[PATCH v4 0/3] perf/core: Check sample_type in sample data saving helper functions

[PATCH v4 0/3] perf/core: Check sample_type in sample data saving helper functions

[Yabin Cui]

Hello,

We use helper functions to save raw data, callchain and branch stack in
perf_sample_data. These functions update perf_sample_data->dyn_size without
checking event->attr.sample_type, which may result in unused space allocated in
sample records. To prevent this from happening, this patchset enforces checking
sample_type of an event in these helper functions.

Thanks,
Yabin


Changes since v1:
 - Check event->attr.sample_type & PERF_SAMPLE_RAW before
   calling perf_sample_save_raw_data().
 - Subject has been changed to reflect the change of solution.

Changes since v2:
 - Move sample_type check into perf_sample_save_raw_data().
 - (New patch) Move sample_type check into perf_sample_save_callchain().
 - (New patch) Move sample_type check into perf_sample_save_brstack().

Changes since v3:
 - Fix -Werror=implicit-function-declaration by moving has_branch_stack().

Original commit message from v1:
  perf/core: Trim dyn_size if raw data is absent

Original commit message from v2/v3:
  perf/core: Save raw sample data conditionally based on sample type

Yabin Cui (3):
  perf/core: Save raw sample data conditionally based on sample type
  perf/core: Check sample_type in perf_sample_save_callchain
  perf/core: Check sample_type in perf_sample_save_brstack

 arch/s390/kernel/perf_cpum_cf.c    |  2 +-
 arch/s390/kernel/perf_pai_crypto.c |  2 +-
 arch/s390/kernel/perf_pai_ext.c    |  2 +-
 arch/x86/events/amd/core.c         |  3 +--
 arch/x86/events/amd/ibs.c          |  5 ++---
 arch/x86/events/core.c             |  3 +--
 arch/x86/events/intel/ds.c         |  9 +++-----
 include/linux/perf_event.h         | 20 ++++++++++++-----
 kernel/events/core.c               | 35 +++++++++++++++---------------
 kernel/trace/bpf_trace.c           | 11 +++++-----
 10 files changed, 49 insertions(+), 43 deletions(-)

-- 
2.45.0.118.g7fe29c98d7-goog

[PATCH v4 1/3] perf/core: Save raw sample data conditionally based on sample type

[Yabin Cui]

Currently, space for raw sample data is always allocated within sample
records for both BPF output and tracepoint events. This leads to unused
space in sample records when raw sample data is not requested.

This patch enforces checking sample type of an event in
perf_sample_save_raw_data(). So raw sample data will only be saved if
explicitly requested, reducing overhead when it is not needed.

Fixes: 0a9081cf0a11 ("perf/core: Add perf_sample_save_raw_data() helper")
Signed-off-by: Yabin Cui <yabinc@google.com>
---
 arch/s390/kernel/perf_cpum_cf.c    |  2 +-
 arch/s390/kernel/perf_pai_crypto.c |  2 +-
 arch/s390/kernel/perf_pai_ext.c    |  2 +-
 arch/x86/events/amd/ibs.c          |  2 +-
 include/linux/perf_event.h         |  4 ++++
 kernel/events/core.c               | 35 +++++++++++++++---------------
 kernel/trace/bpf_trace.c           | 11 +++++-----
 7 files changed, 32 insertions(+), 26 deletions(-)

diff --git a/arch/s390/kernel/perf_cpum_cf.c b/arch/s390/kernel/perf_cpum_cf.c
index 41ed6e0f0a2a..c7fb99cb1e15 100644
--- a/arch/s390/kernel/perf_cpum_cf.c
+++ b/arch/s390/kernel/perf_cpum_cf.c
@@ -971,7 +971,7 @@ static int cfdiag_push_sample(struct perf_event *event,
 	if (event->attr.sample_type & PERF_SAMPLE_RAW) {
 		raw.frag.size = cpuhw->usedss;
 		raw.frag.data = cpuhw->stop;
-		perf_sample_save_raw_data(&data, &raw);
+		perf_sample_save_raw_data(&data, event, &raw);
 	}
 
 	overflow = perf_event_overflow(event, &data, &regs);
diff --git a/arch/s390/kernel/perf_pai_crypto.c b/arch/s390/kernel/perf_pai_crypto.c
index 4ad472d130a3..2fb8aeba4872 100644
--- a/arch/s390/kernel/perf_pai_crypto.c
+++ b/arch/s390/kernel/perf_pai_crypto.c
@@ -444,7 +444,7 @@ static int paicrypt_push_sample(size_t rawsize, struct paicrypt_map *cpump,
 	if (event->attr.sample_type & PERF_SAMPLE_RAW) {
 		raw.frag.size = rawsize;
 		raw.frag.data = cpump->save;
-		perf_sample_save_raw_data(&data, &raw);
+		perf_sample_save_raw_data(&data, event, &raw);
 	}
 
 	overflow = perf_event_overflow(event, &data, &regs);
diff --git a/arch/s390/kernel/perf_pai_ext.c b/arch/s390/kernel/perf_pai_ext.c
index a6da7e0cc7a6..b2914df2107a 100644
--- a/arch/s390/kernel/perf_pai_ext.c
+++ b/arch/s390/kernel/perf_pai_ext.c
@@ -458,7 +458,7 @@ static int paiext_push_sample(size_t rawsize, struct paiext_map *cpump,
 	if (event->attr.sample_type & PERF_SAMPLE_RAW) {
 		raw.frag.size = rawsize;
 		raw.frag.data = cpump->save;
-		perf_sample_save_raw_data(&data, &raw);
+		perf_sample_save_raw_data(&data, event, &raw);
 	}
 
 	overflow = perf_event_overflow(event, &data, &regs);
diff --git a/arch/x86/events/amd/ibs.c b/arch/x86/events/amd/ibs.c
index e91970b01d62..c3a2f6f57770 100644
--- a/arch/x86/events/amd/ibs.c
+++ b/arch/x86/events/amd/ibs.c
@@ -1118,7 +1118,7 @@ static int perf_ibs_handle_irq(struct perf_ibs *perf_ibs, struct pt_regs *iregs)
 				.data = ibs_data.data,
 			},
 		};
-		perf_sample_save_raw_data(&data, &raw);
+		perf_sample_save_raw_data(&data, event, &raw);
 	}
 
 	if (perf_ibs == &perf_ibs_op)
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index d2a15c0c6f8a..9fc55193ff99 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -1240,12 +1240,16 @@ static inline void perf_sample_save_callchain(struct perf_sample_data *data,
 }
 
 static inline void perf_sample_save_raw_data(struct perf_sample_data *data,
+					     struct perf_event *event,
 					     struct perf_raw_record *raw)
 {
 	struct perf_raw_frag *frag = &raw->frag;
 	u32 sum = 0;
 	int size;
 
+	if (!(event->attr.sample_type & PERF_SAMPLE_RAW))
+		return;
+
 	do {
 		sum += frag->size;
 		if (perf_raw_frag_last(frag))
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 724e6d7e128f..3031cade53bb 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -10120,9 +10120,9 @@ static struct pmu perf_tracepoint = {
 };
 
 static int perf_tp_filter_match(struct perf_event *event,
-				struct perf_sample_data *data)
+				struct perf_raw_record *raw)
 {
-	void *record = data->raw->frag.data;
+	void *record = raw->frag.data;
 
 	/* only top level events have filters set */
 	if (event->parent)
@@ -10134,7 +10134,7 @@ static int perf_tp_filter_match(struct perf_event *event,
 }
 
 static int perf_tp_event_match(struct perf_event *event,
-				struct perf_sample_data *data,
+				struct perf_raw_record *raw,
 				struct pt_regs *regs)
 {
 	if (event->hw.state & PERF_HES_STOPPED)
@@ -10145,7 +10145,7 @@ static int perf_tp_event_match(struct perf_event *event,
 	if (event->attr.exclude_kernel && !user_mode(regs))
 		return 0;
 
-	if (!perf_tp_filter_match(event, data))
+	if (!perf_tp_filter_match(event, raw))
 		return 0;
 
 	return 1;
@@ -10171,6 +10171,7 @@ EXPORT_SYMBOL_GPL(perf_trace_run_bpf_submit);
 static void __perf_tp_event_target_task(u64 count, void *record,
 					struct pt_regs *regs,
 					struct perf_sample_data *data,
+					struct perf_raw_record *raw,
 					struct perf_event *event)
 {
 	struct trace_entry *entry = record;
@@ -10180,13 +10181,17 @@ static void __perf_tp_event_target_task(u64 count, void *record,
 	/* Cannot deliver synchronous signal to other task. */
 	if (event->attr.sigtrap)
 		return;
-	if (perf_tp_event_match(event, data, regs))
+	if (perf_tp_event_match(event, raw, regs)) {
+		perf_sample_data_init(data, 0, 0);
+		perf_sample_save_raw_data(data, event, raw);
 		perf_swevent_event(event, count, data, regs);
+	}
 }
 
 static void perf_tp_event_target_task(u64 count, void *record,
 				      struct pt_regs *regs,
 				      struct perf_sample_data *data,
+				      struct perf_raw_record *raw,
 				      struct perf_event_context *ctx)
 {
 	unsigned int cpu = smp_processor_id();
@@ -10194,15 +10199,15 @@ static void perf_tp_event_target_task(u64 count, void *record,
 	struct perf_event *event, *sibling;
 
 	perf_event_groups_for_cpu_pmu(event, &ctx->pinned_groups, cpu, pmu) {
-		__perf_tp_event_target_task(count, record, regs, data, event);
+		__perf_tp_event_target_task(count, record, regs, data, raw, event);
 		for_each_sibling_event(sibling, event)
-			__perf_tp_event_target_task(count, record, regs, data, sibling);
+			__perf_tp_event_target_task(count, record, regs, data, raw, sibling);
 	}
 
 	perf_event_groups_for_cpu_pmu(event, &ctx->flexible_groups, cpu, pmu) {
-		__perf_tp_event_target_task(count, record, regs, data, event);
+		__perf_tp_event_target_task(count, record, regs, data, raw, event);
 		for_each_sibling_event(sibling, event)
-			__perf_tp_event_target_task(count, record, regs, data, sibling);
+			__perf_tp_event_target_task(count, record, regs, data, raw, sibling);
 	}
 }
 
@@ -10220,15 +10225,10 @@ void perf_tp_event(u16 event_type, u64 count, void *record, int entry_size,
 		},
 	};
 
-	perf_sample_data_init(&data, 0, 0);
-	perf_sample_save_raw_data(&data, &raw);
-
 	perf_trace_buf_update(record, event_type);
 
 	hlist_for_each_entry_rcu(event, head, hlist_entry) {
-		if (perf_tp_event_match(event, &data, regs)) {
-			perf_swevent_event(event, count, &data, regs);
-
+		if (perf_tp_event_match(event, &raw, regs)) {
 			/*
 			 * Here use the same on-stack perf_sample_data,
 			 * some members in data are event-specific and
@@ -10238,7 +10238,8 @@ void perf_tp_event(u16 event_type, u64 count, void *record, int entry_size,
 			 * because data->sample_flags is set.
 			 */
 			perf_sample_data_init(&data, 0, 0);
-			perf_sample_save_raw_data(&data, &raw);
+			perf_sample_save_raw_data(&data, event, &raw);
+			perf_swevent_event(event, count, &data, regs);
 		}
 	}
 
@@ -10255,7 +10256,7 @@ void perf_tp_event(u16 event_type, u64 count, void *record, int entry_size,
 			goto unlock;
 
 		raw_spin_lock(&ctx->lock);
-		perf_tp_event_target_task(count, record, regs, &data, ctx);
+		perf_tp_event_target_task(count, record, regs, &data, &raw, ctx);
 		raw_spin_unlock(&ctx->lock);
 unlock:
 		rcu_read_unlock();
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 9dc605f08a23..23bcf28ccc82 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -620,7 +620,8 @@ static const struct bpf_func_proto bpf_perf_event_read_value_proto = {
 
 static __always_inline u64
 __bpf_perf_event_output(struct pt_regs *regs, struct bpf_map *map,
-			u64 flags, struct perf_sample_data *sd)
+			u64 flags, struct perf_raw_record *raw,
+			struct perf_sample_data *sd)
 {
 	struct bpf_array *array = container_of(map, struct bpf_array, map);
 	unsigned int cpu = smp_processor_id();
@@ -645,6 +646,8 @@ __bpf_perf_event_output(struct pt_regs *regs, struct bpf_map *map,
 	if (unlikely(event->oncpu != cpu))
 		return -EOPNOTSUPP;
 
+	perf_sample_save_raw_data(sd, event, raw);
+
 	return perf_event_output(event, sd, regs);
 }
 
@@ -688,9 +691,8 @@ BPF_CALL_5(bpf_perf_event_output, struct pt_regs *, regs, struct bpf_map *, map,
 	}
 
 	perf_sample_data_init(sd, 0, 0);
-	perf_sample_save_raw_data(sd, &raw);
 
-	err = __bpf_perf_event_output(regs, map, flags, sd);
+	err = __bpf_perf_event_output(regs, map, flags, &raw, sd);
 out:
 	this_cpu_dec(bpf_trace_nest_level);
 	preempt_enable();
@@ -749,9 +751,8 @@ u64 bpf_event_output(struct bpf_map *map, u64 flags, void *meta, u64 meta_size,
 
 	perf_fetch_caller_regs(regs);
 	perf_sample_data_init(sd, 0, 0);
-	perf_sample_save_raw_data(sd, &raw);
 
-	ret = __bpf_perf_event_output(regs, map, flags, sd);
+	ret = __bpf_perf_event_output(regs, map, flags, &raw, sd);
 out:
 	this_cpu_dec(bpf_event_output_nest_level);
 	preempt_enable();
-- 
2.45.0.118.g7fe29c98d7-goog

[PATCH v4 2/3] perf/core: Check sample_type in perf_sample_save_callchain

[Yabin Cui]

Check sample_type in perf_sample_save_callchain() to prevent
saving callchain data when it isn't required.

Suggested-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Yabin Cui <yabinc@google.com>
---
 arch/x86/events/amd/ibs.c  | 3 +--
 arch/x86/events/intel/ds.c | 6 ++----
 include/linux/perf_event.h | 3 +++
 3 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/arch/x86/events/amd/ibs.c b/arch/x86/events/amd/ibs.c
index c3a2f6f57770..f02939655b2a 100644
--- a/arch/x86/events/amd/ibs.c
+++ b/arch/x86/events/amd/ibs.c
@@ -1129,8 +1129,7 @@ static int perf_ibs_handle_irq(struct perf_ibs *perf_ibs, struct pt_regs *iregs)
 	 * recorded as part of interrupt regs. Thus we need to use rip from
 	 * interrupt regs while unwinding call stack.
 	 */
-	if (event->attr.sample_type & PERF_SAMPLE_CALLCHAIN)
-		perf_sample_save_callchain(&data, event, iregs);
+	perf_sample_save_callchain(&data, event, iregs);
 
 	throttle = perf_event_overflow(event, &data, &regs);
 out:
diff --git a/arch/x86/events/intel/ds.c b/arch/x86/events/intel/ds.c
index e010bfed8417..c2b5585aa6d1 100644
--- a/arch/x86/events/intel/ds.c
+++ b/arch/x86/events/intel/ds.c
@@ -1655,8 +1655,7 @@ static void setup_pebs_fixed_sample_data(struct perf_event *event,
 	 * previous PMI context or an (I)RET happened between the record and
 	 * PMI.
 	 */
-	if (sample_type & PERF_SAMPLE_CALLCHAIN)
-		perf_sample_save_callchain(data, event, iregs);
+	perf_sample_save_callchain(data, event, iregs);
 
 	/*
 	 * We use the interrupt regs as a base because the PEBS record does not
@@ -1823,8 +1822,7 @@ static void setup_pebs_adaptive_sample_data(struct perf_event *event,
 	 * previous PMI context or an (I)RET happened between the record and
 	 * PMI.
 	 */
-	if (sample_type & PERF_SAMPLE_CALLCHAIN)
-		perf_sample_save_callchain(data, event, iregs);
+	perf_sample_save_callchain(data, event, iregs);
 
 	*regs = *iregs;
 	/* The ip in basic is EventingIP */
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 9fc55193ff99..8617815456b0 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -1232,6 +1232,9 @@ static inline void perf_sample_save_callchain(struct perf_sample_data *data,
 {
 	int size = 1;
 
+	if (!(event->attr.sample_type & PERF_SAMPLE_CALLCHAIN))
+		return;
+
 	data->callchain = perf_callchain(event, regs);
 	size += data->callchain->nr;
 
-- 
2.45.0.118.g7fe29c98d7-goog

[PATCH v4 3/3] perf/core: Check sample_type in perf_sample_save_brstack

[Yabin Cui]

Check sample_type in perf_sample_save_brstack() to prevent
saving branch stack data when it isn't required.

Suggested-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Yabin Cui <yabinc@google.com>
---
 arch/x86/events/amd/core.c |  3 +--
 arch/x86/events/core.c     |  3 +--
 arch/x86/events/intel/ds.c |  3 +--
 include/linux/perf_event.h | 13 ++++++++-----
 4 files changed, 11 insertions(+), 11 deletions(-)

diff --git a/arch/x86/events/amd/core.c b/arch/x86/events/amd/core.c
index 985ef3b47919..fb9bf3aa1b42 100644
--- a/arch/x86/events/amd/core.c
+++ b/arch/x86/events/amd/core.c
@@ -967,8 +967,7 @@ static int amd_pmu_v2_handle_irq(struct pt_regs *regs)
 		if (!x86_perf_event_set_period(event))
 			continue;
 
-		if (has_branch_stack(event))
-			perf_sample_save_brstack(&data, event, &cpuc->lbr_stack, NULL);
+		perf_sample_save_brstack(&data, event, &cpuc->lbr_stack, NULL);
 
 		if (perf_event_overflow(event, &data, regs))
 			x86_pmu_stop(event, 0);
diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
index 5b0dd07b1ef1..ff5577315938 100644
--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -1702,8 +1702,7 @@ int x86_pmu_handle_irq(struct pt_regs *regs)
 
 		perf_sample_data_init(&data, 0, event->hw.last_period);
 
-		if (has_branch_stack(event))
-			perf_sample_save_brstack(&data, event, &cpuc->lbr_stack, NULL);
+		perf_sample_save_brstack(&data, event, &cpuc->lbr_stack, NULL);
 
 		if (perf_event_overflow(event, &data, regs))
 			x86_pmu_stop(event, 0);
diff --git a/arch/x86/events/intel/ds.c b/arch/x86/events/intel/ds.c
index c2b5585aa6d1..f25236ffa28f 100644
--- a/arch/x86/events/intel/ds.c
+++ b/arch/x86/events/intel/ds.c
@@ -1754,8 +1754,7 @@ static void setup_pebs_fixed_sample_data(struct perf_event *event,
 	if (x86_pmu.intel_cap.pebs_format >= 3)
 		setup_pebs_time(event, data, pebs->tsc);
 
-	if (has_branch_stack(event))
-		perf_sample_save_brstack(data, event, &cpuc->lbr_stack, NULL);
+	perf_sample_save_brstack(data, event, &cpuc->lbr_stack, NULL);
 }
 
 static void adaptive_pebs_save_regs(struct pt_regs *regs,
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 8617815456b0..ecfbe22ff299 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -1269,6 +1269,11 @@ static inline void perf_sample_save_raw_data(struct perf_sample_data *data,
 	data->sample_flags |= PERF_SAMPLE_RAW;
 }
 
+static inline bool has_branch_stack(struct perf_event *event)
+{
+	return event->attr.sample_type & PERF_SAMPLE_BRANCH_STACK;
+}
+
 static inline void perf_sample_save_brstack(struct perf_sample_data *data,
 					    struct perf_event *event,
 					    struct perf_branch_stack *brs,
@@ -1276,6 +1281,9 @@ static inline void perf_sample_save_brstack(struct perf_sample_data *data,
 {
 	int size = sizeof(u64); /* nr */
 
+	if (!has_branch_stack(event))
+		return;
+
 	if (branch_sample_hw_index(event))
 		size += sizeof(u64);
 	size += brs->nr * sizeof(struct perf_branch_entry);
@@ -1665,11 +1673,6 @@ extern void perf_bp_event(struct perf_event *event, void *data);
 # define perf_arch_bpf_user_pt_regs(regs) regs
 #endif
 
-static inline bool has_branch_stack(struct perf_event *event)
-{
-	return event->attr.sample_type & PERF_SAMPLE_BRANCH_STACK;
-}
-
 static inline bool needs_branch_stack(struct perf_event *event)
 {
 	return event->attr.branch_sample_type != 0;
-- 
2.45.0.118.g7fe29c98d7-goog

Re: [PATCH v4 0/3] perf/core: Check sample_type in sample data saving helper functions

[Ian Rogers]

On Fri, May 10, 2024 at 12:14 PM Yabin Cui <yabinc@google.com> wrote:
>
> Hello,
>
> We use helper functions to save raw data, callchain and branch stack in
> perf_sample_data. These functions update perf_sample_data->dyn_size without
> checking event->attr.sample_type, which may result in unused space allocated in
> sample records. To prevent this from happening, this patchset enforces checking
> sample_type of an event in these helper functions.
>
> Thanks,
> Yabin
>
>
> Changes since v1:
>  - Check event->attr.sample_type & PERF_SAMPLE_RAW before
>    calling perf_sample_save_raw_data().
>  - Subject has been changed to reflect the change of solution.
>
> Changes since v2:
>  - Move sample_type check into perf_sample_save_raw_data().
>  - (New patch) Move sample_type check into perf_sample_save_callchain().
>  - (New patch) Move sample_type check into perf_sample_save_brstack().
>
> Changes since v3:
>  - Fix -Werror=implicit-function-declaration by moving has_branch_stack().
>
> Original commit message from v1:
>   perf/core: Trim dyn_size if raw data is absent
>
> Original commit message from v2/v3:
>   perf/core: Save raw sample data conditionally based on sample type
>
> Yabin Cui (3):
>   perf/core: Save raw sample data conditionally based on sample type
>   perf/core: Check sample_type in perf_sample_save_callchain
>   perf/core: Check sample_type in perf_sample_save_brstack

Reviewed-by: Ian Rogers <irogers@google.com>

Thanks,
Ian

>  arch/s390/kernel/perf_cpum_cf.c    |  2 +-
>  arch/s390/kernel/perf_pai_crypto.c |  2 +-
>  arch/s390/kernel/perf_pai_ext.c    |  2 +-
>  arch/x86/events/amd/core.c         |  3 +--
>  arch/x86/events/amd/ibs.c          |  5 ++---
>  arch/x86/events/core.c             |  3 +--
>  arch/x86/events/intel/ds.c         |  9 +++-----
>  include/linux/perf_event.h         | 20 ++++++++++++-----
>  kernel/events/core.c               | 35 +++++++++++++++---------------
>  kernel/trace/bpf_trace.c           | 11 +++++-----
>  10 files changed, 49 insertions(+), 43 deletions(-)
>
> --
> 2.45.0.118.g7fe29c98d7-goog
>

Re: [PATCH v4 0/3] perf/core: Check sample_type in sample data saving helper functions

[Namhyung Kim]

Hi Yabin,

On Fri, May 10, 2024 at 12:14 PM Yabin Cui <yabinc@google.com> wrote:
>
> Hello,
>
> We use helper functions to save raw data, callchain and branch stack in
> perf_sample_data. These functions update perf_sample_data->dyn_size without
> checking event->attr.sample_type, which may result in unused space allocated in
> sample records. To prevent this from happening, this patchset enforces checking
> sample_type of an event in these helper functions.
>
> Thanks,
> Yabin
>
>
> Changes since v1:
>  - Check event->attr.sample_type & PERF_SAMPLE_RAW before
>    calling perf_sample_save_raw_data().
>  - Subject has been changed to reflect the change of solution.
>
> Changes since v2:
>  - Move sample_type check into perf_sample_save_raw_data().
>  - (New patch) Move sample_type check into perf_sample_save_callchain().
>  - (New patch) Move sample_type check into perf_sample_save_brstack().
>
> Changes since v3:
>  - Fix -Werror=implicit-function-declaration by moving has_branch_stack().
>
> Original commit message from v1:
>   perf/core: Trim dyn_size if raw data is absent
>
> Original commit message from v2/v3:
>   perf/core: Save raw sample data conditionally based on sample type
>
> Yabin Cui (3):
>   perf/core: Save raw sample data conditionally based on sample type
>   perf/core: Check sample_type in perf_sample_save_callchain
>   perf/core: Check sample_type in perf_sample_save_brstack

Thanks for doing this!

Acked-by: Namhyung Kim <namhyung@kernel.org>

Thanks,
Namhyung

>
>  arch/s390/kernel/perf_cpum_cf.c    |  2 +-
>  arch/s390/kernel/perf_pai_crypto.c |  2 +-
>  arch/s390/kernel/perf_pai_ext.c    |  2 +-
>  arch/x86/events/amd/core.c         |  3 +--
>  arch/x86/events/amd/ibs.c          |  5 ++---
>  arch/x86/events/core.c             |  3 +--
>  arch/x86/events/intel/ds.c         |  9 +++-----
>  include/linux/perf_event.h         | 20 ++++++++++++-----
>  kernel/events/core.c               | 35 +++++++++++++++---------------
>  kernel/trace/bpf_trace.c           | 11 +++++-----
>  10 files changed, 49 insertions(+), 43 deletions(-)
>
> --
> 2.45.0.118.g7fe29c98d7-goog
>

Re: [PATCH v4 3/3] perf/core: Check sample_type in perf_sample_save_brstack

[Namhyung Kim]

On Fri, May 10, 2024 at 12:14 PM Yabin Cui <yabinc@google.com> wrote:
>
> Check sample_type in perf_sample_save_brstack() to prevent
> saving branch stack data when it isn't required.
>
> Suggested-by: Namhyung Kim <namhyung@kernel.org>
> Signed-off-by: Yabin Cui <yabinc@google.com>

It seems powerpc has the similar bug, then you need this:

Fixes: eb55b455ef9c ("perf/core: Add perf_sample_save_brstack() helper")

Thanks,
Namhyung

> ---
>  arch/x86/events/amd/core.c |  3 +--
>  arch/x86/events/core.c     |  3 +--
>  arch/x86/events/intel/ds.c |  3 +--
>  include/linux/perf_event.h | 13 ++++++++-----
>  4 files changed, 11 insertions(+), 11 deletions(-)
>
> diff --git a/arch/x86/events/amd/core.c b/arch/x86/events/amd/core.c
> index 985ef3b47919..fb9bf3aa1b42 100644
> --- a/arch/x86/events/amd/core.c
> +++ b/arch/x86/events/amd/core.c
> @@ -967,8 +967,7 @@ static int amd_pmu_v2_handle_irq(struct pt_regs *regs)
>                 if (!x86_perf_event_set_period(event))
>                         continue;
>
> -               if (has_branch_stack(event))
> -                       perf_sample_save_brstack(&data, event, &cpuc->lbr_stack, NULL);
> +               perf_sample_save_brstack(&data, event, &cpuc->lbr_stack, NULL);
>
>                 if (perf_event_overflow(event, &data, regs))
>                         x86_pmu_stop(event, 0);
> diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
> index 5b0dd07b1ef1..ff5577315938 100644
> --- a/arch/x86/events/core.c
> +++ b/arch/x86/events/core.c
> @@ -1702,8 +1702,7 @@ int x86_pmu_handle_irq(struct pt_regs *regs)
>
>                 perf_sample_data_init(&data, 0, event->hw.last_period);
>
> -               if (has_branch_stack(event))
> -                       perf_sample_save_brstack(&data, event, &cpuc->lbr_stack, NULL);
> +               perf_sample_save_brstack(&data, event, &cpuc->lbr_stack, NULL);
>
>                 if (perf_event_overflow(event, &data, regs))
>                         x86_pmu_stop(event, 0);
> diff --git a/arch/x86/events/intel/ds.c b/arch/x86/events/intel/ds.c
> index c2b5585aa6d1..f25236ffa28f 100644
> --- a/arch/x86/events/intel/ds.c
> +++ b/arch/x86/events/intel/ds.c
> @@ -1754,8 +1754,7 @@ static void setup_pebs_fixed_sample_data(struct perf_event *event,
>         if (x86_pmu.intel_cap.pebs_format >= 3)
>                 setup_pebs_time(event, data, pebs->tsc);
>
> -       if (has_branch_stack(event))
> -               perf_sample_save_brstack(data, event, &cpuc->lbr_stack, NULL);
> +       perf_sample_save_brstack(data, event, &cpuc->lbr_stack, NULL);
>  }
>
>  static void adaptive_pebs_save_regs(struct pt_regs *regs,
> diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
> index 8617815456b0..ecfbe22ff299 100644
> --- a/include/linux/perf_event.h
> +++ b/include/linux/perf_event.h
> @@ -1269,6 +1269,11 @@ static inline void perf_sample_save_raw_data(struct perf_sample_data *data,
>         data->sample_flags |= PERF_SAMPLE_RAW;
>  }
>
> +static inline bool has_branch_stack(struct perf_event *event)
> +{
> +       return event->attr.sample_type & PERF_SAMPLE_BRANCH_STACK;
> +}
> +
>  static inline void perf_sample_save_brstack(struct perf_sample_data *data,
>                                             struct perf_event *event,
>                                             struct perf_branch_stack *brs,
> @@ -1276,6 +1281,9 @@ static inline void perf_sample_save_brstack(struct perf_sample_data *data,
>  {
>         int size = sizeof(u64); /* nr */
>
> +       if (!has_branch_stack(event))
> +               return;
> +
>         if (branch_sample_hw_index(event))
>                 size += sizeof(u64);
>         size += brs->nr * sizeof(struct perf_branch_entry);
> @@ -1665,11 +1673,6 @@ extern void perf_bp_event(struct perf_event *event, void *data);
>  # define perf_arch_bpf_user_pt_regs(regs) regs
>  #endif
>
> -static inline bool has_branch_stack(struct perf_event *event)
> -{
> -       return event->attr.sample_type & PERF_SAMPLE_BRANCH_STACK;
> -}
> -
>  static inline bool needs_branch_stack(struct perf_event *event)
>  {
>         return event->attr.branch_sample_type != 0;
> --
> 2.45.0.118.g7fe29c98d7-goog
>

Re: [PATCH v4 3/3] perf/core: Check sample_type in perf_sample_save_brstack

[Yabin Cui]

arch/powerpc/perf/core-book3s.c checks sample_type, see
   if (event->attr.sample_type & PERF_SAMPLE_BRANCH_STACK) {
     ...
     perf_sample_save_brstack(&data, event, &cpuhw->bhrb_stack, NULL);
  }
So I think we don't need the "fixes:" line.

On Fri, May 10, 2024 at 2:30 PM Namhyung Kim <namhyung@kernel.org> wrote:
>
> On Fri, May 10, 2024 at 12:14 PM Yabin Cui <yabinc@google.com> wrote:
> >
> > Check sample_type in perf_sample_save_brstack() to prevent
> > saving branch stack data when it isn't required.
> >
> > Suggested-by: Namhyung Kim <namhyung@kernel.org>
> > Signed-off-by: Yabin Cui <yabinc@google.com>
>
> It seems powerpc has the similar bug, then you need this:
>
> Fixes: eb55b455ef9c ("perf/core: Add perf_sample_save_brstack() helper")
>
> Thanks,
> Namhyung
>
> > ---
> >  arch/x86/events/amd/core.c |  3 +--
> >  arch/x86/events/core.c     |  3 +--
> >  arch/x86/events/intel/ds.c |  3 +--
> >  include/linux/perf_event.h | 13 ++++++++-----
> >  4 files changed, 11 insertions(+), 11 deletions(-)
> >
> > diff --git a/arch/x86/events/amd/core.c b/arch/x86/events/amd/core.c
> > index 985ef3b47919..fb9bf3aa1b42 100644
> > --- a/arch/x86/events/amd/core.c
> > +++ b/arch/x86/events/amd/core.c
> > @@ -967,8 +967,7 @@ static int amd_pmu_v2_handle_irq(struct pt_regs *regs)
> >                 if (!x86_perf_event_set_period(event))
> >                         continue;
> >
> > -               if (has_branch_stack(event))
> > -                       perf_sample_save_brstack(&data, event, &cpuc->lbr_stack, NULL);
> > +               perf_sample_save_brstack(&data, event, &cpuc->lbr_stack, NULL);
> >
> >                 if (perf_event_overflow(event, &data, regs))
> >                         x86_pmu_stop(event, 0);
> > diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
> > index 5b0dd07b1ef1..ff5577315938 100644
> > --- a/arch/x86/events/core.c
> > +++ b/arch/x86/events/core.c
> > @@ -1702,8 +1702,7 @@ int x86_pmu_handle_irq(struct pt_regs *regs)
> >
> >                 perf_sample_data_init(&data, 0, event->hw.last_period);
> >
> > -               if (has_branch_stack(event))
> > -                       perf_sample_save_brstack(&data, event, &cpuc->lbr_stack, NULL);
> > +               perf_sample_save_brstack(&data, event, &cpuc->lbr_stack, NULL);
> >
> >                 if (perf_event_overflow(event, &data, regs))
> >                         x86_pmu_stop(event, 0);
> > diff --git a/arch/x86/events/intel/ds.c b/arch/x86/events/intel/ds.c
> > index c2b5585aa6d1..f25236ffa28f 100644
> > --- a/arch/x86/events/intel/ds.c
> > +++ b/arch/x86/events/intel/ds.c
> > @@ -1754,8 +1754,7 @@ static void setup_pebs_fixed_sample_data(struct perf_event *event,
> >         if (x86_pmu.intel_cap.pebs_format >= 3)
> >                 setup_pebs_time(event, data, pebs->tsc);
> >
> > -       if (has_branch_stack(event))
> > -               perf_sample_save_brstack(data, event, &cpuc->lbr_stack, NULL);
> > +       perf_sample_save_brstack(data, event, &cpuc->lbr_stack, NULL);
> >  }
> >
> >  static void adaptive_pebs_save_regs(struct pt_regs *regs,
> > diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
> > index 8617815456b0..ecfbe22ff299 100644
> > --- a/include/linux/perf_event.h
> > +++ b/include/linux/perf_event.h
> > @@ -1269,6 +1269,11 @@ static inline void perf_sample_save_raw_data(struct perf_sample_data *data,
> >         data->sample_flags |= PERF_SAMPLE_RAW;
> >  }
> >
> > +static inline bool has_branch_stack(struct perf_event *event)
> > +{
> > +       return event->attr.sample_type & PERF_SAMPLE_BRANCH_STACK;
> > +}
> > +
> >  static inline void perf_sample_save_brstack(struct perf_sample_data *data,
> >                                             struct perf_event *event,
> >                                             struct perf_branch_stack *brs,
> > @@ -1276,6 +1281,9 @@ static inline void perf_sample_save_brstack(struct perf_sample_data *data,
> >  {
> >         int size = sizeof(u64); /* nr */
> >
> > +       if (!has_branch_stack(event))
> > +               return;
> > +
> >         if (branch_sample_hw_index(event))
> >                 size += sizeof(u64);
> >         size += brs->nr * sizeof(struct perf_branch_entry);
> > @@ -1665,11 +1673,6 @@ extern void perf_bp_event(struct perf_event *event, void *data);
> >  # define perf_arch_bpf_user_pt_regs(regs) regs
> >  #endif
> >
> > -static inline bool has_branch_stack(struct perf_event *event)
> > -{
> > -       return event->attr.sample_type & PERF_SAMPLE_BRANCH_STACK;
> > -}
> > -
> >  static inline bool needs_branch_stack(struct perf_event *event)
> >  {
> >         return event->attr.branch_sample_type != 0;
> > --
> > 2.45.0.118.g7fe29c98d7-goog
> >

Re: [PATCH v4 3/3] perf/core: Check sample_type in perf_sample_save_brstack

[Namhyung Kim]

On Mon, May 13, 2024 at 11:31 AM Yabin Cui <yabinc@google.com> wrote:
>
> arch/powerpc/perf/core-book3s.c checks sample_type, see
>    if (event->attr.sample_type & PERF_SAMPLE_BRANCH_STACK) {
>      ...
>      perf_sample_save_brstack(&data, event, &cpuhw->bhrb_stack, NULL);
>   }
> So I think we don't need the "fixes:" line.

Oh, ok.  Thanks for the correction!

Namhyung

Re: [PATCH v4 1/3] perf/core: Save raw sample data conditionally based on sample type

[Peter Zijlstra]

On Fri, May 10, 2024 at 12:14:21PM -0700, Yabin Cui wrote:

> diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
> index d2a15c0c6f8a..9fc55193ff99 100644
> --- a/include/linux/perf_event.h
> +++ b/include/linux/perf_event.h
> @@ -1240,12 +1240,16 @@ static inline void perf_sample_save_callchain(struct perf_sample_data *data,
>  }
>  
>  static inline void perf_sample_save_raw_data(struct perf_sample_data *data,
> +					     struct perf_event *event,
>  					     struct perf_raw_record *raw)
>  {
>  	struct perf_raw_frag *frag = &raw->frag;
>  	u32 sum = 0;
>  	int size;
>  
> +	if (!(event->attr.sample_type & PERF_SAMPLE_RAW))
> +		return;
> +

Should we add something like:

	if (WARN_ON_ONCE(data->sample_flags & PERF_SAMPLE_RAW))
		return;

? And I suppose the same for all these other patches.

>  	do {
>  		sum += frag->size;
>  		if (perf_raw_frag_last(frag))

Re: [PATCH v4 3/3] perf/core: Check sample_type in perf_sample_save_brstack

[Peter Zijlstra]

On Fri, May 10, 2024 at 02:29:58PM -0700, Namhyung Kim wrote:
> On Fri, May 10, 2024 at 12:14 PM Yabin Cui <yabinc@google.com> wrote:
> >
> > Check sample_type in perf_sample_save_brstack() to prevent
> > saving branch stack data when it isn't required.
> >
> > Suggested-by: Namhyung Kim <namhyung@kernel.org>
> > Signed-off-by: Yabin Cui <yabinc@google.com>
> 
> It seems powerpc has the similar bug, then you need this:
> 
> Fixes: eb55b455ef9c ("perf/core: Add perf_sample_save_brstack() helper")

Is this really a bug? AFAICT it just does unneeded work, no?

Re: [PATCH v4 1/3] perf/core: Save raw sample data conditionally based on sample type

[Yabin Cui]

Good suggestion! I will send a new version.



On Wed, May 15, 2024 at 1:58 AM Peter Zijlstra <peterz@infradead.org> wrote:
>
> On Fri, May 10, 2024 at 12:14:21PM -0700, Yabin Cui wrote:
>
> > diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
> > index d2a15c0c6f8a..9fc55193ff99 100644
> > --- a/include/linux/perf_event.h
> > +++ b/include/linux/perf_event.h
> > @@ -1240,12 +1240,16 @@ static inline void perf_sample_save_callchain(struct perf_sample_data *data,
> >  }
> >
> >  static inline void perf_sample_save_raw_data(struct perf_sample_data *data,
> > +                                          struct perf_event *event,
> >                                            struct perf_raw_record *raw)
> >  {
> >       struct perf_raw_frag *frag = &raw->frag;
> >       u32 sum = 0;
> >       int size;
> >
> > +     if (!(event->attr.sample_type & PERF_SAMPLE_RAW))
> > +             return;
> > +
>
> Should we add something like:
>
>         if (WARN_ON_ONCE(data->sample_flags & PERF_SAMPLE_RAW))
>                 return;
>
> ? And I suppose the same for all these other patches.
>
> >       do {
> >               sum += frag->size;
> >               if (perf_raw_frag_last(frag))
>
>

Re: [PATCH v4 3/3] perf/core: Check sample_type in perf_sample_save_brstack

[Yabin Cui]

On Wed, May 15, 2024 at 1:58 AM Peter Zijlstra <peterz@infradead.org> wrote:
>
> On Fri, May 10, 2024 at 02:29:58PM -0700, Namhyung Kim wrote:
> > On Fri, May 10, 2024 at 12:14 PM Yabin Cui <yabinc@google.com> wrote:
> > >
> > > Check sample_type in perf_sample_save_brstack() to prevent
> > > saving branch stack data when it isn't required.
> > >
> > > Suggested-by: Namhyung Kim <namhyung@kernel.org>
> > > Signed-off-by: Yabin Cui <yabinc@google.com>
> >
> > It seems powerpc has the similar bug, then you need this:
> >
> > Fixes: eb55b455ef9c ("perf/core: Add perf_sample_save_brstack() helper")
>
> Is this really a bug? AFAICT it just does unneeded work, no?

It's not a bug. As I replied to Namhyuang, the powerpc code checks
sample_type before calling perf_sample_save_brstack().