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

[Yu, Yu-cheng]

On 4/28/2021 1:33 PM, Kees Cook wrote:
> On Tue, Apr 27, 2021 at 01:47:17PM -0700, Yu-cheng Yu wrote:
> > 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.
>
> 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

> > Signed-off-by: H.J. Lu <hjl.tools@xxxxxxxxx>
> > Signed-off-by: Yu-cheng Yu <yu-cheng.yu@xxxxxxxxx>
> > Cc: Andy Lutomirski <luto@xxxxxxxxxx>
> > Cc: Kees Cook <keescook@xxxxxxxxxxxx>
>
> Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
>
> -Kees
>
> > ---
> > 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