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.
--
Josh
