bpf tools: Read eBPF object from buffer
To support dynamic compiling, this patch allows caller to pass a
in-memory buffer to libbpf by bpf_object__open_buffer(). libbpf calls
elf_memory() to open it as ELF object file.
Because __bpf_object__open() collects all required data and won't need
that buffer anymore, libbpf uses that buffer directly instead of clone a
new buffer. Caller of libbpf can free that buffer or use it do other
things after bpf_object__open_buffer() return.
Signed-off-by: Wang Nan <wangnan0@huawei.com>
Acked-by: 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: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/1435716878-189507-7-git-send-email-wangnan0@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 9e44608..36dfbc1 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -84,6 +84,8 @@
*/
struct {
int fd;
+ void *obj_buf;
+ size_t obj_buf_sz;
Elf *elf;
GElf_Ehdr ehdr;
} efile;
@@ -91,7 +93,9 @@
};
#define obj_elf_valid(o) ((o)->efile.elf)
-static struct bpf_object *bpf_object__new(const char *path)
+static struct bpf_object *bpf_object__new(const char *path,
+ void *obj_buf,
+ size_t obj_buf_sz)
{
struct bpf_object *obj;
@@ -103,6 +107,16 @@
strcpy(obj->path, path);
obj->efile.fd = -1;
+
+ /*
+ * Caller of this function should also calls
+ * bpf_object__elf_finish() after data collection to return
+ * obj_buf to user. If not, we should duplicate the buffer to
+ * avoid user freeing them before elf finish.
+ */
+ obj->efile.obj_buf = obj_buf;
+ obj->efile.obj_buf_sz = obj_buf_sz;
+
return obj;
}
@@ -116,6 +130,8 @@
obj->efile.elf = NULL;
}
zclose(obj->efile.fd);
+ obj->efile.obj_buf = NULL;
+ obj->efile.obj_buf_sz = 0;
}
static int bpf_object__elf_init(struct bpf_object *obj)
@@ -128,16 +144,26 @@
return -EEXIST;
}
- obj->efile.fd = open(obj->path, O_RDONLY);
- if (obj->efile.fd < 0) {
- pr_warning("failed to open %s: %s\n", obj->path,
- strerror(errno));
- return -errno;
+ if (obj->efile.obj_buf_sz > 0) {
+ /*
+ * obj_buf should have been validated by
+ * bpf_object__open_buffer().
+ */
+ obj->efile.elf = elf_memory(obj->efile.obj_buf,
+ obj->efile.obj_buf_sz);
+ } else {
+ obj->efile.fd = open(obj->path, O_RDONLY);
+ if (obj->efile.fd < 0) {
+ pr_warning("failed to open %s: %s\n", obj->path,
+ strerror(errno));
+ return -errno;
+ }
+
+ obj->efile.elf = elf_begin(obj->efile.fd,
+ LIBBPF_ELF_C_READ_MMAP,
+ NULL);
}
- obj->efile.elf = elf_begin(obj->efile.fd,
- LIBBPF_ELF_C_READ_MMAP,
- NULL);
if (!obj->efile.elf) {
pr_warning("failed to open %s as ELF file\n",
obj->path);
@@ -167,7 +193,7 @@
}
static struct bpf_object *
-__bpf_object__open(const char *path)
+__bpf_object__open(const char *path, void *obj_buf, size_t obj_buf_sz)
{
struct bpf_object *obj;
@@ -176,7 +202,7 @@
return NULL;
}
- obj = bpf_object__new(path);
+ obj = bpf_object__new(path, obj_buf, obj_buf_sz);
if (!obj)
return NULL;
@@ -198,7 +224,19 @@
pr_debug("loading %s\n", path);
- return __bpf_object__open(path);
+ return __bpf_object__open(path, NULL, 0);
+}
+
+struct bpf_object *bpf_object__open_buffer(void *obj_buf,
+ size_t obj_buf_sz)
+{
+ /* param validation */
+ if (!obj_buf || obj_buf_sz <= 0)
+ return NULL;
+
+ pr_debug("loading object from buffer\n");
+
+ return __bpf_object__open("[buffer]", obj_buf, obj_buf_sz);
}
void bpf_object__close(struct bpf_object *obj)
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index ec3301c..dc966dd 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -26,6 +26,8 @@
struct bpf_object;
struct bpf_object *bpf_object__open(const char *path);
+struct bpf_object *bpf_object__open_buffer(void *obj_buf,
+ size_t obj_buf_sz);
void bpf_object__close(struct bpf_object *object);
#endif