btf: Optimize type lookup with binary search

Improve btf_find_by_name_kind() performance by adding binary search
support for sorted types. Falls back to linear search for compatibility.

Signed-off-by: Donglin Peng <pengdonglin@xiaomi.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20260109130003.3313716-7-dolinux.peng@gmail.com

diff --git a/include/linux/btf.h b/include/linux/btf.h
index 691f097849331b19d78344f0f991dfd177f5f04c..78dc79810c7ddb8c773591fc266c6bb535d0d022 100644 (file)
--- a/include/linux/btf.h
+++ b/include/linux/btf.h
@@ -219,6 +219,7 @@ bool btf_is_module(const struct btf *btf);
 bool btf_is_vmlinux(const struct btf *btf);
 struct module *btf_try_get_module(const struct btf *btf);
 u32 btf_nr_types(const struct btf *btf);
+u32 btf_named_start_id(const struct btf *btf, bool own);
 struct btf *btf_base_btf(const struct btf *btf);
 bool btf_type_is_i32(const struct btf_type *t);
 bool btf_type_is_i64(const struct btf_type *t);

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 2c6076fc29b9478a9347d7d57aaca748ed033e39..be8aa31e9e94225d37666db4063fe0d403abe206 100644 (file)
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -259,6 +259,7 @@ struct btf {
        void *nohdr_data;
        struct btf_header hdr;
        u32 nr_types; /* includes VOID for base BTF */
+       u32 named_start_id;
        u32 types_size;
        u32 data_size;
        refcount_t refcnt;
@@ -494,6 +495,11 @@ static bool btf_type_is_modifier(const struct btf_type *t)
        return false;
 }
 
+static int btf_start_id(const struct btf *btf)
+{
+       return btf->start_id + (btf->base_btf ? 0 : 1);
+}
+
 bool btf_type_is_void(const struct btf_type *t)
 {
        return t == &btf_void;
@@ -544,21 +550,84 @@ u32 btf_nr_types(const struct btf *btf)
        return total;
 }
 
+/*
+ * btf_named_start_id - Get the named starting ID for the BTF
+ * @btf: Pointer to the target BTF object
+ * @own: Flag indicating whether to query only the current BTF (true = current BTF only,
+ *       false = recursively traverse the base BTF chain)
+ *
+ * Return value rules:
+ * 1. For a sorted btf, return its named_start_id
+ * 2. Else for a split BTF, return its start_id
+ * 3. Else for a base BTF, return 1
+ */
+u32 btf_named_start_id(const struct btf *btf, bool own)
+{
+       const struct btf *base_btf = btf;
+
+       while (!own && base_btf->base_btf)
+               base_btf = base_btf->base_btf;
+
+       return base_btf->named_start_id ?: (base_btf->start_id ?: 1);
+}
+
+static s32 btf_find_by_name_kind_bsearch(const struct btf *btf, const char *name)
+{
+       const struct btf_type *t;
+       const char *tname;
+       s32 l, r, m;
+
+       l = btf_named_start_id(btf, true);
+       r = btf_nr_types(btf) - 1;
+       while (l <= r) {
+               m = l + (r - l) / 2;
+               t = btf_type_by_id(btf, m);
+               tname = btf_name_by_offset(btf, t->name_off);
+               if (strcmp(tname, name) >= 0) {
+                       if (l == r)
+                               return r;
+                       r = m;
+               } else {
+                       l = m + 1;
+               }
+       }
+
+       return btf_nr_types(btf);
+}
+
 s32 btf_find_by_name_kind(const struct btf *btf, const char *name, u8 kind)
 {
+       const struct btf *base_btf = btf_base_btf(btf);
        const struct btf_type *t;
        const char *tname;
-       u32 i, total;
+       s32 id, total;
 
-       total = btf_nr_types(btf);
-       for (i = 1; i < total; i++) {
-               t = btf_type_by_id(btf, i);
-               if (BTF_INFO_KIND(t->info) != kind)
-                       continue;
+       if (base_btf) {
+               id = btf_find_by_name_kind(base_btf, name, kind);
+               if (id > 0)
+                       return id;
+       }
 
-               tname = btf_name_by_offset(btf, t->name_off);
-               if (!strcmp(tname, name))
-                       return i;
+       total = btf_nr_types(btf);
+       if (btf->named_start_id > 0 && name[0]) {
+               id = btf_find_by_name_kind_bsearch(btf, name);
+               for (; id < total; id++) {
+                       t = btf_type_by_id(btf, id);
+                       tname = btf_name_by_offset(btf, t->name_off);
+                       if (strcmp(tname, name) != 0)
+                               return -ENOENT;
+                       if (BTF_INFO_KIND(t->info) == kind)
+                               return id;
+               }
+       } else {
+               for (id = btf_start_id(btf); id < total; id++) {
+                       t = btf_type_by_id(btf, id);
+                       if (BTF_INFO_KIND(t->info) != kind)
+                               continue;
+                       tname = btf_name_by_offset(btf, t->name_off);
+                       if (strcmp(tname, name) == 0)
+                               return id;
+               }
        }
 
        return -ENOENT;
@@ -5791,6 +5860,7 @@ static struct btf *btf_parse(const union bpf_attr *attr, bpfptr_t uattr, u32 uat
                goto errout;
        }
        env->btf = btf;
+       btf->named_start_id = 0;
 
        data = kvmalloc(attr->btf_size, GFP_KERNEL | __GFP_NOWARN);
        if (!data) {
@@ -6210,6 +6280,7 @@ static struct btf *btf_parse_base(struct btf_verifier_env *env, const char *name
        btf->data = data;
        btf->data_size = data_size;
        btf->kernel_btf = true;
+       btf->named_start_id = 0;
        snprintf(btf->name, sizeof(btf->name), "%s", name);
 
        err = btf_parse_hdr(env);
@@ -6327,6 +6398,7 @@ static struct btf *btf_parse_module(const char *module_name, const void *data,
        btf->start_id = base_btf->nr_types;
        btf->start_str_off = base_btf->hdr.str_len;
        btf->kernel_btf = true;
+       btf->named_start_id = 0;
        snprintf(btf->name, sizeof(btf->name), "%s", module_name);
 
        btf->data = kvmemdup(data, data_size, GFP_KERNEL | __GFP_NOWARN);