| Message ID | 20210707214751.159713-7-jolsa@kernel.org |
|---|---|
| State | New |
| Headers | show |
| Series | bpf, x86: Add bpf_get_func_ip helper | expand |
On Wed, Jul 7, 2021 at 2:54 PM Jiri Olsa <jolsa@redhat.com> wrote: > > From: Alan Maguire <alan.maguire@oracle.com> > > 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> > --- > 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) I think we should add bpf_program__attach_kprobe_opts instead for the programmatic API instead of parsing it here from func_name. It's a cumbersome API. Parsing SEC() is fine, of course, but then it has to call into bpf_program__attach_kprobe_opts() internally. > { > 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 >
On Wed, Jul 07, 2021 at 05:14:20PM -0700, Andrii Nakryiko wrote: > On Wed, Jul 7, 2021 at 2:54 PM Jiri Olsa <jolsa@redhat.com> wrote: > > > > From: Alan Maguire <alan.maguire@oracle.com> > > > > 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> > > --- > > 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) > > I think we should add bpf_program__attach_kprobe_opts instead for the > programmatic API instead of parsing it here from func_name. It's a > cumbersome API. > > Parsing SEC() is fine, of course, but then it has to call into > bpf_program__attach_kprobe_opts() internally. ok, Alan, will you make the change, or should I do that? thanks, jirka > > > { > > 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 > > >
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,