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Subject[PATCH 1/3] perf tools: Set proper module name when build-id event found
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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>
---
tools/perf/util/header.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index 314a07151fb7..56b8a479223b 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -1469,8 +1469,16 @@ static int __event_process_build_id(struct build_id_event *bev,

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 = {};
+
+ 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);
--
2.13.0
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