Commit d83caf7c authored by Anton Protopopov's avatar Anton Protopopov Committed by Alexei Starovoitov
Browse files

bpf: add btf_type_is_i{32,64} helpers 

There are places in BPF code which check if a BTF type is an integer
of particular size. This code can be made simpler by using helpers.
Add new btf_type_is_i{32,64} helpers, and simplify code in a few
files. (Suggested by Eduard for a patch which copy-pasted such a
check [1].)

  v1 -> v2:
    * export less generic helpers (Eduard)
    * make subject less generic than in [v1] (Eduard)

[1] https://lore.kernel.org/bpf/7edb47e73baa46705119a23c6bf4af26517a640f.camel@gmail.com/
[v1] https://lore.kernel.org/bpf/20250624193655.733050-1-a.s.protopopov@gmail.com/



Suggested-by: default avatarEduard Zingerman <eddyz87@gmail.com>
Signed-off-by: default avatarAnton Protopopov <a.s.protopopov@gmail.com>
Acked-by: default avatarEduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20250625151621.1000584-1-a.s.protopopov@gmail.com


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 0ed5f799

include/linux/btf.h

+2 −0
Original line number Diff line number Diff line
@@ -221,6 +221,8 @@ 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);

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);

bool btf_member_is_reg_int(const struct btf *btf, const struct btf_type *s,

			   const struct btf_member *m,

			   u32 expected_offset, u32 expected_size);

kernel/bpf/arraymap.c

+3 −8
Original line number Diff line number Diff line
@@ -530,8 +530,6 @@ static int array_map_check_btf(const struct bpf_map *map, 
			       const struct btf_type *key_type,

			       const struct btf_type *value_type)

{

	u32 int_data;



	/* One exception for keyless BTF: .bss/.data/.rodata map */

	if (btf_type_is_void(key_type)) {

		if (map->map_type != BPF_MAP_TYPE_ARRAY ||
@@ -544,14 +542,11 @@ static int array_map_check_btf(const struct bpf_map *map, 
		return 0;

	}



	if (BTF_INFO_KIND(key_type->info) != BTF_KIND_INT)

		return -EINVAL;



	int_data = *(u32 *)(key_type + 1);

	/* bpf array can only take a u32 key. This check makes sure

	/*

	 * Bpf array can only take a u32 key. This check makes sure

	 * that the btf matches the attr used during map_create.

	 */

	if (BTF_INT_BITS(int_data) != 32 || BTF_INT_OFFSET(int_data))

	if (!btf_type_is_i32(key_type))

		return -EINVAL;



	return 0;

kernel/bpf/bpf_local_storage.c

+1 −7
Original line number Diff line number Diff line
@@ -722,13 +722,7 @@ int bpf_local_storage_map_check_btf(const struct bpf_map *map, 
				    const struct btf_type *key_type,

				    const struct btf_type *value_type)

{

	u32 int_data;



	if (BTF_INFO_KIND(key_type->info) != BTF_KIND_INT)

		return -EINVAL;



	int_data = *(u32 *)(key_type + 1);

	if (BTF_INT_BITS(int_data) != 32 || BTF_INT_OFFSET(int_data))

	if (!btf_type_is_i32(key_type))

		return -EINVAL;



	return 0;

kernel/bpf/btf.c

+26 −15
Original line number Diff line number Diff line
@@ -858,26 +858,37 @@ const struct btf_type *btf_type_by_id(const struct btf *btf, u32 type_id) 
EXPORT_SYMBOL_GPL(btf_type_by_id);



/*

 * Regular int is not a bit field and it must be either

 * u8/u16/u32/u64 or __int128.

 * Check that the type @t is a regular int. This means that @t is not

 * a bit field and it has the same size as either of u8/u16/u32/u64

 * or __int128. If @expected_size is not zero, then size of @t should

 * be the same. A caller should already have checked that the type @t

 * is an integer.

 */

static bool __btf_type_int_is_regular(const struct btf_type *t, size_t expected_size)

{

	u32 int_data = btf_type_int(t);

	u8 nr_bits = BTF_INT_BITS(int_data);

	u8 nr_bytes = BITS_ROUNDUP_BYTES(nr_bits);



	return BITS_PER_BYTE_MASKED(nr_bits) == 0 &&

	       BTF_INT_OFFSET(int_data) == 0 &&

	       (nr_bytes <= 16 && is_power_of_2(nr_bytes)) &&

	       (expected_size == 0 || nr_bytes == expected_size);

}



static bool btf_type_int_is_regular(const struct btf_type *t)

{

	u8 nr_bits, nr_bytes;

	u32 int_data;

	return __btf_type_int_is_regular(t, 0);

}



	int_data = btf_type_int(t);

	nr_bits = BTF_INT_BITS(int_data);

	nr_bytes = BITS_ROUNDUP_BYTES(nr_bits);

	if (BITS_PER_BYTE_MASKED(nr_bits) ||

	    BTF_INT_OFFSET(int_data) ||

	    (nr_bytes != sizeof(u8) && nr_bytes != sizeof(u16) &&

	     nr_bytes != sizeof(u32) && nr_bytes != sizeof(u64) &&

	     nr_bytes != (2 * sizeof(u64)))) {

		return false;

bool btf_type_is_i32(const struct btf_type *t)

{

	return btf_type_is_int(t) && __btf_type_int_is_regular(t, 4);

}



	return true;

bool btf_type_is_i64(const struct btf_type *t)

{

	return btf_type_is_int(t) && __btf_type_int_is_regular(t, 8);

}



/*

kernel/bpf/local_storage.c

+1 −8
Original line number Diff line number Diff line
@@ -394,17 +394,10 @@ static int cgroup_storage_check_btf(const struct bpf_map *map, 
		if (!btf_member_is_reg_int(btf, key_type, m, offset, size))

			return -EINVAL;

	} else {

		u32 int_data;



		/*

		 * Key is expected to be u64, which stores the cgroup_inode_id

		 */



		if (BTF_INFO_KIND(key_type->info) != BTF_KIND_INT)

			return -EINVAL;



		int_data = *(u32 *)(key_type + 1);

		if (BTF_INT_BITS(int_data) != 64 || BTF_INT_OFFSET(int_data))

		if (!btf_type_is_i64(key_type))

			return -EINVAL;

	}