[tip:perf/core] tools lib bpf: Extract and collect map names from BPF object file

[tip-bot for Wang Nan]

Commit-ID:  561bbccac72d08babafaa33fd7fa9100ec4c9fb6
Gitweb: http://git.kernel.org/tip/561bbccac72d08babafaa33fd7fa9100ec4c9fb6
Author: Wang Nan 
AuthorDate: Fri, 27 Nov 2015 08:47:36 +
Committer:  Arnaldo Carvalho de Melo 
CommitDate: Fri, 27 Nov 2015 21:59:53 -0300

tools lib bpf: Extract and collect map names from BPF object file

This patch collects name of maps in BPF object files and saves them into
'maps' field in 'struct bpf_object'. 'bpf_object__get_map_by_name' is
introduced to retrive fd and definitions of a map through its name.

Signed-off-by: He Kuang 
Cc: Alexei Starovoitov 
Cc: He Kuang 
Cc: Masami Hiramatsu 
Cc: Namhyung Kim 
Cc: Zefan Li 
Cc: pi3or...@163.com
Link: 
http://lkml.kernel.org/r/1448614067-197576-3-git-send-email-wangn...@huawei.com
Signed-off-by: Wang Nan 
Signed-off-by: Arnaldo Carvalho de Melo 
---
 tools/lib/bpf/libbpf.c | 65 +++---
 tools/lib/bpf/libbpf.h |  3 +++
 2 files changed, 65 insertions(+), 3 deletions(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index f509825..a298614 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -165,6 +165,7 @@ struct bpf_program {
 
 struct bpf_map {
int fd;
+   char *name;
struct bpf_map_def def;
void *priv;
bpf_map_clear_priv_t clear_priv;
@@ -526,12 +527,46 @@ bpf_object__init_maps(struct bpf_object *obj, void *data,
return 0;
 }
 
+static void
+bpf_object__init_maps_name(struct bpf_object *obj, int maps_shndx)
+{
+   int i;
+   Elf_Data *symbols = obj->efile.symbols;
+
+   if (!symbols || maps_shndx < 0)
+   return;
+
+   for (i = 0; i < symbols->d_size / sizeof(GElf_Sym); i++) {
+   GElf_Sym sym;
+   size_t map_idx;
+   const char *map_name;
+
+   if (!gelf_getsym(symbols, i, ))
+   continue;
+   if (sym.st_shndx != maps_shndx)
+   continue;
+
+   map_name = elf_strptr(obj->efile.elf,
+ obj->efile.ehdr.e_shstrndx,
+ sym.st_name);
+   map_idx = sym.st_value / sizeof(struct bpf_map_def);
+   if (map_idx >= obj->nr_maps) {
+   pr_warning("index of map \"%s\" is buggy: %zu > %zu\n",
+  map_name, map_idx, obj->nr_maps);
+   continue;
+   }
+   obj->maps[map_idx].name = strdup(map_name);
+   pr_debug("map %zu is \"%s\"\n", map_idx,
+obj->maps[map_idx].name);
+   }
+}
+
 static int bpf_object__elf_collect(struct bpf_object *obj)
 {
Elf *elf = obj->efile.elf;
GElf_Ehdr *ep = >efile.ehdr;
Elf_Scn *scn = NULL;
-   int idx = 0, err = 0;
+   int idx = 0, err = 0, maps_shndx = -1;
 
/* Elf is corrupted/truncated, avoid calling elf_strptr. */
if (!elf_rawdata(elf_getscn(elf, ep->e_shstrndx), NULL)) {
@@ -581,10 +616,11 @@ static int bpf_object__elf_collect(struct bpf_object *obj)
err = bpf_object__init_kversion(obj,
data->d_buf,
data->d_size);
-   else if (strcmp(name, "maps") == 0)
+   else if (strcmp(name, "maps") == 0) {
err = bpf_object__init_maps(obj, data->d_buf,
data->d_size);
-   else if (sh.sh_type == SHT_SYMTAB) {
+   maps_shndx = idx;
+   } else if (sh.sh_type == SHT_SYMTAB) {
if (obj->efile.symbols) {
pr_warning("bpf: multiple SYMTAB in %s\n",
   obj->path);
@@ -625,6 +661,9 @@ static int bpf_object__elf_collect(struct bpf_object *obj)
if (err)
goto out;
}
+
+   if (maps_shndx >= 0)
+   bpf_object__init_maps_name(obj, maps_shndx);
 out:
return err;
 }
@@ -1086,6 +1125,7 @@ void bpf_object__close(struct bpf_object *obj)
bpf_object__unload(obj);
 
for (i = 0; i < obj->nr_maps; i++) {
+   zfree(>maps[i].name);
if (obj->maps[i].clear_priv)
obj->maps[i].clear_priv(>maps[i],
obj->maps[i].priv);
@@ -1266,6 +1306,13 @@ int bpf_map__get_def(struct bpf_map *map, struct 
bpf_map_def *pdef)
return 0;
 }
 
+const char *bpf_map__get_name(struct bpf_map *map)
+{
+   if (!map)
+   return NULL;
+   return map->name;
+}
+
 int bpf_map__set_private(struct bpf_map *map, void *priv,
 bpf_map_clear_priv_t clear_priv)
 {
@@ -1318,3 +1365,15 @@ bpf_map__next(struct bpf_map *prev, struct bpf_object 
*obj)
   

[tip:perf/core] tools lib bpf: Extract and collect map names from BPF object file

[tip-bot for Wang Nan]

Commit-ID:  561bbccac72d08babafaa33fd7fa9100ec4c9fb6
Gitweb: http://git.kernel.org/tip/561bbccac72d08babafaa33fd7fa9100ec4c9fb6
Author: Wang Nan 
AuthorDate: Fri, 27 Nov 2015 08:47:36 +
Committer:  Arnaldo Carvalho de Melo 
CommitDate: Fri, 27 Nov 2015 21:59:53 -0300

tools lib bpf: Extract and collect map names from BPF object file

This patch collects name of maps in BPF object files and saves them into
'maps' field in 'struct bpf_object'. 'bpf_object__get_map_by_name' is
introduced to retrive fd and definitions of a map through its name.

Signed-off-by: He Kuang 
Cc: Alexei Starovoitov 
Cc: He Kuang 
Cc: Masami Hiramatsu 
Cc: Namhyung Kim 
Cc: Zefan Li 
Cc: pi3or...@163.com
Link: 
http://lkml.kernel.org/r/1448614067-197576-3-git-send-email-wangn...@huawei.com
Signed-off-by: Wang Nan 
Signed-off-by: Arnaldo Carvalho de Melo 
---
 tools/lib/bpf/libbpf.c | 65 +++---
 tools/lib/bpf/libbpf.h |  3 +++
 2 files changed, 65 insertions(+), 3 deletions(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index f509825..a298614 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -165,6 +165,7 @@ struct bpf_program {
 
 struct bpf_map {
int fd;
+   char *name;
struct bpf_map_def def;
void *priv;
bpf_map_clear_priv_t clear_priv;
@@ -526,12 +527,46 @@ bpf_object__init_maps(struct bpf_object *obj, void *data,
return 0;
 }
 
+static void
+bpf_object__init_maps_name(struct bpf_object *obj, int maps_shndx)
+{
+   int i;
+   Elf_Data *symbols = obj->efile.symbols;
+
+   if (!symbols || maps_shndx < 0)
+   return;
+
+   for (i = 0; i < symbols->d_size / sizeof(GElf_Sym); i++) {
+   GElf_Sym sym;
+   size_t map_idx;
+   const char *map_name;
+
+   if (!gelf_getsym(symbols, i, ))
+   continue;
+   if (sym.st_shndx != maps_shndx)
+   continue;
+
+   map_name = elf_strptr(obj->efile.elf,
+ obj->efile.ehdr.e_shstrndx,
+ sym.st_name);
+   map_idx = sym.st_value / sizeof(struct bpf_map_def);
+   if (map_idx >= obj->nr_maps) {
+   pr_warning("index of map \"%s\" is buggy: %zu > %zu\n",
+  map_name, map_idx, obj->nr_maps);
+   continue;
+   }
+   obj->maps[map_idx].name = strdup(map_name);
+   pr_debug("map %zu is \"%s\"\n", map_idx,
+obj->maps[map_idx].name);
+   }
+}
+
 static int bpf_object__elf_collect(struct bpf_object *obj)
 {
Elf *elf = obj->efile.elf;
GElf_Ehdr *ep = >efile.ehdr;
Elf_Scn *scn = NULL;
-   int idx = 0, err = 0;
+   int idx = 0, err = 0, maps_shndx = -1;
 
/* Elf is corrupted/truncated, avoid calling elf_strptr. */
if (!elf_rawdata(elf_getscn(elf, ep->e_shstrndx), NULL)) {
@@ -581,10 +616,11 @@ static int bpf_object__elf_collect(struct bpf_object *obj)
err = bpf_object__init_kversion(obj,
data->d_buf,
data->d_size);
-   else if (strcmp(name, "maps") == 0)
+   else if (strcmp(name, "maps") == 0) {
err = bpf_object__init_maps(obj, data->d_buf,
data->d_size);
-   else if (sh.sh_type == SHT_SYMTAB) {
+   maps_shndx = idx;
+   } else if (sh.sh_type == SHT_SYMTAB) {
if (obj->efile.symbols) {
pr_warning("bpf: multiple SYMTAB in %s\n",
   obj->path);
@@ -625,6 +661,9 @@ static int bpf_object__elf_collect(struct bpf_object *obj)
if (err)
goto out;
}
+
+   if (maps_shndx >= 0)
+   bpf_object__init_maps_name(obj, maps_shndx);
 out:
return err;
 }
@@ -1086,6 +1125,7 @@ void bpf_object__close(struct bpf_object *obj)
bpf_object__unload(obj);
 
for (i = 0; i < obj->nr_maps; i++) {
+   zfree(>maps[i].name);
if (obj->maps[i].clear_priv)
obj->maps[i].clear_priv(>maps[i],
obj->maps[i].priv);
@@ -1266,6 +1306,13 @@ int bpf_map__get_def(struct bpf_map *map, struct 
bpf_map_def *pdef)
return 0;
 }
 
+const char *bpf_map__get_name(struct bpf_map *map)
+{
+   if (!map)
+   return NULL;
+   return map->name;
+}
+