csky: Reconstruct VDSO framework

Reconstruct vdso framework to support future vsyscall,
vgettimeofday features. These are very important features to reduce
system calls into the kernel for performance improvement.

The patch is reference RISC-V's

Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Cc: Palmer Dabbelt <palmerdabbelt@google.com>

7 files changed, 172 insertions, 0 deletions

diff --git a/arch/csky/kernel/vdso/.gitignore b/arch/csky/kernel/vdso/.gitignore
new file mode 100644
index 000000000000..3a19def868ec
--- /dev/null
+++ b/arch/csky/kernel/vdso/.gitignore
@@ -0,0 +1,4 @@
+# SPDX-License-Identifier: GPL-2.0-only
+vdso.lds
+*.tmp
+vdso-syms.S
diff --git a/arch/csky/kernel/vdso/Makefile b/arch/csky/kernel/vdso/Makefile
new file mode 100644
index 000000000000..13ac549c6587
--- /dev/null
+++ b/arch/csky/kernel/vdso/Makefile
@@ -0,0 +1,67 @@
+# SPDX-License-Identifier: GPL-2.0-only
+
+# Absolute relocation type $(ARCH_REL_TYPE_ABS) needs to be defined before
+# the inclusion of generic Makefile.
+ARCH_REL_TYPE_ABS := R_CKCORE_ADDR32|R_CKCORE_JUMP_SLOT
+include $(srctree)/lib/vdso/Makefile
+
+# Symbols present in the vdso
+vdso-syms  = rt_sigreturn
+
+# Files to link into the vdso
+obj-vdso = $(patsubst %, %.o, $(vdso-syms)) note.o
+
+ccflags-y := -fno-stack-protector
+
+# Build rules
+targets := $(obj-vdso) vdso.so vdso.so.dbg vdso.lds vdso-dummy.o
+obj-vdso := $(addprefix $(obj)/, $(obj-vdso))
+
+obj-y += vdso.o vdso-syms.o
+CPPFLAGS_vdso.lds += -P -C -U$(ARCH)
+
+# Disable gcov profiling for VDSO code
+GCOV_PROFILE := n
+KCOV_INSTRUMENT := n
+
+# Force dependency
+$(obj)/vdso.o: $(obj)/vdso.so
+
+SYSCFLAGS_vdso.so.dbg = $(c_flags)
+$(obj)/vdso.so.dbg: $(src)/vdso.lds $(obj-vdso) FORCE
+	$(call if_changed,vdsold)
+SYSCFLAGS_vdso.so.dbg = -shared -s -Wl,-soname=linux-vdso.so.1 \
+	-Wl,--build-id=sha1 -Wl,--hash-style=both
+
+$(obj)/vdso-syms.S: $(obj)/vdso.so FORCE
+	$(call if_changed,so2s)
+
+# strip rule for the .so file
+$(obj)/%.so: OBJCOPYFLAGS := -S
+$(obj)/%.so: $(obj)/%.so.dbg FORCE
+	$(call if_changed,objcopy)
+
+# actual build commands
+# The DSO images are built using a special linker script
+# Make sure only to export the intended __vdso_xxx symbol offsets.
+quiet_cmd_vdsold = VDSOLD  $@
+      cmd_vdsold = $(CC) $(KBUILD_CFLAGS) $(call cc-option, -no-pie) -nostdlib -nostartfiles $(SYSCFLAGS_$(@F)) \
+                           -Wl,-T,$(filter-out FORCE,$^) -o $@.tmp && \
+                   $(CROSS_COMPILE)objcopy \
+                           $(patsubst %, -G __vdso_%, $(vdso-syms)) $@.tmp $@ && \
+                   rm $@.tmp
+
+# Extracts symbol offsets from the VDSO, converting them into an assembly file
+# that contains the same symbols at the same offsets.
+quiet_cmd_so2s = SO2S    $@
+      cmd_so2s = $(NM) -D $< | $(srctree)/$(src)/so2s.sh > $@
+
+# install commands for the unstripped file
+quiet_cmd_vdso_install = INSTALL $@
+      cmd_vdso_install = cp $(obj)/$@.dbg $(MODLIB)/vdso/$@
+
+vdso.so: $(obj)/vdso.so.dbg
+	@mkdir -p $(MODLIB)/vdso
+	$(call cmd,vdso_install)
+
+vdso_install: vdso.so
diff --git a/arch/csky/kernel/vdso/note.S b/arch/csky/kernel/vdso/note.S
new file mode 100644
index 000000000000..2a956c942211
--- /dev/null
+++ b/arch/csky/kernel/vdso/note.S
@@ -0,0 +1,12 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * This supplies .note.* sections to go into the PT_NOTE inside the vDSO text.
+ * Here we can supply some information useful to userland.
+ */
+
+#include <linux/elfnote.h>
+#include <linux/version.h>
+
+ELFNOTE_START(Linux, 0, "a")
+	.long LINUX_VERSION_CODE
+ELFNOTE_END
diff --git a/arch/csky/kernel/vdso/rt_sigreturn.S b/arch/csky/kernel/vdso/rt_sigreturn.S
new file mode 100644
index 000000000000..0a6bd1216118
--- /dev/null
+++ b/arch/csky/kernel/vdso/rt_sigreturn.S
@@ -0,0 +1,14 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <linux/linkage.h>
+#include <asm/unistd.h>
+#include <abi/vdso.h>
+
+	.text
+ENTRY(__vdso_rt_sigreturn)
+	.cfi_startproc
+	.cfi_signal_frame
+	SET_SYSCALL_ID
+	trap	0
+	.cfi_endproc
+ENDPROC(__vdso_rt_sigreturn)
diff --git a/arch/csky/kernel/vdso/so2s.sh b/arch/csky/kernel/vdso/so2s.sh
new file mode 100755
index 000000000000..69da3d529c6d
--- /dev/null
+++ b/arch/csky/kernel/vdso/so2s.sh
@@ -0,0 +1,5 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0+
+
+sed 's!\([0-9a-f]*\) T \([a-z0-9_]*\)\(@@LINUX_5.10\)*!.global \2\n.set \2,0x\1!' \
+| grep '^\.'
diff --git a/arch/csky/kernel/vdso/vdso.S b/arch/csky/kernel/vdso/vdso.S
new file mode 100644
index 000000000000..5162ca069494
--- /dev/null
+++ b/arch/csky/kernel/vdso/vdso.S
@@ -0,0 +1,16 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <linux/init.h>
+#include <linux/linkage.h>
+#include <asm/page.h>
+
+	__PAGE_ALIGNED_DATA
+
+	.globl vdso_start, vdso_end
+	.balign PAGE_SIZE
+vdso_start:
+	.incbin "arch/csky/kernel/vdso/vdso.so"
+	.balign PAGE_SIZE
+vdso_end:
+
+	.previous
diff --git a/arch/csky/kernel/vdso/vdso.lds.S b/arch/csky/kernel/vdso/vdso.lds.S
new file mode 100644
index 000000000000..8d226252d439
--- /dev/null
+++ b/arch/csky/kernel/vdso/vdso.lds.S
@@ -0,0 +1,54 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <asm/page.h>
+
+OUTPUT_ARCH(csky)
+
+SECTIONS
+{
+	PROVIDE(_vdso_data = . + PAGE_SIZE);
+	. = SIZEOF_HEADERS;
+
+	.hash		: { *(.hash) }			:text
+	.gnu.hash	: { *(.gnu.hash) }
+	.dynsym		: { *(.dynsym) }
+	.dynstr		: { *(.dynstr) }
+	.gnu.version	: { *(.gnu.version) }
+	.gnu.version_d	: { *(.gnu.version_d) }
+	.gnu.version_r	: { *(.gnu.version_r) }
+
+	.note		: { *(.note.*) }		:text	:note
+	.dynamic	: { *(.dynamic) }		:text	:dynamic
+
+	.eh_frame_hdr	: { *(.eh_frame_hdr) }		:text	:eh_frame_hdr
+	.eh_frame	: { KEEP (*(.eh_frame)) }	:text
+
+	.rodata		: { *(.rodata .rodata.* .gnu.linkonce.r.*) }
+
+	. = 0x800;
+	.text		: { *(.text .text.*) }		:text
+
+	.data		: {
+		*(.got.plt) *(.got)
+		*(.data .data.* .gnu.linkonce.d.*)
+		*(.dynbss)
+		*(.bss .bss.* .gnu.linkonce.b.*)
+	}
+}
+
+PHDRS
+{
+	text		PT_LOAD		FLAGS(5) FILEHDR PHDRS; /* PF_R|PF_X */
+	dynamic		PT_DYNAMIC	FLAGS(4);		/* PF_R */
+	note		PT_NOTE		FLAGS(4);		/* PF_R */
+	eh_frame_hdr	PT_GNU_EH_FRAME;
+}
+
+VERSION
+{
+	LINUX_5.10 {
+	global:
+		__vdso_rt_sigreturn;
+	local: *;
+	};
+}