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SubjectRe: Re: Re: [PATCH v3 -tip] [BUGFIX] x86/kprobes: Fix to recover instructions on optimized path
(2012/02/28 17:48), Ingo Molnar wrote:
>
> * Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> wrote:
>
>> (2012/02/27 18:34), Ingo Molnar wrote:
>>>
>>> * Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> wrote:
>>>
>>>> +
>>>> +#ifdef CONFIG_OPTPROBES
>>>> +static unsigned long __recover_optprobed_insn(struct kprobe *kp,
>>>> + kprobe_opcode_t *buf,
>>>> + unsigned long addr)
>>>> +{
>>>> + long offs = addr - (unsigned long)kp->addr - 1;
>>>> + struct optimized_kprobe *op = container_of(kp, struct optimized_kprobe, kp);
>>>> +
>>>> + /*
>>>> + * If the kprobe can be optimized, original bytes which can be
>>>> + * overwritten by jump destination address. In this case, original
>>>> + * bytes must be recovered from op->optinsn.copied_insn buffer.
>>>> + */
>>>> + memcpy(buf, (void *)addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
>>>> + if (addr == (unsigned long)kp->addr) {
>>>> + buf[0] = kp->opcode;
>>>> + memcpy(buf + 1, op->optinsn.copied_insn, RELATIVE_ADDR_SIZE);
>>>> + } else
>>>> + memcpy(buf, op->optinsn.copied_insn + offs, RELATIVE_ADDR_SIZE - offs);
>>>> +
>>>> + return (unsigned long)buf;
>>>> +}
>>>> +#endif
>>>
>>> Why not stick this into a new kprobes-opt.c file?
>>
>> Would you mean that I should split all optprobe stuffs into
>> new file?
>
> Yeah, that would be sensible I think - and it might help avoid
> similar complications in the future.
>
> Could (and probably should) be done in a separate patch - to
> keep the bits that you already fixed and tested intact.

OK, I'll make a separate patch.

>>> This should be a separate, kprobes_recover_opt() method and
>>> be inside kprobes-opt.c as well.
>>
>> OK, I'll do that. But I think it should be separated work.
>> Just for the bugfix, I think this should go into this style,
>> because this should be pushed into stable tree too.
>
> I don't think we can push such a large and complex looking patch
> into v3.3 (let alone into -stable) - it's v3.4 material, and
> that's why I asked for the cleaner split-out as well. This
> optprobes code is really non-obvious at the moment and a
> split-out might improve that and might make future fixes easier
> to merge.

Yeah, agreed. it's bigger for stable tree.

Thank you,

>
> Thanks,
>
> Ingo
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--
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@hitachi.com


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