[PATCH v12 7/8] 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>
---
v12:
- Replace object file list with $(vobjs) $(vobjs32).

 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..3f8b5f513adb 100644
--- a/arch/x86/entry/vdso/Makefile
+++ b/arch/x86/entry/vdso/Makefile
@@ -94,6 +94,10 @@ endif
 
 $(vobjs): KBUILD_CFLAGS := $(filter-out $(GCC_PLUGINS_CFLAGS) $(RETPOLINE_CFLAGS),$(KBUILD_CFLAGS)) $(CFL)
 
+ifdef CONFIG_X86_INTEL_BRANCH_TRACKING_USER
+$(vobjs) $(vobjs32): KBUILD_CFLAGS += -fcf-protection=branch
+endif
+
 #
 # vDSO code runs in userspace and -pg doesn't help with profiling anyway.
 #
-- 
2.21.0