linux-kernel - [PATCH v1 1/5] perf build-id: Reduce size of "size" variable

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Message-ID: <20250424061943.1321025-2-irogers@google.com>
Date: Wed, 23 Apr 2025 23:19:39 -0700
From: Ian Rogers <irogers@...gle.com>
To: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>, 
	Mark Rutland <mark.rutland@....com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	Ian Rogers <irogers@...gle.com>, Adrian Hunter <adrian.hunter@...el.com>, 
	Kan Liang <kan.liang@...ux.intel.com>, Athira Rajeev <atrajeev@...ux.ibm.com>, 
	Kajol Jain <kjain@...ux.ibm.com>, Li Huafei <lihuafei1@...wei.com>, 
	"Steinar H. Gunderson" <sesse@...gle.com>, Stephen Brennan <stephen.s.brennan@...cle.com>, 
	James Clark <james.clark@...aro.org>, Andi Kleen <ak@...ux.intel.com>, 
	Dmitry Vyukov <dvyukov@...gle.com>, Zhongqiu Han <quic_zhonhan@...cinc.com>, 
	Yicong Yang <yangyicong@...ilicon.com>, Michael Petlan <mpetlan@...hat.com>, 
	"Krzysztof Łopatowski" <krzysztof.m.lopatowski@...il.com>, 
	"Dr. David Alan Gilbert" <linux@...blig.org>, Leo Yan <leo.yan@....com>, 
	Steve Clevenger <scclevenger@...amperecomputing.com>, Zixian Cai <fzczx123@...il.com>, 
	Thomas Falcon <thomas.falcon@...el.com>, Martin Liska <martin.liska@....com>, 
	"Martin Liška" <m.liska@...link.cz>, linux-perf-users@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: [PATCH v1 1/5] perf build-id: Reduce size of "size" variable

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@...gle.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;
-- 
2.49.0.805.g082f7c87e0-goog