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libbpf: Add support for BTF_KIND_TAG 

Add BTF_KIND_TAG support for parsing and dedup.
Also added sanitization for BTF_KIND_TAG. If BTF_KIND_TAG is not
supported in the kernel, sanitize it to INTs.

Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210914223025.246687-1-yhs@fb.com
This commit is contained in:
Yonghong Song 2021-09-14 15:30:25 -07:00 committed by Alexei Starovoitov
parent 30025e8bd8
commit 5b84bd1036
6 changed files with 118 additions and 3 deletions
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68
tools/lib/bpf/btf.c
View File

@ -304,6 +304,8 @@ static int btf_type_size(const struct btf_type *t)
return base_size + sizeof(struct btf_var);
case BTF_KIND_DATASEC:
return base_size + vlen * sizeof(struct btf_var_secinfo);
case BTF_KIND_TAG:
return base_size + sizeof(struct btf_tag);
default:
pr_debug("Unsupported BTF_KIND:%u\n", btf_kind(t));
return -EINVAL;
@ -376,6 +378,9 @@ static int btf_bswap_type_rest(struct btf_type *t)
v->size = bswap_32(v->size);
}
return 0;
case BTF_KIND_TAG:
btf_tag(t)->component_idx = bswap_32(btf_tag(t)->component_idx);
return 0;
default:
pr_debug("Unsupported BTF_KIND:%u\n", btf_kind(t));
return -EINVAL;
@ -586,6 +591,7 @@ __s64 btf__resolve_size(const struct btf *btf, __u32 type_id)
case BTF_KIND_CONST:
case BTF_KIND_RESTRICT:
case BTF_KIND_VAR:
case BTF_KIND_TAG:
type_id = t->type;
break;
case BTF_KIND_ARRAY:
@ -2440,6 +2446,48 @@ int btf__add_datasec_var_info(struct btf *btf, int var_type_id, __u32 offset, __
return 0;
}
/*
* Append new BTF_KIND_TAG type with:
* - *value* - non-empty/non-NULL string;
* - *ref_type_id* - referenced type ID, it might not exist yet;
* - *component_idx* - -1 for tagging reference type, otherwise struct/union
* member or function argument index;
* Returns:
* - >0, type ID of newly added BTF type;
* - <0, on error.
*/
int btf__add_tag(struct btf *btf, const char *value, int ref_type_id,
int component_idx)
{
struct btf_type *t;
int sz, value_off;
if (!value || !value[0] || component_idx < -1)
return libbpf_err(-EINVAL);
if (validate_type_id(ref_type_id))
return libbpf_err(-EINVAL);
if (btf_ensure_modifiable(btf))
return libbpf_err(-ENOMEM);
sz = sizeof(struct btf_type) + sizeof(struct btf_tag);
t = btf_add_type_mem(btf, sz);
if (!t)
return libbpf_err(-ENOMEM);
value_off = btf__add_str(btf, value);
if (value_off < 0)
return value_off;
t->name_off = value_off;
t->info = btf_type_info(BTF_KIND_TAG, 0, false);
t->type = ref_type_id;
btf_tag(t)->component_idx = component_idx;
return btf_commit_type(btf, sz);
}
struct btf_ext_sec_setup_param {
__u32 off;
__u32 len;
@ -3535,6 +3583,7 @@ static int btf_dedup_prep(struct btf_dedup *d)
h = btf_hash_common(t);
break;
case BTF_KIND_INT:
case BTF_KIND_TAG:
h = btf_hash_int_tag(t);
break;
case BTF_KIND_ENUM:
@ -3590,6 +3639,7 @@ static int btf_dedup_prim_type(struct btf_dedup *d, __u32 type_id)
case BTF_KIND_FUNC_PROTO:
case BTF_KIND_VAR:
case BTF_KIND_DATASEC:
case BTF_KIND_TAG:
return 0;
case BTF_KIND_INT:
@ -4210,6 +4260,23 @@ static int btf_dedup_ref_type(struct btf_dedup *d, __u32 type_id)
}
break;
case BTF_KIND_TAG:
ref_type_id = btf_dedup_ref_type(d, t->type);
if (ref_type_id < 0)
return ref_type_id;
t->type = ref_type_id;
h = btf_hash_int_tag(t);
for_each_dedup_cand(d, hash_entry, h) {
cand_id = (__u32)(long)hash_entry->value;
cand = btf_type_by_id(d->btf, cand_id);
if (btf_equal_int_tag(t, cand)) {
new_id = cand_id;
break;
}
}
break;
case BTF_KIND_ARRAY: {
struct btf_array *info = btf_array(t);
@ -4482,6 +4549,7 @@ int btf_type_visit_type_ids(struct btf_type *t, type_id_visit_fn visit, void *ct
case BTF_KIND_TYPEDEF:
case BTF_KIND_FUNC:
case BTF_KIND_VAR:
case BTF_KIND_TAG:
return visit(&t->type, ctx);
case BTF_KIND_ARRAY: {

15
tools/lib/bpf/btf.h
View File

@ -143,6 +143,10 @@ LIBBPF_API int btf__add_datasec(struct btf *btf, const char *name, __u32 byte_sz
LIBBPF_API int btf__add_datasec_var_info(struct btf *btf, int var_type_id,
__u32 offset, __u32 byte_sz);
/* tag construction API */
LIBBPF_API int btf__add_tag(struct btf *btf, const char *value, int ref_type_id,
int component_idx);
struct btf_dedup_opts {
unsigned int dedup_table_size;
bool dont_resolve_fwds;
@ -330,6 +334,11 @@ static inline bool btf_is_float(const struct btf_type *t)
return btf_kind(t) == BTF_KIND_FLOAT;
}
static inline bool btf_is_tag(const struct btf_type *t)
{
return btf_kind(t) == BTF_KIND_TAG;
}
static inline __u8 btf_int_encoding(const struct btf_type *t)
{
return BTF_INT_ENCODING(*(__u32 *)(t + 1));
@ -398,6 +407,12 @@ btf_var_secinfos(const struct btf_type *t)
return (struct btf_var_secinfo *)(t + 1);
}
struct btf_tag;
static inline struct btf_tag *btf_tag(const struct btf_type *t)
{
return (struct btf_tag *)(t + 1);
}
#ifdef __cplusplus
} /* extern "C" */
#endif

3
tools/lib/bpf/btf_dump.c
View File

@ -316,6 +316,7 @@ static int btf_dump_mark_referenced(struct btf_dump *d)
case BTF_KIND_TYPEDEF:
case BTF_KIND_FUNC:
case BTF_KIND_VAR:
case BTF_KIND_TAG:
d->type_states[t->type].referenced = 1;
break;
@ -583,6 +584,7 @@ static int btf_dump_order_type(struct btf_dump *d, __u32 id, bool through_ptr)
case BTF_KIND_FUNC:
case BTF_KIND_VAR:
case BTF_KIND_DATASEC:
case BTF_KIND_TAG:
d->type_states[id].order_state = ORDERED;
return 0;
@ -2215,6 +2217,7 @@ static int btf_dump_dump_type_data(struct btf_dump *d,
case BTF_KIND_FWD:
case BTF_KIND_FUNC:
case BTF_KIND_FUNC_PROTO:
case BTF_KIND_TAG:
err = btf_dump_unsupported_data(d, t, id);
break;
case BTF_KIND_INT:

31
tools/lib/bpf/libbpf.c
View File

@ -195,6 +195,8 @@ enum kern_feature_id {
FEAT_BTF_FLOAT,
/* BPF perf link support */
FEAT_PERF_LINK,
/* BTF_KIND_TAG support */
FEAT_BTF_TAG,
__FEAT_CNT,
};
@ -1986,6 +1988,7 @@ static const char *__btf_kind_str(__u16 kind)
case BTF_KIND_VAR: return "var";
case BTF_KIND_DATASEC: return "datasec";
case BTF_KIND_FLOAT: return "float";
case BTF_KIND_TAG: return "tag";
default: return "unknown";
}
}
@ -2485,8 +2488,9 @@ static bool btf_needs_sanitization(struct bpf_object *obj)
bool has_datasec = kernel_supports(obj, FEAT_BTF_DATASEC);
bool has_float = kernel_supports(obj, FEAT_BTF_FLOAT);
bool has_func = kernel_supports(obj, FEAT_BTF_FUNC);
bool has_tag = kernel_supports(obj, FEAT_BTF_TAG);
return !has_func || !has_datasec || !has_func_global || !has_float;
return !has_func || !has_datasec || !has_func_global || !has_float || !has_tag;
}
static void bpf_object__sanitize_btf(struct bpf_object *obj, struct btf *btf)
@ -2495,14 +2499,15 @@ static void bpf_object__sanitize_btf(struct bpf_object *obj, struct btf *btf)
bool has_datasec = kernel_supports(obj, FEAT_BTF_DATASEC);
bool has_float = kernel_supports(obj, FEAT_BTF_FLOAT);
bool has_func = kernel_supports(obj, FEAT_BTF_FUNC);
bool has_tag = kernel_supports(obj, FEAT_BTF_TAG);
struct btf_type *t;
int i, j, vlen;
for (i = 1; i <= btf__get_nr_types(btf); i++) {
t = (struct btf_type *)btf__type_by_id(btf, i);
if (!has_datasec && btf_is_var(t)) {
/* replace VAR with INT */
if ((!has_datasec && btf_is_var(t)) || (!has_tag && btf_is_tag(t))) {
/* replace VAR/TAG with INT */
t->info = BTF_INFO_ENC(BTF_KIND_INT, 0, 0);
/*
* using size = 1 is the safest choice, 4 will be too
@ -4212,6 +4217,23 @@ static int probe_kern_btf_float(void)
strs, sizeof(strs)));
}
static int probe_kern_btf_tag(void)
{
static const char strs[] = "\0tag";
__u32 types[] = {
/* int */
BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4), /* [1] */
/* VAR x */ /* [2] */
BTF_TYPE_ENC(1, BTF_INFO_ENC(BTF_KIND_VAR, 0, 0), 1),
BTF_VAR_STATIC,
/* attr */
BTF_TYPE_TAG_ENC(1, 2, -1),
};
return probe_fd(libbpf__load_raw_btf((char *)types, sizeof(types),
strs, sizeof(strs)));
}
static int probe_kern_array_mmap(void)
{
struct bpf_create_map_attr attr = {
@ -4428,6 +4450,9 @@ static struct kern_feature_desc {
[FEAT_PERF_LINK] = {
"BPF perf link support", probe_perf_link,
},
[FEAT_BTF_TAG] = {
"BTF_KIND_TAG support", probe_kern_btf_tag,
},
};
static bool kernel_supports(const struct bpf_object *obj, enum kern_feature_id feat_id)

2
tools/lib/bpf/libbpf.map
View File

@ -388,4 +388,6 @@ LIBBPF_0.5.0 {
} LIBBPF_0.4.0;
LIBBPF_0.6.0 {
global:
btf__add_tag;
} LIBBPF_0.5.0;

2
tools/lib/bpf/libbpf_internal.h
View File

@ -69,6 +69,8 @@
#define BTF_VAR_SECINFO_ENC(type, offset, size) (type), (offset), (size)
#define BTF_TYPE_FLOAT_ENC(name, sz) \
BTF_TYPE_ENC(name, BTF_INFO_ENC(BTF_KIND_FLOAT, 0, 0), sz)
#define BTF_TYPE_TAG_ENC(value, type, component_idx) \
BTF_TYPE_ENC(value, BTF_INFO_ENC(BTF_KIND_TAG, 0, 0), type), (component_idx)
#ifndef likely
#define likely(x) __builtin_expect(!!(x), 1)