From: Alan Maguire <alan.maguire@oracle.com>
Date: Wed, 14 Jul 2021 11:43:59 +0200
Subject: libbpf: Allow specification of "kprobe/function+offset"
Patch-mainline: v5.15-rc1
Git-commit: a2488b5f483f18e6e34be2a15eb4a79f4a0d8728
References: jsc#PED-1377
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 <alan.maguire@oracle.com>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210714094400.396467-8-jolsa@kernel.org
Acked-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
---
tools/lib/bpf/libbpf.c | 24 ++++++++++++++++++++++--
1 file changed, 22 insertions(+), 2 deletions(-)
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -10348,6 +10348,7 @@ static int perf_event_open_probe(bool up
struct bpf_program_attach_kprobe_opts {
bool retprobe;
+ unsigned long offset;
};
static struct bpf_link*
@@ -10360,7 +10361,7 @@ bpf_program__attach_kprobe_opts(struct b
int pfd, err;
pfd = perf_event_open_probe(false /* uprobe */, opts->retprobe, func_name,
- 0 /* offset */, -1 /* pid */);
+ opts->offset, -1 /* pid */);
if (pfd < 0) {
pr_warn("prog '%s': failed to create %s '%s' perf event: %s\n",
prog->name, opts->retprobe ? "kretprobe" : "kprobe", func_name,
@@ -10394,12 +10395,31 @@ static struct bpf_link *attach_kprobe(co
struct bpf_program *prog)
{
struct bpf_program_attach_kprobe_opts opts;
+ unsigned long offset = 0;
+ struct bpf_link *link;
const char *func_name;
+ char *func;
+ int n, err;
func_name = prog->sec_name + sec->len;
opts.retprobe = strcmp(sec->sec, "kretprobe/") == 0;
- return bpf_program__attach_kprobe_opts(prog, func_name, &opts);
+ n = sscanf(func_name, "%m[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 (opts.retprobe && offset != 0) {
+ err = -EINVAL;
+ pr_warn("kretprobes do not support offset specification\n");
+ return libbpf_err_ptr(err);
+ }
+
+ opts.offset = offset;
+ link = bpf_program__attach_kprobe_opts(prog, func, &opts);
+ free(func);
+ return link;
}
struct bpf_link *bpf_program__attach_uprobe(struct bpf_program *prog,