@@ -2626,6 +2626,7 @@ static int btf_ext_setup_info(struct btf_ext *btf_ext,
const struct btf_ext_info_sec *sinfo;
struct btf_ext_info *ext_info;
__u32 info_left, record_size;
+ size_t sec_cnt = 0;
/* The start of the info sec (including the __u32 record_size). */
void *info;
@@ -2689,8 +2690,7 @@ static int btf_ext_setup_info(struct btf_ext *btf_ext,
return -EINVAL;
}
- total_record_size = sec_hdrlen +
- (__u64)num_records * record_size;
+ total_record_size = sec_hdrlen + (__u64)num_records * record_size;
if (info_left < total_record_size) {
pr_debug("%s section has incorrect num_records in .BTF.ext\n",
ext_sec->desc);
@@ -2699,12 +2699,14 @@ static int btf_ext_setup_info(struct btf_ext *btf_ext,
info_left -= total_record_size;
sinfo = (void *)sinfo + total_record_size;
+ sec_cnt++;
}
ext_info = ext_sec->ext_info;
ext_info->len = ext_sec->len - sizeof(__u32);
ext_info->rec_size = record_size;
ext_info->info = info + sizeof(__u32);
+ ext_info->sec_cnt = sec_cnt;
return 0;
}
@@ -2788,6 +2790,9 @@ void btf_ext__free(struct btf_ext *btf_ext)
{
if (IS_ERR_OR_NULL(btf_ext))
return;
+ free(btf_ext->func_info.sec_idxs);
+ free(btf_ext->line_info.sec_idxs);
+ free(btf_ext->core_relo_info.sec_idxs);
free(btf_ext->data);
free(btf_ext);
}
@@ -2765,6 +2765,9 @@ static int bpf_object__init_btf(struct bpf_object *obj,
btf__set_pointer_size(obj->btf, 8);
}
if (btf_ext_data) {
+ struct btf_ext_info *ext_segs[3];
+ int seg_num, sec_num;
+
if (!obj->btf) {
pr_debug("Ignore ELF section %s because its depending ELF section %s is not found.\n",
BTF_EXT_ELF_SEC, BTF_ELF_SEC);
@@ -2778,6 +2781,43 @@ static int bpf_object__init_btf(struct bpf_object *obj,
obj->btf_ext = NULL;
goto out;
}
+
+ /* setup .BTF.ext to ELF section mapping */
+ ext_segs[0] = &obj->btf_ext->func_info;
+ ext_segs[1] = &obj->btf_ext->line_info;
+ ext_segs[2] = &obj->btf_ext->core_relo_info;
+ for (seg_num = 0; seg_num < ARRAY_SIZE(ext_segs); seg_num++) {
+ struct btf_ext_info *seg = ext_segs[seg_num];
+ const struct btf_ext_info_sec *sec;
+ const char *sec_name;
+ Elf_Scn *scn;
+
+ if (seg->sec_cnt == 0)
+ continue;
+
+ seg->sec_idxs = calloc(seg->sec_cnt, sizeof(*seg->sec_idxs));
+ if (!seg->sec_idxs) {
+ err = -ENOMEM;
+ goto out;
+ }
+
+ sec_num = 0;
+ for_each_btf_ext_sec(seg, sec) {
+ /* preventively increment index to avoid doing
+ * this before every continue below
+ */
+ sec_num++;
+
+ sec_name = btf__name_by_offset(obj->btf, sec->sec_name_off);
+ if (str_is_empty(sec_name))
+ continue;
+ scn = elf_sec_by_name(obj, sec_name);
+ if (!scn)
+ continue;
+
+ seg->sec_idxs[sec_num - 1] = elf_ndxscn(scn);
+ }
+ }
}
out:
if (err && libbpf_needs_btf(obj)) {
@@ -5642,7 +5682,7 @@ bpf_object__relocate_core(struct bpf_object *obj, const char *targ_btf_path)
struct bpf_program *prog;
struct bpf_insn *insn;
const char *sec_name;
- int i, err = 0, insn_idx, sec_idx;
+ int i, err = 0, insn_idx, sec_idx, sec_num;
if (obj->btf_ext->core_relo_info.len == 0)
return 0;
@@ -5663,33 +5703,18 @@ bpf_object__relocate_core(struct bpf_object *obj, const char *targ_btf_path)
}
seg = &obj->btf_ext->core_relo_info;
+ sec_num = 0;
for_each_btf_ext_sec(seg, sec) {
+ sec_idx = seg->sec_idxs[sec_num];
+ sec_num++;
+
sec_name = btf__name_by_offset(obj->btf, sec->sec_name_off);
if (str_is_empty(sec_name)) {
err = -EINVAL;
goto out;
}
- /* bpf_object's ELF is gone by now so it's not easy to find
- * section index by section name, but we can find *any*
- * bpf_program within desired section name and use it's
- * prog->sec_idx to do a proper search by section index and
- * instruction offset
- */
- prog = NULL;
- for (i = 0; i < obj->nr_programs; i++) {
- if (strcmp(obj->programs[i].sec_name, sec_name) == 0) {
- prog = &obj->programs[i];
- break;
- }
- }
- if (!prog) {
- pr_warn("sec '%s': failed to find a BPF program\n", sec_name);
- return -ENOENT;
- }
- sec_idx = prog->sec_idx;
- pr_debug("sec '%s': found %d CO-RE relocations\n",
- sec_name, sec->num_info);
+ pr_debug("sec '%s': found %d CO-RE relocations\n", sec_name, sec->num_info);
for_each_btf_ext_rec(seg, sec, i, rec) {
if (rec->insn_off % BPF_INSN_SZ)
@@ -5873,14 +5898,13 @@ static int adjust_prog_btf_ext_info(const struct bpf_object *obj,
void *rec, *rec_end, *new_prog_info;
const struct btf_ext_info_sec *sec;
size_t old_sz, new_sz;
- const char *sec_name;
- int i, off_adj;
+ int i, sec_num, sec_idx, off_adj;
+ sec_num = 0;
for_each_btf_ext_sec(ext_info, sec) {
- sec_name = btf__name_by_offset(obj->btf, sec->sec_name_off);
- if (!sec_name)
- return -EINVAL;
- if (strcmp(sec_name, prog->sec_name) != 0)
+ sec_idx = ext_info->sec_idxs[sec_num];
+ sec_num++;
+ if (prog->sec_idx != sec_idx)
continue;
for_each_btf_ext_rec(ext_info, sec, i, rec) {
@@ -376,6 +376,13 @@ struct btf_ext_info {
void *info;
__u32 rec_size;
__u32 len;
+ /* optional (maintained internally by libbpf) mapping between .BTF.ext
+ * section and corresponding ELF section. This is used to join
+ * information like CO-RE relocation records with corresponding BPF
+ * programs defined in ELF sections
+ */
+ __u32 *sec_idxs;
+ int sec_cnt;
};
#define for_each_btf_ext_sec(seg, sec) \
Instead of using ELF section names as a joining key between .BTF.ext and corresponding BPF programs, pre-build .BTF.ext section number to ELF section index mapping during bpf_object__open() and use it later for matching .BTF.ext information (func/line info or CO-RE relocations) to their respective BPF programs and subprograms. This simplifies corresponding joining logic and let's libbpf do manipulations with BPF program's ELF sections like dropping leading '?' character for non-autoloaded programs. Original joining logic in bpf_object__relocate_core() (see relevant comment that's now removed) was never elegant, so it's a good improvement regardless. But it also avoids unnecessary internal assumptions about preserving original ELF section name as BPF program's section name (which was broken when SEC("?abc") support was added). Fixes: a3820c481112 ("libbpf: Support opting out from autoloading BPF programs declaratively") Signed-off-by: Andrii Nakryiko <andrii@kernel.org> --- tools/lib/bpf/btf.c | 9 +++- tools/lib/bpf/libbpf.c | 78 +++++++++++++++++++++------------ tools/lib/bpf/libbpf_internal.h | 7 +++ 3 files changed, 65 insertions(+), 29 deletions(-)