Re: [PATCH 2/5] x86/uprobes: implement x86 specific arch_uprobe_*_step

[Sebastian Andrzej Siewior <bigeasy@linutronix.de>]

On 08/08/2012 04:53 PM, Oleg Nesterov wrote:
>> Why? I tried 'lock popf' and I got invalid instruction. The same for
>> 'rep popf'.
>
> 	int main(void)
> 	{
> 		asm volatile ("pushf; rep; popf");
>
> 		return 0;
> 	}
>

Just tested and it works. Hmm.

> OK, probably nobody should do this (although the kernel should not
> assume this imho), but
>
> 	asm volatile ("pushfw; popfw");
>
> doesn't look bad and the code is
>
> 	000000000040047c<main>:
> 	  40047c:       55                      push   %rbp
> 	  40047d:       48 89 e5                mov    %rsp,%rbp
> 	  400480:       66 9c                   pushfw
> 	  400482:       66 9d                   popfw
> 	  400484:       b8 00 00 00 00          mov    $0x0,%eax
> 	  400489:       c9                      leaveq
> 	  40048a:       c3                      retq

Yes, that one works as well.

> And in any case it would be better to re-use auprobe->fixups.

Okay.

> Oleg.
>

Sebastian