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perf tools: Avoid unaligned pointer operations

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The sample data is 64-bit aligned basically but raw data starts with
32-bit length field and data follows.  In perf_event__synthesize_sample
it treats the sample data as a 64-bit array.  And it needs some trick
to update the raw data properly.

But it seems some compilers are not happy with this and the program dies
siliently.  I found the sample parsing test failed without any messages
on affected systems.

Let's update the code to use a 32-bit pointer directly and make sure the
result is 64-bit aligned again.  No functional changes intended.

Reviewed-by: Ian Rogers <irogers@google.com>
Reviewed-by: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20241128010325.946897-1-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Namhyung Kim 2024-11-27 17:03:25 -08:00 committed by Arnaldo Carvalho de Melo
parent b1ef2559d5
commit ad5d76aecd
1 changed files with 9 additions and 5 deletions
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14
tools/perf/util/synthetic-events.c
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@ -1686,12 +1686,16 @@ int perf_event__synthesize_sample(union perf_event *event, u64 type, u64 read_fo
}
if (type & PERF_SAMPLE_RAW) {
u.val32[0] = sample->raw_size;
*array = u.val64;
array = (void *)array + sizeof(u32);
u32 *array32 = (void *)array;
memcpy(array, sample->raw_data, sample->raw_size);
array = (void *)array + sample->raw_size;
*array32 = sample->raw_size;
array32++;
memcpy(array32, sample->raw_data, sample->raw_size);
array = (void *)(array32 + (sample->raw_size / sizeof(u32)));
/* make sure the array is 64-bit aligned */
BUG_ON(((long)array) % sizeof(u64));
}
if (type & PERF_SAMPLE_BRANCH_STACK) {