[PATCH bpf-next v7 1/3] bpf: Show precise link_type for {uprobe,kprobe}_multi fdinfo

[PATCH bpf-next v7 1/3] bpf: Show precise link_type for {uprobe,kprobe}_multi fdinfo

[Tao Chen]

Alexei suggested, 'link_type' can be more precise and differentiate
for human in fdinfo. In fact BPF_LINK_TYPE_KPROBE_MULTI includes
kretprobe_multi type, the same as BPF_LINK_TYPE_UPROBE_MULTI, so we
can show it more concretely.

link_type:	kprobe_multi
link_id:	1
prog_tag:	d2b307e915f0dd37
...
link_type:	kretprobe_multi
link_id:	2
prog_tag:	ab9ea0545870781d
...
link_type:	uprobe_multi
link_id:	9
prog_tag:	e729f789e34a8eca
...
link_type:	uretprobe_multi
link_id:	10
prog_tag:	7db356c03e61a4d4

Co-developed-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Tao Chen <chen.dylane@linux.dev>
---
 include/linux/bpf.h      |  1 +
 kernel/bpf/syscall.c     |  9 ++++++++-
 kernel/trace/bpf_trace.c | 10 ++++------
 3 files changed, 13 insertions(+), 7 deletions(-)

Change list:
  v6 -> v7:
    - Show the same order cookie for kprobe/uprobe.(Andrii)
    - Use tab format to show multi events for kprobe/uprobe.(Andrii)
    - Use u32 flags in bpf_link.(Alexei)
  v6:
  https://lore.kernel.org/bpf/20250627082252.431209-1-chen.dylane@linux.dev

  v5 -> v6:
    - Move flags into bpf_link to get retprobe info
      directly.(Alexei, Jiri)
  v5:
  https://lore.kernel.org/bpf/20250623134342.227347-1-chen.dylane@linux.dev

  v4 -> v5:
    - Add patch1 to show precise link_type for
      {uprobe,kprobe}_multi.(Alexei)
    - patch2,3 just remove type field, which will be showed in
      link_type
  v4:
  https://lore.kernel.org/bpf/20250619034257.70520-1-chen.dylane@linux.dev

  v3 -> v4:
    - use %pS to print func info.(Alexei)
  v3:
  https://lore.kernel.org/bpf/20250616130233.451439-1-chen.dylane@linux.dev

  v2 -> v3:
    - show info in one line for multi events.(Jiri)
  v2:
  https://lore.kernel.org/bpf/20250615150514.418581-1-chen.dylane@linux.dev

  v1 -> v2:
    - replace 'func_cnt' with 'uprobe_cnt'.(Andrii)
    - print func name is more readable and security for kprobe_multi.(Alexei)
  v1:
  https://lore.kernel.org/bpf/20250612115556.295103-1-chen.dylane@linux.dev

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 5b25d278409..751ea3f5480 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1702,6 +1702,7 @@ struct bpf_link {
 	 * link's semantics is determined by target attach hook
 	 */
 	bool sleepable;
+	u32 flags;
 	/* rcu is used before freeing, work can be used to schedule that
 	 * RCU-based freeing before that, so they never overlap
 	 */
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 51ba1a7aa43..e6eea594f1c 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -3228,7 +3228,14 @@ static void bpf_link_show_fdinfo(struct seq_file *m, struct file *filp)
 	char prog_tag[sizeof(prog->tag) * 2 + 1] = { };
 
 	if (type < ARRAY_SIZE(bpf_link_type_strs) && bpf_link_type_strs[type]) {
-		seq_printf(m, "link_type:\t%s\n", bpf_link_type_strs[type]);
+		if (link->type == BPF_LINK_TYPE_KPROBE_MULTI)
+			seq_printf(m, "link_type:\t%s\n", link->flags == BPF_F_KPROBE_MULTI_RETURN ?
+				   "kretprobe_multi" : "kprobe_multi");
+		else if (link->type == BPF_LINK_TYPE_UPROBE_MULTI)
+			seq_printf(m, "link_type:\t%s\n", link->flags == BPF_F_UPROBE_MULTI_RETURN ?
+				   "uretprobe_multi" : "uprobe_multi");
+		else
+			seq_printf(m, "link_type:\t%s\n", bpf_link_type_strs[type]);
 	} else {
 		WARN_ONCE(1, "missing BPF_LINK_TYPE(...) for link type %u\n", type);
 		seq_printf(m, "link_type:\t<%u>\n", type);
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 24b94870b50..85f07f662fe 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -2469,7 +2469,6 @@ struct bpf_kprobe_multi_link {
 	u32 cnt;
 	u32 mods_cnt;
 	struct module **mods;
-	u32 flags;
 };
 
 struct bpf_kprobe_multi_run_ctx {
@@ -2589,7 +2588,7 @@ static int bpf_kprobe_multi_link_fill_link_info(const struct bpf_link *link,
 
 	kmulti_link = container_of(link, struct bpf_kprobe_multi_link, link);
 	info->kprobe_multi.count = kmulti_link->cnt;
-	info->kprobe_multi.flags = kmulti_link->flags;
+	info->kprobe_multi.flags = kmulti_link->link.flags;
 	info->kprobe_multi.missed = kmulti_link->fp.nmissed;
 
 	if (!uaddrs)
@@ -2979,7 +2978,7 @@ int bpf_kprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *pr
 	link->addrs = addrs;
 	link->cookies = cookies;
 	link->cnt = cnt;
-	link->flags = flags;
+	link->link.flags = flags;
 
 	if (cookies) {
 		/*
@@ -3048,7 +3047,6 @@ struct bpf_uprobe_multi_link {
 	struct path path;
 	struct bpf_link link;
 	u32 cnt;
-	u32 flags;
 	struct bpf_uprobe *uprobes;
 	struct task_struct *task;
 };
@@ -3112,7 +3110,7 @@ static int bpf_uprobe_multi_link_fill_link_info(const struct bpf_link *link,
 
 	umulti_link = container_of(link, struct bpf_uprobe_multi_link, link);
 	info->uprobe_multi.count = umulti_link->cnt;
-	info->uprobe_multi.flags = umulti_link->flags;
+	info->uprobe_multi.flags = umulti_link->link.flags;
 	info->uprobe_multi.pid = umulti_link->task ?
 				 task_pid_nr_ns(umulti_link->task, task_active_pid_ns(current)) : 0;
 
@@ -3372,7 +3370,7 @@ int bpf_uprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *pr
 	link->uprobes = uprobes;
 	link->path = path;
 	link->task = task;
-	link->flags = flags;
+	link->link.flags = flags;
 
 	bpf_link_init(&link->link, BPF_LINK_TYPE_UPROBE_MULTI,
 		      &bpf_uprobe_multi_link_lops, prog);
-- 
2.48.1

[PATCH bpf-next v7 2/3] bpf: Add show_fdinfo for uprobe_multi

[Tao Chen]

Show uprobe_multi link info with fdinfo, the info as follows:

link_type:	uprobe_multi
link_id:	9
prog_tag:	e729f789e34a8eca
prog_id:	39
uprobe_cnt:	3
pid:	0
path:	/home/dylane/bpf/tools/testing/selftests/bpf/test_progs
cookie	 offset	 ref_ctr_offset
3	 0xa69f13	 0x0
1	 0xa69f1e	 0x0
2	 0xa69f29	 0x0

Signed-off-by: Tao Chen <chen.dylane@linux.dev>
---
 kernel/trace/bpf_trace.c | 44 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 44 insertions(+)

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 85f07f662fe..9161a1b3418 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -3155,10 +3155,54 @@ static int bpf_uprobe_multi_link_fill_link_info(const struct bpf_link *link,
 	return err;
 }
 
+#ifdef CONFIG_PROC_FS
+static void bpf_uprobe_multi_show_fdinfo(const struct bpf_link *link,
+					 struct seq_file *seq)
+{
+	struct bpf_uprobe_multi_link *umulti_link;
+	char *p, *buf;
+	pid_t pid;
+
+	umulti_link = container_of(link, struct bpf_uprobe_multi_link, link);
+
+	buf = kmalloc(PATH_MAX, GFP_KERNEL);
+	if (!buf)
+		return;
+
+	p = d_path(&umulti_link->path, buf, PATH_MAX);
+	if (IS_ERR(p)) {
+		kfree(buf);
+		return;
+	}
+
+	pid = umulti_link->task ?
+	      task_pid_nr_ns(umulti_link->task, task_active_pid_ns(current)) : 0;
+	seq_printf(seq,
+		   "uprobe_cnt:\t%u\n"
+		   "pid:\t%u\n"
+		   "path:\t%s\n",
+		   umulti_link->cnt, pid, p);
+
+	seq_printf(seq, "%s\t %s\t %s\n", "cookie", "offset", "ref_ctr_offset");
+	for (int i = 0; i < umulti_link->cnt; i++) {
+		seq_printf(seq,
+			   "%llu\t %#llx\t %#lx\n",
+			   umulti_link->uprobes[i].cookie,
+			   umulti_link->uprobes[i].offset,
+			   umulti_link->uprobes[i].ref_ctr_offset);
+	}
+
+	kfree(buf);
+}
+#endif
+
 static const struct bpf_link_ops bpf_uprobe_multi_link_lops = {
 	.release = bpf_uprobe_multi_link_release,
 	.dealloc_deferred = bpf_uprobe_multi_link_dealloc,
 	.fill_link_info = bpf_uprobe_multi_link_fill_link_info,
+#ifdef CONFIG_PROC_FS
+	.show_fdinfo = bpf_uprobe_multi_show_fdinfo,
+#endif
 };
 
 static int uprobe_prog_run(struct bpf_uprobe *uprobe,
-- 
2.48.1

[PATCH bpf-next v7 3/3] bpf: Add show_fdinfo for kprobe_multi

[Tao Chen]

Show kprobe_multi link info with fdinfo, the info as follows:

link_type:	kprobe_multi
link_id:	1
prog_tag:	a69740b9746f7da8
prog_id:	21
kprobe_cnt:	8
missed:	0
cookie	 func
1	 bpf_fentry_test1+0x0/0x20
7	 bpf_fentry_test2+0x0/0x20
2	 bpf_fentry_test3+0x0/0x20
3	 bpf_fentry_test4+0x0/0x20
4	 bpf_fentry_test5+0x0/0x20
5	 bpf_fentry_test6+0x0/0x20
6	 bpf_fentry_test7+0x0/0x20
8	 bpf_fentry_test8+0x0/0x10

Signed-off-by: Tao Chen <chen.dylane@linux.dev>
---
 kernel/trace/bpf_trace.c | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 9161a1b3418..49d594b8c71 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -2622,10 +2622,37 @@ static int bpf_kprobe_multi_link_fill_link_info(const struct bpf_link *link,
 	return err;
 }
 
+#ifdef CONFIG_PROC_FS
+static void bpf_kprobe_multi_show_fdinfo(const struct bpf_link *link,
+					 struct seq_file *seq)
+{
+	struct bpf_kprobe_multi_link *kmulti_link;
+
+	kmulti_link = container_of(link, struct bpf_kprobe_multi_link, link);
+
+	seq_printf(seq,
+		   "kprobe_cnt:\t%u\n"
+		   "missed:\t%lu\n",
+		   kmulti_link->cnt,
+		   kmulti_link->fp.nmissed);
+
+	seq_printf(seq, "%s\t %s\n", "cookie", "func");
+	for (int i = 0; i < kmulti_link->cnt; i++) {
+		seq_printf(seq,
+			   "%llu\t %pS\n",
+			   kmulti_link->cookies[i],
+			   (void *)kmulti_link->addrs[i]);
+	}
+}
+#endif
+
 static const struct bpf_link_ops bpf_kprobe_multi_link_lops = {
 	.release = bpf_kprobe_multi_link_release,
 	.dealloc_deferred = bpf_kprobe_multi_link_dealloc,
 	.fill_link_info = bpf_kprobe_multi_link_fill_link_info,
+#ifdef CONFIG_PROC_FS
+	.show_fdinfo = bpf_kprobe_multi_show_fdinfo,
+#endif
 };
 
 static void bpf_kprobe_multi_cookie_swap(void *a, void *b, int size, const void *priv)
-- 
2.48.1

Re: [PATCH bpf-next v7 1/3] bpf: Show precise link_type for {uprobe,kprobe}_multi fdinfo

[patchwork-bot+netdevbpf]

Hello:

This series was applied to bpf/bpf-next.git (master)
by Alexei Starovoitov <ast@kernel.org>:

On Wed,  2 Jul 2025 23:39:56 +0800 you wrote:
> Alexei suggested, 'link_type' can be more precise and differentiate
> for human in fdinfo. In fact BPF_LINK_TYPE_KPROBE_MULTI includes
> kretprobe_multi type, the same as BPF_LINK_TYPE_UPROBE_MULTI, so we
> can show it more concretely.
> 
> link_type:	kprobe_multi
> link_id:	1
> prog_tag:	d2b307e915f0dd37
> ...
> link_type:	kretprobe_multi
> link_id:	2
> prog_tag:	ab9ea0545870781d
> ...
> link_type:	uprobe_multi
> link_id:	9
> prog_tag:	e729f789e34a8eca
> ...
> link_type:	uretprobe_multi
> link_id:	10
> prog_tag:	7db356c03e61a4d4
> 
> [...]

Here is the summary with links:
  - [bpf-next,v7,1/3] bpf: Show precise link_type for {uprobe,kprobe}_multi fdinfo
    https://git.kernel.org/bpf/bpf-next/c/803f0700a3bb
  - [bpf-next,v7,2/3] bpf: Add show_fdinfo for uprobe_multi
    https://git.kernel.org/bpf/bpf-next/c/b4dfe26fbf56
  - [bpf-next,v7,3/3] bpf: Add show_fdinfo for kprobe_multi
    https://git.kernel.org/bpf/bpf-next/c/da7e9c0a7fbc

You are awesome, thank you!
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