Commit 6c956392 authored by Wang Nan's avatar Wang Nan Committed by Arnaldo Carvalho de Melo
Browse files

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: default avatarWang Nan <wangnan0@huawei.com>
Acked-by: default avatarAlexei 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: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent 1a5e3fb1

tools/lib/bpf/libbpf.c

+50 −12
Original line number Diff line number Diff line
@@ -84,6 +84,8 @@ struct bpf_object { 
	 */

	struct {

		int fd;

		void *obj_buf;

		size_t obj_buf_sz;

		Elf *elf;

		GElf_Ehdr ehdr;

	} efile;
@@ -91,7 +93,9 @@ struct bpf_object { 
};

#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 @@ static struct bpf_object *bpf_object__new(const char *path) 


	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 @@ static void bpf_object__elf_finish(struct bpf_object *obj) 
		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)
@@ -128,6 +144,14 @@ static int bpf_object__elf_init(struct bpf_object *obj) 
		return -EEXIST;

	}



	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,
@@ -138,6 +162,8 @@ static int bpf_object__elf_init(struct bpf_object *obj) 
		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 @@ errout: 
}



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 @@ __bpf_object__open(const char *path) 
		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 @@ struct bpf_object *bpf_object__open(const char *path) 


	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)

tools/lib/bpf/libbpf.h

+2 −0
Original line number Diff line number Diff line
@@ -26,6 +26,8 @@ void libbpf_set_print(libbpf_print_fn_t warn, 
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

CRA Git | Maintained and supported by SUSTech CRA and CCSE