[PATCHv5 bpf-next 12/28] libbpf: Add elf_resolve_pattern_offsets function

Jiri Olsa
2023-07-30T13:44:29Z

Adding elf_resolve_pattern_offsets 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/elf.c | 61 +++++++++++++++++++++++++++++++++
tools/lib/bpf/libbpf.c | 2 +-
tools/lib/bpf/libbpf_internal.h | 5 +++
3 files changed, 67 insertions(+), 1 deletion(-)

diff --git a/tools/lib/bpf/elf.c b/tools/lib/bpf/elf.c
index 8c512641c1d7..9d0296c1726a 100644
--- a/tools/lib/bpf/elf.c
+++ b/tools/lib/bpf/elf.c
@@ -377,3 +377,64 @@ int elf_resolve_syms_offsets(const char *binary_path, int cnt,
elf_close(&elf_fd);
return err;
}
+
+/*
+ * Return offsets in @poffsets for symbols specified by @pattern argument.
+ * On success returns 0 and offsets are returned in allocated @poffsets
+ * array with the @pctn size, that needs to be released by the caller.
+ */
+int elf_resolve_pattern_offsets(const char *binary_path, const char *pattern,
+ unsigned long **poffsets, size_t *pcnt)
+{
+ int sh_types[2] = { SHT_SYMTAB, SHT_DYNSYM };
+ unsigned long *offsets = NULL;
+ size_t cap = 0, cnt = 0;
+ struct elf_fd elf_fd;
+ int err = 0, i;
+
+ err = elf_open(binary_path, &elf_fd);
+ if (err)
+ return err;
+
+ 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))) {
+ if (!glob_match(sym->name, pattern))
+ continue;
+
+ err = libbpf_ensure_mem((void **) &offsets, &cap, sizeof(*offsets),
+ cnt + 1);
+ if (err)
+ goto out;
+
+ offsets[cnt++] = elf_sym_offset(sym);
+ }
+
+ /* If we found anything in the first symbol section,
+ * do not search others to avoid duplicates.
+ */
+ if (cnt)
+ break;
+ }
+
+ if (cnt) {
+ *poffsets = offsets;
+ *pcnt = cnt;
+ } else {
+ err = -ENOENT;
+ }
+
+out:
+ if (err)
+ free(offsets);
+ elf_close(&elf_fd);
+ return err;
+}
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 1bdda3f8c865..445953a4d8fc 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -10551,7 +10551,7 @@ struct bpf_link *bpf_program__attach_ksyscall(const struct bpf_program *prog,
}

/* Adapted from perf/util/string.c */
-static bool glob_match(const char *str, const char *pat)
+bool glob_match(const char *str, const char *pat)
{
while (*str && *pat && *pat != '*') {
if (*pat == '?') { /* Matches any single character */
diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h
index 92851c5f912d..ead551318fec 100644
--- a/tools/lib/bpf/libbpf_internal.h
+++ b/tools/lib/bpf/libbpf_internal.h
@@ -578,6 +578,8 @@ static inline bool is_pow_of_2(size_t x)
#define PROG_LOAD_ATTEMPTS 5
int sys_bpf_prog_load(union bpf_attr *attr, unsigned int size, int attempts);

+bool glob_match(const char *str, const char *pat);
+
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);

@@ -591,4 +593,7 @@ 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);
+int elf_resolve_pattern_offsets(const char *binary_path, const char *pattern,
+ unsigned long **poffsets, size_t *pcnt);
+
#endif /* __LIBBPF_LIBBPF_INTERNAL_H */
--
2.41.0