Re: [PATCH 1/2] uprobes/x86: Change __skip_sstep() to actually skipthe whole insn

[Anton Arapov]

On Sun, Dec 30, 2012 at 04:47:19PM +0100, Oleg Nesterov wrote:
> __skip_sstep() doesn't update regs->ip. Currently this is correct
> but only "by accident" and it doesn't skip the whole insn. Change
> it to advance ->ip by the length of the detected 0x66*0x90 sequence.
> 
> Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
> ---
>  arch/x86/kernel/uprobes.c |    5 ++++-
>  1 files changed, 4 insertions(+), 1 deletions(-)
> 
> diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c
> index c71025b..4e33a35 100644
> --- a/arch/x86/kernel/uprobes.c
> +++ b/arch/x86/kernel/uprobes.c
> @@ -680,8 +680,11 @@ static bool __skip_sstep(struct arch_uprobe *auprobe, struct pt_regs *regs)
>  		if (auprobe->insn[i] == 0x66)
>  			continue;
>  
> -		if (auprobe->insn[i] == 0x90)
> +		if (auprobe->insn[i] == 0x90) {
> +			regs->ip = uprobe_get_swbp_addr(regs);
> +			regs->ip += i + 1;
>  			return true;
> +		}

  This change/routine is not obvious without the patch description, I
would appreciate some comment in the code. :) I believe it could help
some random developer in future.
  / I leave it to your judgement though /

Anton.
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