From a2488b5f483f18e6e34be2a15eb4a79f4a0d8728 Mon Sep 17 00:00:00 2001 From: Alan Maguire Date: Wed, 14 Jul 2021 11:43:59 +0200 Subject: [PATCH] libbpf: Allow specification of "kprobe/function+offset" 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 Signed-off-by: Jiri Olsa Signed-off-by: Alexei Starovoitov Link: https://lore.kernel.org/bpf/20210714094400.396467-8-jolsa@kernel.org --- tools/lib/bpf/libbpf.c | 24 ++++++++++++++++++++++-- 1 file changed, 22 insertions(+), 2 deletions(-) diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index d93a6f9..abe6d48 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -10348,6 +10348,7 @@ static int perf_event_open_probe(bool uprobe, bool retprobe, const char *name, 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 bpf_program *prog, 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(const struct bpf_sec_def *sec, 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, -- 2.7.4