linux-kernel - Re: [PATCH -tip v4 10/12] x86/kprobes: Push a fake return address at kretprobe

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Message-Id: <20210325122524.91bca1233c0c254fdc0678fc@kernel.org>
Date:   Thu, 25 Mar 2021 12:25:24 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Josh Poimboeuf <jpoimboe@...hat.com>,
        Peter Zijlstra <peterz@...radead.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,
        Abhishek Sagar <sagar.abhishek@...il.com>
Subject: Re: [PATCH -tip v4 10/12] x86/kprobes: Push a fake return address
 at kretprobe_trampoline

On Wed, 24 Mar 2021 20:26:13 -0400
Steven Rostedt <rostedt@...dmis.org> wrote:

> On Thu, 25 Mar 2021 08:47:41 +0900
> Masami Hiramatsu <mhiramat@...nel.org> wrote:
> 
> > > I think the REGS and REGS_PARTIAL cases can also be affected by function
> > > graph tracing.  So should they use the generic unwind_recover_ret_addr()
> > > instead of unwind_recover_kretprobe()?  
> > 
> > Yes, but I'm not sure this parameter can be applied.
> > For example, it passed "state->sp - sizeof(unsigned long)" as where the
> > return address stored address. Is that same on ftrace graph too?
> 
> Stack traces on the return side of function graph tracer has never
> worked. It's on my todo list, because that's one of the requirements to
> get right if we every manage to combine kretprobe and function graph
> tracers together.

OK, then at this point let's just fix the kretprobe side.

Thanks,

> 
> -- Steve


-- 
Masami Hiramatsu <mhiramat@...nel.org>