linux-kernel - [RFC PATCH v3 32/37] perf bpf: Parse probe points of eBPF programs during preparation

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Message-ID: <1431860222-61636-33-git-send-email-wangnan0@huawei.com>
Date:	Sun, 17 May 2015 10:56:57 +0000
From:	Wang Nan <wangnan0@...wei.com>
To:	<paulus@...ba.org>, <a.p.zijlstra@...llo.nl>, <mingo@...hat.com>,
	<acme@...nel.org>, <namhyung@...nel.org>, <jolsa@...nel.org>,
	<dsahern@...il.com>, <ast@...mgrid.com>, <daniel@...earbox.net>,
	<brendan.d.gregg@...il.com>, <masami.hiramatsu.pt@...achi.com>
CC:	<lizefan@...wei.com>, <linux-kernel@...r.kernel.org>,
	<pi3orama@....com>
Subject: [RFC PATCH v3 32/37] perf bpf: Parse probe points of eBPF programs during preparation

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 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.

Signed-off-by: Wang Nan <wangnan0@...wei.com>
---
 tools/perf/util/bpf-loader.c | 74 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 74 insertions(+)

diff --git a/tools/perf/util/bpf-loader.c b/tools/perf/util/bpf-loader.c
index 67bfb62..3dc9b61 100644
--- a/tools/perf/util/bpf-loader.c
+++ b/tools/perf/util/bpf-loader.c
@@ -29,6 +29,7 @@ DEFINE_PRINT_FN(debug, 1)
 static bool libbpf_inited = false;
 
 #define MAX_OBJECTS	128
+#define PERF_BPF_PROBE_GROUP "perf_bpf_probe"
 
 struct {
 	struct bpf_object *objects[MAX_OBJECTS];
@@ -36,10 +37,78 @@ struct {
 
 	struct {
 		struct bpf_prog_handler *prog;
+		struct perf_probe_event *pevent;
 	} progs[MAX_PROBES];
 	size_t nr_progs;
+
+	struct perf_probe_event event_array[MAX_PROBES];
+	size_t nr_events;
 } params;
 
+static struct perf_probe_event *
+alloc_perf_probe_event(void)
+{
+	struct perf_probe_event *pev;
+	int n = params.nr_events;
+
+	if (n >= MAX_PROBES) {
+		pr_err("bpf: too many events, increase MAX_PROBES\n");
+		return NULL;
+	}
+
+	params.nr_events = n + 1;
+	pev = &params.event_array[n];
+	bzero(pev, sizeof(*pev));
+	return pev;
+}
+
+static int
+bpf_do_config(size_t prog_idx, const char *config_str)
+{
+	struct perf_probe_event *pev = alloc_perf_probe_event();
+	int err = 0;
+	
+	if (!pev)
+		return -ENOMEM;
+
+	if ((err = parse_perf_probe_command(config_str, pev)) < 0) {
+		pr_err("bpf config: %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 config: '%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 config: strdup failed\n");
+		err = -ENOMEM;
+		goto errout;
+	}
+
+	if (!pev->event) {
+		pr_err("bpf config: '%s': event name is missing\n",
+				config_str);
+		err = -EINVAL;
+		goto errout;
+	}
+
+	pr_debug("bpf config: config '%s' ok\n", config_str);
+	params.progs[prog_idx].pevent = pev;
+	return 0;
+errout:
+	if (pev)
+		clear_perf_probe_event(pev);
+	return err;
+}
+
 int bpf_prepare_load(const char *filename)
 {
 	struct bpf_object *obj;
@@ -81,6 +150,8 @@ int bpf_prepare_load(const char *filename)
 			return -EINVAL;
 		}
 		pr_debug("bpf: add program '%s'\n", title);
+
+		bpf_do_config(params.nr_progs - 1, title);
 	}
 	return 0;
 }
@@ -89,6 +160,9 @@ void bpf_clear(void)
 {
 	size_t i;
 
+	for (i = 0; i < params.nr_events; i++)
+		clear_perf_probe_event(&params.event_array[i]);
+
 	for (i = 0; i < params.nr_objects; i++)
 		bpf_close_object(params.objects[i]);
 }
-- 
1.8.3.4

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