[RFC PATCH 14/22] perf bpf: config eBPF programs based on their names.

Wang Nan
2015-04-30T11:00:21Z

This patch partially implements bpf_obj_config(), which is used for
define k(ret)probe positions which will be attached eBPF programs.

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 together.

This patch deals programs with 'kprobe/myprobe' like name only by
generating perf probe command string then calling
parse_perf_probe_command().

Signed-off-by: Wang Nan <wangnan0@huawei.com>
---
tools/perf/util/bpf-loader.c | 201 +++++++++++++++++++++++++++++++++++++++++++
tools/perf/util/bpf-loader.h | 2 +
2 files changed, 203 insertions(+)

diff --git a/tools/perf/util/bpf-loader.c b/tools/perf/util/bpf-loader.c
index 66fbca2..b2871fc 100644
--- a/tools/perf/util/bpf-loader.c
+++ b/tools/perf/util/bpf-loader.c
@@ -22,6 +22,38 @@

static LIST_HEAD(bpf_obj_list);

+#define MAX_CMDLEN 256
+#define PERF_BPF_PROBE_GROUP "perf_bpf_probe"
+/*
+ * perf probe is no non-reentrantable, so we must group all events
+ * together and call add_perf_probe_events only once.
+ */
+
+struct params {
+ struct perf_probe_event event_array[MAX_PROBES];
+ size_t nr_events;
+};
+static struct params params = {
+ .nr_events = 0,
+};
+
+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 struct bpf_obj *__bpf_obj_alloc(const char *path)
{
struct bpf_obj *obj;
@@ -279,6 +311,10 @@ bpf_perf_prog_free(struct bpf_perf_prog *prog)
free(prog->name);
if (prog->insns)
free(prog->insns);
+ if (prog->pev) {
+ clear_perf_probe_event(prog->pev);
+ bzero(prog->pev, sizeof(*prog->pev));
+ }
free(prog);
}

@@ -448,6 +484,169 @@ static int bpf_obj_validate(struct bpf_obj *obj)
return 0;
}

+static struct bpf_perf_prog *
+bpf_find_prog_by_name(struct bpf_obj *obj, const char *name)
+{
+ struct bpf_perf_prog *prog;
+
+ list_for_each_entry(prog, &obj->progs_list, list)
+ if (strcmp(name, prog->name) == 0)
+ return prog;
+ return NULL;
+}
+
+/*
+ * Use config_str to config program. If prog is NULL, find a
+ * prog based on config_str. config_str should not be NULL.
+ */
+static int __bpf_perf_prog_config(struct bpf_obj *obj,
+ struct bpf_perf_prog *prog,
+ 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;
+ }
+
+ if (!prog)
+ prog = bpf_find_prog_by_name(obj, pev->event);
+ if (!prog) {
+ pr_err("bpf config: section %s not found for"
+ " config '%s'\n", pev->event, config_str);
+ err = -ENOENT;
+ goto errout;
+ }
+
+ if (prog->pev) {
+ pr_err("bpf config: duplicate config for section %s\n",
+ prog->name);
+ err = -EEXIST;
+ goto errout;
+ }
+
+ prog->pev = pev;
+ pr_debug("bpf config: config %s ok\n", prog->name);
+ return 0;
+errout:
+ if (pev)
+ clear_perf_probe_event(pev);
+ return err;
+}
+
+/*
+ * Config specific prog using config_str. Both prog and config_str
+ * can be set to NULL, but not both. If prog is NULL, search prog
+ * based on config_str. If config_str is NULL, try to generate a
+ * config_str using prog->name.
+ */
+static int bpf_perf_prog_config(struct bpf_obj *obj,
+ struct bpf_perf_prog *prog,
+ char *config_str)
+{
+ char __config_str[MAX_CMDLEN];
+ char *func_str;
+ char *name = NULL;
+
+ if (!prog && !config_str) {
+ pr_err("bpf config: internal error\n");
+ return -EINVAL;
+ }
+
+ if (prog)
+ name = prog->name;
+
+ if (name && (func_str = strchr(name, '/'))) {
+ const char *ret_str;
+ int err = 0;
+
+ /* try to config prog based on its name */
+ if (config_str) {
+ pr_err("bpf config: bad config %s for %s\n",
+ config_str, name);
+ return -EINVAL;
+ }
+ config_str = __config_str;
+
+ if (memcmp(name, "kprobe/", 7) == 0)
+ ret_str = "";
+ else if (memcmp(name, "kretprobe/", 10) == 0)
+ ret_str = "%return";
+ else {
+ pr_err("bpf: bad section name: '%s'\n", name);
+ return -EINVAL;
+ }
+
+ /* skip '/' */
+ func_str += 1;
+ err = snprintf(config_str, MAX_CMDLEN, "%s=%s%s",
+ func_str, func_str, ret_str);
+ if (err >= MAX_CMDLEN) {
+ pr_err("bpf: function name %s too long\n", func_str);
+ return -EINVAL;
+ }
+
+ err = __bpf_perf_prog_config(obj, prog, config_str);
+ if (err)
+ return err;
+ return 0;
+ }
+
+ if (config_str)
+ /* prog should be NULL in this case. */
+ return __bpf_perf_prog_config(obj, prog, config_str);
+
+ /*
+ * prog->name is a symbol and config_str is NULL.
+ * Return normally. It will be config again with config_str.
+ */
+ return 0;
+}
+
+static int bpf_obj_config(struct bpf_obj *obj)
+{
+ struct bpf_perf_prog *prog;
+ int err;
+
+ /* try to config progs based on their names */
+ list_for_each_entry(prog, &obj->progs_list, list) {
+ err = bpf_perf_prog_config(obj, prog, NULL);
+ if (err)
+ return err;
+ }
+
+ return 0;
+}
+
int bpf__load(const char *path)
{
struct bpf_obj *obj;
@@ -474,6 +673,8 @@ int bpf__load(const char *path)
goto out;
if ((err = bpf_obj_validate(obj)))
goto out;
+ if ((err = bpf_obj_config(obj)))
+ goto out;

list_add(&obj->list, &bpf_obj_list);
return 0;
diff --git a/tools/perf/util/bpf-loader.h b/tools/perf/util/bpf-loader.h
index 1417c0d..09f77a5 100644
--- a/tools/perf/util/bpf-loader.h
+++ b/tools/perf/util/bpf-loader.h
@@ -27,6 +27,8 @@ struct bpf_perf_prog {
char *name;
struct bpf_insn *insns;
size_t insns_cnt;
+
+ struct perf_probe_event *pev;
};

struct bpf_obj {
--
1.8.3.4