Re: [PATCH v3] x86,entry: Use PUSH_AND_CLEAR_REGS for compat

[Linus Torvalds]

On Fri, Apr 29, 2022 at 2:13 PM Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
>
> (Linus, can I add your SoB to the thing?)

If you teste this with some actual old int80 compat syscalls, then absolutely:

   Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>

> +       pushq   %rdi                    /* pt_regs->di */
>         pushq   %rsi                    /* pt_regs->si */
>         xorl    %esi, %esi              /* nospec   si */

It would probably make sense to add a comment about why %rdi isn't
cleared when pushed, like all the other registers are.

Even if that comment is just "%rdi will be overwritten as arg0 of the
call to C, so no need to clear it".

Maybe as part of the PUSH_AND_CLEAR_REGS changes?

            Linus