641d28d115c 100644
--- a/arch/x86/um/asm/ptrace.h
+++ b/arch/x86/um/asm/ptrace.h
@@ -2,6 +2,16 @@
 #ifndef __UM_X86_PTRACE_H
 #define __UM_X86_PTRACE_H
 
+/* This is here because signal.c needs the REGSET_FP_LEGACY definition */
+enum {
+	REGSET_GENERAL,
+#ifdef CONFIG_X86_32
+	REGSET_FP_LEGACY,
+#endif
+	REGSET_FP,
+	REGSET_XSTATE,
+};
+
 #include <linux/compiler.h>
 #ifndef CONFIG_X86_32
 #define __FRAME_OFFSETS /* Needed to get the R* macros */
diff --git a/arch/x86/um/os-Linux/Makefile b/arch/x86/um/os-Linux/Makefile
index 5249bbc30dcd..77a308aaa5ec 100644
--- a/arch/x86/um/os-Linux/Makefile
+++ b/arch/x86/um/os-Linux/Makefile
@@ -3,7 +3,7 @@
 # Licensed under the GPL
 #
 
-obj-y = registers.o task_size.o mcontext.o
+obj-y = registers.o mcontext.o
 
 obj-$(CONFIG_X86_32) += tls.o
 
diff --git a/arch/x86/um/os-Linux/registers.c b/arch/x86/um/os-Linux/registers.c
index f3638dd09cec..76eaeb93928c 100644
--- a/arch/x86/um/os-Linux/registers.c
+++ b/arch/x86/um/os-Linux/registers.c
@@ -16,133 +16,58 @@
 #include <asm/sigcontext.h>
 #include <linux/elf.h>
 #include <registers.h>
+#include <sys/mman.h>
 
-static int have_xstate_support;
+unsigned long host_fp_size;
 
-int save_i387_registers(int pid, unsigned long *fp_regs)
-{
-	if (ptrace(PTRACE_GETFPREGS, pid, 0, fp_regs) < 0)
-		return -errno;
-	return 0;
-}
-
-int save_fp_registers(int pid, unsigned long *fp_regs)
+int get_fp_registers(int pid, unsigned long *regs)
 {
-#ifdef PTRACE_GETREGSET
-	struct iovec iov;
+	struct iovec iov = {
+		.iov_base = regs,
+		.iov_len = host_fp_size,
+	};
 
-	if (have_xstate_support) {
-		iov.iov_base = fp_regs;
-		iov.iov_len = FP_SIZE * sizeof(unsigned long);
-		if (ptrace(PTRACE_GETREGSET, pid, NT_X86_XSTATE, &iov) < 0)
-			return -errno;
-		return 0;
-	} else
-#endif
-		return save_i387_registers(pid, fp_regs);
-}
-
-int restore_i387_registers(int pid, unsigned long *fp_regs)
-{
-	if (ptrace(PTRACE_SETFPREGS, pid, 0, fp_regs) < 0)
+	if (ptrace(PTRACE_GETREGSET, pid, NT_X86_XSTATE, &iov) < 0)
 		return -errno;
 	return 0;
 }
 
-int restore_fp_registers(int pid, unsigned long *fp_regs)
-{
-#ifdef PTRACE_SETREGSET
-	struct iovec iov;
-	if (have_xstate_support) {
-		iov.iov_base = fp_regs;
-		iov.iov_len = FP_SIZE * sizeof(unsigned long);
-		if (ptrace(PTRACE_SETREGSET, pid, NT_X86_XSTATE, &iov) < 0)
-			return -errno;
-		return 0;
-	} else
-#endif
-		return restore_i387_registers(pid, fp_regs);
-}
-
-#ifdef __i386__
-int have_fpx_regs = 1;
-int save_fpx_registers(int pid, unsigned long *fp_regs)
+int put_fp_registers(int pid, unsigned long *regs)
 {
-	if (ptrace(PTRACE_GETFPXREGS, pid, 0, fp_regs) < 0)
-		return -errno;
-	return 0;
-}
+	struct iovec iov = {
+		.iov_base = regs,
+		.iov_len = host_fp_size,
+	};
 
-int restore_fpx_registers(int pid, unsigned long *fp_regs)
-{
-	if (ptrace(PTRACE_SETFPXREGS, pid, 0, fp_regs) < 0)
+	if (ptrace(PTRACE_SETREGSET, pid, NT_X86_XSTATE, &iov) < 0)
 		return -errno;
 	return 0;
 }
 
-int get_fp_registers(int pid, unsigned long *regs)
-{
-	if (have_fpx_regs)
-		return save_fpx_registers(pid, regs);
-	else
-		return save_fp_registers(pid, regs);
-}
-
-int put_fp_registers(int pid, unsigned long *regs)
-{
-	if (have_fpx_regs)
-		return restore_fpx_registers(pid, regs);
-	else
-		return restore_fp_registers(pid, regs);
-}
-
-void arch_init_registers(int pid)
-{
-	struct user_fpxregs_struct fpx_regs;
-	int err;
-
-	err = ptrace(PTRACE_GETFPXREGS, pid, 0, &fpx_regs);
-	if (!err)
-		return;
-
-	if (errno != EIO)
-		panic("check_ptrace : PTRACE_GETFPXREGS failed, errno = %d",
-		      errno);
-
-	have_fpx_regs = 0;
-}
-#else
-
-int get_fp_registers(int pid, unsigned long *regs)
+int arch_init_registers(int pid)
 {
-	return save_fp_registers(pid, regs);
+	struct iovec iov = {
+		/* Just use plenty of space, it does not cost us anything */
+		.iov_len = 2 * 1024 * 1024,
+	};
+	int ret;
+
+	iov.iov_base = mmap(NULL, iov.iov_len, PROT_WRITE | PROT_READ,
+			    MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
+	if (iov.iov_base == MAP_FAILED)
+		return -ENOMEM;
+
+	/* GDB has x86_xsave_length, which uses x86_cpuid_count */
+	ret = ptrace(PTRACE_GETREGSET, pid, NT_X86_XSTATE, &iov);
+	if (ret)
+		ret = -errno;
+	munmap(iov.iov_base, 2 * 1024 * 1024);
+
+	host_fp_size = iov.iov_len;
+
+	return ret;
 }
 
-int put_fp_registers(int pid, unsigned long *regs)
-{
-	return restore_fp_registers(pid, regs);
-}
-
-void arch_init_registers(int pid)
-{
-#ifdef PTRACE_GETREGSET
-	void * fp_regs;
-	struct iovec iov;
-
-	fp_regs = malloc(FP_SIZE * sizeof(unsigned long));
-	if(fp_regs == NULL)
-		return;
-
-	iov.iov_base = fp_regs;
-	iov.iov_len = FP_SIZE * sizeof(unsigned long);
-	if (ptrace(PTRACE_GETREGSET, pid, NT_X86_XSTATE, &iov) == 0)
-		have_xstate_support = 1;
-
-	free(fp_regs);
-#endif
-}
-#endif
-
 unsigned long get_thread_reg(int reg, jmp_buf *buf)
 {
 	switch (reg) {
diff --git a/arch/x86/um/os-Linux/task_size.c b/arch/x86/um/os-Linux/task_size.c
deleted file mode 100644
index 1dc9adc20b1c..000000000000
--- a/arch/x86/um/os-Linux/task_size.c
+++ /dev/null
@@ -1,151 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0
-#include <stdio.h>
-#include <stdlib.h>
-#include <signal.h>
-#include <sys/mman.h>
-#include <longjmp.h>
-
-#ifdef __i386__
-
-static jmp_buf buf;
-
-static void segfault(int sig)
-{
-	longjmp(buf, 1);
-}
-
-static int page_ok(unsigned long page)
-{
-	unsigned long *address = (unsigned long *) (page << UM_KERN_PAGE_SHIFT);
-	unsigned long n = ~0UL;
-	void *mapped = NULL;
-	int ok = 0;
-
-	/*
-	 * First see if the page is readable.  If it is, it may still
-	 * be a VDSO, so we go on to see if it's writable.  If not
-	 * then try mapping memory there.  If that fails, then we're
-	 * still in the kernel area.  As a sanity check, we'll fail if
-	 * the mmap succeeds, but gives us an address different from
-	 * what we wanted.
-	 */
-	if (setjmp(buf) == 0)
-		n = *address;
-	else {
-		mapped = mmap(address, UM_KERN_PAGE_SIZE,
-			      PROT_READ | PROT_WRITE,
-			      MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
-		if (mapped == MAP_FAILED)
-			return 0;
-		if (mapped != address)
-			goto out;
-	}
-
-	/*
-	 * Now, is it writeable?  If so, then we're in user address
-	 * space.  If not, then try mprotecting it and try the write
-	 * again.
-	 */
-	if (setjmp(buf) == 0) {
-		*address = n;
-		ok = 1;
-		goto out;
-	} else if (mprotect(address, UM_KERN_PAGE_SIZE,
-			    PROT_READ | PROT_WRITE) != 0)
-		goto out;
-
-	if (setjmp(buf) == 0) {
-		*address = n;
-		ok = 1;
-	}
-
- out:
-	if (mapped != NULL)
-		munmap(mapped, UM_KERN_PAGE_SIZE);
-	return ok;
-}
-
-unsigned long os_get_top_address(void)
-{
-	struct sigaction sa, old;
-	unsigned long bottom = 0;
-	/*
-	 * A 32-bit UML on a 64-bit host gets confused about the VDSO at
-	 * 0xffffe000.  It is mapped, is readable, can be reprotected writeable
-	 * and written.  However, exec discovers later that it can't be
-	 * unmapped.  So, just set the highest address to be checked to just
-	 * below it.  This might waste some address space on 4G/4G 32-bit
-	 * hosts, but shouldn't hurt otherwise.
-	 */
-	unsigned long top = 0xffffd000 >> UM_KERN_PAGE_SHIFT;
-	unsigned long test, original;
-
-	printf("Locating the bottom of the address space ... ");
-	fflush(stdout);
-
-	/*
-	 * We're going to be longjmping out of the signal handler, so
-	 * SA_DEFER needs to be set.
-	 */
-	sa.sa_handler = segfault;
-	sigemptyset(&sa.sa_mask);
-	sa.sa_flags = SA_NODEFER;
-	if (sigaction(SIGSEGV, &sa, &old)) {
-		perror("os_get_top_address");
-		exit(1);
-	}
-
-	/* Manually scan the address space, bottom-up, until we find
-	 * the first valid page (or run out of them).
-	 */
-	for (bottom = 0; bottom < top; bottom++) {
-		if (page_ok(bottom))
-			break;
-	}
-
-	/* If we've got this far, we ran out of pages. */
-	if (bottom == top) {
-		fprintf(stderr, "Unable to determine bottom of address "
-			"space.\n");
-		exit(1);
-	}
-
-	printf("0x%lx\n", bottom << UM_KERN_PAGE_SHIFT);
-	printf("Locating the top of the address space ... ");
-	fflush(stdout);
-
-	original = bottom;
-
-	/* This could happen with a 4G/4G split */
-	if (page_ok(top))
-		goto out;
-
-	do {
-		test = bottom + (top - bottom) / 2;
-		if (page_ok(test))
-			bottom = test;
-		else
-			top = test;
-	} while (top - bottom > 1);
-
-out:
-	/* Restore the old SIGSEGV handling */
-	if (sigaction(SIGSEGV, &old, NULL)) {
-		perror("os_get_top_address");
-		exit(1);
-	}
-	top <<= UM_KERN_PAGE_SHIFT;
-	printf("0x%lx\n", top);
-
-	return top;
-}
-
-#else
-
-unsigned long os_get_top_address(void)
-{
-	/* The old value of CONFIG_TOP_ADDR */
-	return 0x7fc0002000;
-}
-
-#endif
diff --git a/arch/x86/um/ptrace.c b/arch/x86/um/ptrace.c
new file mode 100644
index 000000000000..57c504fd5626
--- /dev/null
+++ b/arch/x86/um/ptrace.c
@@ -0,0 +1,267 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/sched.h>
+#include <linux/elf.h>
+#include <linux/regset.h>
+#include <asm/user32.h>
+#include <asm/sigcontext.h>
+
+#ifdef CONFIG_X86_32
+/*
+ * FPU tag word conversions.
+ */
+
+static inline unsigned short twd_i387_to_fxsr(unsigned short twd)
+{
+	unsigned int tmp; /* to avoid 16 bit prefixes in the code */
+
+	/* Transform each pair of bits into 01 (valid) or 00 (empty) */
+	tmp = ~twd;
+	tmp = (tmp | (tmp>>1)) & 0x5555; /* 0V0V0V0V0V0V0V0V */
+	/* and move the valid bits to the lower byte. */
+	tmp = (tmp | (tmp >> 1)) & 0x3333; /* 00VV00VV00VV00VV */
+	tmp = (tmp | (tmp >> 2)) & 0x0f0f; /* 0000VVVV0000VVVV */
+	tmp = (tmp | (tmp >> 4)) & 0x00ff; /* 00000000VVVVVVVV */
+	return tmp;
+}
+
+static inline unsigned long twd_fxsr_to_i387(struct user_fxsr_struct *fxsave)
+{
+	struct _fpxreg *st = NULL;
+	unsigned long twd = (unsigned long) fxsave->twd;
+	unsigned long tag;
+	unsigned long ret = 0xffff0000;
+	int i;
+
+#define FPREG_ADDR(f, n)	((char *)&(f)->st_space + (n) * 16)
+
+	for (i = 0; i < 8; i++) {
+		if (twd & 0x1) {
+			st = (struct _fpxreg *) FPREG_ADDR(fxsave, i);
+
+			switch (st->exponent & 0x7fff) {
+			case 0x7fff:
+				tag = 2;		/* Special */
+				break;
+			case 0x0000:
+				if (!st->significand[0] &&
+				    !st->significand[1] &&
+				    !st->significand[2] &&
+				    !st->significand[3]) {
+					tag = 1;	/* Zero */
+				} else {
+					tag = 2;	/* Special */
+				}
+				break;
+			default:
+				if (st->significand[3] & 0x8000)
+					tag = 0;	/* Valid */
+				else
+					tag = 2;	/* Special */
+				break;
+			}
+		} else {
+			tag = 3;			/* Empty */
+		}
+		ret |= (tag << (2 * i));
+		twd = twd >> 1;
+	}
+	return ret;
+}
+
+/* Get/set the old 32bit i387 registers (pre-FPX) */
+static int fpregs_legacy_get(struct task_struct *target,
+			     const struct user_regset *regset,
+			     struct membuf to)
+{
+	struct user_fxsr_struct *fxsave = (void *)target->thread.regs.regs.fp;
+	int i;
+
+	membuf_store(&to, (unsigned long)fxsave->cwd | 0xffff0000ul);
+	membuf_store(&to, (unsigned long)fxsave->swd | 0xffff0000ul);
+	membuf_store(&to, twd_fxsr_to_i387(fxsave));
+	membuf_store(&to, fxsave->fip);
+	membuf_store(&to, fxsave->fcs | ((unsigned long)fxsave->fop << 16));
+	membuf_store(&to, fxsave->foo);
+	membuf_store(&to, fxsave->fos);
+
+	for (i = 0; i < 8; i++)
+		membuf_write(&to, (void *)fxsave->st_space + i * 16, 10);
+
+	return 0;
+}
+
+static int fpregs_legacy_set(struct task_struct *target,
+			     const struct user_regset *regset,
+			     unsigned int pos, unsigned int count,
+			     const void *kbuf, const void __user *ubuf)
+{
+	struct user_fxsr_struct *fxsave = (void *)target->thread.regs.regs.fp;
+	const struct user_i387_struct *from;
+	struct user_i387_struct buf;
+	int i;
+
+	if (ubuf) {
+		if (copy_from_user(&buf, ubuf, sizeof(buf)))
+			return -EFAULT;
+		from = &buf;
+	} else {
+		from = kbuf;
+	}
+
+	fxsave->cwd = (unsigned short)(from->cwd & 0xffff);
+	fxsave->swd = (unsigned short)(from->swd & 0xffff);
+	fxsave->twd = twd_i387_to_fxsr((unsigned short)(from->twd & 0xffff));
+	fxsave->fip = from->fip;
+	fxsave->fop = (unsigned short)((from->fcs & 0xffff0000ul) >> 16);
+	fxsave->fcs = (from->fcs & 0xffff);
+	fxsave->foo = from->foo;
+	fxsave->fos = from->fos;
+
+	for (i = 0; i < 8; i++) {
+		memcpy((void *)fxsave->st_space + i * 16,
+		       (void *)from->st_space + i * 10, 10);
+	}
+
+	return 0;
+}
+#endif
+
+static int genregs_get(struct task_struct *target,
+		       const struct user_regset *regset,
+		       struct membuf to)
+{
+	int reg;
+
+	for (reg = 0; to.left; reg++)
+		membuf_store(&to, getreg(target, reg * sizeof(unsigned long)));
+	return 0;
+}
+
+static int genregs_set(struct task_struct *target,
+		       const struct user_regset *regset,
+		       unsigned int pos, unsigned int count,
+		       const void *kbuf, const void __user *ubuf)
+{
+	int ret = 0;
+
+	if (kbuf) {
+		const unsigned long *k = kbuf;
+
+		while (count >= sizeof(*k) && !ret) {
+			ret = putreg(target, pos, *k++);
+			count -= sizeof(*k);
+			pos += sizeof(*k);
+		}
+	} else {
+		const unsigned long  __user *u = ubuf;
+
+		while (count >= sizeof(*u) && !ret) {
+			unsigned long word;
+
+			ret = __get_user(word, u++);
+			if (ret)
+				break;
+			ret = putreg(target, pos, word);
+			count -= sizeof(*u);
+			pos += sizeof(*u);
+		}
+	}
+	return ret;
+}
+
+static int generic_fpregs_active(struct task_struct *target, const struct user_regset *regset)
+{
+	return regset->n;
+}
+
+static int generic_fpregs_get(struct task_struct *target,
+			      const struct user_regset *regset,
+			      struct membuf to)
+{
+	void *fpregs = task_pt_regs(target)->regs.fp;
+
+	membuf_write(&to, fpregs, regset->size * regset->n);
+	return 0;
+}
+
+static int generic_fpregs_set(struct task_struct *target,
+			      const struct user_regset *regset,
+			      unsigned int pos, unsigned int count,
+			      const void *kbuf, const void __user *ubuf)
+{
+	void *fpregs = task_pt_regs(target)->regs.fp;
+
+	return user_regset_copyin(&pos, &count, &kbuf, &ubuf,
+				  fpregs, 0, regset->size * regset->n);
+}
+
+static struct user_regset uml_regsets[] __ro_after_init = {
+	[REGSET_GENERAL] = {
+		.core_note_type	= NT_PRSTATUS,
+		.n		= sizeof(struct user_regs_struct) / sizeof(long),
+		.size		= sizeof(long),
+		.align		= sizeof(long),
+		.regset_get	= genregs_get,
+		.set		= genregs_set
+	},
+#ifdef CONFIG_X86_32
+	/* Old FP registers, they are needed in signal frames */
+	[REGSET_FP_LEGACY] = {
+		.core_note_type	= NT_PRFPREG,
+		.n		= sizeof(struct user_i387_ia32_struct) / sizeof(long),
+		.size		= sizeof(long),
+		.align		= sizeof(long),
+		.active		= generic_fpregs_active,
+		.regset_get	= fpregs_legacy_get,
+		.set		= fpregs_legacy_set,
+	},
+#endif
+	[REGSET_FP] = {
+#ifdef CONFIG_X86_32
+		.core_note_type	= NT_PRXFPREG,
+		.n		= sizeof(struct user32_fxsr_struct) / sizeof(long),
+#else
+		.core_note_type	= NT_PRFPREG,
+		.n		= sizeof(struct user_i387_struct) / sizeof(long),
+#endif
+		.size		= sizeof(long),
+		.align		= sizeof(long),
+		.active		= generic_fpregs_active,
+		.regset_get	= generic_fpregs_get,
+		.set		= generic_fpregs_set,
+	},
+	[REGSET_XSTATE] = {
+		.core_note_type	= NT_X86_XSTATE,
+		.size		= sizeof(long),
+		.align		= sizeof(long),
+		.active		= generic_fpregs_active,
+		.regset_get	= generic_fpregs_get,
+		.set		= generic_fpregs_set,
+	},
+	/* TODO: Add TLS regset for 32bit */
+};
+
+static const struct user_regset_view user_uml_view = {
+#ifdef CONFIG_X86_32
+	.name = "i386", .e_machine = EM_386,
+#else
+	.name = "x86_64", .e_machine = EM_X86_64,
+#endif
+	.regsets = uml_regsets, .n = ARRAY_SIZE(uml_regsets)
+};
+
+const struct user_regset_view *
+task_user_regset_view(struct task_struct *tsk)
+{
+	return &user_uml_view;
+}
+
+static int __init init_regset_xstate_info(void)
+{
+	uml_regsets[REGSET_XSTATE].n =
+		host_fp_size / uml_regsets[REGSET_XSTATE].size;
+
+	return 0;
+}
+arch_initcall(init_regset_xstate_info);
diff --git a/arch/x86/um/ptrace_32.c b/arch/x86/um/ptrace_32.c
index b0a71c6cdc6e..3af3cb821524 100644
--- a/arch/x86/um/ptrace_32.c
+++ b/arch/x86/um/ptrace_32.c
@@ -6,6 +6,7 @@
 #include <linux/mm.h>
 #include <linux/sched.h>
 #include <linux/uaccess.h>
+#include <linux/regset.h>
 #include <asm/ptrace-abi.h>
 #include <registers.h>
 #include <skas.h>
@@ -168,65 +169,6 @@ int peek_user(struct task_struct *child, long addr, long data)
 	return put_user(tmp, (unsigned long __user *) data);
 }
 
-static int get_fpregs(struct user_i387_struct __user *buf, struct task_struct *child)
-{
-	int err, n, cpu = task_cpu(child);
-	struct user_i387_struct fpregs;
-
-	err = save_i387_registers(userspace_pid[cpu],
-				  (unsigned long *) &fpregs);
-	if (err)
-		return err;
-
-	n = copy_to_user(buf, &fpregs, sizeof(fpregs));
-	if(n > 0)
-		return -EFAULT;
-
-	return n;
-}
-
-static int set_fpregs(struct user_i387_struct __user *buf, struct task_struct *child)
-{
-	int n, cpu = task_cpu(child);
-	struct user_i387_struct fpregs;
-
-	n = copy_from_user(&fpregs, buf, sizeof(fpregs));
-	if (n > 0)
-		return -EFAULT;
-
-	return restore_i387_registers(userspace_pid[cpu],
-				    (unsigned long *) &fpregs);
-}
-
-static int get_fpxregs(struct user_fxsr_struct __user *buf, struct task_struct *child)
-{
-	int err, n, cpu = task_cpu(child);
-	struct user_fxsr_struct fpregs;
-
-	err = save_fpx_registers(userspace_pid[cpu], (unsigned long *) &fpregs);
-	if (err)
-		return err;
-
-	n = copy_to_user(buf, &fpregs, sizeof(fpregs));
-	if(n > 0)
-		return -EFAULT;
-
-	return n;
-}
-
-static int set_fpxregs(struct user_fxsr_struct __user *buf, struct task_struct *child)
-{
-	int n, cpu = task_cpu(child);
-	struct user_fxsr_struct fpregs;
-
-	n = copy_from_user(&fpregs, buf, sizeof(fpregs));
-	if (n > 0)
-		return -EFAULT;
-
-	return restore_fpx_registers(userspace_pid[cpu],
-				     (unsigned long *) &fpregs);
-}
-
 long subarch_ptrace(struct task_struct *child, long request,
 		    unsigned long addr, unsigned long data)
 {
@@ -234,17 +176,25 @@ long subarch_ptrace(struct task_struct *child, long request,
 	void __user *datap = (void __user *) data;
 	switch (request) {
 	case PTRACE_GETFPREGS: /* Get the child FPU state. */
-		ret = get_fpregs(datap, child);
-		break;
+		return copy_regset_to_user(child, task_user_regset_view(child),
+					   REGSET_FP_LEGACY,
+					   0, sizeof(struct user_i387_struct),
+					   datap);
 	case PTRACE_SETFPREGS: /* Set the child FPU state. */
-		ret = set_fpregs(datap, child);
-		break;
+		return copy_regset_from_user(child, task_user_regset_view(child),
+					     REGSET_FP_LEGACY,
+					     0, sizeof(struct user_i387_struct),
+					     datap);
 	case PTRACE_GETFPXREGS: /* Get the child FPU state. */
-		ret = get_fpxregs(datap, child);
-		break;
+		return copy_regset_to_user(child, task_user_regset_view(child),
+					   REGSET_FP,
+					   0, sizeof(struct user_fxsr_struct),
+					   datap);
 	case PTRACE_SETFPXREGS: /* Set the child FPU state. */
-		ret = set_fpxregs(datap, child);
-		break;
+		return copy_regset_from_user(child, task_user_regset_view(child),
+					     REGSET_FP,
+					     0, sizeof(struct user_fxsr_struct),
+					     datap);
 	default:
 		ret = -EIO;
 	}
diff --git a/arch/x86/um/ptrace_64.c b/arch/x86/um/ptrace_64.c
index aa68d83d3f44..e0d4120a45c8 100644
--- a/arch/x86/um/ptrace_64.c
+++ b/arch/x86/um/ptrace_64.c
@@ -8,6 +8,7 @@
 #include <linux/mm.h>
 #include <linux/sched.h>
 #include <linux/errno.h>
+#include <linux/regset.h>
 #define __FRAME_OFFSETS
 #include <asm/ptrace.h>
 #include <linux/uaccess.h>
@@ -188,36 +189,6 @@ int peek_user(struct task_struct *child, long addr, long data)
 	return put_user(tmp, (unsigned long *) data);
 }
 
-static int get_fpregs(struct user_i387_struct __user *buf, struct task_struct *child)
-{
-	int err, n, cpu = ((struct thread_info *) child->stack)->cpu;
-	struct user_i387_struct fpregs;
-
-	err = save_i387_registers(userspace_pid[cpu],
-				  (unsigned long *) &fpregs);
-	if (err)
-		return err;
-
-	n = copy_to_user(buf, &fpregs, sizeof(fpregs));
-	if (n > 0)
-		return -EFAULT;
-
-	return n;
-}
-
-static int set_fpregs(struct user_i387_struct __user *buf, struct task_struct *child)
-{
-	int n, cpu = ((struct thread_info *) child->stack)->cpu;
-	struct user_i387_struct fpregs;
-
-	n = copy_from_user(&fpregs, buf, sizeof(fpregs));
-	if (n > 0)
-		return -EFAULT;
-
-	return restore_i387_registers(userspace_pid[cpu],
-				      (unsigned long *) &fpregs);
-}
-
 long subarch_ptrace(struct task_struct *child, long request,
 		    unsigned long addr, unsigned long data)
 {
@@ -226,11 +197,15 @@ long subarch_ptrace(struct task_struct *child, long request,
 
 	switch (request) {
 	case PTRACE_GETFPREGS: /* Get the child FPU state. */
-		ret = get_fpregs(datap, child);
-		break;
+		return copy_regset_to_user(child, task_user_regset_view(child),
+					   REGSET_FP,
+					   0, sizeof(struct user_i387_struct),
+					   datap);
 	case PTRACE_SETFPREGS: /* Set the child FPU state. */
-		ret = set_fpregs(datap, child);
-		break;
+		return copy_regset_from_user(child, task_user_regset_view(child),
+					     REGSET_FP,
+					     0, sizeof(struct user_i387_struct),
+					     datap);
 	case PTRACE_ARCH_PRCTL:
 		/* XXX Calls ptrace on the host - needs some SMP thinking */
 		ret = arch_prctl(child, data, (void __user *) addr);
diff --git a/arch/x86/um/shared/sysdep/ptrace.h b/arch/x86/um/shared/sysdep/ptrace.h
index 6ca4ecabc55b..2dd4ca6713f8 100644
--- a/arch/x86/um/shared/sysdep/ptrace.h
+++ b/arch/x86/um/shared/sysdep/ptrace.h
@@ -56,12 +56,16 @@ struct syscall_args {
 				     UPT_SYSCALL_ARG5(r),	 \
 				     UPT_SYSCALL_ARG6(r) } } )
 
+extern unsigned long host_fp_size;
+
 struct uml_pt_regs {
 	unsigned long gp[MAX_REG_NR];
-	unsigned long fp[MAX_FP_NR];
 	struct faultinfo faultinfo;
 	long syscall;
 	int is_user;
+
+	/* Dynamically sized FP registers (holds an XSTATE) */
+	unsigned long fp[];
 };
 
 #define EMPTY_UML_PT_REGS { }
@@ -72,4 +76,6 @@ struct uml_pt_regs {
 
 extern int user_context(unsigned long sp);
 
+extern int arch_init_registers(int pid);
+
 #endif /* __SYSDEP_X86_PTRACE_H */
diff --git a/arch/x86/um/shared/sysdep/ptrace_32.h b/arch/x86/um/shared/sysdep/ptrace_32.h
index 0c4989842fbe..2392470cac4d 100644
--- a/arch/x86/um/shared/sysdep/ptrace_32.h
+++ b/arch/x86/um/shared/sysdep/ptrace_32.h
@@ -6,8 +6,6 @@
 #ifndef __SYSDEP_I386_PTRACE_H
 #define __SYSDEP_I386_PTRACE_H
 
-#define MAX_FP_NR HOST_FPX_SIZE
-
 #define UPT_SYSCALL_ARG1(r) UPT_BX(r)
 #define UPT_SYSCALL_ARG2(r) UPT_CX(r)
 #define UPT_SYSCALL_ARG3(r) UPT_DX(r)
@@ -15,6 +13,4 @@
 #define UPT_SYSCALL_ARG5(r) UPT_DI(r)
 #define UPT_SYSCALL_ARG6(r) UPT_BP(r)
 
-extern void arch_init_registers(int pid);
-
 #endif
diff --git a/arch/x86/um/shared/sysdep/ptrace_64.h b/arch/x86/um/shared/sysdep/ptrace_64.h
index 0dc223aa1c2d..e73573ac871f 100644
--- a/arch/x86/um/shared/sysdep/ptrace_64.h
+++ b/arch/x86/um/shared/sysdep/ptrace_64.h
@@ -8,8 +8,6 @@
 #ifndef __SYSDEP_X86_64_PTRACE_H
 #define __SYSDEP_X86_64_PTRACE_H
 
-#define MAX_FP_NR HOST_FP_SIZE
-
 #define REGS_R8(r) ((r)[HOST_R8])
 #define REGS_R9(r) ((r)[HOST_R9])
 #define REGS_R10(r) ((r)[HOST_R10])
@@ -57,6 +55,4 @@
 #define UPT_SYSCALL_ARG5(r) UPT_R8(r)
 #define UPT_SYSCALL_ARG6(r) UPT_R9(r)
 
-extern void arch_init_registers(int pid);
-
 #endif
diff --git a/arch/x86/um/shared/sysdep/ptrace_user.h b/arch/x86/um/shared/sysdep/ptrace_user.h
index 1d1a824fa652..98da23120538 100644
--- a/arch/x86/um/shared/sysdep/ptrace_user.h
+++ b/arch/x86/um/shared/sysdep/ptrace_user.h
@@ -11,12 +11,6 @@
 #define REGS_IP_INDEX HOST_IP
 #define REGS_SP_INDEX HOST_SP
 
-#ifdef __i386__
-#define FP_SIZE ((HOST_FPX_SIZE > HOST_FP_SIZE) ? HOST_FPX_SIZE : HOST_FP_SIZE)
-#else
-#define FP_SIZE HOST_FP_SIZE
-#endif
-
 /*
  * glibc before 2.27 does not include PTRACE_SYSEMU_SINGLESTEP in its enum,
  * ensure we have a definition by (re-)defining it here.
diff --git a/arch/x86/um/shared/sysdep/stub_32.h b/arch/x86/um/shared/sysdep/stub_32.h
index 0b44a86dd346..390988132c0a 100644
--- a/arch/x86/um/shared/sysdep/stub_32.h
+++ b/arch/x86/um/shared/sysdep/stub_32.h
@@ -112,11 +112,23 @@ static __always_inline void *get_stub_data(void)
 	unsigned long ret;
 
 	asm volatile (
-		"movl %%esp,%0 ;"
-		"andl %1,%0"
+		"call _here_%=;"
+		"_here_%=:"
+		"popl %0;"
+		"andl %1, %0 ;"
+		"addl %2, %0 ;"
 		: "=a" (ret)
-		: "g" (~(STUB_DATA_PAGES * UM_KERN_PAGE_SIZE - 1)));
+		: "g" (~(UM_KERN_PAGE_SIZE - 1)),
+		  "g" (UM_KERN_PAGE_SIZE));
 
 	return (void *)ret;
 }
+
+#define stub_start(fn)							\
+	asm volatile (							\
+		"subl %0,%%esp ;"					\
+		"movl %1, %%eax ; "					\
+		"call *%%eax ;"						\
+		:: "i" ((1 + STUB_DATA_PAGES) * UM_KERN_PAGE_SIZE),	\
+		   "i" (&fn))
 #endif
diff --git a/arch/x86/um/shared/sysdep/stub_64.h b/arch/x86/um/shared/sysdep/stub_64.h
index 67f44284f1aa..294affbec742 100644
--- a/arch/x86/um/shared/sysdep/stub_64.h
+++ b/arch/x86/um/shared/sysdep/stub_64.h
@@ -28,6 +28,17 @@ static __always_inline long stub_syscall0(long syscall)
 	return ret;
 }
 
+static __always_inline long stub_syscall1(long syscall, long arg1)
+{
+	long ret;
+
+	__asm__ volatile (__syscall
+		: "=a" (ret)
+		: "0" (syscall), "D" (arg1) : __syscall_clobber );
+
+	return ret;
+}
+
 static __always_inline long stub_syscall2(long syscall, long arg1, long arg2)
 {
 	long ret;
@@ -106,11 +117,21 @@ static __always_inline void *get_stub_data(void)
 	unsigned long ret;
 
 	asm volatile (
-		"movq %%rsp,%0 ;"
-		"andq %1,%0"
+		"lea 0(%%rip), %0;"
+		"andq %1, %0 ;"
+		"addq %2, %0 ;"
 		: "=a" (ret)
-		: "g" (~(STUB_DATA_PAGES * UM_KERN_PAGE_SIZE - 1)));
+		: "g" (~(UM_KERN_PAGE_SIZE - 1)),
+		  "g" (UM_KERN_PAGE_SIZE));
 
 	return (void *)ret;
 }
+
+#define stub_start(fn)							\
+	asm volatile (							\
+		"subq %0,%%rsp ;"					\
+		"movq %1,%%rax ;"					\
+		"call *%%rax ;"						\
+		:: "i" ((1 + STUB_DATA_PAGES) * UM_KERN_PAGE_SIZE),	\
+		   "i" (&fn))
 #endif
diff --git a/arch/x86/um/signal.c b/arch/x86/um/signal.c
index 2cc8c2309022..75087e85b6fd 100644
--- a/arch/x86/um/signal.c
+++ b/arch/x86/um/signal.c
@@ -16,145 +16,24 @@
 #include <registers.h>
 #include <skas.h>
 
-#ifdef CONFIG_X86_32
-
-/*
- * FPU tag word conversions.
- */
-
-static inline unsigned short twd_i387_to_fxsr(unsigned short twd)
-{
-	unsigned int tmp; /* to avoid 16 bit prefixes in the code */
-
-	/* Transform each pair of bits into 01 (valid) or 00 (empty) */
-	tmp = ~twd;
-	tmp = (tmp | (tmp>>1)) & 0x5555; /* 0V0V0V0V0V0V0V0V */
-	/* and move the valid bits to the lower byte. */
-	tmp = (tmp | (tmp >> 1)) & 0x3333; /* 00VV00VV00VV00VV */
-	tmp = (tmp | (tmp >> 2)) & 0x0f0f; /* 0000VVVV0000VVVV */
-	tmp = (tmp | (tmp >> 4)) & 0x00ff; /* 00000000VVVVVVVV */
-	return tmp;
-}
-
-static inline unsigned long twd_fxsr_to_i387(struct user_fxsr_struct *fxsave)
-{
-	struct _fpxreg *st = NULL;
-	unsigned long twd = (unsigned long) fxsave->twd;
-	unsigned long tag;
-	unsigned long ret = 0xffff0000;
-	int i;
-
-#define FPREG_ADDR(f, n)	((char *)&(f)->st_space + (n) * 16)
-
-	for (i = 0; i < 8; i++) {
-		if (twd & 0x1) {
-			st = (struct _fpxreg *) FPREG_ADDR(fxsave, i);
-
-			switch (st->exponent & 0x7fff) {
-			case 0x7fff:
-				tag = 2;		/* Special */
-				break;
-			case 0x0000:
-				if ( !st->significand[0] &&
-				     !st->significand[1] &&
-				     !st->significand[2] &&
-				     !st->significand[3] ) {
-					tag = 1;	/* Zero */
-				} else {
-					tag = 2;	/* Special */
-				}
-				break;
-			default:
-				if (st->significand[3] & 0x8000) {
-					tag = 0;	/* Valid */
-				} else {
-					tag = 2;	/* Special */
-				}
-				break;
-			}
-		} else {
-			tag = 3;			/* Empty */
-		}
-		ret |= (tag << (2 * i));
-		twd = twd >> 1;
-	}
-	return ret;
-}
-
-static int convert_fxsr_to_user(struct _fpstate __user *buf,
-				struct user_fxsr_struct *fxsave)
-{
-	unsigned long env[7];
-	struct _fpreg __user *to;
-	struct _fpxreg *from;
-	int i;
-
-	env[0] = (unsigned long)fxsave->cwd | 0xffff0000ul;
-	env[1] = (unsigned long)fxsave->swd | 0xffff0000ul;
-	env[2] = twd_fxsr_to_i387(fxsave);
-	env[3] = fxsave->fip;
-	env[4] = fxsave->fcs | ((unsigned long)fxsave->fop << 16);
-	env[5] = fxsave->foo;
-	env[6] = fxsave->fos;
-
-	if (__copy_to_user(buf, env, 7 * sizeof(unsigned long)))
-		return 1;
-
-	to = &buf->_st[0];
-	from = (struct _fpxreg *) &fxsave->st_space[0];
-	for (i = 0; i < 8; i++, to++, from++) {
-		unsigned long __user *t = (unsigned long __user *)to;
-		unsigned long *f = (unsigned long *)from;
-
-		if (__put_user(*f, t) ||
-				__put_user(*(f + 1), t + 1) ||
-				__put_user(from->exponent, &to->exponent))
-			return 1;
-	}
-	return 0;
-}
-
-static int convert_fxsr_from_user(struct user_fxsr_struct *fxsave,
-				  struct _fpstate __user *buf)
-{
-	unsigned long env[7];
-	struct _fpxreg *to;
-	struct _fpreg __user *from;
-	int i;
-
-	if (copy_from_user( env, buf, 7 * sizeof(long)))
-		return 1;
-
-	fxsave->cwd = (unsigned short)(env[0] & 0xffff);
-	fxsave->swd = (unsigned short)(env[1] & 0xffff);
-	fxsave->twd = twd_i387_to_fxsr((unsigned short)(env[2] & 0xffff));
-	fxsave->fip = env[3];
-	fxsave->fop = (unsigned short)((env[4] & 0xffff0000ul) >> 16);
-	fxsave->fcs = (env[4] & 0xffff);
-	fxsave->foo = env[5];
-	fxsave->fos = env[6];
-
-	to = (struct _fpxreg *) &fxsave->st_space[0];
-	from = &buf->_st[0];
-	for (i = 0; i < 8; i++, to++, from++) {
-		unsigned long *t = (unsigned long *)to;
-		unsigned long __user *f = (unsigned long __user *)from;
-
-		if (__get_user(*t, f) ||
-		    __get_user(*(t + 1), f + 1) ||
-		    __get_user(to->exponent, &from->exponent))
-			return 1;
-	}
-	return 0;
-}
-
-extern int have_fpx_regs;
+#include <linux/regset.h>
+#include <asm/sigframe.h>
 
+#ifdef CONFIG_X86_32
+struct _xstate_64 {
+	struct _fpstate_64		fpstate;
+	struct _header			xstate_hdr;
+	struct _ymmh_state		ymmh;
+	/* New processor state extensions go here: */
+};
+#else
+#define _xstate_64 _xstate
 #endif
 
 static int copy_sc_from_user(struct pt_regs *regs,
 			     struct sigcontext __user *from)
 {
+	struct _xstate_64 __user *from_fp64;
 	struct sigcontext sc;
 	int err;
 
@@ -203,35 +82,27 @@ static int copy_sc_from_user(struct pt_regs *regs,
 #undef GETREG
 
 #ifdef CONFIG_X86_32
-	if (have_fpx_regs) {
-		struct user_fxsr_struct fpx;
-		int pid = userspace_pid[current_thread_info()->cpu];
+	from_fp64 = ((void __user *)sc.fpstate) +
+		    offsetof(struct _fpstate_32, _fxsr_env);
+#else
+	from_fp64 = (void __user *)sc.fpstate;
+#endif
 
-		err = copy_from_user(&fpx,
-			&((struct _fpstate __user *)sc.fpstate)->_fxsr_env[0],
-				     sizeof(struct user_fxsr_struct));
-		if (err)
-			return 1;
+	err = copy_from_user(regs->regs.fp, from_fp64, host_fp_size);
+	if (err)
+		return 1;
 
-		err = convert_fxsr_from_user(&fpx, (void *)sc.fpstate);
-		if (err)
-			return 1;
-
-		err = restore_fpx_registers(pid, (unsigned long *) &fpx);
-		if (err < 0) {
-			printk(KERN_ERR "copy_sc_from_user - "
-			       "restore_fpx_registers failed, errno = %d\n",
-			       -err);
-			return 1;
-		}
-	} else
+#ifdef CONFIG_X86_32
+	/* Data is duplicated and this copy is the important one */
+	err = copy_regset_from_user(current,
+				    task_user_regset_view(current),
+				    REGSET_FP_LEGACY, 0,
+				    sizeof(struct user_i387_struct),
+				    (void __user *)sc.fpstate);
+	if (err < 0)
+		return err;
 #endif
-	{
-		err = copy_from_user(regs->regs.fp, (void *)sc.fpstate,
-				     sizeof(struct _xstate));
-		if (err)
-			return 1;
-	}
+
 	return 0;
 }
 
@@ -239,6 +110,7 @@ static int copy_sc_to_user(struct sigcontext __user *to,
 			   struct _xstate __user *to_fp, struct pt_regs *regs,
 			   unsigned long mask)
 {
+	struct _xstate_64 __user *to_fp64;
 	struct sigcontext sc;
 	struct faultinfo * fi = &current->thread.arch.faultinfo;
 	int err;
@@ -290,35 +162,46 @@ static int copy_sc_to_user(struct sigcontext __user *to,
 		return 1;
 
 #ifdef CONFIG_X86_32
-	if (have_fpx_regs) {
-		int pid = userspace_pid[current_thread_info()->cpu];
-		struct user_fxsr_struct fpx;
-
-		err = save_fpx_registers(pid, (unsigned long *) &fpx);
-		if (err < 0){
-			printk(KERN_ERR "copy_sc_to_user - save_fpx_registers "
-			       "failed, errno = %d\n", err);
-			return 1;
-		}
-
-		err = convert_fxsr_to_user(&to_fp->fpstate, &fpx);
-		if (err)
-			return 1;
+	err = copy_regset_to_user(current,
+				  task_user_regset_view(current),
+				  REGSET_FP_LEGACY, 0,
+				  sizeof(struct _fpstate_32), to_fp);
+	if (err < 0)
+		return err;
 
-		err |= __put_user(fpx.swd, &to_fp->fpstate.status);
-		err |= __put_user(X86_FXSR_MAGIC, &to_fp->fpstate.magic);
-		if (err)
-			return 1;
+	__put_user(X86_FXSR_MAGIC, &to_fp->fpstate.magic);
+
+	BUILD_BUG_ON(offsetof(struct _xstate, xstate_hdr) !=
+		     offsetof(struct _xstate_64, xstate_hdr) +
+			offsetof(struct _fpstate_32, _fxsr_env));
+	to_fp64 = (void __user *)to_fp +
+		  offsetof(struct _fpstate_32, _fxsr_env);
+#else
+	to_fp64 = to_fp;
+#endif /* CONFIG_X86_32 */
+
+	if (copy_to_user(to_fp64, regs->regs.fp, host_fp_size))
+		return 1;
 
-		if (copy_to_user(&to_fp->fpstate._fxsr_env[0], &fpx,
-				 sizeof(struct user_fxsr_struct)))
-			return 1;
-	} else
+	/*
+	 * Put magic/size values for userspace. We do not bother to verify them
+	 * later on, however, userspace needs them should it try to read the
+	 * XSTATE data. And ptrace does not fill in these parts.
+	 */
+	BUILD_BUG_ON(sizeof(int) != FP_XSTATE_MAGIC2_SIZE);
+#ifdef CONFIG_X86_32
+	__put_user(offsetof(struct _fpstate_32, _fxsr_env) +
+		   host_fp_size + FP_XSTATE_MAGIC2_SIZE,
+		   &to_fp64->fpstate.sw_reserved.extended_size);
+#else
+	__put_user(host_fp_size + FP_XSTATE_MAGIC2_SIZE,
+		   &to_fp64->fpstate.sw_reserved.extended_size);
 #endif
-	{
-		if (copy_to_user(to_fp, regs->regs.fp, sizeof(struct _xstate)))
-			return 1;
-	}
+	__put_user(host_fp_size, &to_fp64->fpstate.sw_reserved.xstate_size);
+
+	__put_user(FP_XSTATE_MAGIC1, &to_fp64->fpstate.sw_reserved.magic1);
+	__put_user(FP_XSTATE_MAGIC2,
+		   (int __user *)((void __user *)to_fp64 + host_fp_size));
 
 	return 0;
 }
@@ -336,34 +219,15 @@ static int copy_ucontext_to_user(struct ucontext __user *uc,
 	return err;
 }
 
-struct sigframe
-{
-	char __user *pretcode;
-	int sig;
-	struct sigcontext sc;
-	struct _xstate fpstate;
-	unsigned long extramask[_NSIG_WORDS-1];
-	char retcode[8];
-};
-
-struct rt_sigframe
-{
-	char __user *pretcode;
-	int sig;
-	struct siginfo __user *pinfo;
-	void __user *puc;
-	struct siginfo info;
-	struct ucontext uc;
-	struct _xstate fpstate;
-	char retcode[8];
-};
-
 int setup_signal_stack_sc(unsigned long stack_top, struct ksignal *ksig,
 			  struct pt_regs *regs, sigset_t *mask)
 {
+	size_t math_size = offsetof(struct _fpstate_32, _fxsr_env) +
+			   host_fp_size + FP_XSTATE_MAGIC2_SIZE;
 	struct sigframe __user *frame;
 	void __user *restorer;
 	int err = 0, sig = ksig->sig;
+	unsigned long fp_to;
 
 	/* This is the same calculation as i386 - ((sp + 4) & 15) == 0 */
 	stack_top = ((stack_top + 4) & -16UL) - 4;
@@ -371,13 +235,21 @@ int setup_signal_stack_sc(unsigned long stack_top, struct ksignal *ksig,
 	if (!access_ok(frame, sizeof(*frame)))
 		return 1;
 
+	/* Add required space for math frame */
+	frame = (struct sigframe __user *)((unsigned long)frame - math_size);
+
 	restorer = frame->retcode;
 	if (ksig->ka.sa.sa_flags & SA_RESTORER)
 		restorer = ksig->ka.sa.sa_restorer;
 
-	err |= __put_user(restorer, &frame->pretcode);
+	err |= __put_user(restorer, (void __user * __user *)&frame->pretcode);
 	err |= __put_user(sig, &frame->sig);
-	err |= copy_sc_to_user(&frame->sc, &frame->fpstate, regs, mask->sig[0]);
+
+	fp_to = (unsigned long)frame + sizeof(*frame);
+
+	err |= copy_sc_to_user(&frame->sc,
+			       (struct _xstate __user *)fp_to,
+			       regs, mask->sig[0]);
 	if (_NSIG_WORDS > 1)
 		err |= __copy_to_user(&frame->extramask, &mask->sig[1],
 				      sizeof(frame->extramask));
@@ -407,26 +279,35 @@ int setup_signal_stack_sc(unsigned long stack_top, struct ksignal *ksig,
 int setup_signal_stack_si(unsigned long stack_top, struct ksignal *ksig,
 			  struct pt_regs *regs, sigset_t *mask)
 {
+	size_t math_size = offsetof(struct _fpstate_32, _fxsr_env) +
+			   host_fp_size + FP_XSTATE_MAGIC2_SIZE;
 	struct rt_sigframe __user *frame;
 	void __user *restorer;
 	int err = 0, sig = ksig->sig;
+	unsigned long fp_to;
 
 	stack_top &= -8UL;
 	frame = (struct rt_sigframe __user *) stack_top - 1;
 	if (!access_ok(frame, sizeof(*frame)))
 		return 1;
 
+	/* Add required space for math frame */
+	frame = (struct rt_sigframe __user *)((unsigned long)frame - math_size);
+
 	restorer = frame->retcode;
 	if (ksig->ka.sa.sa_flags & SA_RESTORER)
 		restorer = ksig->ka.sa.sa_restorer;
 
-	err |= __put_user(restorer, &frame->pretcode);
+	err |= __put_user(restorer, (void __user * __user *)&frame->pretcode);
 	err |= __put_user(sig, &frame->sig);
-	err |= __put_user(&frame->info, &frame->pinfo);
-	err |= __put_user(&frame->uc, &frame->puc);
+	err |= __put_user(&frame->info, (void __user * __user *)&frame->pinfo);
+	err |= __put_user(&frame->uc, (void __user * __user *)&frame->puc);
 	err |= copy_siginfo_to_user(&frame->info, &ksig->info);
-	err |= copy_ucontext_to_user(&frame->uc, &frame->fpstate, mask,
-					PT_REGS_SP(regs));
+
+	fp_to = (unsigned long)frame + sizeof(*frame);
+
+	err |= copy_ucontext_to_user(&frame->uc, (struct _xstate __user *)fp_to,
+				     mask, PT_REGS_SP(regs));
 
 	/*
 	 * This is movl $,%eax ; int $0x80
@@ -478,27 +359,24 @@ SYSCALL_DEFINE0(sigreturn)
 
 #else
 
-struct rt_sigframe
-{
-	char __user *pretcode;
-	struct ucontext uc;
-	struct siginfo info;
-	struct _xstate fpstate;
-};
-
 int setup_signal_stack_si(unsigned long stack_top, struct ksignal *ksig,
 			  struct pt_regs *regs, sigset_t *set)
 {
+	unsigned long math_size = host_fp_size + FP_XSTATE_MAGIC2_SIZE;
 	struct rt_sigframe __user *frame;
 	int err = 0, sig = ksig->sig;
 	unsigned long fp_to;
 
 	frame = (struct rt_sigframe __user *)
 		round_down(stack_top - sizeof(struct rt_sigframe), 16);
+
+	/* Add required space for math frame */
+	frame = (struct rt_sigframe __user *)((unsigned long)frame - math_size);
+
 	/* Subtract 128 for a red zone and 8 for proper alignment */
 	frame = (struct rt_sigframe __user *) ((unsigned long) frame - 128 - 8);
 
-	if (!access_ok(frame, sizeof(*frame)))
+	if (!access_ok(frame, sizeof(*frame) + math_size))
 		goto out;
 
 	if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
@@ -509,12 +387,14 @@ int setup_signal_stack_si(unsigned long stack_top, struct ksignal *ksig,
 
 	/* Create the ucontext.  */
 	err |= __put_user(0, &frame->uc.uc_flags);
-	err |= __put_user(0, &frame->uc.uc_link);
+	err |= __put_user(NULL, &frame->uc.uc_link);
 	err |= __save_altstack(&frame->uc.uc_stack, PT_REGS_SP(regs));
-	err |= copy_sc_to_user(&frame->uc.uc_mcontext, &frame->fpstate, regs,
-			       set->sig[0]);
 
-	fp_to = (unsigned long)&frame->fpstate;
+	fp_to = (unsigned long)frame + sizeof(*frame);
+
+	err |= copy_sc_to_user(&frame->uc.uc_mcontext,
+			       (struct _xstate __user *)fp_to,
+			       regs, set->sig[0]);
 
 	err |= __put_user(fp_to, &frame->uc.uc_mcontext.fpstate);
 	if (sizeof(*set) == 16) {
@@ -531,7 +411,7 @@ int setup_signal_stack_si(unsigned long stack_top, struct ksignal *ksig,
 	 */
 	/* x86-64 should always use SA_RESTORER. */
 	if (ksig->ka.sa.sa_flags & SA_RESTORER)
-		err |= __put_user((void *)ksig->ka.sa.sa_restorer,
+		err |= __put_user((void __user *)ksig->ka.sa.sa_restorer,
 				  &frame->pretcode);
 	else
 		/* could use a vstub here */
diff --git a/arch/x86/um/user-offsets.c b/arch/x86/um/user-offsets.c
index 1c77d9946199..d6e1cd9956bf 100644
--- a/arch/x86/um/user-offsets.c
+++ b/arch/x86/um/user-offsets.c
@@ -20,9 +20,6 @@ void foo(void);
 void foo(void)
 {
 #ifdef __i386__
-	DEFINE_LONGS(HOST_FP_SIZE, sizeof(struct user_fpregs_struct));
-	DEFINE_LONGS(HOST_FPX_SIZE, sizeof(struct user_fpxregs_struct));
-
 	DEFINE(HOST_IP, EIP);
 	DEFINE(HOST_SP, UESP);
 	DEFINE(HOST_EFLAGS, EFL);
@@ -41,11 +38,6 @@ void foo(void)
 	DEFINE(HOST_GS, GS);
 	DEFINE(HOST_ORIG_AX, ORIG_EAX);
 #else
-#ifdef FP_XSTATE_MAGIC1
-	DEFINE_LONGS(HOST_FP_SIZE, 2696);
-#else
-	DEFINE(HOST_FP_SIZE, sizeof(struct _fpstate) / sizeof(unsigned long));
-#endif
 	DEFINE_LONGS(HOST_BX, RBX);
 	DEFINE_LONGS(HOST_CX, RCX);
 	DEFINE_LONGS(HOST_DI, RDI);
diff --git a/arch/x86/um/vdso/Makefile b/arch/x86/um/vdso/Makefile
index 6a77ea6434ff..7478d11dacb7 100644
--- a/arch/x86/um/vdso/Makefile
+++ b/arch/x86/um/vdso/Makefile
@@ -56,7 +56,6 @@ CFLAGS_REMOVE_um_vdso.o = -pg -fprofile-arcs -ftest-coverage
 quiet_cmd_vdso = VDSO    $@
       cmd_vdso = $(CC) -nostdlib -o $@ \
 		       $(CC_FLAGS_LTO) $(VDSO_LDFLAGS) $(VDSO_LDFLAGS_$(filter %.lds,$(^F))) \
-		       -Wl,-T,$(filter %.lds,$^) $(filter %.o,$^) && \
-		 sh $(src)/checkundef.sh '$(NM)' '$@'
+		       -Wl,-T,$(filter %.lds,$^) $(filter %.o,$^)
 
-VDSO_LDFLAGS = -fPIC -shared -Wl,--hash-style=sysv -z noexecstack
+VDSO_LDFLAGS = -fPIC -shared -Wl,--hash-style=sysv -z noexecstack -Wl,--no-undefined
diff --git a/arch/x86/um/vdso/checkundef.sh b/arch/x86/um/vdso/checkundef.sh
deleted file mode 100644
index 8e3ea6bb956f..000000000000
--- a/arch/x86/um/vdso/checkundef.sh
+++ /dev/null
@@ -1,11 +0,0 @@
-#!/bin/sh
-# SPDX-License-Identifier: GPL-2.0
-nm="$1"
-file="$2"
-$nm "$file" | grep '^ *U' > /dev/null 2>&1
-if [ $? -eq 1 ]; then
-    exit 0
-else
-    echo "$file: undefined symbols found" >&2
-    exit 1
-fi
diff --git a/fs/hostfs/hostfs_kern.c b/fs/hostfs/hostfs_kern.c
index 6d1cf2436ead..7e51d2cec64b 100644
--- a/fs/hostfs/hostfs_kern.c
+++ b/fs/hostfs/hostfs_kern.c
@@ -57,6 +57,7 @@ static int __init hostfs_args(char *options, int *add)
 {
 	char *ptr;
 
+	*add = 0;
 	ptr = strchr(options, ',');
 	if (ptr != NULL)
 		*ptr++ = '\0';
@@ -471,8 +472,8 @@ static int hostfs_write_begin(struct file *file, struct address_space *mapping,
 
 	*foliop = __filemap_get_folio(mapping, index, FGP_WRITEBEGIN,
 			mapping_gfp_mask(mapping));
-	if (!*foliop)
-		return -ENOMEM;
+	if (IS_ERR(*foliop))
+		return PTR_ERR(*foliop);
 	return 0;
 }
author	Linus Torvalds <torvalds@linux-foundation.org>	2024-11-30 10:34:54 -0800
committer	Linus Torvalds <torvalds@linux-foundation.org>	2024-11-30 10:34:54 -0800
commit	831c1926ee728c3e747255f7c0f434762e8e863d (patch)
tree	92d1c73842c3f95b362810aba2080b7582c12c11
parent	04b43ea325d21c4c98e831383a1b7d540721898a (diff)
parent	bed2cc482600296fe04edbc38005ba2851449c10 (diff)