perf bench inject-buildid: Handle writen() errors

The build on fedora:35 and fedora:rawhide with clang is failing with:

  49    41.00 fedora:35                     : FAIL clang version 13.0.0 (Fedora 13.0.0~rc1-1.fc35)
    bench/inject-buildid.c:351:6: error: variable 'len' set but not used [-Werror,-Wunused-but-set-variable]
            u64 len = 0;
                ^
    1 error generated.
    make[3]: *** [/git/perf-5.14.0-rc7/tools/build/Makefile.build:139: bench] Error 2
  50    41.11 fedora:rawhide                : FAIL clang version 13.0.0 (Fedora 13.0.0~rc1-1.fc35)
    bench/inject-buildid.c:351:6: error: variable 'len' set but not used [-Werror,-Wunused-but-set-variable]
            u64 len = 0;
                ^
    1 error generated.
    make[3]: *** [/git/perf-5.14.0-rc7/tools/build/Makefile.build:139: bench] Error 2

That 'len' variable is not used at all, so just make sure all the
synthesize_RECORD() routines return ssize_t to propagate the writen()
return, as it may fail, ditch the 'ret' var and bail out if those
routines fail.

Fixes: 0bf02a0d80 ("perf bench: Add build-id injection benchmark")
Acked-by: Namhyung Kim <namhyung@kernel.org>
Link: http://lore.kernel.org/lkml/CAM9d7cgEZNSor+B+7Y2C+QYGme_v5aH0Zn0RLfxoQ+Fy83EHrg@mail.gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/bench/inject-buildid.c

@@ -133,7 +133,7 @@ static u64 dso_map_addr(struct bench_dso *dso)
 	return 0x400000ULL + dso->ino * 8192ULL;
 }
 
-static u32 synthesize_attr(struct bench_data *data)
+static ssize_t synthesize_attr(struct bench_data *data)
 {
 	union perf_event event;
 
@@ -151,7 +151,7 @@ static u32 synthesize_attr(struct bench_data *data)
 	return writen(data->input_pipe[1], &event, event.header.size);
 }
 
-static u32 synthesize_fork(struct bench_data *data)
+static ssize_t synthesize_fork(struct bench_data *data)
 {
 	union perf_event event;
 
@@ -169,8 +169,7 @@ static u32 synthesize_fork(struct bench_data *data)
 	return writen(data->input_pipe[1], &event, event.header.size);
 }
 
-static u32 synthesize_mmap(struct bench_data *data, struct bench_dso *dso,
-			   u64 timestamp)
+static ssize_t synthesize_mmap(struct bench_data *data, struct bench_dso *dso, u64 timestamp)
 {
 	union perf_event event;
 	size_t len = offsetof(struct perf_record_mmap2, filename);
@@ -198,23 +197,25 @@ static u32 synthesize_mmap(struct bench_data *data, struct bench_dso *dso,
 
 	if (len > sizeof(event.mmap2)) {
 		/* write mmap2 event first */
-		writen(data->input_pipe[1], &event, len - bench_id_hdr_size);
+		if (writen(data->input_pipe[1], &event, len - bench_id_hdr_size) < 0)
+			return -1;
 		/* zero-fill sample id header */
 		memset(id_hdr_ptr, 0, bench_id_hdr_size);
 		/* put timestamp in the right position */
 		ts_idx = (bench_id_hdr_size / sizeof(u64)) - 2;
 		id_hdr_ptr[ts_idx] = timestamp;
-		writen(data->input_pipe[1], id_hdr_ptr, bench_id_hdr_size);
-	} else {
-		ts_idx = (len / sizeof(u64)) - 2;
-		id_hdr_ptr[ts_idx] = timestamp;
-		writen(data->input_pipe[1], &event, len);
-	}
+		if (writen(data->input_pipe[1], id_hdr_ptr, bench_id_hdr_size) < 0)
+			return -1;
+
 		return len;
 	}
 
-static u32 synthesize_sample(struct bench_data *data, struct bench_dso *dso,
-			     u64 timestamp)
+	ts_idx = (len / sizeof(u64)) - 2;
+	id_hdr_ptr[ts_idx] = timestamp;
+	return writen(data->input_pipe[1], &event, len);
+}
+
+static ssize_t synthesize_sample(struct bench_data *data, struct bench_dso *dso, u64 timestamp)
 {
 	union perf_event event;
 	struct perf_sample sample = {
@@ -233,7 +234,7 @@ static u32 synthesize_sample(struct bench_data *data, struct bench_dso *dso,
 	return writen(data->input_pipe[1], &event, event.header.size);
 }
 
-static u32 synthesize_flush(struct bench_data *data)
+static ssize_t synthesize_flush(struct bench_data *data)
 {
 	struct perf_event_header header = {
 		.size = sizeof(header),
@@ -348,14 +349,16 @@ static int inject_build_id(struct bench_data *data, u64 *max_rss)
 	int status;
 	unsigned int i, k;
 	struct rusage rusage;
-	u64 len = 0;
 
 	/* this makes the child to run */
 	if (perf_header__write_pipe(data->input_pipe[1]) < 0)
 		return -1;
 
-	len += synthesize_attr(data);
-	len += synthesize_fork(data);
+	if (synthesize_attr(data) < 0)
+		return -1;
+
+	if (synthesize_fork(data) < 0)
+		return -1;
 
 	for (i = 0; i < nr_mmaps; i++) {
 		int idx = rand() % (nr_dsos - 1);
@@ -363,13 +366,18 @@ static int inject_build_id(struct bench_data *data, u64 *max_rss)
 		u64 timestamp = rand() % 1000000;
 
 		pr_debug2("   [%d] injecting: %s\n", i+1, dso->name);
-		len += synthesize_mmap(data, dso, timestamp);
+		if (synthesize_mmap(data, dso, timestamp) < 0)
+			return -1;
 
-		for (k = 0; k < nr_samples; k++)
-			len += synthesize_sample(data, dso, timestamp + k * 1000);
+		for (k = 0; k < nr_samples; k++) {
+			if (synthesize_sample(data, dso, timestamp + k * 1000) < 0)
+				return -1;
+		}
 
-		if ((i + 1) % 10 == 0)
-			len += synthesize_flush(data);
+		if ((i + 1) % 10 == 0) {
+			if (synthesize_flush(data) < 0)
+				return -1;
+		}
 	}
 
 	/* this makes the child to finish */