[PATCH v11 8/9] x86/vdso: Insert endbr32/endbr64 to vDSO

[Yu-cheng Yu]

From: "H.J. Lu" <hjl.tools@xxxxxxxxx>

When Indirect Branch Tracking (IBT) is enabled, vDSO functions may be
called indirectly, and must have ENDBR32 or ENDBR64 as the first
instruction.  The compiler must support -fcf-protection=branch so that it
can be used to compile vDSO.

Signed-off-by: H.J. Lu <hjl.tools@xxxxxxxxx>
Signed-off-by: Yu-cheng Yu <yu-cheng.yu@xxxxxxxxx>
Acked-by: Andy Lutomirski <luto@xxxxxxxxxx>
---
 arch/x86/entry/vdso/Makefile | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/x86/entry/vdso/Makefile b/arch/x86/entry/vdso/Makefile
index 215376d975a2..82f8e25e139f 100644
--- a/arch/x86/entry/vdso/Makefile
+++ b/arch/x86/entry/vdso/Makefile
@@ -130,6 +130,10 @@ $(obj)/%-x32.o: $(obj)/%.o FORCE
 
 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 FORCE
 	$(call if_changed,objcopy)
-- 
2.21.0