linux-kernel - Re: [PATCH -tip 0/5] kprobes: Fix stacktrace in kretprobes

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Message-ID: <20210310150845.7kctaox34yrfyjxt@treble>
Date:   Wed, 10 Mar 2021 09:08:45 -0600
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     Daniel Xu <dxu@...uu.xyz>, Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...nel.org>, X86 ML <x86@...nel.org>,
        linux-kernel@...r.kernel.org, bpf@...r.kernel.org, kuba@...nel.org,
        mingo@...hat.com, ast@...nel.org, tglx@...utronix.de,
        kernel-team@...com, yhs@...com
Subject: Re: [PATCH -tip 0/5] kprobes: Fix stacktrace in kretprobes

On Wed, Mar 10, 2021 at 06:57:34PM +0900, Masami Hiramatsu wrote:
> > If I understand correctly, for #1 you need an unwind hint which treats
> > the instruction *after* the "pushq %rsp" as the beginning of the
> > function.
> 
> Thanks for the patch. In that case, should I still change the stack allocation?
> Or can I continue to use a series of "push/pop" ?

You can continue to use push/pop.  Objtool is only getting confused by
the unbalanced stack of the function (more pushes than pops).  The
unwind hint should fix that.

-- 
Josh