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Date:   Thu, 9 Jul 2020 07:37:43 -0700
From:   Andi Kleen <andi@firstfloor.org>
To:     Masami Hiramatsu <mhiramat@kernel.org>
Cc:     Arnaldo Carvalho de Melo <acme@kernel.org>,
        Arnaldo Carvalho de Melo <acme@redhat.com>,
        Oleg Nesterov <oleg@redhat.com>,
        Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
        linux-kernel@vger.kernel.org, Andi Kleen <andi@firstfloor.org>,
        Andi Kleen <ak@linux.intel.com>
Subject: Re: [PATCH 2/4] perf-probe: Fix wrong variable warning when the
 probe point is not found
Message-ID: <20200709143743.gux2xsfq4wo2xeo3@two.firstfloor.org>
References: <159428201109.56570.3802208017109058146.stgit@devnote2>
 <159428203219.56570.8289435784233418736.stgit@devnote2>
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On Thu, Jul 09, 2020 at 05:07:12PM +0900, Masami Hiramatsu wrote:
> Fix a wrong "variable not found" warning when the probe point is
> not found in the debuginfo.
> Since the debuginfo__find_probes() can return 0 even if it does not
> find given probe point in the debuginfo, fill_empty_trace_arg() can
> be called with tf.ntevs == 0 and it can warn a wrong warning.
> To fix this, reject ntevs == 0 in fill_empty_trace_arg().
> 
> E.g. without this patch;
> 
>   # perf probe -x /lib64/libc-2.30.so -a "memcpy arg1=%di"
>   Failed to find the location of the '%di' variable at this address.
>    Perhaps it has been optimized out.
>    Use -V with the --range option to show '%di' location range.
>   Added new events:
>     probe_libc:memcpy    (on memcpy in /usr/lib64/libc-2.30.so with arg1=%di)
>     probe_libc:memcpy    (on memcpy in /usr/lib64/libc-2.30.so with arg1=%di)
> 
>   You can now use it in all perf tools, such as:
> 
>   	perf record -e probe_libc:memcpy -aR sleep 1
> 
> With this;
> 
>   # perf probe -x /lib64/libc-2.30.so -a "memcpy arg1=%di"
>   Added new events:
>     probe_libc:memcpy    (on memcpy in /usr/lib64/libc-2.30.so with arg1=%di)
>     probe_libc:memcpy    (on memcpy in /usr/lib64/libc-2.30.so with arg1=%di)
> 
>   You can now use it in all perf tools, such as:
> 
>   	perf record -e probe_libc:memcpy -aR sleep 1
> 
> 
> Reported-by: Andi Kleen <andi@firstfloor.org>
> Fixes: cb4027308570 ("perf probe: Trace a magic number if variable is not found")
> Cc: stable@vger.kernel.org
> Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>

Tested-by: Andi Kleen <ak@linux.intel.com>

Except for the minor nit on the message all patches look good to me.

-Andi