[RFC PATCH v6 26/32] perf tools: Parse probe points of eBPF programs during preparation

Wang Nan
2015-06-09T05:52:47Z

This patch parses section name of each program, and creates
corresponding 'struct perf_probe_event' structure.

parse_perf_probe_command() is used to do the main parsing works.
Parsing result is stored into a global array. This is because
add_perf_probe_events() is non-reentrantable. In following patch,
add_perf_probe_events will be introduced to insert kprobes. It accepts
an array of 'struct perf_probe_event' and do all works in one call.

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

This patch utilizes bpf_program__set_private(), bind perf_probe_event
with bpf program by private field.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
---
tools/perf/util/bpf-loader.c | 124 ++++++++++++++++++++++++++++++++++++++++++-
tools/perf/util/bpf-loader.h | 2 +
2 files changed, 124 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/bpf-loader.c b/tools/perf/util/bpf-loader.c
index f33fd47..d786efc 100644
--- a/tools/perf/util/bpf-loader.c
+++ b/tools/perf/util/bpf-loader.c
@@ -10,6 +10,8 @@
#include "debug.h"
#include "util.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, ...) \
@@ -29,6 +31,9 @@ DEFINE_PRINT_FN(debug, 1)

static bool libbpf_initialized = false;

+static struct perf_probe_event probe_event_array[MAX_PROBES];
+static size_t nr_probe_events;
+
/*
* Group all bpf related programs together. Futher we can config them
* using perf_default_config().
@@ -211,9 +216,117 @@ out:
return err;
}

+static struct perf_probe_event *
+alloc_perf_probe_event(void)
+{
+ struct perf_probe_event *pev;
+ int n = nr_probe_events;
+ if (n >= MAX_PROBES) {
+ pr_err("bpf: too many events, increase MAX_PROBES\n");
+ return NULL;
+ }
+
+ nr_probe_events = n + 1;
+ pev = &probe_event_array[n];
+ bzero(pev, sizeof(*pev));
+ return pev;
+}
+
+struct bpf_prog_priv {
+ struct perf_probe_event *pev;
+};
+
+static void
+bpf_prog_priv__clear(struct bpf_program *prog __maybe_unused,
+ void *_priv)
+{
+ struct bpf_prog_priv *priv = _priv;
+ if (priv->pev)
+ clear_perf_probe_event(priv->pev);
+ free(priv);
+}
+
+static int
+config_bpf_program(struct bpf_program *prog)
+{
+ struct perf_probe_event *pev = alloc_perf_probe_event();
+ struct bpf_prog_priv *priv = NULL;
+ const char *config_str;
+ int err;
+
+ /* pr_err has been done by alloc_perf_probe_event */
+ if (!pev)
+ return -ENOMEM;
+
+ err = bpf_program__get_title(prog, &config_str, false);
+ if (err || !config_str) {
+ pr_err("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_err("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_err("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_err("bpf: strdup failed\n");
+ err = -ENOMEM;
+ goto errout;
+ }
+
+ if (!pev->event) {
+ pr_err("bpf: '%s': event name is missing\n",
+ config_str);
+ err = -EINVAL;
+ goto errout;
+ }
+
+ pr_debug("bpf: config '%s' is ok\n", config_str);
+
+ priv = calloc(1, sizeof(*priv));
+ if (!priv) {
+ pr_err("bpf: failed to alloc memory\n");
+ err = -ENOMEM;
+ goto errout;
+ }
+
+ priv->pev = pev;
+
+ err = bpf_program__set_private(prog, priv,
+ bpf_prog_priv__clear);
+ if (err) {
+ pr_err("bpf: set program private failed\n");
+ err = -ENOMEM;
+ goto errout;
+ }
+ return 0;
+
+errout:
+ if (pev)
+ clear_perf_probe_event(pev);
+ if (priv)
+ free(priv);
+ return err;
+}
+
int bpf__prepare_load(const char *filename, bool source)
{
struct bpf_object *obj;
+ struct bpf_program *prog;
+ int err = 0;

if (!libbpf_initialized)
libbpf_set_print(libbpf_warning,
@@ -223,7 +336,6 @@ int bpf__prepare_load(const char *filename, bool source)
if (source) {
void *obj_buf;
size_t obj_buf_sz;
- int err;

err = bpf__compile(filename, &obj_buf, &obj_buf_sz);
if (err)
@@ -238,12 +350,20 @@ int bpf__prepare_load(const char *filename, bool source)
return -EINVAL;
}

+ bpf_object__for_each_program(prog, obj) {
+ err = config_bpf_program(prog);
+ if (err)
+ goto errout;
+ }
+
/*
* Throw object pointer away: it will be retrived using
* bpf_objects iterater.
*/
-
return 0;
+errout:
+ bpf_object__close(obj);
+ return err;
}

void bpf__clear(void)
diff --git a/tools/perf/util/bpf-loader.h b/tools/perf/util/bpf-loader.h
index edc211e..2ed7a16 100644
--- a/tools/perf/util/bpf-loader.h
+++ b/tools/perf/util/bpf-loader.h
@@ -17,6 +17,8 @@ struct bpf_param {
extern struct bpf_param bpf_param;
extern int perf_bpf_config(const char *var, const char *value);

+#define PERF_BPF_PROBE_GROUP "perf_bpf_probe"
+
#ifdef HAVE_LIBBPF_SUPPORT
int bpf__prepare_load(const char *filename, bool source);

--
1.8.3.4