Commit f90eb70d authored by Jiri Olsa's avatar Jiri Olsa Committed by Alexei Starovoitov
Browse files

libbpf: Add elf_open/elf_close functions 



Adding elf_open/elf_close functions and using it in
elf_find_func_offset_from_file function. It will be
used in following changes to save some common code.

Acked-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Signed-off-by: default avatarJiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20230809083440.3209381-10-jolsa@kernel.org


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 5c742725

tools/lib/bpf/elf.c

+41 −20
Original line number Diff line number Diff line
@@ -10,6 +10,42 @@ 


#define STRERR_BUFSIZE  128



int elf_open(const char *binary_path, struct elf_fd *elf_fd)

{

	char errmsg[STRERR_BUFSIZE];

	int fd, ret;

	Elf *elf;



	if (elf_version(EV_CURRENT) == EV_NONE) {

		pr_warn("elf: failed to init libelf for %s\n", binary_path);

		return -LIBBPF_ERRNO__LIBELF;

	}

	fd = open(binary_path, O_RDONLY | O_CLOEXEC);

	if (fd < 0) {

		ret = -errno;

		pr_warn("elf: failed to open %s: %s\n", binary_path,

			libbpf_strerror_r(ret, errmsg, sizeof(errmsg)));

		return ret;

	}

	elf = elf_begin(fd, ELF_C_READ_MMAP, NULL);

	if (!elf) {

		pr_warn("elf: could not read elf from %s: %s\n", binary_path, elf_errmsg(-1));

		close(fd);

		return -LIBBPF_ERRNO__FORMAT;

	}

	elf_fd->fd = fd;

	elf_fd->elf = elf;

	return 0;

}



void elf_close(struct elf_fd *elf_fd)

{

	if (!elf_fd)

		return;

	elf_end(elf_fd->elf);

	close(elf_fd->fd);

}



/* Return next ELF section of sh_type after scn, or first of that type if scn is NULL. */

static Elf_Scn *elf_find_next_scn_by_type(Elf *elf, int sh_type, Elf_Scn *scn)

{
@@ -170,28 +206,13 @@ long elf_find_func_offset(Elf *elf, const char *binary_path, const char *name) 
 */

long elf_find_func_offset_from_file(const char *binary_path, const char *name)

{

	char errmsg[STRERR_BUFSIZE];

	struct elf_fd elf_fd;

	long ret = -ENOENT;

	Elf *elf;

	int fd;



	fd = open(binary_path, O_RDONLY | O_CLOEXEC);

	if (fd < 0) {

		ret = -errno;

		pr_warn("failed to open %s: %s\n", binary_path,

			libbpf_strerror_r(ret, errmsg, sizeof(errmsg)));

	ret = elf_open(binary_path, &elf_fd);

	if (ret)

		return ret;

	}

	elf = elf_begin(fd, ELF_C_READ_MMAP, NULL);

	if (!elf) {

		pr_warn("elf: could not read elf from %s: %s\n", binary_path, elf_errmsg(-1));

		close(fd);

		return -LIBBPF_ERRNO__FORMAT;

	}



	ret = elf_find_func_offset(elf, binary_path, name);

	elf_end(elf);

	close(fd);

	ret = elf_find_func_offset(elf_fd.elf, binary_path, name);

	elf_close(&elf_fd);

	return ret;

}

tools/lib/bpf/libbpf_internal.h

+8 −0
Original line number Diff line number Diff line
@@ -581,4 +581,12 @@ int sys_bpf_prog_load(union bpf_attr *attr, unsigned int size, int attempts); 
long elf_find_func_offset(Elf *elf, const char *binary_path, const char *name);

long elf_find_func_offset_from_file(const char *binary_path, const char *name);



struct elf_fd {

	Elf *elf;

	int fd;

};



int elf_open(const char *binary_path, struct elf_fd *elf_fd);

void elf_close(struct elf_fd *elf_fd);



#endif /* __LIBBPF_LIBBPF_INTERNAL_H */

tools/lib/bpf/usdt.c

+8 −22
Original line number Diff line number Diff line
@@ -946,32 +946,22 @@ struct bpf_link *usdt_manager_attach_usdt(struct usdt_manager *man, const struct 
					  const char *usdt_provider, const char *usdt_name,

					  __u64 usdt_cookie)

{

	int i, fd, err, spec_map_fd, ip_map_fd;

	int i, err, spec_map_fd, ip_map_fd;

	LIBBPF_OPTS(bpf_uprobe_opts, opts);

	struct hashmap *specs_hash = NULL;

	struct bpf_link_usdt *link = NULL;

	struct usdt_target *targets = NULL;

	struct elf_fd elf_fd;

	size_t target_cnt;

	Elf *elf;



	spec_map_fd = bpf_map__fd(man->specs_map);

	ip_map_fd = bpf_map__fd(man->ip_to_spec_id_map);



	fd = open(path, O_RDONLY | O_CLOEXEC);

	if (fd < 0) {

		err = -errno;

		pr_warn("usdt: failed to open ELF binary '%s': %d\n", path, err);

	err = elf_open(path, &elf_fd);

	if (err)

		return libbpf_err_ptr(err);

	}



	elf = elf_begin(fd, ELF_C_READ_MMAP, NULL);

	if (!elf) {

		err = -EBADF;

		pr_warn("usdt: failed to parse ELF binary '%s': %s\n", path, elf_errmsg(-1));

		goto err_out;

	}



	err = sanity_check_usdt_elf(elf, path);

	err = sanity_check_usdt_elf(elf_fd.elf, path);

	if (err)

		goto err_out;
@@ -984,7 +974,7 @@ struct bpf_link *usdt_manager_attach_usdt(struct usdt_manager *man, const struct 
	/* discover USDT in given binary, optionally limiting

	 * activations to a given PID, if pid > 0

	 */

	err = collect_usdt_targets(man, elf, path, pid, usdt_provider, usdt_name,

	err = collect_usdt_targets(man, elf_fd.elf, path, pid, usdt_provider, usdt_name,

				   usdt_cookie, &targets, &target_cnt);

	if (err <= 0) {

		err = (err == 0) ? -ENOENT : err;
@@ -1069,9 +1059,7 @@ struct bpf_link *usdt_manager_attach_usdt(struct usdt_manager *man, const struct 


	free(targets);

	hashmap__free(specs_hash);

	elf_end(elf);

	close(fd);



	elf_close(&elf_fd);

	return &link->link;



err_out:
@@ -1079,9 +1067,7 @@ struct bpf_link *usdt_manager_attach_usdt(struct usdt_manager *man, const struct 
		bpf_link__destroy(&link->link);

	free(targets);

	hashmap__free(specs_hash);

	if (elf)

		elf_end(elf);

	close(fd);

	elf_close(&elf_fd);

	return libbpf_err_ptr(err);

}