On Fri, Jun 30, 2023 at 1:36 AM Jiri Olsa <jolsa@xxxxxxxxxx> wrote:
>
> 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@xxxxxxxxxx>
> ---
> tools/lib/bpf/elf.c | 57 +++++++++++++++++++++++++++++++++
> tools/lib/bpf/libbpf.c | 2 +-
> tools/lib/bpf/libbpf_elf.h | 3 ++
> tools/lib/bpf/libbpf_internal.h | 1 +
> 4 files changed, 62 insertions(+), 1 deletion(-)
>
> diff --git a/tools/lib/bpf/elf.c b/tools/lib/bpf/elf.c
> index 7e2f3b2e1fb6..f2d1a8cc2f9d 100644
> --- a/tools/lib/bpf/elf.c
> +++ b/tools/lib/bpf/elf.c
> @@ -376,3 +376,60 @@ int elf_resolve_syms_offsets(const char *binary_path, int cnt,
> elf_close(&elf_fd);
> return err;
> }
> +
same, leave comment that caller should free offsets on success?
> +int elf_resolve_pattern_offsets(const char *binary_path, const char *pattern,
> + unsigned long **poffsets, size_t *pcnt)
> +{
> + int sh_types[2] = { SHT_DYNSYM, SHT_SYMTAB };
> + 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) {
> + if (err == -ENOENT)
> + continue;
> + goto out;
> + }
ditto, minimize nesting, please
> +
> + 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.
DYNSYM is going to have only exposed symbols, so for this pattern
matching, maybe it's best to start with SYMTAB and only fallback to
DYNSYM if we didn't find anything in SYMTAB (more realistically it
would be that SYMTAB section is missing, so we fallback to DYNSYM;
otherwise neither DYNSYM nor SYMTAB will have matching symbols, most
probably, but that's minor)
other than that, LGTM
> + */
> + 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 093add8124d8..f33ef7cb1adc 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -10509,7 +10509,7 @@ 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_elf.h b/tools/lib/bpf/libbpf_elf.h
> index 026c7b378727..0c75d3b2398b 100644
> --- a/tools/lib/bpf/libbpf_elf.h
> +++ b/tools/lib/bpf/libbpf_elf.h
> @@ -18,4 +18,7 @@ long elf_find_func_offset_from_file(const char *binary_path, const char *name);
>
> 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_ELF_H */
> diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h
> index e4d05662a96c..7d75b92e531a 100644
> --- a/tools/lib/bpf/libbpf_internal.h
> +++ b/tools/lib/bpf/libbpf_internal.h
> @@ -577,4 +577,5 @@ 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);
> #endif /* __LIBBPF_LIBBPF_INTERNAL_H */
> --
> 2.41.0
>
