linux-kernel - Re: [PATCH] kretprobe: produce sane stack traces

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Message-ID: <20181101104948.bc7wk453bfryhhk7@yavin>
Date:   Thu, 1 Nov 2018 21:49:48 +1100
From:   Aleksa Sarai <cyphar@...har.com>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>,
        Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
        "David S. Miller" <davem@...emloft.net>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Brendan Gregg <bgregg@...flix.com>,
        Christian Brauner <christian@...uner.io>,
        Aleksa Sarai <asarai@...e.de>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kretprobe: produce sane stack traces

On 2018-11-01, Masami Hiramatsu <mhiramat@...nel.org> wrote:
> > > > Anyway, until that merge happens, this patch looks good to avoid
> > > > this issue for generic solution (e.g. for the arch which doesn't
> > > > supports retstack).
> > > 
> > > I think its time to come up with an algorithm that makes function graph
> > > work with multiple users, and have kretprobes be able to hook into it
> > > just like kprobes hooks into function tracer.
> > > 
> > > I have some ideas on how to get this done, and will try to have an RFC
> > > patch set ready by plumbers.
> > 
> > Should I continue working on this patchset?
> 
> Yes, until we finally introduce Steven's algorithm on all arch (yeah, we still
> have some archs which don't support graph-tracer but supports kprobes),
> I think your patch is the best fix for this issue.

Thanks, I just sent a v3.

Though, even with Steven's hooking of kprobes I think you'd still need
to stash away the stack trace somewhere (or am I misunderstanding the
proposal?).

-- 
Aleksa Sarai
Senior Software Engineer (Containers)
SUSE Linux GmbH
<https://www.cyphar.com/>

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