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bpf: add btf_type_is_i{32,64} helpers

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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: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Anton Protopopov <a.s.protopopov@gmail.com>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20250625151621.1000584-1-a.s.protopopov@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Anton Protopopov 2025-06-25 15:16:21 +00:00 committed by Alexei Starovoitov
parent 0ed5f79987
commit d83caf7c8d
5 changed files with 33 additions and 38 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
include/linux/btf.h
View File

@ -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);

11
kernel/bpf/arraymap.c
View File

@ -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;

8
kernel/bpf/bpf_local_storage.c
View File

@ -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;

41
kernel/bpf/btf.c
View File

@ -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)
static bool __btf_type_int_is_regular(const struct btf_type *t, size_t expected_size)
{
u8 nr_bits, nr_bytes;
u32 int_data;
u32 int_data = btf_type_int(t);
u8 nr_bits = BTF_INT_BITS(int_data);
u8 nr_bytes = BITS_ROUNDUP_BYTES(nr_bits);
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;
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);
}
return true;
static bool btf_type_int_is_regular(const struct btf_type *t)
{
return __btf_type_int_is_regular(t, 0);
}
bool btf_type_is_i32(const struct btf_type *t)
{
return btf_type_is_int(t) && __btf_type_int_is_regular(t, 4);
}
bool btf_type_is_i64(const struct btf_type *t)
{
return btf_type_is_int(t) && __btf_type_int_is_regular(t, 8);
}
/*

9
kernel/bpf/local_storage.c
View File

@ -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;
}