[v3,03/30] tools lib bpf: Retrive bpf_map through offset of bpf_map_def

Message ID 20161126070354.141764-4-wangnan0@huawei.com
State New
Headers show

Commit Message

Wang Nan Nov. 26, 2016, 7:03 a.m.
Add a new API to libbpf, caller is able to get bpf_map through the
offset of bpf_map_def to 'maps' section.

The API will be used to help jitted perf hook code find fd of a map.

Signed-off-by: Wang Nan <wangnan0@huawei.com>

Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
---
 tools/lib/bpf/libbpf.c | 12 ++++++++++++
 tools/lib/bpf/libbpf.h |  8 ++++++++
 2 files changed, 20 insertions(+)

-- 
2.10.1

Comments

Alexei Starovoitov Nov. 26, 2016, 5:12 p.m. | #1
On Sat, Nov 26, 2016 at 07:03:27AM +0000, Wang Nan wrote:
> Add a new API to libbpf, caller is able to get bpf_map through the

> offset of bpf_map_def to 'maps' section.

> 

> The API will be used to help jitted perf hook code find fd of a map.

> 

> Signed-off-by: Wang Nan <wangnan0@huawei.com>

...
> +struct bpf_map *

> +bpf_object__find_map_by_offset(struct bpf_object *obj, size_t offset)

> +{

> +	int i;

> +

> +	for (i = 0; i < obj->nr_maps; i++) {

> +		if (obj->maps[i].offset == offset)

> +			return &obj->maps[i];

> +	}

> +	return ERR_PTR(-ENOENT);

> +}


Acked-by: Alexei Starovoitov <ast@kernel.org>

Patch

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 866d5cd..2e97459 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -1524,3 +1524,15 @@  bpf_object__find_map_by_name(struct bpf_object *obj, const char *name)
 	}
 	return NULL;
 }
+
+struct bpf_map *
+bpf_object__find_map_by_offset(struct bpf_object *obj, size_t offset)
+{
+	int i;
+
+	for (i = 0; i < obj->nr_maps; i++) {
+		if (obj->maps[i].offset == offset)
+			return &obj->maps[i];
+	}
+	return ERR_PTR(-ENOENT);
+}
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 0c0b012..a5a8b86 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -24,6 +24,7 @@ 
 #include <stdio.h>
 #include <stdbool.h>
 #include <linux/err.h>
+#include <sys/types.h>  // for size_t
 
 enum libbpf_errno {
 	__LIBBPF_ERRNO__START = 4000,
@@ -200,6 +201,13 @@  struct bpf_map;
 struct bpf_map *
 bpf_object__find_map_by_name(struct bpf_object *obj, const char *name);
 
+/*
+ * Get bpf_map through the offset of corresponding struct bpf_map_def
+ * in the bpf object file.
+ */
+struct bpf_map *
+bpf_object__find_map_by_offset(struct bpf_object *obj, size_t offset);
+
 struct bpf_map *
 bpf_map__next(struct bpf_map *map, struct bpf_object *obj);
 #define bpf_map__for_each(pos, obj)		\