On Fri, Nov 15, 2024 at 10:40:56AM -0800, Josh Poimboeuf wrote:
> On Mon, Nov 11, 2024 at 12:59:45PM +0100, Peter Zijlstra wrote:
> > Counterpart to 09d09531a51a ("x86,nospec: Simplify
> > {JMP,CALL}_NOSPEC"), x86_64 will rewrite all this anyway, see
> > apply_retpoline.
> >
> > Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
> > ---
> > arch/x86/include/asm/nospec-branch.h | 29 +++++++++++------------------
> > 1 file changed, 11 insertions(+), 18 deletions(-)
> >
> > --- a/arch/x86/include/asm/nospec-branch.h
> > +++ b/arch/x86/include/asm/nospec-branch.h
> > @@ -429,31 +429,24 @@ static inline void call_depth_return_thu
> >
> > #ifdef CONFIG_X86_64
> >
> > +#define __CS_PREFIX \
> > + ".irp rs,r8,r9,r10,r11,r12,r13,r14,r15\n" \
> > + ".ifc %V[thunk_target],\\rs\n" \
> > + ".byte 0x2e\n" \
> > + ".endif\n" \
> > + ".endr\n"
>
> After staring at this for some minutes I'm thinking it would be helpful
> to add a comment saying this is equivalent to
> -mindirect-branch-cs-prefix.
I'll just copy-paste the comment from the other __CS_PREFIX elsewhere in
this file :-)
