Re: [PATCHv3 bpf-next 07/26] libbpf: Move elf_find_func_offset* functions to elf object

[Jiri Olsa <olsajiri@gmail.com>]

On Thu, Jul 06, 2023 at 04:02:22PM -0700, Andrii Nakryiko wrote:
> On Fri, Jun 30, 2023 at 1:35 AM Jiri Olsa <jolsa@kernel.org> wrote:
> >
> > Adding new elf object that will contain elf related functions.
> > There's no functional change.
> >
> > Suggested-by: Andrii Nakryiko <andrii@kernel.org>
> > Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> > ---
> >  tools/lib/bpf/Build        |   2 +-
> >  tools/lib/bpf/elf.c        | 198 +++++++++++++++++++++++++++++++++++++
> >  tools/lib/bpf/libbpf.c     | 186 +---------------------------------
> >  tools/lib/bpf/libbpf_elf.h |  11 +++
> >  4 files changed, 211 insertions(+), 186 deletions(-)
> >  create mode 100644 tools/lib/bpf/elf.c
> >  create mode 100644 tools/lib/bpf/libbpf_elf.h
> >
> 
> [...]
> 
> > diff --git a/tools/lib/bpf/libbpf_elf.h b/tools/lib/bpf/libbpf_elf.h
> > new file mode 100644
> > index 000000000000..1b652220fabf
> > --- /dev/null
> > +++ b/tools/lib/bpf/libbpf_elf.h
> > @@ -0,0 +1,11 @@
> > +/* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */
> > +
> > +#ifndef __LIBBPF_LIBBPF_ELF_H
> > +#define __LIBBPF_LIBBPF_ELF_H
> > +
> > +#include <libelf.h>
> > +
> > +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);
> > +
> > +#endif /* *__LIBBPF_LIBBPF_ELF_H */
> 
> we have libbpf_internal.h, let's put all this there for now, it's
> already all the internal stuff together, I don't know if separate
> header with few functions gives us much

there's more functions coming later in the patchset

	struct elf_fd {
		Elf *elf;
		int 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);

	int elf_resolve_pattern_offsets(const char *binary_path, const char *pattern,
					 unsigned long **poffsets, size_t *pcnt);


and there's probably more elf helpers to eventually move in:

	libbpf.c:static const char *elf_sym_str(const struct bpf_object *obj, size_t off);
	libbpf.c:static const char *elf_sec_str(const struct bpf_object *obj, size_t off);
	libbpf.c:static Elf_Scn *elf_sec_by_idx(const struct bpf_object *obj, size_t idx);
	libbpf.c:static Elf_Scn *elf_sec_by_name(const struct bpf_object *obj, const char *name);
	libbpf.c:static Elf64_Shdr *elf_sec_hdr(const struct bpf_object *obj, Elf_Scn *scn);
	libbpf.c:static const char *elf_sec_name(const struct bpf_object *obj, Elf_Scn *scn);
	libbpf.c:static Elf_Data *elf_sec_data(const struct bpf_object *obj, Elf_Scn *scn);
	libbpf.c:static Elf64_Sym *elf_sym_by_idx(const struct bpf_object *obj, size_t idx);
	libbpf.c:static Elf64_Rel *elf_rel_by_idx(Elf_Data *data, size_t idx);

	usdt.c:static int find_elf_sec_by_name(Elf *elf, const char *sec_name, GElf_Shdr *shdr, Elf_Scn **scn)

	'struct elf_seg' stuff

	usdt.c:static int cmp_elf_segs(const void *_a, const void *_b)
	usdt.c:static int parse_elf_segs(Elf *elf, const char *path, struct elf_seg **segs, size_t *seg_cnt)
	usdt.c:static int parse_vma_segs(int pid, const char *lib_path, struct elf_seg **segs, size_t *seg_cnt)
	usdt.c:static struct elf_seg *find_elf_seg(struct elf_seg *segs, size_t seg_cnt, long virtaddr)
	usdt.c:static struct elf_seg *find_vma_seg(struct elf_seg *segs, size_t seg_cnt, long offset)


but I can add the new header file later in follow up changes when
we have more elf functions in

jirka