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Subject[RFC PATCH v2 24/27] x86: Insert endbr32/endbr64 to vDSO
Date
From: "H.J. Lu" <hjl.tools@gmail.com>

When Intel indirect branch tracking is enabled, functions in vDSO which
may be called indirectly must have endbr32 or endbr64 as the first
instruction. Compiler must support -fcf-protection=branch so that it
can be used to compile vDSO.

Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
---
arch/x86/entry/vdso/.gitignore | 4 ++++
arch/x86/entry/vdso/Makefile | 12 +++++++++++-
arch/x86/entry/vdso/vdso-layout.lds.S | 1 +
3 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/arch/x86/entry/vdso/.gitignore b/arch/x86/entry/vdso/.gitignore
index aae8ffdd5880..552941fdfae0 100644
--- a/arch/x86/entry/vdso/.gitignore
+++ b/arch/x86/entry/vdso/.gitignore
@@ -5,3 +5,7 @@ vdso32-sysenter-syms.lds
vdso32-int80-syms.lds
vdso-image-*.c
vdso2c
+vclock_gettime.S
+vgetcpu.S
+vclock_gettime.asm
+vgetcpu.asm
diff --git a/arch/x86/entry/vdso/Makefile b/arch/x86/entry/vdso/Makefile
index 261802b1cc50..d49548ebec6f 100644
--- a/arch/x86/entry/vdso/Makefile
+++ b/arch/x86/entry/vdso/Makefile
@@ -108,13 +108,17 @@ vobjx32s := $(foreach F,$(vobjx32s-y),$(obj)/$F)

# Convert 64bit object file to x32 for x32 vDSO.
quiet_cmd_x32 = X32 $@
- cmd_x32 = $(OBJCOPY) -O elf32-x86-64 $< $@
+ cmd_x32 = $(OBJCOPY) -R .note.gnu.property -O elf32-x86-64 $< $@

$(obj)/%-x32.o: $(obj)/%.o FORCE
$(call if_changed,x32)

targets += vdsox32.lds $(vobjx32s-y)

+ifdef CONFIG_X86_INTEL_BRANCH_TRACKING_USER
+ $(obj)/vclock_gettime.o $(obj)/vgetcpu.o $(obj)/vdso32/vclock_gettime.o: KBUILD_CFLAGS += -fcf-protection=branch
+endif
+
$(obj)/%.so: OBJCOPYFLAGS := -S
$(obj)/%.so: $(obj)/%.so.dbg
$(call if_changed,objcopy)
@@ -164,6 +168,12 @@ quiet_cmd_vdso = VDSO $@

VDSO_LDFLAGS = -fPIC -shared $(call cc-ldoption, -Wl$(comma)--hash-style=both) \
$(call cc-ldoption, -Wl$(comma)--build-id) -Wl,-Bsymbolic $(LTO_CFLAGS)
+ifdef CONFIG_X86_INTEL_BRANCH_TRACKING_USER
+ VDSO_LDFLAGS += $(call cc-ldoption, -Wl$(comma)-z$(comma)ibt)
+endif
+ifdef CONFIG_X86_INTEL_SHADOW_STACK_USER
+ VDSO_LDFLAGS += $(call cc-ldoption, -Wl$(comma)-z$(comma)shstk)
+endif
GCOV_PROFILE := n

#
diff --git a/arch/x86/entry/vdso/vdso-layout.lds.S b/arch/x86/entry/vdso/vdso-layout.lds.S
index acfd5ba7d943..cabaeedfed78 100644
--- a/arch/x86/entry/vdso/vdso-layout.lds.S
+++ b/arch/x86/entry/vdso/vdso-layout.lds.S
@@ -74,6 +74,7 @@ SECTIONS
.fake_shstrtab : { *(.fake_shstrtab) } :text


+ .note.gnu.property : { *(.note.gnu.property) } :text :note
.note : { *(.note.*) } :text :note

.eh_frame_hdr : { *(.eh_frame_hdr) } :text :eh_frame_hdr
--
2.17.1
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