linux-kernel - Re: [PATCH v2 1/5] perf/x86: Always store regs->ip in perf_callchain

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Message-ID: <20190614210619.su5cr55eah5ks7ur@treble>
Date:   Fri, 14 Jun 2019 16:06:19 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:     x86@...nel.org, Alexei Starovoitov <ast@...nel.org>,
        linux-kernel@...r.kernel.org,
        Daniel Borkmann <daniel@...earbox.net>, netdev@...r.kernel.org,
        bpf@...r.kernel.org, Peter Zijlstra <peterz@...radead.org>,
        Song Liu <songliubraving@...com>,
        Kairui Song <kasong@...hat.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        David Laight <David.Laight@...LAB.COM>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>, Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH v2 1/5] perf/x86: Always store regs->ip in
 perf_callchain_kernel()

On Fri, Jun 14, 2019 at 01:56:15PM -0700, Alexei Starovoitov wrote:
> On Fri, Jun 14, 2019 at 12:56:40PM -0500, Josh Poimboeuf wrote:
> > From: Song Liu <songliubraving@...com>
> > 
> > The stacktrace_map_raw_tp BPF selftest is failing because the RIP saved
> > by perf_arch_fetch_caller_regs() isn't getting saved by
> > perf_callchain_kernel().
> > 
> > This was broken by the following commit:
> > 
> >   d15d356887e7 ("perf/x86: Make perf callchains work without CONFIG_FRAME_POINTER")
> > 
> > With that change, when starting with non-HW regs, the unwinder starts
> > with the current stack frame and unwinds until it passes up the frame
> > which called perf_arch_fetch_caller_regs().  So regs->ip needs to be
> > saved deliberately.
> > 
> > Fixes: d15d356887e7 ("perf/x86: Make perf callchains work without CONFIG_FRAME_POINTER")
> > Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
> > Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> 
> It's not cool to remove people's SOB.
> It's Song's patch. His should be first and your second.

His original patch didn't have an SOB.  I preserved the "From" field.

-- 
Josh