[bpf-next,v2,01/20] bpf: Add two helpers to facilitate the parsing of bpf_dynptr

Commit Message

Hou Tao Jan. 25, 2025, 11:10 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.

With the introduction of BPF_DYNPTR, BTF_FIELDS_MAX is changed from 11
to 13, therefore, update the hard-coded number in cpumask test as well.

Signed-off-by: Hou Tao <[e-mail]>
---
 include/linux/bpf.h                           |  5 ++-
 include/linux/btf.h                           |  2 +
 kernel/bpf/btf.c                              | 42 ++++++++++++++++---
 .../selftests/bpf/progs/cpumask_common.h      |  2 +-
 4 files changed, 43 insertions(+), 8 deletions(-)

Patch

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index feda0ce90f5a3..0ee14ae30100f 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -184,8 +184,8 @@  struct bpf_map_ops {
 };
 
 enum {
-	/* Support at most 11 fields in a BTF type */
-	BTF_FIELDS_MAX	   = 11,
+	/* Support at most 13 fields in a BTF type */
+	BTF_FIELDS_MAX	   = 13,
 };
 
 enum btf_field_type {
@@ -204,6 +204,7 @@  enum btf_field_type {
 	BPF_REFCOUNT   = (1 << 9),
 	BPF_WORKQUEUE  = (1 << 10),
 	BPF_UPTR       = (1 << 11),
+	BPF_DYNPTR     = (1 << 12),
 };
 
 typedef void (*btf_dtor_kfunc_t)(void *);
diff --git a/include/linux/btf.h b/include/linux/btf.h
index 2a08a2b55592e..ee1488494c73d 100644
--- a/include/linux/btf.h
+++ b/include/linux/btf.h
@@ -223,8 +223,10 @@  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 8396ce1d0fba3..b316631b614fa 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -3925,6 +3925,16 @@  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->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)
 {
@@ -3943,14 +3953,11 @@  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->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) {
@@ -4041,6 +4048,25 @@  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;
@@ -7439,6 +7465,12 @@  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;
diff --git a/tools/testing/selftests/bpf/progs/cpumask_common.h b/tools/testing/selftests/bpf/progs/cpumask_common.h
index 4ece7873ba609..afbf2e99b1bb8 100644
--- a/tools/testing/selftests/bpf/progs/cpumask_common.h
+++ b/tools/testing/selftests/bpf/progs/cpumask_common.h
@@ -10,7 +10,7 @@ 
 /* Should use BTF_FIELDS_MAX, but it is not always available in vmlinux.h,
  * so use the hard-coded number as a workaround.
  */
-#define CPUMASK_KPTR_FIELDS_MAX 11
+#define CPUMASK_KPTR_FIELDS_MAX 13
 
 int err;