Re: [PATCH] x86/signal: Remove pax argument from restore_sigcontext

From: Ingo Molnar
Date: Sat Apr 04 2015 - 10:14:42 EST



* Brian Gerst <brgerst@xxxxxxxxx> wrote:

> The pax argument is unnecesary. Instead, store the RAX value directly
> in regs.
>
> Signed-off-by: Brian Gerst <brgerst@xxxxxxxxx>
> Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
> Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
> Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> Cc: Borislav Petkov <bp@xxxxxxxxx>
> Cc: x86@xxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> ---
> arch/x86/ia32/ia32_signal.c | 17 ++++++-----------
> arch/x86/include/asm/sighandling.h | 4 +---
> arch/x86/kernel/signal.c | 22 ++++++++--------------
> 3 files changed, 15 insertions(+), 28 deletions(-)
>
> diff --git a/arch/x86/ia32/ia32_signal.c b/arch/x86/ia32/ia32_signal.c
> index 1f5e2b0..c81d35e6 100644
> --- a/arch/x86/ia32/ia32_signal.c
> +++ b/arch/x86/ia32/ia32_signal.c
> @@ -161,8 +161,7 @@ int copy_siginfo_from_user32(siginfo_t *to, compat_siginfo_t __user *from)
> }
>
> static int ia32_restore_sigcontext(struct pt_regs *regs,
> - struct sigcontext_ia32 __user *sc,
> - unsigned int *pax)
> + struct sigcontext_ia32 __user *sc)
> {
> unsigned int tmpflags, err = 0;
> void __user *buf;
> @@ -184,7 +183,7 @@ static int ia32_restore_sigcontext(struct pt_regs *regs,
> RELOAD_SEG(es);
>
> COPY(di); COPY(si); COPY(bp); COPY(sp); COPY(bx);
> - COPY(dx); COPY(cx); COPY(ip);
> + COPY(dx); COPY(cx); COPY(ip); COPY(ax);
> /* Don't touch extended registers */
>
> COPY_SEG_CPL3(cs);
> @@ -197,8 +196,6 @@ static int ia32_restore_sigcontext(struct pt_regs *regs,
>
> get_user_ex(tmp, &sc->fpstate);
> buf = compat_ptr(tmp);
> -
> - get_user_ex(*pax, &sc->ax);
> } get_user_catch(err);

Note that arch/x86/kernel/signal.c appears to have a similar pattern -
and there it could be removed as well?

I'm wondering what the original reason for adding the extra handling
of regs->ax was. Maybe something changed regs->ax - but I cannot find
such code path anymore.

It would be nice to try to do a bit of Git archeology to figure out
the origins of this complication - maybe it's something subtle - or
it's something that has changed meanwhile.

Thanks,

Ingo
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