Re: [PATCH v26 6/9] x86/vdso: Insert endbr32/endbr64 to vDSO

On 4/28/2021 1:33 PM, Kees Cook wrote:

On Tue, Apr 27, 2021 at 01:47:17PM -0700, Yu-cheng Yu wrote:

quoted

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.

If you respin this, you can maybe rephrase this since CONFIG_X86_IBT
has already tested for the compiler support.

Yes, I will fix this.  Thanks for reviewing!

Yu-cheng

quoted

Signed-off-by: H.J. Lu <redacted>
Signed-off-by: Yu-cheng Yu <redacted>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Kees Cook <redacted>

Reviewed-by: Kees Cook <redacted>

-Kees

quoted

---
v24:
- Replace CONFIG_X86_CET with CONFIG_X86_IBT to reflect splitting of shadow
   stack and ibt.

  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 05c4abc2fdfd..a773a5f03b63 100644
--- a/arch/x86/entry/vdso/Makefile
+++ b/arch/x86/entry/vdso/Makefile

@@ -93,6 +93,10 @@ endif
  
  $(vobjs): KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_LTO) $(GCC_PLUGINS_CFLAGS) $(RETPOLINE_CFLAGS),$(KBUILD_CFLAGS)) $(CFL)
  
+ifdef CONFIG_X86_IBT
+$(vobjs) $(vobjs32): KBUILD_CFLAGS += -fcf-protection=branch
+endif
+
  #
  # vDSO code runs in userspace and -pg doesn't help with profiling anyway.
  #

-- 
2.21.0