linux-kernel - Re: [PATCH -tip v3 05/11] x86/kprobes: Add UNWIND_HINT_FUNC on kretprobe

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Date:   Sun, 21 Mar 2021 12:50:04 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...nel.org>, X86 ML <x86@...nel.org>,
        Daniel Xu <dxu@...uu.xyz>, 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,
        linux-ia64@...r.kernel.org
Subject: Re: [PATCH -tip v3 05/11] x86/kprobes: Add UNWIND_HINT_FUNC on
 kretprobe_trampoline code

On Sat, Mar 20, 2021 at 09:16:16PM +0900, Masami Hiramatsu wrote:
> On Fri, 19 Mar 2021 21:22:39 +0900
> Masami Hiramatsu <mhiramat@...nel.org> wrote:
> 
> > From: Josh Poimboeuf <jpoimboe@...hat.com>
> > 
> > Add UNWIND_HINT_FUNC on kretporbe_trampoline code so that ORC
> > information is generated on the kretprobe_trampoline correctly.
> > 
> 
> Test bot also found a new warning for this.
> 
> > >> arch/x86/kernel/kprobes/core.o: warning: objtool: kretprobe_trampoline()+0x25: call without frame pointer save/setup
> 
> With CONFIG_FRAME_POINTER=y.
> 
> Of course this can be fixed with additional "push %bp; mov %sp, %bp" before calling
> trampoline_handler. But actually we know that this function has a bit special
> stack frame too. 
> 
> Can I recover STACK_FRAME_NON_STANDARD(kretprobe_trampoline) when CONFIG_FRAME_POINTER=y ?

Yes, that's what I'd recommend.

-- 
Josh