perf bpf: Collect perf_evsel in BPF object files
This patch creates a 'struct perf_evsel' for every probe in a BPF object
file(s) and fills 'struct evlist' with them. The previously introduced
dummy event is now removed. After this patch, the following command:
# perf record --event filter.o ls
Can trace on each of the probes defined in filter.o.
The core of this patch is bpf__foreach_tev(), which calls a callback
function for each 'struct probe_trace_event' event for a bpf program
with each associated file descriptors. The add_bpf_event() callback
creates evsels by calling parse_events_add_tracepoint().
Since bpf-loader.c will not be built if libbpf is turned off, an empty
bpf__foreach_tev() is defined in bpf-loader.h to avoid build errors.
Committer notes:
Before:
# /tmp/oldperf record --event /tmp/foo.o -a usleep 1
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.198 MB perf.data ]
# perf evlist
/tmp/foo.o
# perf evlist -v
/tmp/foo.o: type: 1, size: 112, config: 0x9, { sample_period,
sample_freq }: 4000, sample_type: IP|TID|TIME|CPU|PERIOD, disabled: 1,
inherit: 1, mmap: 1, comm: 1, freq: 1, task: 1, sample_id_all: 1,
exclude_guest: 1, mmap2: 1, comm_exec: 1
I.e. we create just the PERF_TYPE_SOFTWARE (type: 1),
PERF_COUNT_SW_DUMMY(config 0x9) event, now, with this patch:
# perf record --event /tmp/foo.o -a usleep 1
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.210 MB perf.data ]
# perf evlist -v
perf_bpf_probe:fork: type: 2, size: 112, config: 0x6bd, { sample_period,
sample_freq }: 1, sample_type: IP|TID|TIME|CPU|PERIOD|RAW, disabled: 1,
inherit: 1, mmap: 1, comm: 1, task: 1, sample_id_all: 1, exclude_guest:
1, mmap2: 1, comm_exec: 1
#
We now have a PERF_TYPE_SOFTWARE (type: 1), but the config states 0x6bd,
which is how, after setting up the event via the kprobes interface, the
'perf_bpf_probe:fork' event is accessible via the perf_event_open
syscall. This is all transient, as soon as the 'perf record' session
ends, these probes will go away.
To see how it looks like, lets try doing a neverending session, one that
expects a control+C to end:
# perf record --event /tmp/foo.o -a
So, with that in place, we can use 'perf probe' to see what is in place:
# perf probe -l
perf_bpf_probe:fork (on _do_fork@acme/git/linux/kernel/fork.c)
We also can use debugfs:
[root@felicio ~]# cat /sys/kernel/debug/tracing/kprobe_events
p:perf_bpf_probe/fork _text+638512
Ok, now lets stop and see if we got some forks:
[root@felicio linux]# perf record --event /tmp/foo.o -a
^C[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.325 MB perf.data (111 samples) ]
[root@felicio linux]# perf script
sshd 1271 [003] 81797.507678: perf_bpf_probe:fork: (ffffffff8109be30)
sshd 18309 [000] 81797.524917: perf_bpf_probe:fork: (ffffffff8109be30)
sshd 18309 [001] 81799.381603: perf_bpf_probe:fork: (ffffffff8109be30)
sshd 18309 [001] 81799.408635: perf_bpf_probe:fork: (ffffffff8109be30)
<SNIP>
Sure enough, we have 111 forks :-)
Callchains seems to work as well:
# perf report --stdio --no-child
# To display the perf.data header info, please use --header/--header-only options.
#
# Total Lost Samples: 0
#
# Samples: 562 of event 'perf_bpf_probe:fork'
# Event count (approx.): 562
#
# Overhead Command Shared Object Symbol
# ........ ........ ................ ............
#
44.66% sh [kernel.vmlinux] [k] _do_fork
|
---_do_fork
entry_SYSCALL_64_fastpath
__libc_fork
make_child
26.16% make [kernel.vmlinux] [k] _do_fork
<SNIP>
#
Signed-off-by: Wang Nan <wangnan0@huawei.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: Brendan Gregg <brendan.d.gregg@gmail.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: David Ahern <dsahern@gmail.com>
Cc: He Kuang <hekuang@huawei.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kaixu Xia <xiakaixu@huawei.com>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/1444826502-49291-7-git-send-email-wangnan0@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Wang Nan
Arnaldo Carvalho de Melo
Родитель
1e5e3ee8ff
Коммит
4edf30e39e
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@ -255,6 +255,46 @@ int bpf__load(struct bpf_object *obj)
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return 0;
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}
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int bpf__foreach_tev(struct bpf_object *obj,
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bpf_prog_iter_callback_t func,
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void *arg)
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{
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struct bpf_program *prog;
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int err;
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bpf_object__for_each_program(prog, obj) {
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struct probe_trace_event *tev;
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struct perf_probe_event *pev;
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struct bpf_prog_priv *priv;
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int i, fd;
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err = bpf_program__get_private(prog,
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(void **)&priv);
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if (err || !priv) {
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pr_debug("bpf: failed to get private field\n");
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return -EINVAL;
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}
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pev = &priv->pev;
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for (i = 0; i < pev->ntevs; i++) {
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tev = &pev->tevs[i];
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fd = bpf_program__fd(prog);
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if (fd < 0) {
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pr_debug("bpf: failed to get file descriptor\n");
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return fd;
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}
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err = (*func)(tev, fd, arg);
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if (err) {
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pr_debug("bpf: call back failed, stop iterate\n");
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return err;
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}
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}
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}
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return 0;
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}
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#define bpf__strerror_head(err, buf, size) \
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char sbuf[STRERR_BUFSIZE], *emsg;\
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if (!size)\
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@ -8,11 +8,15 @@
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#include <linux/compiler.h>
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#include <linux/err.h>
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#include <string.h>
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#include "probe-event.h"
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#include "debug.h"
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struct bpf_object;
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#define PERF_BPF_PROBE_GROUP "perf_bpf_probe"
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typedef int (*bpf_prog_iter_callback_t)(struct probe_trace_event *tev,
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int fd, void *arg);
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#ifdef HAVE_LIBBPF_SUPPORT
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struct bpf_object *bpf__prepare_load(const char *filename);
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@ -26,6 +30,8 @@ int bpf__strerror_probe(struct bpf_object *obj, int err,
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int bpf__load(struct bpf_object *obj);
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int bpf__strerror_load(struct bpf_object *obj, int err,
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char *buf, size_t size);
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int bpf__foreach_tev(struct bpf_object *obj,
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bpf_prog_iter_callback_t func, void *arg);
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#else
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static inline struct bpf_object *
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bpf__prepare_load(const char *filename __maybe_unused)
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@ -40,6 +46,14 @@ static inline int bpf__probe(struct bpf_object *obj __maybe_unused) { return 0;}
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static inline int bpf__unprobe(struct bpf_object *obj __maybe_unused) { return 0;}
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static inline int bpf__load(struct bpf_object *obj __maybe_unused) { return 0; }
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static inline int
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bpf__foreach_tev(struct bpf_object *obj __maybe_unused,
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bpf_prog_iter_callback_t func __maybe_unused,
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void *arg __maybe_unused)
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{
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return 0;
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}
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static inline int
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__bpf_strerror(char *buf, size_t size)
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{
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@ -530,12 +530,49 @@ static int add_tracepoint_multi_sys(struct list_head *list, int *idx,
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return ret;
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}
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struct __add_bpf_event_param {
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struct parse_events_evlist *data;
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struct list_head *list;
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};
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static int add_bpf_event(struct probe_trace_event *tev, int fd,
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void *_param)
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{
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LIST_HEAD(new_evsels);
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struct __add_bpf_event_param *param = _param;
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struct parse_events_evlist *evlist = param->data;
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struct list_head *list = param->list;
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int err;
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pr_debug("add bpf event %s:%s and attach bpf program %d\n",
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tev->group, tev->event, fd);
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err = parse_events_add_tracepoint(&new_evsels, &evlist->idx, tev->group,
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tev->event, evlist->error, NULL);
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if (err) {
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struct perf_evsel *evsel, *tmp;
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pr_debug("Failed to add BPF event %s:%s\n",
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tev->group, tev->event);
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list_for_each_entry_safe(evsel, tmp, &new_evsels, node) {
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list_del(&evsel->node);
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perf_evsel__delete(evsel);
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}
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return err;
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}
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pr_debug("adding %s:%s\n", tev->group, tev->event);
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list_splice(&new_evsels, list);
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return 0;
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}
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int parse_events_load_bpf_obj(struct parse_events_evlist *data,
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struct list_head *list,
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struct bpf_object *obj)
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{
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int err;
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char errbuf[BUFSIZ];
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struct __add_bpf_event_param param = {data, list};
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static bool registered_unprobe_atexit = false;
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if (IS_ERR(obj) || !obj) {
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@ -567,13 +604,14 @@ int parse_events_load_bpf_obj(struct parse_events_evlist *data,
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goto errout;
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}
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/*
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* Temporary add a dummy event here so we can check whether
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* basic bpf loader works. Following patches will replace
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* dummy event by useful evsels.
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*/
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return parse_events_add_numeric(data, list, PERF_TYPE_SOFTWARE,
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PERF_COUNT_SW_DUMMY, NULL);
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err = bpf__foreach_tev(obj, add_bpf_event, ¶m);
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if (err) {
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snprintf(errbuf, sizeof(errbuf),
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"Attach events in BPF object failed");
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goto errout;
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}
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return 0;
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errout:
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data->error->help = strdup("(add -v to see detail)");
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data->error->str = strdup(errbuf);
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