# \[PATCH v19 7/7\] x86/vdso: Insert endbr32/endbr64 to vDSO

- From: Yu-cheng Yu \<hidden\>
- Date: 2021-02-03 23:13:38 
- List: linux-arch
- Page: https://ratatoskr.run/linux-arch/2021/02/6257809
- Thread: https://ratatoskr.run/linux-doc/2021/02/6257808/t.md

```text
From: "H.J. Lu" <redacted>

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 <redacted>
Signed-off-by: Yu-cheng Yu <redacted>
Acked-by: Andy Lutomirski <luto@kernel.org>
---
 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 02e3e42f380b..ff7b56feb5c3 100644
--- a/arch/x86/entry/vdso/Makefile
+++ b/arch/x86/entry/vdso/Makefile
@@ -93,6 +93,10 @@ endif
 
 $(vobjs): KBUILD_CFLAGS := $(filter-out $(GCC_PLUGINS_CFLAGS) $(RETPOLINE_CFLAGS),$(KBUILD_CFLAGS)) $(CFL)
 
+ifdef CONFIG_X86_CET
+$(vobjs) $(vobjs32): KBUILD_CFLAGS += -fcf-protection=branch
+endif
+
 #
 # vDSO code runs in userspace and -pg doesn't help with profiling anyway.
 #
-- 
2.21.0

```