libbpf: Support repeated legacy kprobes on same function

frankQAQ-wang · anakryiko · commit 51a33c60f1c2 · 2022-01-05T15:38:21.000-08:00
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 <zhouchengming@bytedance.com> Signed-off-by: Qiang Wang <wangqiang.wq.frank@bytedance.com> Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/bpf/20211227130713.66933-2-wangqiang.wq.frank@bytedance.com
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
@@ -9916,7 +9916,10 @@ 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
`@@ -9916,7 +9916,10 @@ static int append_to_file(const char file, const char fmt, ...)`
`9916`	`9916`	`static void gen_kprobe_legacy_event_name(char *buf, size_t buf_sz,`
`9917`	`9917`	`const char *kfunc_name, size_t offset)`
`9918`	`9918`	`{`
`9919`		`- snprintf(buf, buf_sz, "libbpf_%u_%s_0x%zx", getpid(), kfunc_name, offset);`
	`9919`	`+ static int index = 0;`
	`9920`	`+`
	`9921`	`+ snprintf(buf, buf_sz, "libbpf_%u_%s_0x%zx_%d", getpid(), kfunc_name, offset,`
	`9922`	`+ __sync_fetch_and_add(&index, 1));`
`9920`	`9923`	`}`
`9921`	`9924`
`9922`	`9925`	`static int add_kprobe_event_legacy(const char *probe_name, bool retprobe,`