[PATCHv2 bpf-next 07/24] libbpf: Add open_elf/close_elf functions

Jiri Olsa
2023-06-20T08:37:03Z

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

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
tools/lib/bpf/libbpf.c | 62 ++++++++++++++++++++++++++++++------------
1 file changed, 44 insertions(+), 18 deletions(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index cdac368c7ce1..30d9e3b69114 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -10927,6 +10927,45 @@ static struct elf_symbol *elf_symbol_iter_next(struct elf_symbol_iter *iter)
return ret;
}

+struct elf_fd {
+ Elf *elf;
+ int fd;
+};
+
+static int open_elf(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("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("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;
+}
+
+static void close_elf(struct elf_fd *elf_fd)
+{
+ elf_end(elf_fd->elf);
+ close(elf_fd->fd);
+}
+
/* Find offset of function name in the provided ELF object. "binary_path" is
* the path to the ELF binary represented by "elf", and only used for error
* reporting matters. "name" matches symbol name or name@@LIB for library
@@ -11019,28 +11058,15 @@ static long elf_find_func_offset(Elf *elf, const char *binary_path, const char *
*/
static 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 = open_elf(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);
+ close_elf(&elf_fd);
return ret;
}

--
2.41.0