libbpf: Support repeated legacy kprobes on same function

frankQAQ-wang · Nobody · commit 0120982b42db · 2021-12-25T00:41:56.000-08:00
If repeated legacy kprobes on same function in one process,
libbpf will register using the same probe name and got -EBUSY
error. So append index to the probe name format to fix this
problem.

Co-developed-by: Chengming Zhou &lt;zhouchengming@bytedance.com&gt;
Signed-off-by: Qiang Wang &lt;wangqiang.wq.frank@bytedance.com&gt;
Signed-off-by: Chengming Zhou &lt;zhouchengming@bytedance.com&gt;
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
@@ -9891,7 +9891,9 @@ static int append_to_file(const char *file, const char *fmt, ...)
 static void gen_kprobe_legacy_event_name(char *buf, size_t buf_sz,
 					 const char *kfunc_name, size_t offset)
 {
-	snprintf(buf, buf_sz, "libbpf_%u_%s_0x%zx", getpid(), kfunc_name, offset);
+	static int index = 0;
+	snprintf(buf, buf_sz, "libbpf_%u_%s_0x%zx_%d", getpid(), kfunc_name, offset
+		 __sync_fetch_and_add(&index, 1));
 }
 
 static int add_kprobe_event_legacy(const char *probe_name, bool retprobe,

Original file line number	Diff line number	Diff line change
`@@ -9891,7 +9891,9 @@ static int append_to_file(const char file, const char fmt, ...)`
`9891`	`9891`	`static void gen_kprobe_legacy_event_name(char *buf, size_t buf_sz,`
`9892`	`9892`	`const char *kfunc_name, size_t offset)`
`9893`	`9893`	`{`
`9894`		`- snprintf(buf, buf_sz, "libbpf_%u_%s_0x%zx", getpid(), kfunc_name, offset);`
	`9894`	`+ static int index = 0;`
	`9895`	`+ snprintf(buf, buf_sz, "libbpf_%u_%s_0x%zx_%d", getpid(), kfunc_name, offset`
	`9896`	`+ __sync_fetch_and_add(&index, 1));`
`9895`	`9897`	`}`
`9896`	`9898`
`9897`	`9899`	`static int add_kprobe_event_legacy(const char *probe_name, bool retprobe,`