bpftool: use libbpf's btf__parse_elf API

Use btf__parse_elf() API, provided by libbpf, instead of implementing
ELF parsing by itself.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/tools/bpf/bpftool/btf.c b/tools/bpf/bpftool/btf.c
index 7317438..a22ef65 100644 (file)
--- a/tools/bpf/bpftool/btf.c
+++ b/tools/bpf/bpftool/btf.c
@@ -8,8 +8,8 @@
 #include <stdio.h>
 #include <string.h>
 #include <unistd.h>
-#include <gelf.h>
 #include <bpf.h>
+#include <libbpf.h>
 #include <linux/btf.h>
 
 #include "btf.h"
@@ -340,112 +340,6 @@ static int dump_btf_raw(const struct btf *btf,
        return 0;
 }
 
-static bool check_btf_endianness(GElf_Ehdr *ehdr)
-{
-       static unsigned int const endian = 1;
-
-       switch (ehdr->e_ident[EI_DATA]) {
-       case ELFDATA2LSB:
-               return *(unsigned char const *)&endian == 1;
-       case ELFDATA2MSB:
-               return *(unsigned char const *)&endian == 0;
-       default:
-               return 0;
-       }
-}
-
-static int btf_load_from_elf(const char *path, struct btf **btf)
-{
-       int err = -1, fd = -1, idx = 0;
-       Elf_Data *btf_data = NULL;
-       Elf_Scn *scn = NULL;
-       Elf *elf = NULL;
-       GElf_Ehdr ehdr;
-
-       if (elf_version(EV_CURRENT) == EV_NONE) {
-               p_err("failed to init libelf for %s", path);
-               return -1;
-       }
-
-       fd = open(path, O_RDONLY);
-       if (fd < 0) {
-               p_err("failed to open %s: %s", path, strerror(errno));
-               return -1;
-       }
-
-       elf = elf_begin(fd, ELF_C_READ, NULL);
-       if (!elf) {
-               p_err("failed to open %s as ELF file", path);
-               goto done;
-       }
-       if (!gelf_getehdr(elf, &ehdr)) {
-               p_err("failed to get EHDR from %s", path);
-               goto done;
-       }
-       if (!check_btf_endianness(&ehdr)) {
-               p_err("non-native ELF endianness is not supported");
-               goto done;
-       }
-       if (!elf_rawdata(elf_getscn(elf, ehdr.e_shstrndx), NULL)) {
-               p_err("failed to get e_shstrndx from %s\n", path);
-               goto done;
-       }
-
-       while ((scn = elf_nextscn(elf, scn)) != NULL) {
-               GElf_Shdr sh;
-               char *name;
-
-               idx++;
-               if (gelf_getshdr(scn, &sh) != &sh) {
-                       p_err("failed to get section(%d) header from %s",
-                             idx, path);
-                       goto done;
-               }
-               name = elf_strptr(elf, ehdr.e_shstrndx, sh.sh_name);
-               if (!name) {
-                       p_err("failed to get section(%d) name from %s",
-                             idx, path);
-                       goto done;
-               }
-               if (strcmp(name, BTF_ELF_SEC) == 0) {
-                       btf_data = elf_getdata(scn, 0);
-                       if (!btf_data) {
-                               p_err("failed to get section(%d, %s) data from %s",
-                                     idx, name, path);
-                               goto done;
-                       }
-                       break;
-               }
-       }
-
-       if (!btf_data) {
-               p_err("%s ELF section not found in %s", BTF_ELF_SEC, path);
-               goto done;
-       }
-
-       *btf = btf__new(btf_data->d_buf, btf_data->d_size);
-       if (IS_ERR(*btf)) {
-               err = PTR_ERR(*btf);
-               *btf = NULL;
-               p_err("failed to load BTF data from %s: %s",
-                     path, strerror(err));
-               goto done;
-       }
-
-       err = 0;
-done:
-       if (err) {
-               if (*btf) {
-                       btf__free(*btf);
-                       *btf = NULL;
-               }
-       }
-       if (elf)
-               elf_end(elf);
-       close(fd);
-       return err;
-}
-
 static int do_dump(int argc, char **argv)
 {
        struct btf *btf = NULL;
@@ -522,9 +416,14 @@ static int do_dump(int argc, char **argv)
                }
                NEXT_ARG();
        } else if (is_prefix(src, "file")) {
-               err = btf_load_from_elf(*argv, &btf);
-               if (err)
+               btf = btf__parse_elf(*argv, NULL);
+               if (IS_ERR(btf)) {
+                       err = PTR_ERR(btf);
+                       btf = NULL;
+                       p_err("failed to load BTF from %s: %s", 
+                             *argv, strerror(err));
                        goto done;
+               }
                NEXT_ARG();
        } else {
                err = -1;