tools lib bpf: Collect map definition in bpf_object

This patch collects more information from maps sections in BPF object
files into 'struct bpf_object', enables later patches access those
information (such as the type and size of the map).

In this patch, a new handler 'struct bpf_map' is extracted in parallel
with bpf_object and bpf_program. Its iterator and accessor is also
created.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/1448614067-197576-2-git-send-email-wangnan0@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

2 files changed, 148 insertions, 60 deletions

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index e3f4c3379f14..f50982579aa8 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -163,22 +163,24 @@ struct bpf_program {
         bpf_program_clear_priv_t clear_priv;
 };
 
+struct bpf_map {
+        int fd;
+        struct bpf_map_def def;
+        void *priv;
+        bpf_map_clear_priv_t clear_priv;
+};
+
 static LIST_HEAD(bpf_objects_list);
 
 struct bpf_object {
         char license[64];
         u32 kern_version;
-        void *maps_buf;
-        size_t maps_buf_sz;
 
         struct bpf_program *programs;
         size_t nr_programs;
-        int *map_fds;
-        /*
-         * This field is required because maps_buf will be freed and
-         * maps_buf_sz will be set to 0 after loaded.
-         */
-        size_t nr_map_fds;
+        struct bpf_map *maps;
+        size_t nr_maps;
+
         bool loaded;
 
         /*
@@ -489,21 +491,38 @@ static int
 bpf_object__init_maps(struct bpf_object *obj, void *data,
                       size_t size)
 {
-        if (size == 0) {
+        size_t nr_maps;
+        int i;
+
+        nr_maps = size / sizeof(struct bpf_map_def);
+        if (!data || !nr_maps) {
                 pr_debug("%s doesn't need map definition\n",
                          obj->path);
                 return 0;
         }
 
-        obj->maps_buf = malloc(size);
-        if (!obj->maps_buf) {
-                pr_warning("malloc maps failed: %s\n", obj->path);
+        pr_debug("maps in %s: %zd bytes\n", obj->path, size);
+
+        obj->maps = calloc(nr_maps, sizeof(obj->maps[0]));
+        if (!obj->maps) {
+                pr_warning("alloc maps for object failed\n");
                 return -ENOMEM;
         }
+        obj->nr_maps = nr_maps;
+
+        for (i = 0; i < nr_maps; i++) {
+                struct bpf_map_def *def = &obj->maps[i].def;
 
-        obj->maps_buf_sz = size;
-        memcpy(obj->maps_buf, data, size);
-        pr_debug("maps in %s: %ld bytes\n", obj->path, (long)size);
+                /*
+                 * fill all fd with -1 so won't close incorrect
+                 * fd (fd=0 is stdin) when failure (zclose won't close
+                 * negative fd)).
+                 */
+                obj->maps[i].fd = -1;
+
+                /* Save map definition into obj->maps */
+                *def = ((struct bpf_map_def *)data)[i];
+        }
         return 0;
 }
 
@@ -688,37 +707,15 @@ static int
 bpf_object__create_maps(struct bpf_object *obj)
 {
         unsigned int i;
-        size_t nr_maps;
-        int *pfd;
-
-        nr_maps = obj->maps_buf_sz / sizeof(struct bpf_map_def);
-        if (!obj->maps_buf || !nr_maps) {
-                pr_debug("don't need create maps for %s\n",
-                         obj->path);
-                return 0;
-        }
 
-        obj->map_fds = malloc(sizeof(int) * nr_maps);
-        if (!obj->map_fds) {
-                pr_warning("realloc perf_bpf_map_fds failed\n");
-                return -ENOMEM;
-        }
-        obj->nr_map_fds = nr_maps;
-
-        /* fill all fd with -1 */
-        memset(obj->map_fds, -1, sizeof(int) * nr_maps);
+        for (i = 0; i < obj->nr_maps; i++) {
+                struct bpf_map_def *def = &obj->maps[i].def;
+                int *pfd = &obj->maps[i].fd;
 
-        pfd = obj->map_fds;
-        for (i = 0; i < nr_maps; i++) {
-                struct bpf_map_def def;
-
-                def = *(struct bpf_map_def *)(obj->maps_buf +
-                                i * sizeof(struct bpf_map_def));
-
-                *pfd = bpf_create_map(def.type,
-                                      def.key_size,
-                                      def.value_size,
-                                      def.max_entries);
+                *pfd = bpf_create_map(def->type,
+                                      def->key_size,
+                                      def->value_size,
+                                      def->max_entries);
                 if (*pfd < 0) {
                         size_t j;
                         int err = *pfd;
@@ -726,22 +723,17 @@ bpf_object__create_maps(struct bpf_object *obj)
                         pr_warning("failed to create map: %s\n",
                                    strerror(errno));
                         for (j = 0; j < i; j++)
-                                zclose(obj->map_fds[j]);
-                        obj->nr_map_fds = 0;
-                        zfree(&obj->map_fds);
+                                zclose(obj->maps[j].fd);
                         return err;
                 }
                 pr_debug("create map: fd=%d\n", *pfd);
-                pfd++;
         }
 
-        zfree(&obj->maps_buf);
-        obj->maps_buf_sz = 0;
         return 0;
 }
 
 static int
-bpf_program__relocate(struct bpf_program *prog, int *map_fds)
+bpf_program__relocate(struct bpf_program *prog, struct bpf_object *obj)
 {
         int i;
 
@@ -761,7 +753,7 @@ bpf_program__relocate(struct bpf_program *prog, int *map_fds)
                         return -LIBBPF_ERRNO__RELOC;
                 }
                 insns[insn_idx].src_reg = BPF_PSEUDO_MAP_FD;
-                insns[insn_idx].imm = map_fds[map_idx];
+                insns[insn_idx].imm = obj->maps[map_idx].fd;
         }
 
         zfree(&prog->reloc_desc);
@@ -780,7 +772,7 @@ bpf_object__relocate(struct bpf_object *obj)
         for (i = 0; i < obj->nr_programs; i++) {
                 prog = &obj->programs[i];
 
-                err = bpf_program__relocate(prog, obj->map_fds);
+                err = bpf_program__relocate(prog, obj);
                 if (err) {
                         pr_warning("failed to relocate '%s'\n",
                                    prog->section_name);
@@ -804,8 +796,7 @@ static int bpf_object__collect_reloc(struct bpf_object *obj)
                 Elf_Data *data = obj->efile.reloc[i].data;
                 int idx = shdr->sh_info;
                 struct bpf_program *prog;
-                size_t nr_maps = obj->maps_buf_sz /
-                                 sizeof(struct bpf_map_def);
+                size_t nr_maps = obj->nr_maps;
 
                 if (shdr->sh_type != SHT_REL) {
                         pr_warning("internal error at %d\n", __LINE__);
@@ -1050,10 +1041,8 @@ int bpf_object__unload(struct bpf_object *obj)
         if (!obj)
                 return -EINVAL;
 
-        for (i = 0; i < obj->nr_map_fds; i++)
-                zclose(obj->map_fds[i]);
-        zfree(&obj->map_fds);
-        obj->nr_map_fds = 0;
+        for (i = 0; i < obj->nr_maps; i++)
+                zclose(obj->maps[i].fd);
 
         for (i = 0; i < obj->nr_programs; i++)
                 bpf_program__unload(&obj->programs[i]);
@@ -1096,7 +1085,15 @@ void bpf_object__close(struct bpf_object *obj)
         bpf_object__elf_finish(obj);
         bpf_object__unload(obj);
 
-        zfree(&obj->maps_buf);
+        for (i = 0; i < obj->nr_maps; i++) {
+                if (obj->maps[i].clear_priv)
+                        obj->maps[i].clear_priv(&obj->maps[i],
+                                                obj->maps[i].priv);
+                obj->maps[i].priv = NULL;
+                obj->maps[i].clear_priv = NULL;
+        }
+        zfree(&obj->maps);
+        obj->nr_maps = 0;
 
         if (obj->programs && obj->nr_programs) {
                 for (i = 0; i < obj->nr_programs; i++)
@@ -1251,3 +1248,73 @@ int bpf_program__nth_fd(struct bpf_program *prog, int n)
 
         return fd;
 }
+
+int bpf_map__get_fd(struct bpf_map *map)
+{
+        if (!map)
+                return -EINVAL;
+
+        return map->fd;
+}
+
+int bpf_map__get_def(struct bpf_map *map, struct bpf_map_def *pdef)
+{
+        if (!map || !pdef)
+                return -EINVAL;
+
+        *pdef = map->def;
+        return 0;
+}
+
+int bpf_map__set_private(struct bpf_map *map, void *priv,
+                         bpf_map_clear_priv_t clear_priv)
+{
+        if (!map)
+                return -EINVAL;
+
+        if (map->priv) {
+                if (map->clear_priv)
+                        map->clear_priv(map, map->priv);
+        }
+
+        map->priv = priv;
+        map->clear_priv = clear_priv;
+        return 0;
+}
+
+int bpf_map__get_private(struct bpf_map *map, void **ppriv)
+{
+        if (!map)
+                return -EINVAL;
+
+        if (ppriv)
+                *ppriv = map->priv;
+        return 0;
+}
+
+struct bpf_map *
+bpf_map__next(struct bpf_map *prev, struct bpf_object *obj)
+{
+        size_t idx;
+        struct bpf_map *s, *e;
+
+        if (!obj || !obj->maps)
+                return NULL;
+
+        s = obj->maps;
+        e = obj->maps + obj->nr_maps;
+
+        if (prev == NULL)
+                return s;
+
+        if ((prev < s) || (prev >= e)) {
+                pr_warning("error in %s: map handler doesn't belong to object\n",
+                           __func__);
+                return NULL;
+        }
+
+        idx = (prev - obj->maps) + 1;
+        if (idx >= obj->nr_maps)
+                return NULL;
+        return &obj->maps[idx];
+}
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 949df4b346cf..ef631255dfaa 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -165,4 +165,25 @@ struct bpf_map_def {
         unsigned int max_entries;
 };
 
+/*
+ * There is another 'struct bpf_map' in include/linux/map.h. However,
+ * it is not a uapi header so no need to consider name clash.
+ */
+struct bpf_map;
+
+struct bpf_map *
+bpf_map__next(struct bpf_map *map, struct bpf_object *obj);
+#define bpf_map__for_each(pos, obj)             \
+        for ((pos) = bpf_map__next(NULL, (obj));        \
+             (pos) != NULL;                             \
+             (pos) = bpf_map__next((pos), (obj)))
+
+int bpf_map__get_fd(struct bpf_map *map);
+int bpf_map__get_def(struct bpf_map *map, struct bpf_map_def *pdef);
+
+typedef void (*bpf_map_clear_priv_t)(struct bpf_map *, void *);
+int bpf_map__set_private(struct bpf_map *map, void *priv,
+                         bpf_map_clear_priv_t clear_priv);
+int bpf_map__get_private(struct bpf_map *map, void **ppriv);
+
 #endif