Re: [PATCH v2] uprobes: fix scratch register selection for rip-relative fixups

From: Oleg Nesterov
Date: Mon May 05 2014 - 11:46:25 EST


On 05/02, Denys Vlasenko wrote:
>
> v2: More robust checks of vex.vvvv (32-bit mode safe),
> simplified scratch reg selection code,
> moved comments around as requested by Oleg.

OK, thanks. Given that this patch was acked by Jim, I am going to
apply it. I'll try to run a couple of systemtap scripts with this
patch, but unfortunately the "full" testing is simply impossible.

Denys, I'll also include your test-case into the changelog.

And,

> static inline unsigned long *
> scratch_reg(struct arch_uprobe *auprobe, struct pt_regs *regs)
> {
> - return (auprobe->def.fixups & UPROBE_FIX_RIP_AX) ? &regs->ax : &regs->cx;
> + /* Order is important - more than one bit can be set! */

Really?

Should I remove this comment or I misread the change in riprel_analyze?

Oleg.

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