perf/core: Add perf_sample_save_callchain() helper

When we save the callchain to the perf sample data, we need to update
the sample flags and the dynamic size.  To ensure this is done consistently,
add the perf_sample_save_callchain() helper and convert all call sites.
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: Song Liu <song@kernel.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20230118060559.615653-3-namhyung@kernel.org

arch/x86/events/amd/ibs.c

@@ -1122,10 +1122,8 @@ 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) {
-		data.callchain = perf_callchain(event, iregs);
-		data.sample_flags |= PERF_SAMPLE_CALLCHAIN;
-	}
+	if (event->attr.sample_type & PERF_SAMPLE_CALLCHAIN)
+		perf_sample_save_callchain(&data, event, iregs);
 
 	throttle = perf_event_overflow(event, &data, &regs);
 out:

arch/x86/events/intel/ds.c

@@ -1617,10 +1617,8 @@ 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) {
-		data->callchain = perf_callchain(event, iregs);
-		data->sample_flags |= PERF_SAMPLE_CALLCHAIN;
-	}
+	if (sample_type & PERF_SAMPLE_CALLCHAIN)
+		perf_sample_save_callchain(data, event, iregs);
 
 	/*
 	 * We use the interrupt regs as a base because the PEBS record does not
@@ -1795,10 +1793,8 @@ 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) {
-		data->callchain = perf_callchain(event, iregs);
-		data->sample_flags |= PERF_SAMPLE_CALLCHAIN;
-	}
+	if (sample_type & PERF_SAMPLE_CALLCHAIN)
+		perf_sample_save_callchain(data, event, iregs);
 
 	*regs = *iregs;
 	/* The ip in basic is EventingIP */

include/linux/perf_event.h

@@ -1095,6 +1095,8 @@ int perf_event_read_local(struct perf_event *event, u64 *value,
 extern u64 perf_event_read_value(struct perf_event *event,
 				 u64 *enabled, u64 *running);
 
+extern struct perf_callchain_entry *perf_callchain(struct perf_event *event, struct pt_regs *regs);
+
 
 struct perf_sample_data {
 	/*
@@ -1167,6 +1169,19 @@ static inline void perf_sample_data_init(struct perf_sample_data *data,
 	}
 }
 
+static inline void perf_sample_save_callchain(struct perf_sample_data *data,
+					      struct perf_event *event,
+					      struct pt_regs *regs)
+{
+	int size = 1;
+
+	data->callchain = perf_callchain(event, regs);
+	size += data->callchain->nr;
+
+	data->dyn_size += size * sizeof(u64);
+	data->sample_flags |= PERF_SAMPLE_CALLCHAIN;
+}
+
 /*
  * Clear all bitfields in the perf_branch_entry.
  * The to and from fields are not cleared because they are
@@ -1408,7 +1423,6 @@ extern void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry, struct
 extern struct perf_callchain_entry *
 get_perf_callchain(struct pt_regs *regs, u32 init_nr, bool kernel, bool user,
 		   u32 max_stack, bool crosstask, bool add_mark);
-extern struct perf_callchain_entry *perf_callchain(struct perf_event *event, struct pt_regs *regs);
 extern int get_callchain_buffers(int max_stack);
 extern void put_callchain_buffers(void);
 extern struct perf_callchain_entry *get_callchain_entry(int *rctx);

kernel/events/core.c

@@ -7578,16 +7578,8 @@ void perf_prepare_sample(struct perf_event_header *header,
 	if (sample_type & (PERF_SAMPLE_IP | PERF_SAMPLE_CODE_PAGE_SIZE))
 		data->ip = perf_instruction_pointer(regs);
 
-	if (sample_type & PERF_SAMPLE_CALLCHAIN) {
-		int size = 1;
-
-		if (filtered_sample_type & PERF_SAMPLE_CALLCHAIN)
-			data->callchain = perf_callchain(event, regs);
-
-		size += data->callchain->nr;
-
-		data->dyn_size += size * sizeof(u64);
-	}
+	if (filtered_sample_type & PERF_SAMPLE_CALLCHAIN)
+		perf_sample_save_callchain(data, event, regs);
 
 	if (sample_type & PERF_SAMPLE_RAW) {
 		struct perf_raw_record *raw = data->raw;