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.

And fix a bug in commit 46ed5fc33db9, which wrongly used the
func_name instead of probe_name to register.

Fixes: 46ed5fc33db9 ("libbpf: Refactor and simplify legacy kprobe code")
Co-developed-by: Chengming Zhou <redacted>
Signed-off-by: Qiang Wang <redacted>
Signed-off-by: Chengming Zhou <redacted>

---
  tools/lib/bpf/libbpf.c | 5 +++--
  1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 7c74342bb668..7d1097958459 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c

@@ -9634,7 +9634,8 @@ 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, index++);

  }

  static int add_kprobe_event_legacy(const char *probe_name, bool retprobe,

@@ -9735,7 +9736,7 @@ bpf_program__attach_kprobe_opts(const struct

bpf_program *prog,
                 gen_kprobe_legacy_event_name(probe_name,
sizeof(probe_name),
                                              func_name, offset);

-               legacy_probe = strdup(func_name);
+               legacy_probe = strdup(probe_name);