From ad5d76aecdcfe73a4093a9755a991f172d2d2492 Mon Sep 17 00:00:00 2001 From: Namhyung Kim Date: Wed, 27 Nov 2024 17:03:25 -0800 Subject: [PATCH] perf tools: Avoid unaligned pointer operations 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 Reviewed-by: Kan Liang Signed-off-by: Namhyung Kim Cc: Adrian Hunter Cc: Ingo Molnar Cc: Jiri Olsa Cc: Peter Zijlstra Link: https://lore.kernel.org/r/20241128010325.946897-1-namhyung@kernel.org Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/util/synthetic-events.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) diff --git a/tools/perf/util/synthetic-events.c b/tools/perf/util/synthetic-events.c index a58444c4aed1f1..6923b0d5efede4 100644 --- a/tools/perf/util/synthetic-events.c +++ b/tools/perf/util/synthetic-events.c @@ -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; + + *array32 = sample->raw_size; + array32++; + + memcpy(array32, sample->raw_data, sample->raw_size); + array = (void *)(array32 + (sample->raw_size / sizeof(u32))); - memcpy(array, sample->raw_data, sample->raw_size); - array = (void *)array + sample->raw_size; + /* make sure the array is 64-bit aligned */ + BUG_ON(((long)array) % sizeof(u64)); } if (type & PERF_SAMPLE_BRANCH_STACK) {