From 76366050eb1b3151c4b4110c76538ff14dffb74c Mon Sep 17 00:00:00 2001 From: Daniel Díaz Date: Wed, 19 Aug 2020 12:32:24 -0500 Subject: x86/defconfigs: Explicitly unset CONFIG_64BIT in i386_defconfig MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit A recent refresh of the defconfigs got rid of the following (unset) config: # CONFIG_64BIT is not set Innocuous as it seems, when the config file is saved again the behavior is changed so that CONFIG_64BIT=y. Currently, $ make i386_defconfig $ grep CONFIG_64BIT .config CONFIG_64BIT=y whereas previously (and with this patch): $ make i386_defconfig $ grep CONFIG_64BIT .config # CONFIG_64BIT is not set ( This was found with weird compiler errors on OpenEmbedded builds, as the compiler was unable to cope with 64-bits data types. ) Fixes: 1d0e12fd3a84 ("x86/defconfigs: Refresh defconfig files") Reported-by: Jarkko Nikula Reported-by: Andy Shevchenko Tested-by: Sedat Dilek Signed-off-by: Daniel Díaz Signed-off-by: Ingo Molnar --- arch/x86/configs/i386_defconfig | 1 + 1 file changed, 1 insertion(+) (limited to 'arch') diff --git a/arch/x86/configs/i386_defconfig b/arch/x86/configs/i386_defconfig index d7577fece9eb..4cfdf5755ab5 100644 --- a/arch/x86/configs/i386_defconfig +++ b/arch/x86/configs/i386_defconfig @@ -19,6 +19,7 @@ CONFIG_CGROUP_CPUACCT=y CONFIG_BLK_DEV_INITRD=y # CONFIG_COMPAT_BRK is not set CONFIG_PROFILING=y +# CONFIG_64BIT is not set CONFIG_SMP=y CONFIG_X86_GENERIC=y CONFIG_HPET_TIMER=y -- cgit v1.2.3-70-g09d2 From 09e43968db40c33a73e9ddbfd937f46d5c334924 Mon Sep 17 00:00:00 2001 From: Arvind Sankar Date: Tue, 11 Aug 2020 20:43:08 -0400 Subject: x86/boot/compressed: Disable relocation relaxation The x86-64 psABI [0] specifies special relocation types (R_X86_64_[REX_]GOTPCRELX) for indirection through the Global Offset Table, semantically equivalent to R_X86_64_GOTPCREL, which the linker can take advantage of for optimization (relaxation) at link time. This is supported by LLD and binutils versions 2.26 onwards. The compressed kernel is position-independent code, however, when using LLD or binutils versions before 2.27, it must be linked without the -pie option. In this case, the linker may optimize certain instructions into a non-position-independent form, by converting foo@GOTPCREL(%rip) to $foo. This potential issue has been present with LLD and binutils-2.26 for a long time, but it has never manifested itself before now: - LLD and binutils-2.26 only relax movq foo@GOTPCREL(%rip), %reg to leaq foo(%rip), %reg which is still position-independent, rather than mov $foo, %reg which is permitted by the psABI when -pie is not enabled. - GCC happens to only generate GOTPCREL relocations on mov instructions. - CLang does generate GOTPCREL relocations on non-mov instructions, but when building the compressed kernel, it uses its integrated assembler (due to the redefinition of KBUILD_CFLAGS dropping -no-integrated-as), which has so far defaulted to not generating the GOTPCRELX relocations. Nick Desaulniers reports [1,2]: "A recent change [3] to a default value of configuration variable (ENABLE_X86_RELAX_RELOCATIONS OFF -> ON) in LLVM now causes Clang's integrated assembler to emit R_X86_64_GOTPCRELX/R_X86_64_REX_GOTPCRELX relocations. LLD will relax instructions with these relocations based on whether the image is being linked as position independent or not. When not, then LLD will relax these instructions to use absolute addressing mode (R_RELAX_GOT_PC_NOPIC). This causes kernels built with Clang and linked with LLD to fail to boot." Patch series [4] is a solution to allow the compressed kernel to be linked with -pie unconditionally, but even if merged is unlikely to be backported. As a simple solution that can be applied to stable as well, prevent the assembler from generating the relaxed relocation types using the -mrelax-relocations=no option. For ease of backporting, do this unconditionally. [0] https://gitlab.com/x86-psABIs/x86-64-ABI/-/blob/master/x86-64-ABI/linker-optimization.tex#L65 [1] https://lore.kernel.org/lkml/20200807194100.3570838-1-ndesaulniers@google.com/ [2] https://github.com/ClangBuiltLinux/linux/issues/1121 [3] https://reviews.llvm.org/rGc41a18cf61790fc898dcda1055c3efbf442c14c0 [4] https://lore.kernel.org/lkml/20200731202738.2577854-1-nivedita@alum.mit.edu/ Reported-by: Nick Desaulniers Signed-off-by: Arvind Sankar Signed-off-by: Ingo Molnar Tested-by: Nick Desaulniers Tested-by: Sedat Dilek Acked-by: Ard Biesheuvel Reviewed-by: Nick Desaulniers Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20200812004308.1448603-1-nivedita@alum.mit.edu --- arch/x86/boot/compressed/Makefile | 2 ++ 1 file changed, 2 insertions(+) (limited to 'arch') diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile index 3962f592633d..ff7894f39e0e 100644 --- a/arch/x86/boot/compressed/Makefile +++ b/arch/x86/boot/compressed/Makefile @@ -43,6 +43,8 @@ KBUILD_CFLAGS += -Wno-pointer-sign KBUILD_CFLAGS += $(call cc-option,-fmacro-prefix-map=$(srctree)/=) KBUILD_CFLAGS += -fno-asynchronous-unwind-tables KBUILD_CFLAGS += -D__DISABLE_EXPORTS +# Disable relocation relaxation in case the link is not PIE. +KBUILD_CFLAGS += $(call as-option,-Wa$(comma)-mrelax-relocations=no) KBUILD_AFLAGS := $(KBUILD_CFLAGS) -D__ASSEMBLY__ GCOV_PROFILE := n -- cgit v1.2.3-70-g09d2 From 6f9885a36c006d798319661fa849f9c2922223b9 Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Mon, 14 Sep 2020 12:04:22 -0500 Subject: x86/unwind/fp: Fix FP unwinding in ret_from_fork There have been some reports of "bad bp value" warnings printed by the frame pointer unwinder: WARNING: kernel stack regs at 000000005bac7112 in sh:1014 has bad 'bp' value 0000000000000000 This warning happens when unwinding from an interrupt in ret_from_fork(). If entry code gets interrupted, the state of the frame pointer (rbp) may be undefined, which can confuse the unwinder, resulting in warnings like the above. There's an in_entry_code() check which normally silences such warnings for entry code. But in this case, ret_from_fork() is getting interrupted. It recently got moved out of .entry.text, so the in_entry_code() check no longer works. It could be moved back into .entry.text, but that would break the noinstr validation because of the call to schedule_tail(). Instead, initialize each new task's RBP to point to the task's entry regs via an encoded frame pointer. That will allow the unwinder to reach the end of the stack gracefully. Fixes: b9f6976bfb94 ("x86/entry/64: Move non entry code into .text section") Reported-by: Naresh Kamboju Reported-by: Logan Gunthorpe Signed-off-by: Josh Poimboeuf Signed-off-by: Borislav Petkov Acked-by: Peter Zijlstra (Intel) Acked-by: Thomas Gleixner Link: https://lkml.kernel.org/r/f366bbf5a8d02e2318ee312f738112d0af74d16f.1600103007.git.jpoimboe@redhat.com --- arch/x86/include/asm/frame.h | 19 +++++++++++++++++++ arch/x86/kernel/process.c | 3 ++- 2 files changed, 21 insertions(+), 1 deletion(-) (limited to 'arch') diff --git a/arch/x86/include/asm/frame.h b/arch/x86/include/asm/frame.h index 296b346184b2..fb42659f6e98 100644 --- a/arch/x86/include/asm/frame.h +++ b/arch/x86/include/asm/frame.h @@ -60,12 +60,26 @@ #define FRAME_END "pop %" _ASM_BP "\n" #ifdef CONFIG_X86_64 + #define ENCODE_FRAME_POINTER \ "lea 1(%rsp), %rbp\n\t" + +static inline unsigned long encode_frame_pointer(struct pt_regs *regs) +{ + return (unsigned long)regs + 1; +} + #else /* !CONFIG_X86_64 */ + #define ENCODE_FRAME_POINTER \ "movl %esp, %ebp\n\t" \ "andl $0x7fffffff, %ebp\n\t" + +static inline unsigned long encode_frame_pointer(struct pt_regs *regs) +{ + return (unsigned long)regs & 0x7fffffff; +} + #endif /* CONFIG_X86_64 */ #endif /* __ASSEMBLY__ */ @@ -83,6 +97,11 @@ #define ENCODE_FRAME_POINTER +static inline unsigned long encode_frame_pointer(struct pt_regs *regs) +{ + return 0; +} + #endif #define FRAME_BEGIN diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index 13ce616cc7af..ba4593a913fa 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -42,6 +42,7 @@ #include #include #include +#include #include "process.h" @@ -133,7 +134,7 @@ int copy_thread(unsigned long clone_flags, unsigned long sp, unsigned long arg, fork_frame = container_of(childregs, struct fork_frame, regs); frame = &fork_frame->frame; - frame->bp = 0; + frame->bp = encode_frame_pointer(childregs); frame->ret_addr = (unsigned long) ret_from_fork; p->thread.sp = (unsigned long) fork_frame; p->thread.io_bitmap = NULL; -- cgit v1.2.3-70-g09d2