Re: [PATCH 1/2] x86/kprobes: Fix kprobes instruction boudary check with CONFIG_RETHUNK

Masami Hiramatsu
2022-09-07T13:49:32Z

On Wed, 7 Sep 2022 14:56:52 +0200
Peter Zijlstra <peterz@infradead.org> wrote:

> On Wed, Sep 07, 2022 at 09:55:21AM +0900, Masami Hiramatsu (Google) wrote:
>
> > if (!kallsyms_lookup_size_offset(paddr, NULL, &offset))
> > return 0;
> >
>
> One more thing:
>
> https://lkml.kernel.org/r/20220902130951.853460809@infradead.org
>
> can result in negative offsets. The expression:
>
> 'paddr - offset'
>
> will still get you to +0, but I might not have fully considered things
> when I wrote that patch.

Hmm, isn't 'offset' unsigned? If 'paddr - offset' is still available
to find the function entry address, it is OK to me.

Thank you,

--
Masami Hiramatsu (Google) <mhiramat@kernel.org>