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: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20230809083440.3209381-10-jolsa@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/tools/lib/bpf/elf.c b/tools/lib/bpf/elf.c
index 735ef10..71363ac 100644 (file)
--- a/tools/lib/bpf/elf.c
+++ b/tools/lib/bpf/elf.c
@@ -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 @@ out:
  */
 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;
 }
-

diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h
index 44eb635..0bbcd8e 100644 (file)
--- a/tools/lib/bpf/libbpf_internal.h
+++ b/tools/lib/bpf/libbpf_internal.h
@@ -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 */

diff --git a/tools/lib/bpf/usdt.c b/tools/lib/bpf/usdt.c
index 37455d0..8322337 100644 (file)
--- a/tools/lib/bpf/usdt.c
+++ b/tools/lib/bpf/usdt.c
@@ -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 @@ err_out:
                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);
 }