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| author | Chuang Wang <nashuiliang@gmail.com> | 2022-06-29 18:18:45 +0300 |
|---|---|---|
| committer | Andrii Nakryiko <andrii@kernel.org> | 2022-07-06 07:21:41 +0300 |
| commit | 8094029330a2f03fb406ecff80671cf27ce28d42 (patch) | |
| tree | 64fcb754a070e4312c5c88ee8421646057dc4897 /tools/lib | |
| parent | f6b9f6d57e5c765b5ff358af1d7749df5e30334c (diff) | |
| download | linux-8094029330a2f03fb406ecff80671cf27ce28d42.tar.xz | |
libbpf: Cleanup the legacy kprobe_event on failed add/attach_event()
Before the 0bc11ed5ab60 commit ("kprobes: Allow kprobes coexist with
livepatch"), in a scenario where livepatch and kprobe coexist on the
same function entry, the creation of kprobe_event using
add_kprobe_event_legacy() will be successful, at the same time as a
trace event (e.g. /debugfs/tracing/events/kprobe/XXX) will exist, but
perf_event_open() will return an error because both livepatch and kprobe
use FTRACE_OPS_FL_IPMODIFY. As follows:
1) add a livepatch
$ insmod livepatch-XXX.ko
2) add a kprobe using tracefs API (i.e. add_kprobe_event_legacy)
$ echo 'p:mykprobe XXX' > /sys/kernel/debug/tracing/kprobe_events
3) enable this kprobe (i.e. sys_perf_event_open)
This will return an error, -EBUSY.
On Andrii Nakryiko's comment, few error paths in
bpf_program__attach_kprobe_opts() that should need to call
remove_kprobe_event_legacy().
With this patch, whenever an error is returned after
add_kprobe_event_legacy() or bpf_program__attach_perf_event_opts(), this
ensures that the created kprobe_event is cleaned.
Signed-off-by: Chuang Wang <nashuiliang@gmail.com>
Signed-off-by: Jingren Zhou <zhoujingren@didiglobal.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20220629151848.65587-2-nashuiliang@gmail.com
Diffstat (limited to 'tools/lib')
| -rw-r--r-- | tools/lib/bpf/libbpf.c | 18 |
1 files changed, 14 insertions, 4 deletions
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 64c4cc6140d3..8a441d304924 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -9877,10 +9877,11 @@ static int perf_event_kprobe_open_legacy(const char *probe_name, bool retprobe, } type = determine_kprobe_perf_type_legacy(probe_name, retprobe); if (type < 0) { + err = type; pr_warn("failed to determine legacy kprobe event id for '%s+0x%zx': %s\n", kfunc_name, offset, - libbpf_strerror_r(type, errmsg, sizeof(errmsg))); - return type; + libbpf_strerror_r(err, errmsg, sizeof(errmsg))); + goto err_clean_legacy; } attr.size = sizeof(attr); attr.config = type; @@ -9894,9 +9895,14 @@ static int perf_event_kprobe_open_legacy(const char *probe_name, bool retprobe, err = -errno; pr_warn("legacy kprobe perf_event_open() failed: %s\n", libbpf_strerror_r(err, errmsg, sizeof(errmsg))); - return err; + goto err_clean_legacy; } return pfd; + +err_clean_legacy: + /* Clear the newly added legacy kprobe_event */ + remove_kprobe_event_legacy(probe_name, retprobe); + return err; } struct bpf_link * @@ -9953,7 +9959,7 @@ bpf_program__attach_kprobe_opts(const struct bpf_program *prog, prog->name, retprobe ? "kretprobe" : "kprobe", func_name, offset, libbpf_strerror_r(err, errmsg, sizeof(errmsg))); - goto err_out; + goto err_clean_legacy; } if (legacy) { struct bpf_link_perf *perf_link = container_of(link, struct bpf_link_perf, link); @@ -9964,6 +9970,10 @@ bpf_program__attach_kprobe_opts(const struct bpf_program *prog, } return link; + +err_clean_legacy: + if (legacy) + remove_kprobe_event_legacy(legacy_probe, retprobe); err_out: free(legacy_probe); return libbpf_err_ptr(err); |