[PATCH v2 3/8] perf build-id: Reduce size of "size" variable

Ian Rogers
2025-04-24T19:58:41Z

Later clean up of the dso_id to include a build_id will suffer from
alignment and size issues. The size can only hold up to a value of
BUILD_ID_SIZE (20) and the mmap2 event uses a byte for the value.

Signed-off-by: Ian Rogers <irogers@google.com>
---
tools/perf/util/build-id.h | 2 +-
tools/perf/util/synthetic-events.c | 8 ++++++--
2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/tools/perf/util/build-id.h b/tools/perf/util/build-id.h
index a212497bfdb0..e3e0a446ff0c 100644
--- a/tools/perf/util/build-id.h
+++ b/tools/perf/util/build-id.h
@@ -13,7 +13,7 @@

struct build_id {
u8 data[BUILD_ID_SIZE];
- size_t size;
+ u8 size;
};

struct dso;
diff --git a/tools/perf/util/synthetic-events.c b/tools/perf/util/synthetic-events.c
index 2fc4d0537840..68bb7c5fe1b1 100644
--- a/tools/perf/util/synthetic-events.c
+++ b/tools/perf/util/synthetic-events.c
@@ -2248,7 +2248,9 @@ int perf_event__synthesize_build_id(const struct perf_tool *tool,

memset(&ev, 0, len);

- ev.build_id.size = min(bid->size, sizeof(ev.build_id.build_id));
+ ev.build_id.size = bid->size;
+ if (ev.build_id.size > sizeof(ev.build_id.build_id))
+ ev.build_id.size = sizeof(ev.build_id.build_id);
memcpy(ev.build_id.build_id, bid->data, ev.build_id.size);
ev.build_id.header.type = PERF_RECORD_HEADER_BUILD_ID;
ev.build_id.header.misc = misc | PERF_RECORD_MISC_BUILD_ID_SIZE;
@@ -2308,7 +2310,9 @@ int perf_event__synthesize_mmap2_build_id(const struct perf_tool *tool,
ev.mmap2.len = len;
ev.mmap2.pgoff = pgoff;

- ev.mmap2.build_id_size = min(bid->size, sizeof(ev.mmap2.build_id));
+ ev.mmap2.build_id_size = bid->size;
+ if (ev.mmap2.build_id_size > sizeof(ev.mmap2.build_id))
+ ev.build_id.size = sizeof(ev.mmap2.build_id);
memcpy(ev.mmap2.build_id, bid->data, ev.mmap2.build_id_size);

ev.mmap2.prot = prot;
--
2.49.0.850.g28803427d3-goog