From: Peter Zijlstra <peterz@infradead.org>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>,
Borislav Petkov <bp@suse.de>,
Josh Poimboeuf <jpoimboe@kernel.org>,
linux-kernel@vger.kernel.org, Ingo Molnar <mingo@kernel.org>
Subject: Re: CONFIG_RETHUNK int3 filling prevents kprobes in function body
Date: Mon, 5 Sep 2022 17:20:30 +0200 [thread overview]
Message-ID: <YxYTvgTqRP0GMAjO@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <YxYRYwZ/zYO+u1ij@hirez.programming.kicks-ass.net>
On Mon, Sep 05, 2022 at 05:10:27PM +0200, Peter Zijlstra wrote:
> On Mon, Sep 05, 2022 at 10:57:58AM -0400, Steven Rostedt wrote:
> > On Sun, 4 Sep 2022 23:07:13 +0900
> > Masami Hiramatsu (Google) <mhiramat@kernel.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?
>
> I don't see need for that. If you want to be strict you can simply
> follow the branches found earlier, if you want to be lazy, you can
> decode until you run out of the symbol size.
Another lazy option is to teach the thing that 'ret' is followed by 0,1
or 4 'int3' instructions depending on CONFIG_SLS, CONFIG_RETHUNK, but
that'll get you into trouble with future SLS compiler options, like the
aforementioned JMP-SLS option.
next prev parent reply other threads:[~2022-09-05 15:21 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-04 14:07 CONFIG_RETHUNK int3 filling prevents kprobes in function body Masami Hiramatsu
2022-09-05 14:57 ` Steven Rostedt
2022-09-05 15:10 ` Peter Zijlstra
2022-09-05 15:20 ` Peter Zijlstra [this message]
2022-09-06 1:30 ` Masami Hiramatsu
2022-09-05 15:09 ` Peter Zijlstra
2022-09-05 15:15 ` Peter Zijlstra
2022-09-05 15:52 ` Peter Zijlstra
2022-09-06 1:33 ` Masami Hiramatsu
2022-09-06 8:44 ` Peter Zijlstra
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