[PATCH RFC v2 bpf-next 3/9] perf: Use file object build id in perf_event_mmap_event

Jiri Olsa
2023-02-28T09:33:03Z

Use build id from file's inode object when available for perf's MMAP2
event build id data.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
kernel/events/core.c | 46 ++++++++++++++++++++++++++++++++++++++++----
1 file changed, 42 insertions(+), 4 deletions(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 7099c77bc53b..148f78a88492 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -8527,6 +8527,9 @@ struct perf_mmap_event {
u32 prot, flags;
u8 build_id[BUILD_ID_SIZE_MAX];
u32 build_id_size;
+#ifdef CONFIG_INODE_BUILD_ID
+ struct build_id *i_build_id;
+#endif

struct {
struct perf_event_header header;
@@ -8539,6 +8542,41 @@ struct perf_mmap_event {
} event_id;
};

+#ifdef CONFIG_INODE_BUILD_ID
+static void build_id_read(struct perf_mmap_event *mmap_event)
+{
+ struct vm_area_struct *vma = mmap_event->vma;
+ struct inode *inode = NULL;
+
+ if (vma->vm_file)
+ inode = file_inode(vma->vm_file);
+ mmap_event->i_build_id = inode ? inode->i_build_id : NULL;
+}
+
+static bool has_build_id(struct perf_mmap_event *mmap_event)
+{
+ return !IS_ERR_OR_NULL(mmap_event->i_build_id);
+}
+
+#define build_id_data mmap_event->i_build_id->data
+#define build_id_size mmap_event->i_build_id->sz
+#else
+static void build_id_read(struct perf_mmap_event *mmap_event)
+{
+ struct vm_area_struct *vma = mmap_event->vma;
+
+ build_id_parse(vma, mmap_event->build_id, &mmap_event->build_id_size);
+}
+
+static bool has_build_id(struct perf_mmap_event *mmap_event)
+{
+ return mmap_event->build_id_size;
+}
+
+#define build_id_data mmap_event->build_id
+#define build_id_size mmap_event->build_id_size
+#endif
+
static int perf_event_mmap_match(struct perf_event *event,
void *data)
{
@@ -8583,7 +8621,7 @@ static void perf_event_mmap_output(struct perf_event *event,
mmap_event->event_id.pid = perf_event_pid(event, current);
mmap_event->event_id.tid = perf_event_tid(event, current);

- use_build_id = event->attr.build_id && mmap_event->build_id_size;
+ use_build_id = event->attr.build_id && has_build_id(mmap_event);

if (event->attr.mmap2 && use_build_id)
mmap_event->event_id.header.misc |= PERF_RECORD_MISC_MMAP_BUILD_ID;
@@ -8592,10 +8630,10 @@ static void perf_event_mmap_output(struct perf_event *event,

if (event->attr.mmap2) {
if (use_build_id) {
- u8 size[4] = { (u8) mmap_event->build_id_size, 0, 0, 0 };
+ u8 size[4] = { (u8) build_id_size, 0, 0, 0 };

__output_copy(&handle, size, 4);
- __output_copy(&handle, mmap_event->build_id, BUILD_ID_SIZE_MAX);
+ __output_copy(&handle, build_id_data, BUILD_ID_SIZE_MAX);
} else {
perf_output_put(&handle, mmap_event->maj);
perf_output_put(&handle, mmap_event->min);
@@ -8727,7 +8765,7 @@ static void perf_event_mmap_event(struct perf_mmap_event *mmap_event)
mmap_event->event_id.header.size = sizeof(mmap_event->event_id) + size;

if (atomic_read(&nr_build_id_events))
- build_id_parse(vma, mmap_event->build_id, &mmap_event->build_id_size);
+ build_id_read(mmap_event);

perf_iterate_sb(perf_event_mmap_output,
mmap_event,
--
2.39.2