Message ID | 20190620230951.3155955-5-andriin@fb.com |
---|---|
State | Changes Requested |
Delegated to: | BPF Maintainers |
Headers | show |
Series | libbpf: add tracing attach APIs | expand |
On 06/20, Andrii Nakryiko wrote: > Add APIs allowing to attach BPF program to kernel tracepoints. Raw > tracepoint attach API is also added for uniform per-BPF-program API, > but is mostly a wrapper around existing bpf_raw_tracepoint_open call. > > Signed-off-by: Andrii Nakryiko <andriin@fb.com> > --- > tools/lib/bpf/libbpf.c | 99 ++++++++++++++++++++++++++++++++++++++++ > tools/lib/bpf/libbpf.h | 5 ++ > tools/lib/bpf/libbpf.map | 2 + > 3 files changed, 106 insertions(+) > > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c > index 11329e05530e..cefe67ba160b 100644 > --- a/tools/lib/bpf/libbpf.c > +++ b/tools/lib/bpf/libbpf.c > @@ -4176,6 +4176,105 @@ int bpf_program__attach_uprobe(struct bpf_program *prog, bool retprobe, > return pfd; > } > > +static int determine_tracepoint_id(const char* tp_category, const char* tp_name) > +{ > + char file[PATH_MAX]; > + int ret; > + > + ret = snprintf(file, sizeof(file), > + "/sys/kernel/debug/tracing/events/%s/%s/id", > + tp_category, tp_name); > + if (ret < 0) > + return -errno; > + if (ret >= sizeof(file)) { > + pr_debug("tracepoint %s/%s path is too long\n", > + tp_category, tp_name); > + return -E2BIG; > + } > + return parse_uint_from_file(file); > +} > + > +static int perf_event_open_tracepoint(const char* tp_category, > + const char* tp_name) > +{ > + struct perf_event_attr attr = {}; > + char errmsg[STRERR_BUFSIZE]; > + int tp_id, pfd, err; > + [..] > + tp_id = determine_tracepoint_id(tp_category, tp_name); Why no assign to attr.config directly here? You can move all other constants to the initialization as well: struct perf_event_attr attr = { .type = PERF_TYPE_TRACEPON, .size = sizeof(struct perf_event_attr), }; attr.config = determine_tracepoint_id(...); (I guess that's a matter of style, but something to consider). > + if (tp_id < 0){ > + pr_warning("failed to determine tracepoint '%s/%s' perf ID: %s\n", > + tp_category, tp_name, > + libbpf_strerror_r(tp_id, errmsg, sizeof(errmsg))); > + return tp_id; > + } > + [..] > + memset(&attr, 0, sizeof(attr)); Not needed since you do attr = {}; above? > + attr.type = PERF_TYPE_TRACEPOINT; > + attr.size = sizeof(attr); > + attr.config = tp_id; > + > + pfd = syscall( __NR_perf_event_open, &attr, -1 /* pid */, 0 /* cpu */, > + -1 /* group_fd */, PERF_FLAG_FD_CLOEXEC); > + if (pfd < 0) { > + err = -errno; > + pr_warning("tracepoint '%s/%s' perf_event_open() failed: %s\n", > + tp_category, tp_name, > + libbpf_strerror_r(err, errmsg, sizeof(errmsg))); > + return err; > + } > + return pfd; > +} > + > +int bpf_program__attach_tracepoint(struct bpf_program *prog, > + const char *tp_category, > + const char *tp_name) > +{ > + char errmsg[STRERR_BUFSIZE]; > + int pfd, err; > + > + pfd = perf_event_open_tracepoint(tp_category, tp_name); > + if (pfd < 0) { > + pr_warning("program '%s': failed to create tracepoint '%s/%s' perf event: %s\n", > + bpf_program__title(prog, false), > + tp_category, tp_name, > + libbpf_strerror_r(pfd, errmsg, sizeof(errmsg))); > + return pfd; > + } > + err = bpf_program__attach_perf_event(prog, pfd); > + if (err) { > + libbpf_perf_event_disable_and_close(pfd); > + pr_warning("program '%s': failed to attach to tracepoint '%s/%s': %s\n", > + bpf_program__title(prog, false), > + tp_category, tp_name, > + libbpf_strerror_r(err, errmsg, sizeof(errmsg))); > + return err; > + } > + return pfd; > +} > + > +int bpf_program__attach_raw_tracepoint(struct bpf_program *prog, > + const char *tp_name) > +{ > + char errmsg[STRERR_BUFSIZE]; > + int bpf_fd, pfd; > + > + bpf_fd = bpf_program__fd(prog); > + if (bpf_fd < 0) { > + pr_warning("program '%s': can't attach before loaded\n", > + bpf_program__title(prog, false)); > + return -EINVAL; > + } > + pfd = bpf_raw_tracepoint_open(tp_name, bpf_fd); > + if (pfd < 0) { > + pr_warning("program '%s': failed to attach to raw tracepoint '%s': %s\n", > + bpf_program__title(prog, false), tp_name, > + libbpf_strerror_r(pfd, errmsg, sizeof(errmsg))); > + return pfd; > + } > + return pfd; > +} > + > enum bpf_perf_event_ret > bpf_perf_event_read_simple(void *mmap_mem, size_t mmap_size, size_t page_size, > void **copy_mem, size_t *copy_size, > diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h > index a7264f06aa5f..bf7020a565c6 100644 > --- a/tools/lib/bpf/libbpf.h > +++ b/tools/lib/bpf/libbpf.h > @@ -176,6 +176,11 @@ LIBBPF_API int bpf_program__attach_uprobe(struct bpf_program *prog, > pid_t pid, > const char *binary_path, > size_t func_offset); > +LIBBPF_API int bpf_program__attach_tracepoint(struct bpf_program *prog, > + const char *tp_category, > + const char *tp_name); > +LIBBPF_API int bpf_program__attach_raw_tracepoint(struct bpf_program *prog, > + const char *tp_name); > > struct bpf_insn; > > diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map > index 1a982c2e1751..2382fbda4cbb 100644 > --- a/tools/lib/bpf/libbpf.map > +++ b/tools/lib/bpf/libbpf.map > @@ -174,6 +174,8 @@ LIBBPF_0.0.4 { > bpf_object__load_xattr; > bpf_program__attach_kprobe; > bpf_program__attach_perf_event; > + bpf_program__attach_raw_tracepoint; > + bpf_program__attach_tracepoint; > bpf_program__attach_uprobe; > libbpf_num_possible_cpus; > libbpf_perf_event_disable_and_close; > -- > 2.17.1 >
On Thu, Jun 20, 2019 at 5:07 PM Stanislav Fomichev <sdf@fomichev.me> wrote: > > On 06/20, Andrii Nakryiko wrote: > > Add APIs allowing to attach BPF program to kernel tracepoints. Raw > > tracepoint attach API is also added for uniform per-BPF-program API, > > but is mostly a wrapper around existing bpf_raw_tracepoint_open call. > > > > Signed-off-by: Andrii Nakryiko <andriin@fb.com> > > --- > > tools/lib/bpf/libbpf.c | 99 ++++++++++++++++++++++++++++++++++++++++ > > tools/lib/bpf/libbpf.h | 5 ++ > > tools/lib/bpf/libbpf.map | 2 + > > 3 files changed, 106 insertions(+) > > > > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c > > index 11329e05530e..cefe67ba160b 100644 > > --- a/tools/lib/bpf/libbpf.c > > +++ b/tools/lib/bpf/libbpf.c > > @@ -4176,6 +4176,105 @@ int bpf_program__attach_uprobe(struct bpf_program *prog, bool retprobe, > > return pfd; > > } > > > > +static int determine_tracepoint_id(const char* tp_category, const char* tp_name) > > +{ > > + char file[PATH_MAX]; > > + int ret; > > + > > + ret = snprintf(file, sizeof(file), > > + "/sys/kernel/debug/tracing/events/%s/%s/id", > > + tp_category, tp_name); > > + if (ret < 0) > > + return -errno; > > + if (ret >= sizeof(file)) { > > + pr_debug("tracepoint %s/%s path is too long\n", > > + tp_category, tp_name); > > + return -E2BIG; > > + } > > + return parse_uint_from_file(file); > > +} > > + > > +static int perf_event_open_tracepoint(const char* tp_category, > > + const char* tp_name) > > +{ > > + struct perf_event_attr attr = {}; > > + char errmsg[STRERR_BUFSIZE]; > > + int tp_id, pfd, err; > > + > [..] > > + tp_id = determine_tracepoint_id(tp_category, tp_name); > Why no assign to attr.config directly here? It's used in few places for error-handling branch, so it would look a bit weird and make lines longer. > You can move all other constants to the initialization as well: > > struct perf_event_attr attr = { > .type = PERF_TYPE_TRACEPON, > .size = sizeof(struct perf_event_attr), > }; > > attr.config = determine_tracepoint_id(...); > > (I guess that's a matter of style, but something to consider). Yeah. It seems like explicit initialization of each member of attribute structs is prevalent in libbpf.c. I also don't want to have some fields initialized at declaration site, and some other in code. Better to group all initialization together. > > > + if (tp_id < 0){ > > + pr_warning("failed to determine tracepoint '%s/%s' perf ID: %s\n", > > + tp_category, tp_name, > > + libbpf_strerror_r(tp_id, errmsg, sizeof(errmsg))); > > + return tp_id; > > + } > > + > [..] > > + memset(&attr, 0, sizeof(attr)); > Not needed since you do attr = {}; above? Yep, removed. > > > + attr.type = PERF_TYPE_TRACEPOINT; > > + attr.size = sizeof(attr); > > + attr.config = tp_id; > > + > > + pfd = syscall( __NR_perf_event_open, &attr, -1 /* pid */, 0 /* cpu */, > > + -1 /* group_fd */, PERF_FLAG_FD_CLOEXEC); > > + if (pfd < 0) { > > + err = -errno; > > + pr_warning("tracepoint '%s/%s' perf_event_open() failed: %s\n", > > + tp_category, tp_name, > > + libbpf_strerror_r(err, errmsg, sizeof(errmsg))); > > + return err; > > + } > > + return pfd; > > +} > > + <snip>
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 11329e05530e..cefe67ba160b 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -4176,6 +4176,105 @@ int bpf_program__attach_uprobe(struct bpf_program *prog, bool retprobe, return pfd; } +static int determine_tracepoint_id(const char* tp_category, const char* tp_name) +{ + char file[PATH_MAX]; + int ret; + + ret = snprintf(file, sizeof(file), + "/sys/kernel/debug/tracing/events/%s/%s/id", + tp_category, tp_name); + if (ret < 0) + return -errno; + if (ret >= sizeof(file)) { + pr_debug("tracepoint %s/%s path is too long\n", + tp_category, tp_name); + return -E2BIG; + } + return parse_uint_from_file(file); +} + +static int perf_event_open_tracepoint(const char* tp_category, + const char* tp_name) +{ + struct perf_event_attr attr = {}; + char errmsg[STRERR_BUFSIZE]; + int tp_id, pfd, err; + + tp_id = determine_tracepoint_id(tp_category, tp_name); + if (tp_id < 0){ + pr_warning("failed to determine tracepoint '%s/%s' perf ID: %s\n", + tp_category, tp_name, + libbpf_strerror_r(tp_id, errmsg, sizeof(errmsg))); + return tp_id; + } + + memset(&attr, 0, sizeof(attr)); + attr.type = PERF_TYPE_TRACEPOINT; + attr.size = sizeof(attr); + attr.config = tp_id; + + pfd = syscall( __NR_perf_event_open, &attr, -1 /* pid */, 0 /* cpu */, + -1 /* group_fd */, PERF_FLAG_FD_CLOEXEC); + if (pfd < 0) { + err = -errno; + pr_warning("tracepoint '%s/%s' perf_event_open() failed: %s\n", + tp_category, tp_name, + libbpf_strerror_r(err, errmsg, sizeof(errmsg))); + return err; + } + return pfd; +} + +int bpf_program__attach_tracepoint(struct bpf_program *prog, + const char *tp_category, + const char *tp_name) +{ + char errmsg[STRERR_BUFSIZE]; + int pfd, err; + + pfd = perf_event_open_tracepoint(tp_category, tp_name); + if (pfd < 0) { + pr_warning("program '%s': failed to create tracepoint '%s/%s' perf event: %s\n", + bpf_program__title(prog, false), + tp_category, tp_name, + libbpf_strerror_r(pfd, errmsg, sizeof(errmsg))); + return pfd; + } + err = bpf_program__attach_perf_event(prog, pfd); + if (err) { + libbpf_perf_event_disable_and_close(pfd); + pr_warning("program '%s': failed to attach to tracepoint '%s/%s': %s\n", + bpf_program__title(prog, false), + tp_category, tp_name, + libbpf_strerror_r(err, errmsg, sizeof(errmsg))); + return err; + } + return pfd; +} + +int bpf_program__attach_raw_tracepoint(struct bpf_program *prog, + const char *tp_name) +{ + char errmsg[STRERR_BUFSIZE]; + int bpf_fd, pfd; + + bpf_fd = bpf_program__fd(prog); + if (bpf_fd < 0) { + pr_warning("program '%s': can't attach before loaded\n", + bpf_program__title(prog, false)); + return -EINVAL; + } + pfd = bpf_raw_tracepoint_open(tp_name, bpf_fd); + if (pfd < 0) { + pr_warning("program '%s': failed to attach to raw tracepoint '%s': %s\n", + bpf_program__title(prog, false), tp_name, + libbpf_strerror_r(pfd, errmsg, sizeof(errmsg))); + return pfd; + } + return pfd; +} + enum bpf_perf_event_ret bpf_perf_event_read_simple(void *mmap_mem, size_t mmap_size, size_t page_size, void **copy_mem, size_t *copy_size, diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h index a7264f06aa5f..bf7020a565c6 100644 --- a/tools/lib/bpf/libbpf.h +++ b/tools/lib/bpf/libbpf.h @@ -176,6 +176,11 @@ LIBBPF_API int bpf_program__attach_uprobe(struct bpf_program *prog, pid_t pid, const char *binary_path, size_t func_offset); +LIBBPF_API int bpf_program__attach_tracepoint(struct bpf_program *prog, + const char *tp_category, + const char *tp_name); +LIBBPF_API int bpf_program__attach_raw_tracepoint(struct bpf_program *prog, + const char *tp_name); struct bpf_insn; diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map index 1a982c2e1751..2382fbda4cbb 100644 --- a/tools/lib/bpf/libbpf.map +++ b/tools/lib/bpf/libbpf.map @@ -174,6 +174,8 @@ LIBBPF_0.0.4 { bpf_object__load_xattr; bpf_program__attach_kprobe; bpf_program__attach_perf_event; + bpf_program__attach_raw_tracepoint; + bpf_program__attach_tracepoint; bpf_program__attach_uprobe; libbpf_num_possible_cpus; libbpf_perf_event_disable_and_close;
Add APIs allowing to attach BPF program to kernel tracepoints. Raw tracepoint attach API is also added for uniform per-BPF-program API, but is mostly a wrapper around existing bpf_raw_tracepoint_open call. Signed-off-by: Andrii Nakryiko <andriin@fb.com> --- tools/lib/bpf/libbpf.c | 99 ++++++++++++++++++++++++++++++++++++++++ tools/lib/bpf/libbpf.h | 5 ++ tools/lib/bpf/libbpf.map | 2 + 3 files changed, 106 insertions(+)