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SubjectRe: Re: [PATCH v3 -tip] [BUGFIX] x86/kprobes: Fix to recover instructions on optimized path

* 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.

> > 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.

Thanks,

Ingo


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