[bpf-next,v3,01/16] bpf: Introduce BPF_DYNPTR and helpers to facilitate its parsing

Commit Message

Hou Tao March 27, 2025, 8:34 a.m. UTC

From: Hou Tao <[e-mail]>

Add BPF_DYNPTR in btf_field_type to support bpf_dynptr in map key. The
parsing of bpf_dynptr in btf will be done in the following patch, and
the patch only adds two helpers: btf_new_bpf_dynptr_record() creates an
btf record which only includes a bpf_dynptr and btf_type_is_dynptr()
checks whether the btf_type is a bpf_dynptr or not.

Signed-off-by: Hou Tao <[e-mail]>
---
 include/linux/bpf.h |  1 +
 include/linux/btf.h |  2 ++
 kernel/bpf/btf.c    | 44 ++++++++++++++++++++++++++++++++++++++------
 3 files changed, 41 insertions(+), 6 deletions(-)

Patch

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 2083905a4e9fa..0b65c98d8b7d5 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -206,6 +206,7 @@  enum btf_field_type {
 	BPF_WORKQUEUE  = (1 << 10),
 	BPF_UPTR       = (1 << 11),
 	BPF_RES_SPIN_LOCK = (1 << 12),
+	BPF_DYNPTR     = (1 << 13),
 };
 
 typedef void (*btf_dtor_kfunc_t)(void *);
diff --git a/include/linux/btf.h b/include/linux/btf.h
index ebc0c0c9b9446..2ab48b377d312 100644
--- a/include/linux/btf.h
+++ b/include/linux/btf.h
@@ -226,8 +226,10 @@  bool btf_member_is_reg_int(const struct btf *btf, const struct btf_type *s,
 			   u32 expected_offset, u32 expected_size);
 struct btf_record *btf_parse_fields(const struct btf *btf, const struct btf_type *t,
 				    u32 field_mask, u32 value_size);
+struct btf_record *btf_new_bpf_dynptr_record(void);
 int btf_check_and_fixup_fields(const struct btf *btf, struct btf_record *rec);
 bool btf_type_is_void(const struct btf_type *t);
+bool btf_type_is_dynptr(const struct btf *btf, const struct btf_type *t);
 s32 btf_find_by_name_kind(const struct btf *btf, const char *name, u8 kind);
 s32 bpf_find_btf_id(const char *name, u32 kind, struct btf **btf_p);
 const struct btf_type *btf_type_skip_modifiers(const struct btf *btf,
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 16ba36f34dfab..1054a1e27e9d3 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -3939,6 +3939,17 @@  static int btf_field_cmp(const void *_a, const void *_b, const void *priv)
 	return 0;
 }
 
+static void btf_init_record(struct btf_record *record)
+{
+	record->cnt = 0;
+	record->field_mask = 0;
+	record->spin_lock_off = -EINVAL;
+	record->res_spin_lock_off = -EINVAL;
+	record->timer_off = -EINVAL;
+	record->wq_off = -EINVAL;
+	record->refcount_off = -EINVAL;
+}
+
 struct btf_record *btf_parse_fields(const struct btf *btf, const struct btf_type *t,
 				    u32 field_mask, u32 value_size)
 {
@@ -3957,15 +3968,11 @@  struct btf_record *btf_parse_fields(const struct btf *btf, const struct btf_type
 	/* This needs to be kzalloc to zero out padding and unused fields, see
 	 * comment in btf_record_equal.
 	 */
-	rec = kzalloc(offsetof(struct btf_record, fields[cnt]), GFP_KERNEL | __GFP_NOWARN);
+	rec = kzalloc(struct_size(rec, fields, cnt), GFP_KERNEL | __GFP_NOWARN);
 	if (!rec)
 		return ERR_PTR(-ENOMEM);
 
-	rec->spin_lock_off = -EINVAL;
-	rec->res_spin_lock_off = -EINVAL;
-	rec->timer_off = -EINVAL;
-	rec->wq_off = -EINVAL;
-	rec->refcount_off = -EINVAL;
+	btf_init_record(rec);
 	for (i = 0; i < cnt; i++) {
 		field_type_size = btf_field_type_size(info_arr[i].type);
 		if (info_arr[i].off + field_type_size > value_size) {
@@ -4067,6 +4074,25 @@  struct btf_record *btf_parse_fields(const struct btf *btf, const struct btf_type
 	return ERR_PTR(ret);
 }
 
+struct btf_record *btf_new_bpf_dynptr_record(void)
+{
+	struct btf_record *record;
+
+	record = kzalloc(struct_size(record, fields, 1), GFP_KERNEL | __GFP_NOWARN);
+	if (!record)
+		return ERR_PTR(-ENOMEM);
+
+	btf_init_record(record);
+
+	record->cnt = 1;
+	record->field_mask = BPF_DYNPTR;
+	record->fields[0].offset = 0;
+	record->fields[0].size = sizeof(struct bpf_dynptr);
+	record->fields[0].type = BPF_DYNPTR;
+
+	return record;
+}
+
 int btf_check_and_fixup_fields(const struct btf *btf, struct btf_record *rec)
 {
 	int i;
@@ -7562,6 +7588,12 @@  static bool btf_is_dynptr_ptr(const struct btf *btf, const struct btf_type *t)
 	return false;
 }
 
+bool btf_type_is_dynptr(const struct btf *btf, const struct btf_type *t)
+{
+	return __btf_type_is_struct(t) && t->size == sizeof(struct bpf_dynptr) &&
+	       !strcmp(__btf_name_by_offset(btf, t->name_off), "bpf_dynptr");
+}
+
 struct bpf_cand_cache {
 	const char *name;
 	u32 name_len;