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libbpf: Refactor CO-RE relocs to not assume a single BTF object 

Refactor CO-RE relocation candidate search to not expect a single BTF, rather
return all candidate types with their corresponding BTF objects. This will
allow to extend CO-RE relocations to accommodate kernel module BTFs.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20201203204634.1325171-5-andrii@kernel.org
This commit is contained in:
Andrii Nakryiko 2020-12-03 12:46:24 -08:00 committed by Alexei Starovoitov
parent a19f93cfaf
commit 0f7515ca7c
1 changed files with 111 additions and 76 deletions
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183
tools/lib/bpf/libbpf.c
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@ -462,11 +462,14 @@ struct bpf_object {
struct list_head list;
struct btf *btf;
struct btf_ext *btf_ext;
/* Parse and load BTF vmlinux if any of the programs in the object need
* it at load time.
*/
struct btf *btf_vmlinux;
struct btf_ext *btf_ext;
/* vmlinux BTF override for CO-RE relocations */
struct btf *btf_vmlinux_override;
void *priv;
bpf_object_clear_priv_t clear_priv;
@ -4600,46 +4603,43 @@ static size_t bpf_core_essential_name_len(const char *name)
return n;
}
/* dynamically sized list of type IDs */
struct ids_vec {
__u32 *data;
struct core_cand
{
const struct btf *btf;
const struct btf_type *t;
const char *name;
__u32 id;
};
/* dynamically sized list of type IDs and its associated struct btf */
struct core_cand_list {
struct core_cand *cands;
int len;
};
static void bpf_core_free_cands(struct ids_vec *cand_ids)
static void bpf_core_free_cands(struct core_cand_list *cands)
{
free(cand_ids->data);
free(cand_ids);
free(cands->cands);
free(cands);
}
static struct ids_vec *bpf_core_find_cands(const struct btf *local_btf,
__u32 local_type_id,
const struct btf *targ_btf)
static int bpf_core_add_cands(struct core_cand *local_cand,
size_t local_essent_len,
const struct btf *targ_btf,
const char *targ_btf_name,
int targ_start_id,
struct core_cand_list *cands)
{
size_t local_essent_len, targ_essent_len;
const char *local_name, *targ_name;
const struct btf_type *t, *local_t;
struct ids_vec *cand_ids;
__u32 *new_ids;
int i, err, n;
local_t = btf__type_by_id(local_btf, local_type_id);
if (!local_t)
return ERR_PTR(-EINVAL);
local_name = btf__name_by_offset(local_btf, local_t->name_off);
if (str_is_empty(local_name))
return ERR_PTR(-EINVAL);
local_essent_len = bpf_core_essential_name_len(local_name);
cand_ids = calloc(1, sizeof(*cand_ids));
if (!cand_ids)
return ERR_PTR(-ENOMEM);
struct core_cand *new_cands, *cand;
const struct btf_type *t;
const char *targ_name;
size_t targ_essent_len;
int n, i;
n = btf__get_nr_types(targ_btf);
for (i = 1; i <= n; i++) {
for (i = targ_start_id; i <= n; i++) {
t = btf__type_by_id(targ_btf, i);
if (btf_kind(t) != btf_kind(local_t))
if (btf_kind(t) != btf_kind(local_cand->t))
continue;
targ_name = btf__name_by_offset(targ_btf, t->name_off);
@ -4650,27 +4650,64 @@ static struct ids_vec *bpf_core_find_cands(const struct btf *local_btf,
if (targ_essent_len != local_essent_len)
continue;
if (strncmp(local_name, targ_name, local_essent_len) == 0) {
pr_debug("CO-RE relocating [%d] %s %s: found target candidate [%d] %s %s\n",
local_type_id, btf_kind_str(local_t),
local_name, i, btf_kind_str(t), targ_name);
new_ids = libbpf_reallocarray(cand_ids->data,
cand_ids->len + 1,
sizeof(*cand_ids->data));
if (!new_ids) {
err = -ENOMEM;
goto err_out;
if (strncmp(local_cand->name, targ_name, local_essent_len) != 0)
continue;
pr_debug("CO-RE relocating [%d] %s %s: found target candidate [%d] %s %s in [%s]\n",
local_cand->id, btf_kind_str(local_cand->t),
local_cand->name, i, btf_kind_str(t), targ_name,
targ_btf_name);
new_cands = libbpf_reallocarray(cands->cands, cands->len + 1,
sizeof(*cands->cands));
if (!new_cands)
return -ENOMEM;
cand = &new_cands[cands->len];
cand->btf = targ_btf;
cand->t = t;
cand->name = targ_name;
cand->id = i;
cands->cands = new_cands;
cands->len++;
}
cand_ids->data = new_ids;
cand_ids->data[cand_ids->len++] = i;
return 0;
}
}
return cand_ids;
err_out:
bpf_core_free_cands(cand_ids);
static struct core_cand_list *
bpf_core_find_cands(struct bpf_object *obj, const struct btf *local_btf, __u32 local_type_id)
{
struct core_cand local_cand = {};
struct core_cand_list *cands;
size_t local_essent_len;
int err;
local_cand.btf = local_btf;
local_cand.t = btf__type_by_id(local_btf, local_type_id);
if (!local_cand.t)
return ERR_PTR(-EINVAL);
local_cand.name = btf__name_by_offset(local_btf, local_cand.t->name_off);
if (str_is_empty(local_cand.name))
return ERR_PTR(-EINVAL);
local_essent_len = bpf_core_essential_name_len(local_cand.name);
cands = calloc(1, sizeof(*cands));
if (!cands)
return ERR_PTR(-ENOMEM);
/* Attempt to find target candidates in vmlinux BTF first */
err = bpf_core_add_cands(&local_cand, local_essent_len,
obj->btf_vmlinux_override ?: obj->btf_vmlinux,
"vmlinux", 1, cands);
if (err) {
bpf_core_free_cands(cands);
return ERR_PTR(err);
}
return cands;
}
/* Check two types for compatibility for the purpose of field access
* relocation. const/volatile/restrict and typedefs are skipped to ensure we
* are relocating semantically compatible entities:
@ -5661,7 +5698,6 @@ static int bpf_core_apply_relo(struct bpf_program *prog,
const struct bpf_core_relo *relo,
int relo_idx,
const struct btf *local_btf,
const struct btf *targ_btf,
struct hashmap *cand_cache)
{
struct bpf_core_spec local_spec, cand_spec, targ_spec = {};
@ -5669,8 +5705,8 @@ static int bpf_core_apply_relo(struct bpf_program *prog,
struct bpf_core_relo_res cand_res, targ_res;
const struct btf_type *local_type;
const char *local_name;
struct ids_vec *cand_ids;
__u32 local_id, cand_id;
struct core_cand_list *cands = NULL;
__u32 local_id;
const char *spec_str;
int i, j, err;
@ -5717,24 +5753,24 @@ static int bpf_core_apply_relo(struct bpf_program *prog,
return -EOPNOTSUPP;
}
if (!hashmap__find(cand_cache, type_key, (void **)&cand_ids)) {
cand_ids = bpf_core_find_cands(local_btf, local_id, targ_btf);
if (IS_ERR(cand_ids)) {
if (!hashmap__find(cand_cache, type_key, (void **)&cands)) {
cands = bpf_core_find_cands(prog->obj, local_btf, local_id);
if (IS_ERR(cands)) {
pr_warn("prog '%s': relo #%d: target candidate search failed for [%d] %s %s: %ld",
prog->name, relo_idx, local_id, btf_kind_str(local_type),
local_name, PTR_ERR(cand_ids));
return PTR_ERR(cand_ids);
local_name, PTR_ERR(cands));
return PTR_ERR(cands);
}
err = hashmap__set(cand_cache, type_key, cand_ids, NULL, NULL);
err = hashmap__set(cand_cache, type_key, cands, NULL, NULL);
if (err) {
bpf_core_free_cands(cand_ids);
bpf_core_free_cands(cands);
return err;
}
}
for (i = 0, j = 0; i < cand_ids->len; i++) {
cand_id = cand_ids->data[i];
err = bpf_core_spec_match(&local_spec, targ_btf, cand_id, &cand_spec);
for (i = 0, j = 0; i < cands->len; i++) {
err = bpf_core_spec_match(&local_spec, cands->cands[i].btf,
cands->cands[i].id, &cand_spec);
if (err < 0) {
pr_warn("prog '%s': relo #%d: error matching candidate #%d ",
prog->name, relo_idx, i);
@ -5778,7 +5814,7 @@ static int bpf_core_apply_relo(struct bpf_program *prog,
return -EINVAL;
}
cand_ids->data[j++] = cand_spec.root_type_id;
cands->cands[j++] = cands->cands[i];
}
/*
@ -5790,7 +5826,7 @@ static int bpf_core_apply_relo(struct bpf_program *prog,
* depending on relo's kind.
*/
if (j > 0)
cand_ids->len = j;
cands->len = j;
/*
* If no candidates were found, it might be both a programmer error,
@ -5834,20 +5870,19 @@ bpf_object__relocate_core(struct bpf_object *obj, const char *targ_btf_path)
struct hashmap_entry *entry;
struct hashmap *cand_cache = NULL;
struct bpf_program *prog;
struct btf *targ_btf;
const char *sec_name;
int i, err = 0, insn_idx, sec_idx;
if (obj->btf_ext->core_relo_info.len == 0)
return 0;
if (targ_btf_path)
targ_btf = btf__parse(targ_btf_path, NULL);
else
targ_btf = obj->btf_vmlinux;
if (IS_ERR_OR_NULL(targ_btf)) {
pr_warn("failed to get target BTF: %ld\n", PTR_ERR(targ_btf));
return PTR_ERR(targ_btf);
if (targ_btf_path) {
obj->btf_vmlinux_override = btf__parse(targ_btf_path, NULL);
if (IS_ERR_OR_NULL(obj->btf_vmlinux_override)) {
err = PTR_ERR(obj->btf_vmlinux_override);
pr_warn("failed to parse target BTF: %d\n", err);
return err;
}
}
cand_cache = hashmap__new(bpf_core_hash_fn, bpf_core_equal_fn, NULL);
@ -5899,8 +5934,7 @@ bpf_object__relocate_core(struct bpf_object *obj, const char *targ_btf_path)
if (!prog->load)
continue;
err = bpf_core_apply_relo(prog, rec, i, obj->btf,
targ_btf, cand_cache);
err = bpf_core_apply_relo(prog, rec, i, obj->btf, cand_cache);
if (err) {
pr_warn("prog '%s': relo #%d: failed to relocate: %d\n",
prog->name, i, err);
@ -5911,8 +5945,9 @@ bpf_object__relocate_core(struct bpf_object *obj, const char *targ_btf_path)
out:
/* obj->btf_vmlinux is freed at the end of object load phase */
if (targ_btf != obj->btf_vmlinux)
btf__free(targ_btf);
btf__free(obj->btf_vmlinux_override);
obj->btf_vmlinux_override = NULL;
if (!IS_ERR_OR_NULL(cand_cache)) {
hashmap__for_each_entry(cand_cache, entry, i) {
bpf_core_free_cands(entry->value);