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authorJiri Olsa <jolsa@kernel.org>2023-08-09 11:34:23 +0300
committerAlexei Starovoitov <ast@kernel.org>2023-08-22 01:51:26 +0300
commit7ace84c6892971766b7c252b3998d5662679e472 (patch)
treee5cb1aebd711604dc4719b5ea485efc5004b6491 /tools/lib
parent3774705db1718a671a4ed2ac5066fea839b1d7d1 (diff)
downloadlinux-7ace84c6892971766b7c252b3998d5662679e472.tar.xz
libbpf: Add elf_resolve_syms_offsets function
Adding elf_resolve_syms_offsets function that looks up offsets for symbols specified in syms array argument. Offsets are returned in allocated array with the 'cnt' size, that needs to be released by the caller. Signed-off-by: Jiri Olsa <jolsa@kernel.org> Link: https://lore.kernel.org/r/20230809083440.3209381-12-jolsa@kernel.org Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'tools/lib')
-rw-r--r--tools/lib/bpf/elf.c110
-rw-r--r--tools/lib/bpf/libbpf_internal.h2
2 files changed, 112 insertions, 0 deletions
diff --git a/tools/lib/bpf/elf.c b/tools/lib/bpf/elf.c
index 8a3f8a725981..8c512641c1d7 100644
--- a/tools/lib/bpf/elf.c
+++ b/tools/lib/bpf/elf.c
@@ -267,3 +267,113 @@ long elf_find_func_offset_from_file(const char *binary_path, const char *name)
elf_close(&elf_fd);
return ret;
}
+
+struct symbol {
+ const char *name;
+ int bind;
+ int idx;
+};
+
+static int symbol_cmp(const void *a, const void *b)
+{
+ const struct symbol *sym_a = a;
+ const struct symbol *sym_b = b;
+
+ return strcmp(sym_a->name, sym_b->name);
+}
+
+/*
+ * Return offsets in @poffsets for symbols specified in @syms array argument.
+ * On success returns 0 and offsets are returned in allocated array with @cnt
+ * size, that needs to be released by the caller.
+ */
+int elf_resolve_syms_offsets(const char *binary_path, int cnt,
+ const char **syms, unsigned long **poffsets)
+{
+ int sh_types[2] = { SHT_DYNSYM, SHT_SYMTAB };
+ int err = 0, i, cnt_done = 0;
+ unsigned long *offsets;
+ struct symbol *symbols;
+ struct elf_fd elf_fd;
+
+ err = elf_open(binary_path, &elf_fd);
+ if (err)
+ return err;
+
+ offsets = calloc(cnt, sizeof(*offsets));
+ symbols = calloc(cnt, sizeof(*symbols));
+
+ if (!offsets || !symbols) {
+ err = -ENOMEM;
+ goto out;
+ }
+
+ for (i = 0; i < cnt; i++) {
+ symbols[i].name = syms[i];
+ symbols[i].idx = i;
+ }
+
+ qsort(symbols, cnt, sizeof(*symbols), symbol_cmp);
+
+ for (i = 0; i < ARRAY_SIZE(sh_types); i++) {
+ struct elf_sym_iter iter;
+ struct elf_sym *sym;
+
+ err = elf_sym_iter_new(&iter, elf_fd.elf, binary_path, sh_types[i], STT_FUNC);
+ if (err == -ENOENT)
+ continue;
+ if (err)
+ goto out;
+
+ while ((sym = elf_sym_iter_next(&iter))) {
+ unsigned long sym_offset = elf_sym_offset(sym);
+ int bind = GELF_ST_BIND(sym->sym.st_info);
+ struct symbol *found, tmp = {
+ .name = sym->name,
+ };
+ unsigned long *offset;
+
+ found = bsearch(&tmp, symbols, cnt, sizeof(*symbols), symbol_cmp);
+ if (!found)
+ continue;
+
+ offset = &offsets[found->idx];
+ if (*offset > 0) {
+ /* same offset, no problem */
+ if (*offset == sym_offset)
+ continue;
+ /* handle multiple matches */
+ if (found->bind != STB_WEAK && bind != STB_WEAK) {
+ /* Only accept one non-weak bind. */
+ pr_warn("elf: ambiguous match found '%s@%lu' in '%s' previous offset %lu\n",
+ sym->name, sym_offset, binary_path, *offset);
+ err = -ESRCH;
+ goto out;
+ } else if (bind == STB_WEAK) {
+ /* already have a non-weak bind, and
+ * this is a weak bind, so ignore.
+ */
+ continue;
+ }
+ } else {
+ cnt_done++;
+ }
+ *offset = sym_offset;
+ found->bind = bind;
+ }
+ }
+
+ if (cnt != cnt_done) {
+ err = -ENOENT;
+ goto out;
+ }
+
+ *poffsets = offsets;
+
+out:
+ free(symbols);
+ if (err)
+ free(offsets);
+ elf_close(&elf_fd);
+ return err;
+}
diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h
index 0bbcd8e6fdc5..92851c5f912d 100644
--- a/tools/lib/bpf/libbpf_internal.h
+++ b/tools/lib/bpf/libbpf_internal.h
@@ -589,4 +589,6 @@ struct elf_fd {
int elf_open(const char *binary_path, struct elf_fd *elf_fd);
void elf_close(struct elf_fd *elf_fd);
+int elf_resolve_syms_offsets(const char *binary_path, int cnt,
+ const char **syms, unsigned long **poffsets);
#endif /* __LIBBPF_LIBBPF_INTERNAL_H */