On Thu, Dec 23, 2021 at 8:01 PM Qiang Wang
[off-list ref] wrote:
quoted hunk ↗ jump to hunk
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++);
BCC doesn't add this auto-increment (which is also not thread-safe)
and it seems like that works fine for all users.
What is the use case where you'd like to attach to the same kernel
function multiple times with legacy kprobe?
quoted hunk ↗ jump to hunk
}
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);
please send this as a separate fix
if (!legacy_probe)
return libbpf_err_ptr(-ENOMEM);
--
2.20.1