[PATCHv3 bpf-next 3/9] bpf: Use file object build id in stackmap

[Jiri Olsa]

Use build id from file object in stackmap if it's available.

The file's f_build_id is available (for CONFIG_FILE_BUILD_ID option)
when the file is mmap-ed, so it will be available (if present) when
used by stackmap.

Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
---
 kernel/bpf/stackmap.c | 24 +++++++++++++++++++++++-
 1 file changed, 23 insertions(+), 1 deletion(-)

diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c
index 0f1d8dced933..14d27bd83081 100644
--- a/kernel/bpf/stackmap.c
+++ b/kernel/bpf/stackmap.c
@@ -124,6 +124,28 @@ static struct bpf_map *stack_map_alloc(union bpf_attr *attr)
 	return ERR_PTR(err);
 }
 
+#ifdef CONFIG_FILE_BUILD_ID
+static int vma_get_build_id(struct vm_area_struct *vma, unsigned char *build_id)
+{
+	struct build_id *bid;
+
+	if (!vma->vm_file)
+		return -EINVAL;
+	bid = vma->vm_file->f_build_id;
+	if (IS_ERR_OR_NULL(bid))
+		return bid ? PTR_ERR(bid) : -ENOENT;
+	if (bid->sz > BUILD_ID_SIZE_MAX)
+		return -EINVAL;
+	memcpy(build_id, bid->data, bid->sz);
+	return 0;
+}
+#else
+static int vma_get_build_id(struct vm_area_struct *vma, unsigned char *build_id)
+{
+	return build_id_parse(vma, build_id, NULL);
+}
+#endif
+
 static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs,
 					  u64 *ips, u32 trace_nr, bool user)
 {
@@ -156,7 +178,7 @@ static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs,
 			goto build_id_valid;
 		}
 		vma = find_vma(current->mm, ips[i]);
-		if (!vma || build_id_parse(vma, id_offs[i].build_id, NULL)) {
+		if (!vma || vma_get_build_id(vma, id_offs[i].build_id)) {
 			/* per entry fall back to ips */
 			id_offs[i].status = BPF_STACK_BUILD_ID_IP;
 			id_offs[i].ip = ips[i];
-- 
2.39.2