[PATCHv2 bpf-next 09/24] libbpf: Add elf_find_pattern_func_offset function

Jiri Olsa
2023-06-20T08:37:23Z

Adding elf_find_pattern_func_offset function that looks up
offsets for symbols specified by pattern argument.

The 'pattern' argument allows wildcards (*?' supported).

Offsets are returned in allocated array together with its
size and needs to be released by the caller.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
tools/lib/bpf/libbpf.c | 78 +++++++++++++++++++++++++++++++++
tools/lib/bpf/libbpf_internal.h | 3 ++
2 files changed, 81 insertions(+)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 1c310b718961..3e5c88caf5d5 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -11165,6 +11165,84 @@ int elf_find_multi_func_offset(const char *binary_path, int cnt,
return ret;
}

+static int
+__elf_find_pattern_func_offset(Elf *elf, const char *binary_path, const char *pattern,
+ const char ***pnames, unsigned long **poffsets, size_t *pcnt)
+{
+ int sh_types[2] = { SHT_DYNSYM, SHT_SYMTAB };
+ struct elf_symbol_offset *func_offs = NULL;
+ unsigned long *offsets = NULL;
+ const char **names = NULL;
+ size_t func_offs_cnt = 0;
+ size_t func_offs_cap = 0;
+ int err = 0, i;
+
+ for (i = 0; i < ARRAY_SIZE(sh_types); i++) {
+ struct elf_symbol_iter iter;
+ struct elf_symbol *sym;
+
+ if (elf_symbol_iter_new(&iter, elf, binary_path, sh_types[i]))
+ continue;
+
+ while ((sym = elf_symbol_iter_next(&iter))) {
+ if (!glob_match(sym->name, pattern))
+ continue;
+
+ err = libbpf_ensure_mem((void **) &func_offs, &func_offs_cap,
+ sizeof(*func_offs), func_offs_cnt + 1);
+ if (err)
+ goto out;
+
+ func_offs[func_offs_cnt].offset = sym->offset;
+ func_offs[func_offs_cnt].name = strdup(sym->name);
+ func_offs_cnt++;
+ }
+
+ /* If we found anything in the first symbol section,
+ * do not search others to avoid duplicates.
+ */
+ if (func_offs_cnt)
+ break;
+ }
+
+ offsets = calloc(func_offs_cnt, sizeof(*offsets));
+ names = calloc(func_offs_cnt, sizeof(*names));
+ if (!offsets || !names) {
+ free(offsets);
+ free(names);
+ err = -ENOMEM;
+ goto out;
+ }
+
+ for (i = 0; i < func_offs_cnt; i++) {
+ offsets[i] = func_offs[i].offset;
+ names[i] = func_offs[i].name;
+ }
+
+ *pnames = names;
+ *poffsets = offsets;
+ *pcnt = func_offs_cnt;
+out:
+ free(func_offs);
+ return err;
+}
+
+int elf_find_pattern_func_offset(const char *binary_path, const char *pattern,
+ const char ***pnames, unsigned long **poffsets,
+ size_t *pcnt)
+{
+ struct elf_fd elf_fd = {};
+ long ret = -ENOENT;
+
+ ret = open_elf(binary_path, &elf_fd);
+ if (ret)
+ return ret;
+
+ ret = __elf_find_pattern_func_offset(elf_fd.elf, binary_path, pattern, pnames, poffsets, pcnt);
+ close_elf(&elf_fd);
+ return ret;
+}
+
/* Find offset of function name in ELF object specified by path. "name" matches
* symbol name or name@@LIB for library functions.
*/
diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h
index 13d5c12fbd0b..22b0834e7fe1 100644
--- a/tools/lib/bpf/libbpf_internal.h
+++ b/tools/lib/bpf/libbpf_internal.h
@@ -579,4 +579,7 @@ int sys_bpf_prog_load(union bpf_attr *attr, unsigned int size, int attempts);

int elf_find_multi_func_offset(const char *binary_path, int cnt,
const char **syms, unsigned long **poffsets);
+int elf_find_pattern_func_offset(const char *binary_path, const char *pattern,
+ const char ***pnames, unsigned long **poffsets,
+ size_t *pcnt);
#endif /* __LIBBPF_LIBBPF_INTERNAL_H */
--
2.41.0