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

diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index 7cb6ebf..6ad63e4 100644 (file)
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -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: {

diff --git a/tools/lib/bpf/btf.h b/tools/lib/bpf/btf.h
index f2e2fab..659ea8a 100644 (file)
--- a/tools/lib/bpf/btf.h
+++ b/tools/lib/bpf/btf.h
@@ -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

diff --git a/tools/lib/bpf/btf_dump.c b/tools/lib/bpf/btf_dump.c
index e4b483f..ad6df97 100644 (file)
--- a/tools/lib/bpf/btf_dump.c
+++ b/tools/lib/bpf/btf_dump.c
@@ -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:

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 62ed073..62a43c4 100644 (file)
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -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)

diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index 78ea62c..9e649cf 100644 (file)
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -388,4 +388,6 @@ LIBBPF_0.5.0 {
 } LIBBPF_0.4.0;
 
 LIBBPF_0.6.0 {
+       global:
+               btf__add_tag;
 } LIBBPF_0.5.0;

diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h
index 4f6ff5c..ceb0c98 100644 (file)
--- a/tools/lib/bpf/libbpf_internal.h
+++ b/tools/lib/bpf/libbpf_internal.h
@@ -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)