[PATCHv2 bpf-next 0/3] bpf: Retrieve ref_ctr_offset from uprobe perf link

[PATCHv2 bpf-next 0/3] bpf: Retrieve ref_ctr_offset from uprobe perf link

[Jiri Olsa]

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


---
Jiri Olsa (3):
      bpf: Add support to retrieve ref_ctr_offset for uprobe perf link
      selftests/bpf: Add link info test for ref_ctr_offset retrieval
      bpftool: Display ref_ctr_offset for uprobe link info

 include/uapi/linux/bpf.h                                |  1 +
 kernel/bpf/syscall.c                                    |  5 +++--
 kernel/trace/trace_uprobe.c                             |  2 +-
 tools/bpf/bpftool/link.c                                |  3 +++
 tools/include/uapi/linux/bpf.h                          |  1 +
 tools/testing/selftests/bpf/prog_tests/fill_link_info.c | 18 ++++++++++++++++--
 6 files changed, 25 insertions(+), 5 deletions(-)

[PATCHv2 bpf-next 1/3] bpf: Add support to retrieve ref_ctr_offset for uprobe perf link

[Jiri Olsa]

Adding support to retrieve ref_ctr_offset for uprobe perf link,
which got somehow omitted from the initial uprobe link info changes.

Acked-by: Yafang Shao <laoar.shao@gmail.com>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 include/uapi/linux/bpf.h       | 1 +
 kernel/bpf/syscall.c           | 5 +++--
 kernel/trace/trace_uprobe.c    | 2 +-
 tools/include/uapi/linux/bpf.h | 1 +
 4 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 71d5ac83cf5d..16e95398c91c 100644
--- a/include/uapi/linux/bpf.h
+++ b/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 */
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index df33d19c5c3b..4b5f29168618 100644
--- a/kernel/bpf/syscall.c
+++ b/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
diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
index 3386439ec9f6..d9cf6ed2c106 100644
--- a/kernel/trace/trace_uprobe.c
+++ b/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 */
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 71d5ac83cf5d..16e95398c91c 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/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 */
-- 
2.49.0

[PATCHv2 bpf-next 2/3] selftests/bpf: Add link info test for ref_ctr_offset retrieval

[Jiri Olsa]

Adding link info test for ref_ctr_offset retrieval for both
uprobe and uretprobe probes.

Acked-by: Yafang Shao <laoar.shao@gmail.com>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 .../selftests/bpf/prog_tests/fill_link_info.c  | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/fill_link_info.c b/tools/testing/selftests/bpf/prog_tests/fill_link_info.c
index e59af2aa6601..e40114620751 100644
--- a/tools/testing/selftests/bpf/prog_tests/fill_link_info.c
+++ b/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)
-- 
2.49.0

[PATCHv2 bpf-next 3/3] bpftool: Display ref_ctr_offset for uprobe link info

[Jiri Olsa]

Adding support to display ref_ctr_offset in link output, like:

  # bpftool link
  ...
  42: perf_event  prog 174
          uprobe /proc/self/exe+0x102f13  cookie 3735928559  ref_ctr_offset 0x303a3fa
          bpf_cookie 3735928559
          pids test_progs(1820)

  # bpftool link -j | jq
  [
    ...
    {
      "id": 42,
       ...
      "ref_ctr_offset": 50500538,
    }
  ]

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 tools/bpf/bpftool/link.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/tools/bpf/bpftool/link.c b/tools/bpf/bpftool/link.c
index 52fd2c9fac56..3535afc80a49 100644
--- a/tools/bpf/bpftool/link.c
+++ b/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)
-- 
2.49.0

Re: [PATCHv2 bpf-next 0/3] bpf: Retrieve ref_ctr_offset from uprobe perf link

[patchwork-bot+netdevbpf]

Hello:

This series was applied to bpf/bpf-next.git (master)
by Andrii Nakryiko <andrii@kernel.org>:

On Fri,  9 May 2025 17:35:36 +0200 you wrote:
> hi,
> adding ref_ctr_offset retrieval for uprobe perf link info.
> 
> v2 changes:
>   - display ref_ctr_offset as hex number [Andrii]
>   - added acks
> 
> [...]

Here is the summary with links:
  - [PATCHv2,bpf-next,1/3] bpf: Add support to retrieve ref_ctr_offset for uprobe perf link
    https://git.kernel.org/bpf/bpf-next/c/823153334042
  - [PATCHv2,bpf-next,2/3] selftests/bpf: Add link info test for ref_ctr_offset retrieval
    https://git.kernel.org/bpf/bpf-next/c/d57293db64f5
  - [PATCHv2,bpf-next,3/3] bpftool: Display ref_ctr_offset for uprobe link info
    https://git.kernel.org/bpf/bpf-next/c/97596edfec01

You are awesome, thank you!
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