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Subject[PATCH 08/31] perf record, bpf: Parse and probe eBPF programs probe points
Date
This patch introduces bpf__{un,}probe() functions to enable callers to
create kprobe points based on section names of BPF programs. It parses
the section names of each eBPF program and creates corresponding 'struct
perf_probe_event' structures. The parse_perf_probe_command() function is
used to do the main parsing work.

Parsing result is stored into an array to satisify
add_perf_probe_events(). It accepts an array of 'struct perf_probe_event'
and do all the work in one call.

Define PERF_BPF_PROBE_GROUP as "perf_bpf_probe", which will be used as
the group name of all eBPF probing points.

probe_conf.max_probes is set to MAX_PROBES to support glob matching.

Before ending of bpf__probe(), data in each 'struct perf_probe_event' is
cleaned. Things will be changed by following patches because they need
'struct probe_trace_event' in them,

Signed-off-by: Wang Nan <wangnan0@huawei.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: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/n/1436445342-1402-21-git-send-email-wangnan0@huawei.com
Link: http://lkml.kernel.org/n/1436445342-1402-23-git-send-email-wangnan0@huawei.com
[Merged by two patches]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/builtin-record.c | 19 ++++++-
tools/perf/util/bpf-loader.c | 133 +++++++++++++++++++++++++++++++++++++++++++
tools/perf/util/bpf-loader.h | 13 +++++
3 files changed, 164 insertions(+), 1 deletion(-)

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 31934b1..8833186 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -1140,7 +1140,23 @@ int cmd_record(int argc, const char **argv, const char *prefix __maybe_unused)
if (err)
goto out_bpf_clear;

- err = -ENOMEM;
+ /*
+ * bpf__probe must be called before symbol__init() because we
+ * need init_symbol_maps. If called after symbol__init,
+ * symbol_conf.sort_by_name won't take effect.
+ *
+ * bpf__unprobe() is safe even if bpf__probe() failed, and it
+ * also calls symbol__init. Therefore, goto out_symbol_exit
+ * is safe when probe failed.
+ */
+ err = bpf__probe();
+ if (err) {
+ bpf__strerror_probe(err, errbuf, sizeof(errbuf));
+
+ pr_err("Probing at events in BPF object failed.\n");
+ pr_err("\t%s\n", errbuf);
+ goto out_symbol_exit;
+ }

symbol__init(NULL);

@@ -1201,6 +1217,7 @@ out_symbol_exit:
perf_evlist__delete(rec->evlist);
symbol__exit();
auxtrace_record__free(rec->itr);
+ bpf__unprobe();
out_bpf_clear:
bpf__clear();
return err;
diff --git a/tools/perf/util/bpf-loader.c b/tools/perf/util/bpf-loader.c
index 88531ea..435f52e 100644
--- a/tools/perf/util/bpf-loader.c
+++ b/tools/perf/util/bpf-loader.c
@@ -9,6 +9,8 @@
#include "perf.h"
#include "debug.h"
#include "bpf-loader.h"
+#include "probe-event.h"
+#include "probe-finder.h"

#define DEFINE_PRINT_FN(name, level) \
static int libbpf_##name(const char *fmt, ...) \
@@ -28,6 +30,58 @@ DEFINE_PRINT_FN(debug, 1)

static bool libbpf_initialized;

+static int
+config_bpf_program(struct bpf_program *prog, struct perf_probe_event *pev)
+{
+ const char *config_str;
+ int err;
+
+ config_str = bpf_program__title(prog, false);
+ if (!config_str) {
+ pr_debug("bpf: unable to get title for program\n");
+ return -EINVAL;
+ }
+
+ pr_debug("bpf: config program '%s'\n", config_str);
+ err = parse_perf_probe_command(config_str, pev);
+ if (err < 0) {
+ pr_debug("bpf: '%s' is not a valid config string\n",
+ config_str);
+ /* parse failed, don't need clear pev. */
+ return -EINVAL;
+ }
+
+ if (pev->group && strcmp(pev->group, PERF_BPF_PROBE_GROUP)) {
+ pr_debug("bpf: '%s': group for event is set and not '%s'.\n",
+ config_str, PERF_BPF_PROBE_GROUP);
+ err = -EINVAL;
+ goto errout;
+ } else if (!pev->group)
+ pev->group = strdup(PERF_BPF_PROBE_GROUP);
+
+ if (!pev->group) {
+ pr_debug("bpf: strdup failed\n");
+ err = -ENOMEM;
+ goto errout;
+ }
+
+ if (!pev->event) {
+ pr_debug("bpf: '%s': event name is missing\n",
+ config_str);
+ err = -EINVAL;
+ goto errout;
+ }
+
+ pr_debug("bpf: config '%s' is ok\n", config_str);
+
+ return 0;
+
+errout:
+ if (pev)
+ clear_perf_probe_event(pev);
+ return err;
+}
+
int bpf__prepare_load(const char *filename)
{
struct bpf_object *obj;
@@ -59,6 +113,74 @@ void bpf__clear(void)
bpf_object__close(obj);
}

+static bool is_probed;
+
+int bpf__unprobe(void)
+{
+ struct strfilter *delfilter;
+ int ret;
+
+ if (!is_probed)
+ return 0;
+
+ delfilter = strfilter__new(PERF_BPF_PROBE_GROUP ":*", NULL);
+ if (!delfilter) {
+ pr_debug("Failed to create delfilter when unprobing\n");
+ return -ENOMEM;
+ }
+
+ ret = del_perf_probe_events(delfilter);
+ strfilter__delete(delfilter);
+ if (ret < 0 && is_probed)
+ pr_debug("Error: failed to delete events: %s\n",
+ strerror(-ret));
+ else
+ is_probed = false;
+ return ret < 0 ? ret : 0;
+}
+
+int bpf__probe(void)
+{
+ int err, nr_events = 0;
+ struct bpf_object *obj, *tmp;
+ struct bpf_program *prog;
+ struct perf_probe_event *pevs;
+
+ pevs = calloc(MAX_PROBES, sizeof(pevs[0]));
+ if (!pevs)
+ return -ENOMEM;
+
+ bpf_object__for_each_safe(obj, tmp) {
+ bpf_object__for_each_program(prog, obj) {
+ err = config_bpf_program(prog, &pevs[nr_events++]);
+ if (err < 0)
+ goto out;
+
+ if (nr_events >= MAX_PROBES) {
+ pr_debug("Too many (more than %d) events\n",
+ MAX_PROBES);
+ err = -ERANGE;
+ goto out;
+ };
+ }
+ }
+
+ probe_conf.max_probes = MAX_PROBES;
+ /* Let add_perf_probe_events generates probe_trace_event (tevs) */
+ err = add_perf_probe_events(pevs, nr_events, false);
+
+ /* add_perf_probe_events return negative when fail */
+ if (err < 0) {
+ pr_debug("bpf probe: failed to probe events\n");
+ } else
+ is_probed = true;
+out:
+ while (nr_events > 0)
+ clear_perf_probe_event(&pevs[--nr_events]);
+ free(pevs);
+ return err < 0 ? err : 0;
+}
+
#define bpf__strerror_head(err, buf, size) \
char sbuf[STRERR_BUFSIZE], *emsg;\
if (!size)\
@@ -90,3 +212,14 @@ int bpf__strerror_prepare_load(const char *filename, int err,
bpf__strerror_end(buf, size);
return 0;
}
+
+int bpf__strerror_probe(int err, char *buf, size_t size)
+{
+ bpf__strerror_head(err, buf, size);
+ bpf__strerror_entry(ERANGE, "Too many (more than %d) events",
+ MAX_PROBES);
+ bpf__strerror_entry(ENOENT, "Selected kprobe point doesn't exist.");
+ bpf__strerror_entry(EEXIST, "Selected kprobe point already exist, try perf probe -d '*'.");
+ bpf__strerror_end(buf, size);
+ return 0;
+}
diff --git a/tools/perf/util/bpf-loader.h b/tools/perf/util/bpf-loader.h
index 12be630..6b09a85 100644
--- a/tools/perf/util/bpf-loader.h
+++ b/tools/perf/util/bpf-loader.h
@@ -9,10 +9,15 @@
#include <string.h>
#include "debug.h"

+#define PERF_BPF_PROBE_GROUP "perf_bpf_probe"
+
#ifdef HAVE_LIBBPF_SUPPORT
int bpf__prepare_load(const char *filename);
int bpf__strerror_prepare_load(const char *filename, int err,
char *buf, size_t size);
+int bpf__probe(void);
+int bpf__unprobe(void);
+int bpf__strerror_probe(int err, char *buf, size_t size);

void bpf__clear(void);
#else
@@ -22,6 +27,8 @@ static inline int bpf__prepare_load(const char *filename __maybe_unused)
return -1;
}

+static inline int bpf__probe(void) { return 0; }
+static inline int bpf__unprobe(void) { return 0; }
static inline void bpf__clear(void) { }

static inline int
@@ -43,5 +50,11 @@ bpf__strerror_prepare_load(const char *filename __maybe_unused,
{
return __bpf_strerror(buf, size);
}
+
+static inline int bpf__strerror_probe(int err __maybe_unused,
+ char *buf, size_t size)
+{
+ return __bpf_strerror(buf, size);
+}
#endif
#endif
--
2.1.0


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