Re: [PATCH bpf-next v4 2/8] libbpf: Implement changes needed for BTFGen in bpftool

This commit extends libbpf with the features that are needed to
implement BTFGen:

- Implement bpf_core_create_cand_cache() and bpf_core_free_cand_cache()
to handle candidates cache.
- Expose bpf_core_add_cands() and bpf_core_free_cands to handle
candidates list.
- Expose bpf_core_calc_relo_insn() to bpftool.

Signed-off-by: Mauricio Vásquez <redacted>
Signed-off-by: Rafael David Tinoco <redacted>
Signed-off-by: Lorenzo Fontana <redacted>
Signed-off-by: Leonardo Di Donato <redacted>
---
 tools/lib/bpf/Makefile          |  2 +-
 tools/lib/bpf/libbpf.c          | 43 +++++++++++++++++++++------------
 tools/lib/bpf/libbpf_internal.h | 12 +++++++++
 3 files changed, 41 insertions(+), 16 deletions(-)

diff --git a/tools/lib/bpf/Makefile b/tools/lib/bpf/Makefile
index f947b61b2107..dba019ee2832 100644
--- a/tools/lib/bpf/Makefile
+++ b/tools/lib/bpf/Makefile

@@ -239,7 +239,7 @@ install_lib: all_cmd

 SRC_HDRS := bpf.h libbpf.h btf.h libbpf_common.h libbpf_legacy.h xsk.h      \
            bpf_helpers.h bpf_tracing.h bpf_endian.h bpf_core_read.h         \
-           skel_internal.h libbpf_version.h
+           skel_internal.h libbpf_version.h relo_core.h libbpf_internal.h

 GEN_HDRS := $(BPF_GENERATED)

 INSTALL_PFX := $(DESTDIR)$(prefix)/include/bpf

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 4959c03a46f4..344b8b8e8a50 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c

@@ -5185,18 +5185,18 @@ size_t bpf_core_essential_name_len(const char *name)
        return n;
 }

-static void bpf_core_free_cands(struct bpf_core_cand_list *cands)
+void bpf_core_free_cands(struct bpf_core_cand_list *cands)
 {
        free(cands->cands);
        free(cands);
 }

-static int bpf_core_add_cands(struct bpf_core_cand *local_cand,
-                             size_t local_essent_len,
-                             const struct btf *targ_btf,
-                             const char *targ_btf_name,
-                             int targ_start_id,
-                             struct bpf_core_cand_list *cands)
+int bpf_core_add_cands(struct bpf_core_cand *local_cand,
+                      size_t local_essent_len,
+                      const struct btf *targ_btf,
+                      const char *targ_btf_name,
+                      int targ_start_id,
+                      struct bpf_core_cand_list *cands)
 {
        struct bpf_core_cand *new_cands, *cand;
        const struct btf_type *t, *local_t;

@@ -5567,6 +5567,24 @@ static int bpf_core_resolve_relo(struct bpf_program *prog,
                                       targ_res);
 }

+struct hashmap *bpf_core_create_cand_cache(void)
+{
+       return hashmap__new(bpf_core_hash_fn, bpf_core_equal_fn, NULL);
+}
+
+void bpf_core_free_cand_cache(struct hashmap *cand_cache)
+{
+       struct hashmap_entry *entry;
+       int i;
+
+       if (!IS_ERR_OR_NULL(cand_cache)) {

+               hashmap__for_each_entry(cand_cache, entry, i) {
+                       bpf_core_free_cands(entry->value);
+               }
+               hashmap__free(cand_cache);
+       }
+}
+