[RFC PATCH 1/7] perf tools: Add API to config maps in bpf object

[Wang Nan <wangnan0@huawei.com>]

bpf__config_obj() is introduced as a core API to config BPF object
after loading. One configuration option of maps is introduced. After
this patch BPF object can accept configuration like:

 maps.my_map.value=1234

This patch is more complex than the work it really does because the
consideration of extension. In designing of BPF map configuration,
following things should be considered:

 1. Array indics selection: perf should allow user setting different
    value to different slots in an array, with syntax like:
    maps.my_map.value[0,3-6]=1234;

 2. Type of value: integer is not the only valid value type. Perf
    event can also be put into a map after commit 35578d7984003097af2b1e3
    (bpf: Implement function bpf_perf_event_read() that get the selected
    hardware PMU conuter);

 3. For hash table, it is possible to use string or other as key;

 4. It is possible that map configuration is unable to be setup
    during parsing. Perf event is an example.

Therefore, this patch does tie following thing for extension:

 1. Instead of update map element during parsing, this patch stores
    map config options in 'struct bpf_map_priv'. Following patches
    would apply those configs at proper time;

 2. Make 'struct bpf_map_priv' extensible so following patches can
    add new key and value operations;

 3. Use bpf_config_map_funcs array to support more maps configuration.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Signed-off-by: He Kuang <hekuang@huawei.com>
Cc: 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: 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/ebpf-36xcrahy9n0ayc05mu7aajpk@git.kernel.org
---
 tools/perf/util/bpf-loader.c | 180 +++++++++++++++++++++++++++++++++++++++++++
 tools/perf/util/bpf-loader.h |  27 +++++++
 2 files changed, 207 insertions(+)

diff --git a/tools/perf/util/bpf-loader.c b/tools/perf/util/bpf-loader.c
index 73ff9a9..a5a1c36 100644
--- a/tools/perf/util/bpf-loader.c
+++ b/tools/perf/util/bpf-loader.c
@@ -10,11 +10,13 @@
 #include <linux/err.h>
 #include "perf.h"
 #include "debug.h"
+#include "util.h"
 #include "bpf-loader.h"
 #include "bpf-prologue.h"
 #include "llvm-utils.h"
 #include "probe-event.h"
 #include "probe-finder.h" // for MAX_PROBES
+#include "parse-events.h"
 #include "llvm-utils.h"
 
 #define DEFINE_PRINT_FN(name, level) \
@@ -633,6 +635,170 @@ int bpf__foreach_tev(struct bpf_object *obj,
 	return 0;
 }
 
+enum bpf_map_priv_key_type {
+	BPF_MAP_PRIV_KEY_ALL,
+};
+
+enum bpf_map_priv_value_type {
+	BPF_MAP_PRIV_VAL_VALUE,
+};
+
+struct bpf_map_priv {
+	struct {
+		enum bpf_map_priv_key_type type;
+	} key;
+
+	struct {
+		enum bpf_map_priv_value_type type;
+		union {
+			u64 val;
+		};
+	} value;
+};
+
+static void
+bpf_map_priv__clear(struct bpf_map *map __maybe_unused,
+		    void *_priv)
+{
+	struct bpf_map_priv *priv = _priv;
+
+	free(priv);
+}
+
+static int
+bpf__config_obj_map_array_value(struct bpf_map *map,
+				struct parse_events_term *term)
+{
+	struct bpf_map_priv *priv;
+	struct bpf_map_def def;
+	const char *map_name;
+	int err;
+
+	map_name = bpf_map__get_name(map);
+
+	err = bpf_map__get_def(map, &def);
+	if (err) {
+		pr_debug("Unable to get map definition from '%s'\n",
+			 map_name);
+		return -EINVAL;
+	}
+
+	if (def.type != BPF_MAP_TYPE_ARRAY) {
+		pr_debug("Map %s type is not BPF_MAP_TYPE_ARRAY\n",
+			 map_name);
+		return -EBADF;
+	}
+	if (def.key_size < sizeof(unsigned int)) {
+		pr_debug("Map %s has incorrect key size\n", map_name);
+		return -EINVAL;
+	}
+	switch (def.value_size) {
+	case 1:
+	case 2:
+	case 4:
+	case 8:
+		break;
+	default:
+		pr_debug("Map %s has incorrect value size\n", map_name);
+		return -EINVAL;
+	}
+
+	priv = zalloc(sizeof(*priv));
+	if (!priv) {
+		pr_debug("No enough memory to alloc map private\n");
+		return -ENOMEM;
+	}
+
+	priv->key.type = BPF_MAP_PRIV_KEY_ALL;
+	priv->value.type = BPF_MAP_PRIV_VAL_VALUE;
+	priv->value.val = term->val.num;
+	return bpf_map__set_private(map, priv, bpf_map_priv__clear);
+}
+
+static int
+bpf__config_obj_map_value(struct bpf_map *map,
+			  struct parse_events_term *term,
+			  struct perf_evlist *evlist __maybe_unused)
+{
+	if (term->type_val == PARSE_EVENTS__TERM_TYPE_NUM)
+		return bpf__config_obj_map_array_value(map, term);
+
+	pr_debug("ERROR: wrong value type\n");
+	return -EINVAL;
+}
+
+struct bpf_config_map_func {
+	const char *config_opt;
+	int (*config_func)(struct bpf_map *, struct parse_events_term *,
+			   struct perf_evlist *);
+};
+
+struct bpf_config_map_func bpf_config_map_funcs[] = {
+	{"value", bpf__config_obj_map_value},
+};
+
+static int
+bpf__config_obj_map(struct bpf_object *obj,
+		    struct parse_events_term *term,
+		    struct perf_evlist *evlist)
+{
+	/* key is "maps.<mapname>.<config opt>" */
+	char *map_name = strdup(term->config + sizeof("maps.") - 1);
+	struct bpf_map *map;
+	int err = -ENOENT;
+	char *map_opt;
+	size_t i;
+
+	if (!map_name)
+		return -ENOMEM;
+
+	map_opt = strchr(map_name, '.');
+	if (!map_opt) {
+		pr_debug("ERROR: Invalid map config: %s\n", map_name);
+		goto out;
+	}
+
+	*map_opt++ = '\0';
+	if (*map_opt == '\0') {
+		pr_debug("ERROR: Invalid map option: %s\n", term->config);
+		goto out;
+	}
+
+	map = bpf_object__get_map_by_name(obj, map_name);
+	if (!map) {
+		pr_debug("ERROR: Map %s doesn't exist\n", map_name);
+		goto out;
+	}
+
+	for (i = 0; i < ARRAY_SIZE(bpf_config_map_funcs); i++) {
+		struct bpf_config_map_func *func = &bpf_config_map_funcs[i];
+
+		if (strcmp(map_opt, func->config_opt) == 0) {
+			err = func->config_func(map, term, evlist);
+			goto out;
+		}
+	}
+
+	pr_debug("ERROR: invalid config option '%s' for maps\n",
+		 map_opt);
+	err = -ENOENT;
+out:
+	free(map_name);
+	return err;
+}
+
+int bpf__config_obj(struct bpf_object *obj,
+		    struct parse_events_term *term,
+		    struct perf_evlist *evlist)
+{
+	if (!obj || !term || !term->config)
+		return -ENODEV;
+
+	if (!prefixcmp(term->config, "maps."))
+		return bpf__config_obj_map(obj, term, evlist);
+	return -ENODEV;
+}
+
 #define bpf__strerror_head(err, buf, size) \
 	char sbuf[STRERR_BUFSIZE], *emsg;\
 	if (!size)\
@@ -675,3 +841,17 @@ int bpf__strerror_load(struct bpf_object *obj __maybe_unused,
 	bpf__strerror_end(buf, size);
 	return 0;
 }
+
+int bpf__strerror_config_obj(struct bpf_object *obj __maybe_unused,
+			     struct parse_events_term *term,
+			     struct perf_evlist *evlist __maybe_unused,
+			     int err, char *buf, size_t size)
+{
+	bpf__strerror_head(err, buf, size);
+	bpf__strerror_entry(ENODEV, "Invalid config option: '%s'", term->config)
+	bpf__strerror_entry(ENOENT, "Config target in '%s' is invalid", term->config)
+	bpf__strerror_entry(EBADF,  "Map type mismatch in '%s'", term->config)
+	bpf__strerror_entry(EINVAL, "Invalid config value")
+	bpf__strerror_end(buf, size);
+	return 0;
+}
diff --git a/tools/perf/util/bpf-loader.h b/tools/perf/util/bpf-loader.h
index d8f1945..dfec9b8 100644
--- a/tools/perf/util/bpf-loader.h
+++ b/tools/perf/util/bpf-loader.h
@@ -9,9 +9,11 @@
 #include <linux/err.h>
 #include <string.h>
 #include "probe-event.h"
+#include "evlist.h"
 #include "debug.h"
 
 struct bpf_object;
+struct parse_events_term;
 #define PERF_BPF_PROBE_GROUP "perf_bpf_probe"
 
 typedef int (*bpf_prog_iter_callback_t)(struct probe_trace_event *tev,
@@ -34,6 +36,13 @@ int bpf__strerror_load(struct bpf_object *obj, int err,
 		       char *buf, size_t size);
 int bpf__foreach_tev(struct bpf_object *obj,
 		     bpf_prog_iter_callback_t func, void *arg);
+
+int bpf__config_obj(struct bpf_object *obj, struct parse_events_term *term,
+		    struct perf_evlist *evlist);
+int bpf__strerror_config_obj(struct bpf_object *obj,
+			     struct parse_events_term *term,
+			     struct perf_evlist *evlist,
+			     int err, char *buf, size_t size);
 #else
 static inline struct bpf_object *
 bpf__prepare_load(const char *filename __maybe_unused,
@@ -65,6 +74,14 @@ bpf__foreach_tev(struct bpf_object *obj __maybe_unused,
 }
 
 static inline int
+bpf__config_obj(struct bpf_object *obj __maybe_unused,
+		struct parse_events_term *term __maybe_unused,
+		struct perf_evlist *evlist __maybe_unused)
+{
+	return 0;
+}
+
+static inline int
 __bpf_strerror(char *buf, size_t size)
 {
 	if (!size)
@@ -90,5 +107,15 @@ static inline int bpf__strerror_load(struct bpf_object *obj __maybe_unused,
 {
 	return __bpf_strerror(buf, size);
 }
+
+static inline int
+bpf__strerror_config_obj(struct bpf_object *obj __maybe_unused,
+			 struct parse_events_term *term __maybe_unused,
+			 struct perf_evlist *evlist __maybe_unused,
+			 int err __maybe_unused,
+			 char *buf, size_t size)
+{
+	return __bpf_strerror(buf, size);
+}
 #endif
 #endif
-- 
1.8.3.4