Re: [PATCH 4/5] x86/asm/entry/32: Replace RESTORE_RSI_RDI[_RDX] with open-coded 32-bit reads

[Andy Lutomirski]

On Tue, Jun 9, 2015 at 11:54 AM, Denys Vlasenko <dvlasenk@xxxxxxxxxx> wrote:
> This doesn't change much, but this uses shorter 32-bit insns:
>
>         -48 8b 74 24 68         mov    0x68(%rsp),%rsi
>         -48 8b 7c 24 70         mov    0x70(%rsp),%rdi
>         -48 8b 54 24 60         mov    0x60(%rsp),%rdx
>         +8b 74 24 68            mov    0x68(%rsp),%esi
>         +8b 7c 24 70            mov    0x70(%rsp),%edi
>         +8b 54 24 60            mov    0x60(%rsp),%edx
>
> Since these are the only uses of RESTORE_RSI_RDI[_RDX], drop these macros.
>

It probably doesn't matter for these fast paths, but, for the full
slow path return, we really do need to restore the full pt_regs.
After all, the syscall we're returning from might be sigreturn.

--Andy
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