From: Ian Rogers <irogers@google.com>
To: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Namhyung Kim <namhyung@kernel.org>,
Adrian Hunter <adrian.hunter@intel.com>,
James Clark <james.clark@linaro.org>,
Leo Yan <leo.yan@linux.dev>,
Ravi Bangoria <ravi.bangoria@amd.com>,
linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org,
thomas.falcon@intel.com, dapeng1.mi@linux.intel.com
Cc: Ian Rogers <irogers@google.com>
Subject: [PATCH v1 1/2] perf event: Fix size of synthesized sample with branch stacks
Date: Tue, 28 Apr 2026 00:03:27 -0700 [thread overview]
Message-ID: <20260428070328.1880314-2-irogers@google.com> (raw)
In-Reply-To: <20260428070328.1880314-1-irogers@google.com>
Synthesizing branch stacks for Intel-PT highlighed an issue where
PERF_SAMPLE_BRANCH_HW_INDEX was assumed to always be set in the
perf_event_attr branch_sample_type. This caused an incorrect size
calculation.
Fix the writing of the nr and hw_idx values during sample event
synthesis.
Assisted-by: Gemini:gemini-3.1-pro-preview
Signed-off-by: Ian Rogers <irogers@google.com>
---
tools/perf/bench/inject-buildid.c | 9 ++++++---
tools/perf/builtin-inject.c | 12 +++++++++---
tools/perf/tests/dlfilter-test.c | 8 ++++++--
tools/perf/tests/sample-parsing.c | 5 +++--
tools/perf/util/arm-spe.c | 7 +++++--
tools/perf/util/cs-etm.c | 6 ++++--
tools/perf/util/intel-bts.c | 3 ++-
tools/perf/util/intel-pt.c | 7 +++++--
tools/perf/util/synthetic-events.c | 25 ++++++++++++++++++-------
tools/perf/util/synthetic-events.h | 6 ++++--
10 files changed, 62 insertions(+), 26 deletions(-)
diff --git a/tools/perf/bench/inject-buildid.c b/tools/perf/bench/inject-buildid.c
index aad572a78d7f..bfd2c5ec9488 100644
--- a/tools/perf/bench/inject-buildid.c
+++ b/tools/perf/bench/inject-buildid.c
@@ -228,9 +228,12 @@ static ssize_t synthesize_sample(struct bench_data *data, struct bench_dso *dso,
event.header.type = PERF_RECORD_SAMPLE;
event.header.misc = PERF_RECORD_MISC_USER;
- event.header.size = perf_event__sample_event_size(&sample, bench_sample_type, 0);
-
- perf_event__synthesize_sample(&event, bench_sample_type, 0, &sample);
+ event.header.size = perf_event__sample_event_size(&sample, bench_sample_type,
+ /*read_format=*/0,
+ /*branch_sample_type=*/0);
+ perf_event__synthesize_sample(&event, bench_sample_type,
+ /*read_format=*/0,
+ /*branch_sample_type=*/0, &sample);
return writen(data->input_pipe[1], &event, event.header.size);
}
diff --git a/tools/perf/builtin-inject.c b/tools/perf/builtin-inject.c
index f174bc69cec4..0c51cb4250d1 100644
--- a/tools/perf/builtin-inject.c
+++ b/tools/perf/builtin-inject.c
@@ -463,8 +463,13 @@ static int perf_event__convert_sample_callchain(const struct perf_tool *tool,
/* remove sample_type {STACK,REGS}_USER for synthesize */
sample_type &= ~(PERF_SAMPLE_STACK_USER | PERF_SAMPLE_REGS_USER);
- perf_event__synthesize_sample(event_copy, sample_type,
- evsel->core.attr.read_format, sample);
+ ret = perf_event__synthesize_sample(event_copy, evsel->core.attr.sample_type,
+ evsel->core.attr.read_format,
+ evsel->core.attr.branch_sample_type, sample);
+ if (ret) {
+ pr_err("Failed to synthesize sample\n");
+ return ret;
+ }
return perf_event__repipe_synth(tool, event_copy);
}
@@ -1100,7 +1105,8 @@ static int perf_inject__sched_stat(const struct perf_tool *tool,
sample_sw.period = sample->period;
sample_sw.time = sample->time;
perf_event__synthesize_sample(event_sw, evsel->core.attr.sample_type,
- evsel->core.attr.read_format, &sample_sw);
+ evsel->core.attr.read_format,
+ evsel->core.attr.branch_sample_type, &sample_sw);
build_id__mark_dso_hit(tool, event_sw, &sample_sw, evsel, machine);
ret = perf_event__repipe(tool, event_sw, &sample_sw, machine);
perf_sample__exit(&sample_sw);
diff --git a/tools/perf/tests/dlfilter-test.c b/tools/perf/tests/dlfilter-test.c
index e63790c61d53..204663571943 100644
--- a/tools/perf/tests/dlfilter-test.c
+++ b/tools/perf/tests/dlfilter-test.c
@@ -188,8 +188,12 @@ static int write_sample(struct test_data *td, u64 sample_type, u64 id, pid_t pid
event->header.type = PERF_RECORD_SAMPLE;
event->header.misc = PERF_RECORD_MISC_USER;
- event->header.size = perf_event__sample_event_size(&sample, sample_type, 0);
- err = perf_event__synthesize_sample(event, sample_type, 0, &sample);
+ event->header.size = perf_event__sample_event_size(&sample, sample_type,
+ /*read_format=*/0,
+ /*branch_sample_type=*/0);
+ err = perf_event__synthesize_sample(event, sample_type,
+ /*read_format=*/0,
+ /*branch_sample_type=*/0, &sample);
if (err)
return test_result("perf_event__synthesize_sample() failed", TEST_FAIL);
diff --git a/tools/perf/tests/sample-parsing.c b/tools/perf/tests/sample-parsing.c
index a7327c942ca2..55f0b73ca20e 100644
--- a/tools/perf/tests/sample-parsing.c
+++ b/tools/perf/tests/sample-parsing.c
@@ -310,7 +310,8 @@ static int do_test(u64 sample_type, u64 sample_regs, u64 read_format)
sample.read.one.lost = 1;
}
- sz = perf_event__sample_event_size(&sample, sample_type, read_format);
+ sz = perf_event__sample_event_size(&sample, sample_type, read_format,
+ evsel.core.attr.branch_sample_type);
bufsz = sz + 4096; /* Add a bit for overrun checking */
event = malloc(bufsz);
if (!event) {
@@ -324,7 +325,7 @@ static int do_test(u64 sample_type, u64 sample_regs, u64 read_format)
event->header.size = sz;
err = perf_event__synthesize_sample(event, sample_type, read_format,
- &sample);
+ evsel.core.attr.branch_sample_type, &sample);
if (err) {
pr_debug("%s failed for sample_type %#"PRIx64", error %d\n",
"perf_event__synthesize_sample", sample_type, err);
diff --git a/tools/perf/util/arm-spe.c b/tools/perf/util/arm-spe.c
index e5835042acdf..c4ed9f10e731 100644
--- a/tools/perf/util/arm-spe.c
+++ b/tools/perf/util/arm-spe.c
@@ -484,8 +484,11 @@ static void arm_spe__prep_branch_stack(struct arm_spe_queue *speq)
static int arm_spe__inject_event(union perf_event *event, struct perf_sample *sample, u64 type)
{
- event->header.size = perf_event__sample_event_size(sample, type, 0);
- return perf_event__synthesize_sample(event, type, 0, sample);
+ event->header.type = PERF_RECORD_SAMPLE;
+ event->header.size = perf_event__sample_event_size(sample, type, /*read_format=*/0,
+ /*branch_sample_type=*/0);
+ return perf_event__synthesize_sample(event, type, /*read_format=*/0,
+ /*branch_sample_type=*/0, sample);
}
static inline int
diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c
index 8a639d2e51a4..1ebc1a6a5e75 100644
--- a/tools/perf/util/cs-etm.c
+++ b/tools/perf/util/cs-etm.c
@@ -1425,8 +1425,10 @@ static void cs_etm__update_last_branch_rb(struct cs_etm_queue *etmq,
static int cs_etm__inject_event(union perf_event *event,
struct perf_sample *sample, u64 type)
{
- event->header.size = perf_event__sample_event_size(sample, type, 0);
- return perf_event__synthesize_sample(event, type, 0, sample);
+ event->header.size = perf_event__sample_event_size(sample, type, /*read_format=*/0,
+ /*branch_sample_type=*/0);
+ return perf_event__synthesize_sample(event, type, /*read_format=*/0,
+ /*branch_sample_type=*/0, sample);
}
diff --git a/tools/perf/util/intel-bts.c b/tools/perf/util/intel-bts.c
index 382255393fb3..0b18ebd13f7c 100644
--- a/tools/perf/util/intel-bts.c
+++ b/tools/perf/util/intel-bts.c
@@ -303,7 +303,8 @@ static int intel_bts_synth_branch_sample(struct intel_bts_queue *btsq,
event.sample.header.size = bts->branches_event_size;
ret = perf_event__synthesize_sample(&event,
bts->branches_sample_type,
- 0, &sample);
+ /*read_format=*/0, /*branch_sample_type=*/0,
+ &sample);
if (ret)
return ret;
}
diff --git a/tools/perf/util/intel-pt.c b/tools/perf/util/intel-pt.c
index fc9eec8b54b8..5142983e3243 100644
--- a/tools/perf/util/intel-pt.c
+++ b/tools/perf/util/intel-pt.c
@@ -1731,8 +1731,11 @@ static void intel_pt_prep_b_sample(struct intel_pt *pt,
static int intel_pt_inject_event(union perf_event *event,
struct perf_sample *sample, u64 type)
{
- event->header.size = perf_event__sample_event_size(sample, type, 0);
- return perf_event__synthesize_sample(event, type, 0, sample);
+ event->header.size = perf_event__sample_event_size(sample, type, /*read_format=*/0,
+ /*branch_sample_type=*/0);
+
+ return perf_event__synthesize_sample(event, type, /*read_format=*/0,
+ /*branch_sample_type=*/0, sample);
}
static inline int intel_pt_opt_inject(struct intel_pt *pt,
diff --git a/tools/perf/util/synthetic-events.c b/tools/perf/util/synthetic-events.c
index 85bee747f4cd..2461f25a4d7d 100644
--- a/tools/perf/util/synthetic-events.c
+++ b/tools/perf/util/synthetic-events.c
@@ -1455,7 +1455,8 @@ int perf_event__synthesize_stat_round(const struct perf_tool *tool,
return process(tool, (union perf_event *) &event, NULL, machine);
}
-size_t perf_event__sample_event_size(const struct perf_sample *sample, u64 type, u64 read_format)
+size_t perf_event__sample_event_size(const struct perf_sample *sample, u64 type, u64 read_format,
+ u64 branch_sample_type)
{
size_t sz, result = sizeof(struct perf_record_sample);
@@ -1515,8 +1516,10 @@ size_t perf_event__sample_event_size(const struct perf_sample *sample, u64 type,
if (type & PERF_SAMPLE_BRANCH_STACK) {
sz = sample->branch_stack->nr * sizeof(struct branch_entry);
- /* nr, hw_idx */
- sz += 2 * sizeof(u64);
+ /* nr */
+ sz += sizeof(u64);
+ if (branch_sample_type & PERF_SAMPLE_BRANCH_HW_INDEX)
+ sz += sizeof(u64);
result += sz;
}
@@ -1605,7 +1608,7 @@ static __u64 *copy_read_group_values(__u64 *array, __u64 read_format,
}
int perf_event__synthesize_sample(union perf_event *event, u64 type, u64 read_format,
- const struct perf_sample *sample)
+ u64 branch_sample_type, const struct perf_sample *sample)
{
__u64 *array;
size_t sz;
@@ -1719,9 +1722,17 @@ int perf_event__synthesize_sample(union perf_event *event, u64 type, u64 read_fo
if (type & PERF_SAMPLE_BRANCH_STACK) {
sz = sample->branch_stack->nr * sizeof(struct branch_entry);
- /* nr, hw_idx */
- sz += 2 * sizeof(u64);
- memcpy(array, sample->branch_stack, sz);
+
+ *array++ = sample->branch_stack->nr;
+
+ if (branch_sample_type & PERF_SAMPLE_BRANCH_HW_INDEX) {
+ if (sample->no_hw_idx)
+ *array++ = 0;
+ else
+ *array++ = sample->branch_stack->hw_idx;
+ }
+
+ memcpy(array, perf_sample__branch_entries((struct perf_sample *)sample), sz);
array = (void *)array + sz;
}
diff --git a/tools/perf/util/synthetic-events.h b/tools/perf/util/synthetic-events.h
index b0edad0c3100..8c7f49f9ccf5 100644
--- a/tools/perf/util/synthetic-events.h
+++ b/tools/perf/util/synthetic-events.h
@@ -81,7 +81,8 @@ int perf_event__synthesize_mmap_events(const struct perf_tool *tool, union perf_
int perf_event__synthesize_modules(const struct perf_tool *tool, perf_event__handler_t process, struct machine *machine);
int perf_event__synthesize_namespaces(const struct perf_tool *tool, union perf_event *event, pid_t pid, pid_t tgid, perf_event__handler_t process, struct machine *machine);
int perf_event__synthesize_cgroups(const struct perf_tool *tool, perf_event__handler_t process, struct machine *machine);
-int perf_event__synthesize_sample(union perf_event *event, u64 type, u64 read_format, const struct perf_sample *sample);
+int perf_event__synthesize_sample(union perf_event *event, u64 type, u64 read_format,
+ u64 branch_sample_type, const struct perf_sample *sample);
int perf_event__synthesize_stat_config(const struct perf_tool *tool, struct perf_stat_config *config, perf_event__handler_t process, struct machine *machine);
int perf_event__synthesize_stat_events(struct perf_stat_config *config, const struct perf_tool *tool, struct evlist *evlist, perf_event__handler_t process, bool attrs);
int perf_event__synthesize_stat_round(const struct perf_tool *tool, u64 time, u64 type, perf_event__handler_t process, struct machine *machine);
@@ -97,7 +98,8 @@ void perf_event__synthesize_final_bpf_metadata(struct perf_session *session,
int perf_tool__process_synth_event(const struct perf_tool *tool, union perf_event *event, struct machine *machine, perf_event__handler_t process);
-size_t perf_event__sample_event_size(const struct perf_sample *sample, u64 type, u64 read_format);
+size_t perf_event__sample_event_size(const struct perf_sample *sample, u64 type,
+ u64 read_format, u64 branch_sample_type);
int __machine__synthesize_threads(struct machine *machine, const struct perf_tool *tool,
struct target *target, struct perf_thread_map *threads,
--
2.54.0.545.g6539524ca2-goog
next prev parent reply other threads:[~2026-04-28 7:03 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-04-28 7:03 [PATCH v1 0/2] perf inject intel-PT LBR/brstack synthesis fixes Ian Rogers
2026-04-28 7:03 ` Ian Rogers [this message]
2026-04-28 23:19 ` [PATCH v1 1/2] perf event: Fix size of synthesized sample with branch stacks Namhyung Kim
2026-04-28 7:03 ` [PATCH v1 2/2] perf inject: Fix itrace branch stack synthesis Ian Rogers
2026-04-28 20:20 ` sashiko-bot
2026-04-29 18:11 ` [PATCH v2 0/2] perf inject intel-PT LBR/brstack synthesis fixes Ian Rogers
2026-04-29 18:11 ` [PATCH v2 1/2] perf event: Fix size of synthesized sample with branch stacks Ian Rogers
2026-04-29 20:51 ` sashiko-bot
2026-04-29 18:11 ` [PATCH v2 2/2] perf inject: Fix itrace branch stack synthesis Ian Rogers
2026-04-29 21:18 ` sashiko-bot
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20260428070328.1880314-2-irogers@google.com \
--to=irogers@google.com \
--cc=acme@kernel.org \
--cc=adrian.hunter@intel.com \
--cc=dapeng1.mi@linux.intel.com \
--cc=james.clark@linaro.org \
--cc=leo.yan@linux.dev \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-perf-users@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=namhyung@kernel.org \
--cc=peterz@infradead.org \
--cc=ravi.bangoria@amd.com \
--cc=thomas.falcon@intel.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.