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    SubjectRe: [PATCH 2/4] perf-probe: Fix wrong variable warning when the probe point is not found
    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

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