linux-kernel - Re: CONFIG_RETHUNK int3 filling prevents kprobes in function body

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Message-ID: <20220905105758.176734eb@gandalf.local.home>
Date:   Mon, 5 Sep 2022 10:57:58 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     "Masami Hiramatsu (Google)" <mhiramat@...nel.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Borislav Petkov <bp@...e.de>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>
Subject: Re: CONFIG_RETHUNK int3 filling prevents kprobes in function body

On Sun, 4 Sep 2022 23:07:13 +0900
Masami Hiramatsu (Google) <mhiramat@...nel.org> wrote:

> Can we use another instruction for padding instead of INT3? (e.g. NOP or UD2)
> 
> Or, can I expect the instruction length in __return_sites[] are always 5?
> If so, I can just skip 5 bytes if the address is in __return_sites[].

Perhaps another option is to have a table of where the padding is placed
(tagged), and that kprobes could check to see if the int3 is due to this
padding or not?

-- Steve