Merge branch 'bpf-retrieve-ref_ctr_offset-from-uprobe-perf-link'

Jiri Olsa says:

====================
bpf: Retrieve ref_ctr_offset from uprobe perf link

hi,
adding ref_ctr_offset retrieval for uprobe perf link info.

v2 changes:
  - display ref_ctr_offset as hex number [Andrii]
  - added acks

thanks,
jirka
---
====================

Link: https://patch.msgid.link/[email protected]
Signed-off-by: Andrii Nakryiko <[email protected]>

Author: anakryiko

include/uapi/linux/bpf.h

@@ -6724,6 +6724,7 @@ struct bpf_link_info {
 					__u32 name_len;
 					__u32 offset; /* offset from file_name */
 					__u64 cookie;
+					__u64 ref_ctr_offset;
 				} uprobe; /* BPF_PERF_EVENT_UPROBE, BPF_PERF_EVENT_URETPROBE */
 				struct {
 					__aligned_u64 func_name; /* in/out */

kernel/bpf/syscall.c

@@ -3800,14 +3800,14 @@ static int bpf_perf_link_fill_kprobe(const struct perf_event *event,
 static int bpf_perf_link_fill_uprobe(const struct perf_event *event,
 				     struct bpf_link_info *info)
 {
+	u64 ref_ctr_offset, offset;
 	char __user *uname;
-	u64 addr, offset;
 	u32 ulen, type;
 	int err;
 
 	uname = u64_to_user_ptr(info->perf_event.uprobe.file_name);
 	ulen = info->perf_event.uprobe.name_len;
-	err = bpf_perf_link_fill_common(event, uname, &ulen, &offset, &addr,
+	err = bpf_perf_link_fill_common(event, uname, &ulen, &offset, &ref_ctr_offset,
 					&type, NULL);
 	if (err)
 		return err;
@@ -3819,6 +3819,7 @@ static int bpf_perf_link_fill_uprobe(const struct perf_event *event,
 	info->perf_event.uprobe.name_len = ulen;
 	info->perf_event.uprobe.offset = offset;
 	info->perf_event.uprobe.cookie = event->bpf_cookie;
+	info->perf_event.uprobe.ref_ctr_offset = ref_ctr_offset;
 	return 0;
 }
 #endif

kernel/trace/trace_uprobe.c

@@ -1489,7 +1489,7 @@ int bpf_get_uprobe_info(const struct perf_event *event, u32 *fd_type,
 				    : BPF_FD_TYPE_UPROBE;
 	*filename = tu->filename;
 	*probe_offset = tu->offset;
-	*probe_addr = 0;
+	*probe_addr = tu->ref_ctr_offset;
 	return 0;
 }
 #endif	/* CONFIG_PERF_EVENTS */

tools/bpf/bpftool/link.c

@@ -380,6 +380,7 @@ show_perf_event_uprobe_json(struct bpf_link_info *info, json_writer_t *wtr)
 			   u64_to_ptr(info->perf_event.uprobe.file_name));
 	jsonw_uint_field(wtr, "offset", info->perf_event.uprobe.offset);
 	jsonw_uint_field(wtr, "cookie", info->perf_event.uprobe.cookie);
+	jsonw_uint_field(wtr, "ref_ctr_offset", info->perf_event.uprobe.ref_ctr_offset);
 }
 
 static void
@@ -823,6 +824,8 @@ static void show_perf_event_uprobe_plain(struct bpf_link_info *info)
 	printf("%s+%#x  ", buf, info->perf_event.uprobe.offset);
 	if (info->perf_event.uprobe.cookie)
 		printf("cookie %llu  ", info->perf_event.uprobe.cookie);
+	if (info->perf_event.uprobe.ref_ctr_offset)
+		printf("ref_ctr_offset 0x%llx  ", info->perf_event.uprobe.ref_ctr_offset);
 }
 
 static void show_perf_event_tracepoint_plain(struct bpf_link_info *info)

tools/include/uapi/linux/bpf.h

@@ -6724,6 +6724,7 @@ struct bpf_link_info {
 					__u32 name_len;
 					__u32 offset; /* offset from file_name */
 					__u64 cookie;
+					__u64 ref_ctr_offset;
 				} uprobe; /* BPF_PERF_EVENT_UPROBE, BPF_PERF_EVENT_URETPROBE */
 				struct {
 					__aligned_u64 func_name; /* in/out */

tools/testing/selftests/bpf/prog_tests/fill_link_info.c

@@ -37,6 +37,7 @@ static noinline void uprobe_func(void)
 static int verify_perf_link_info(int fd, enum bpf_perf_event_type type, long addr,
 				 ssize_t offset, ssize_t entry_offset)
 {
+	ssize_t ref_ctr_offset = entry_offset /* ref_ctr_offset for uprobes */;
 	struct bpf_link_info info;
 	__u32 len = sizeof(info);
 	char buf[PATH_MAX];
@@ -97,6 +98,7 @@ static int verify_perf_link_info(int fd, enum bpf_perf_event_type type, long add
 	case BPF_PERF_EVENT_UPROBE:
 	case BPF_PERF_EVENT_URETPROBE:
 		ASSERT_EQ(info.perf_event.uprobe.offset, offset, "uprobe_offset");
+		ASSERT_EQ(info.perf_event.uprobe.ref_ctr_offset, ref_ctr_offset, "uprobe_ref_ctr_offset");
 
 		ASSERT_EQ(info.perf_event.uprobe.name_len, strlen(UPROBE_FILE) + 1,
 				  "name_len");
@@ -241,20 +243,32 @@ static void test_uprobe_fill_link_info(struct test_fill_link_info *skel,
 		.retprobe = type == BPF_PERF_EVENT_URETPROBE,
 		.bpf_cookie = PERF_EVENT_COOKIE,
 	);
+	const char *sema[1] = {
+		"uprobe_link_info_sema_1",
+	};
+	__u64 *ref_ctr_offset;
 	struct bpf_link *link;
 	int link_fd, err;
 
+	err = elf_resolve_syms_offsets("/proc/self/exe", 1, sema,
+				       (unsigned long **) &ref_ctr_offset, STT_OBJECT);
+	if (!ASSERT_OK(err, "elf_resolve_syms_offsets_object"))
+		return;
+
+	opts.ref_ctr_offset = *ref_ctr_offset;
 	link = bpf_program__attach_uprobe_opts(skel->progs.uprobe_run,
 					       0, /* self pid */
 					       UPROBE_FILE, uprobe_offset,
 					       &opts);
 	if (!ASSERT_OK_PTR(link, "attach_uprobe"))
-		return;
+		goto out;
 
 	link_fd = bpf_link__fd(link);
-	err = verify_perf_link_info(link_fd, type, 0, uprobe_offset, 0);
+	err = verify_perf_link_info(link_fd, type, 0, uprobe_offset, *ref_ctr_offset);
 	ASSERT_OK(err, "verify_perf_link_info");
 	bpf_link__destroy(link);
+out:
+	free(ref_ctr_offset);
 }
 
 static int verify_kmulti_link_info(int fd, bool retprobe, bool has_cookies)