4.9-stable review patch. If anyone has any objections, please let me know.
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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);