linux-kernel - Re: [PATCH v2 1/2] x86/kprobes: Fix kprobes instruction boudary check with CONFIG

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Date:   Thu, 8 Sep 2022 12:08:19 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Josh Poimboeuf <jpoimboe@...nel.org>
Cc:     "Masami Hiramatsu (Google)" <mhiramat@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...nel.org>,
        Suleiman Souhlal <suleiman@...gle.com>,
        bpf <bpf@...r.kernel.org>, linux-kernel@...r.kernel.org,
        Borislav Petkov <bp@...e.de>, x86@...nel.org
Subject: Re: [PATCH v2 1/2] x86/kprobes: Fix kprobes instruction boudary
 check with CONFIG_RETHUNK

On Thu, Sep 08, 2022 at 11:30:41AM +0200, Peter Zijlstra wrote:
> Once that lands the rules are:
> 
>  0-5 INT3 after RET, !CONFIG_RETHUNK && !CONFIG_SLS: 0
>                      CONFIG_SLS: 1
> 		     CONFIG_RETHUNK: 4-5 depending on compiler version
> 
>  0-1 INT3 after RET: !CONFIG_SLS: 0
> 		     CONFIG_SLS: 0-1 depending on compiler version
> 
> Now, given we know the compiler version at build time, this could be
> determined and used in kprobes, but meh.

Oh also, for giggles, we have a number of sites that have ret;int3
independent of CONFIG_SLS because that was easier than figuring out what
all should be done.