Commit 52d3352e authored by Wang Nan's avatar Wang Nan Committed by Arnaldo Carvalho de Melo
Browse files

bpf tools: Create eBPF maps defined in an object file 



This patch creates maps based on 'map' section in object file using
bpf_create_map(), and stores the fds into an array in 'struct
bpf_object'.

Previous patches parse ELF object file and collects required data, but
doesn't play with the kernel. They belong to the 'opening' phase. This
patch is the first patch in 'loading' phase. The 'loaded' field is
introduced in 'struct bpf_object' to avoid loading an object twice,
because the loading phase clears resources collected during the opening
which becomes useless after loading. In this patch, maps_buf is cleared.

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/1435716878-189507-17-git-send-email-wangnan0@huawei.com


Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent e3ed2fef

tools/lib/bpf/libbpf.c

+102 −0
Original line number Diff line number Diff line
@@ -21,6 +21,7 @@ 
#include <gelf.h>



#include "libbpf.h"

#include "bpf.h"



#define __printf(a, b)	__attribute__((format(printf, a, b)))
@@ -105,6 +106,13 @@ struct bpf_object { 


	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;

	bool loaded;



	/*

	 * Information when doing elf related work. Only valid if fd
@@ -233,6 +241,7 @@ static struct bpf_object *bpf_object__new(const char *path, 
	obj->efile.obj_buf = obj_buf;

	obj->efile.obj_buf_sz = obj_buf_sz;



	obj->loaded = false;

	return obj;

}
@@ -565,6 +574,62 @@ bpf_program__collect_reloc(struct bpf_program *prog, 
	return 0;

}



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);



	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);

		if (*pfd < 0) {

			size_t j;

			int err = *pfd;



			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);

			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_object__collect_reloc(struct bpf_object *obj)

{

	int i, err;
@@ -668,6 +733,42 @@ struct bpf_object *bpf_object__open_buffer(void *obj_buf, 
	return __bpf_object__open("[buffer]", obj_buf, obj_buf_sz);

}



int bpf_object__unload(struct bpf_object *obj)

{

	size_t i;



	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;



	return 0;

}



int bpf_object__load(struct bpf_object *obj)

{

	if (!obj)

		return -EINVAL;



	if (obj->loaded) {

		pr_warning("object should not be loaded twice\n");

		return -EINVAL;

	}



	obj->loaded = true;

	if (bpf_object__create_maps(obj))

		goto out;



	return 0;

out:

	bpf_object__unload(obj);

	pr_warning("failed to load object '%s'\n", obj->path);

	return -EINVAL;

}



void bpf_object__close(struct bpf_object *obj)

{

	size_t i;
@@ -676,6 +777,7 @@ void bpf_object__close(struct bpf_object *obj) 
		return;



	bpf_object__elf_finish(obj);

	bpf_object__unload(obj);



	zfree(&obj->maps_buf);

tools/lib/bpf/libbpf.h

+4 −0
Original line number Diff line number Diff line
@@ -30,6 +30,10 @@ struct bpf_object *bpf_object__open_buffer(void *obj_buf, 
					   size_t obj_buf_sz);

void bpf_object__close(struct bpf_object *object);



/* Load/unload object into/from kernel */

int bpf_object__load(struct bpf_object *obj);

int bpf_object__unload(struct bpf_object *obj);



/*

 * We don't need __attribute__((packed)) now since it is

 * unnecessary for 'bpf_map_def' because they are all aligned.

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