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    Subject[PATCH 4.9 195/310] perf header: Set proper module name when build-id event found
    Date
    4.9-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Namhyung Kim <namhyung@kernel.org>


    [ Upstream commit 1deec1bd96ccd8beb04d2112a6d12fe20505c3a6 ]

    When perf processes build-id event, it creates DSOs with the build-id.
    But it didn't set the module short name (like '[module-name]') so when
    processing a kernel mmap event of the module, it cannot found the DSO as
    it only checks the short names.

    That leads for perf to create a same DSO without the build-id info and
    it'll lookup the system path even if the DSO is already in the build-id
    cache. After kernel was updated, perf cannot find the DSO and cannot
    show symbols in it anymore.

    You can see this if you have an old data file (w/ old kernel version):

    $ perf report -i perf.data.old -v |& grep scsi_mod
    build id event received for /lib/modules/3.19.2-1-ARCH/kernel/drivers/scsi/scsi_mod.ko.gz : cafe1ce6ca13a98a5d9ed3425cde249e57a27fc1
    Failed to open /lib/modules/3.19.2-1-ARCH/kernel/drivers/scsi/scsi_mod.ko.gz, continuing without symbols
    ...

    The second message didn't show the build-id. With this patch:

    $ perf report -i perf.data.old -v |& grep scsi_mod
    build id event received for /lib/modules/3.19.2-1-ARCH/kernel/drivers/scsi/scsi_mod.ko.gz: cafe1ce6ca13a98a5d9ed3425cde249e57a27fc1
    /lib/modules/3.19.2-1-ARCH/kernel/drivers/scsi/scsi_mod.ko.gz with build id cafe1ce6ca13a98a5d9ed3425cde249e57a27fc1 not found, continuing without symbols
    ...

    Now it shows the build-id but still cannot load the symbol table. This
    is a different problem which will be fixed in the next patch.

    Signed-off-by: Namhyung Kim <namhyung@kernel.org>
    Acked-by: Jiri Olsa <jolsa@kernel.org>
    Cc: Andi Kleen <andi@firstfloor.org>
    Cc: David Ahern <dsahern@gmail.com>
    Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
    Cc: kernel-team@lge.com
    Link: http://lkml.kernel.org/r/20170531120105.21731-1-namhyung@kernel.org
    [ Fix the build on older compilers (debian <= 8, fedora <= 21, etc) wrt kmod_path var init ]
    Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
    Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    tools/perf/util/header.c | 12 ++++++++++--
    1 file changed, 10 insertions(+), 2 deletions(-)

    --- a/tools/perf/util/header.c
    +++ b/tools/perf/util/header.c
    @@ -1454,8 +1454,16 @@ static int __event_process_build_id(stru

    dso__set_build_id(dso, &bev->build_id);

    - if (!is_kernel_module(filename, cpumode))
    - dso->kernel = dso_type;
    + if (dso_type != DSO_TYPE_USER) {
    + struct kmod_path m = { .name = NULL, };
    +
    + if (!kmod_path__parse_name(&m, filename) && m.kmod)
    + dso__set_short_name(dso, strdup(m.name), true);
    + else
    + dso->kernel = dso_type;
    +
    + free(m.name);
    + }

    build_id__sprintf(dso->build_id, sizeof(dso->build_id),
    sbuild_id);

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