[RFC PATCH v2 24/27] x86: Insert endbr32/endbr64 to vDSO

[Yu-cheng Yu <yu-cheng.yu@intel.com>]

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