[PATCHv3 bpf-next 6/7] libbpf: allow specification of "kprobe/function+offset"
From: Jiri Olsa <hidden>
Date: 2021-07-07 21:49:04
Also in:
bpf
Subsystem:
bpf [general] (safe dynamic programs and tools), bpf [library] (libbpf), the rest · Maintainers:
Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, Linus Torvalds
From: Alan Maguire <redacted>
kprobes can be placed on most instructions in a function, not
just entry, and ftrace and bpftrace support the function+offset
notification for probe placement. Adding parsing of func_name
into func+offset to bpf_program__attach_kprobe() allows the
user to specify
SEC("kprobe/bpf_fentry_test5+0x6")
...for example, and the offset can be passed to perf_event_open_probe()
to support kprobe attachment.
Signed-off-by: Alan Maguire <redacted>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
tools/lib/bpf/libbpf.c | 20 +++++++++++++++++---
1 file changed, 17 insertions(+), 3 deletions(-)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 1e04ce724240..60c9e3e77684 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c@@ -10309,11 +10309,25 @@ struct bpf_link *bpf_program__attach_kprobe(struct bpf_program *prog, const char *func_name) { char errmsg[STRERR_BUFSIZE]; + char func[BPF_OBJ_NAME_LEN]; + unsigned long offset = 0; struct bpf_link *link; - int pfd, err; + int pfd, err, n; + + n = sscanf(func_name, "%[a-zA-Z0-9_.]+%lx", func, &offset); + if (n < 1) { + err = -EINVAL; + pr_warn("kprobe name is invalid: %s\n", func_name); + return libbpf_err_ptr(err); + } + if (retprobe && offset != 0) { + err = -EINVAL; + pr_warn("kretprobes do not support offset specification\n"); + return libbpf_err_ptr(err); + } - pfd = perf_event_open_probe(false /* uprobe */, retprobe, func_name, - 0 /* offset */, -1 /* pid */); + pfd = perf_event_open_probe(false /* uprobe */, retprobe, func, + offset, -1 /* pid */); if (pfd < 0) { pr_warn("prog '%s': failed to create %s '%s' perf event: %s\n", prog->name, retprobe ? "kretprobe" : "kprobe", func_name,
--
2.31.1