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SubjectRe: [PATCH] x86/signal: Remove pax argument from restore_sigcontext
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On Sat, Apr 4, 2015 at 10:14 AM, Ingo Molnar <mingo@kernel.org> wrote:
>
> * Brian Gerst <brgerst@gmail.com> wrote:
>
>> The pax argument is unnecesary. Instead, store the RAX value directly
>> in regs.
>>
>> Signed-off-by: Brian Gerst <brgerst@gmail.com>
>> Cc: Ingo Molnar <mingo@kernel.org>
>> Cc: "H. Peter Anvin" <hpa@zytor.com>
>> Cc: Andy Lutomirski <luto@amacapital.net>
>> Cc: Denys Vlasenko <dvlasenk@redhat.com>
>> Cc: Linus Torvalds <torvalds@linux-foundation.org>
>> Cc: Borislav Petkov <bp@alien8.de>
>> Cc: x86@kernel.org
>> Cc: linux-kernel@vger.kernel.org
>> ---
>> 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 guessing you didn't read the whole patch, because I did change it.

> 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.


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