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bpf: btf: Clean up BTF_INT_BITS() in uapi btf.h

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This patch shrinks the BTF_INT_BITS() mask.  The current
btf_int_check_meta() ensures the nr_bits of an integer
cannot exceed 64.  Hence, it is mostly an uapi cleanup.

The actual btf usage (i.e. seq_show()) is also modified
to use u8 instead of u16.  The verification (e.g. btf_int_check_meta())
path stays as is to deal with invalid BTF situation.

Fixes: 69b693f0ae ("bpf: btf: Introduce BPF Type Format (BTF)")
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This commit is contained in:
Martin KaFai Lau 2018-07-19 22:14:31 -07:00 committed by Daniel Borkmann
parent 759b94a00a
commit 36fc3c8c28
2 changed files with 11 additions and 7 deletions
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2
include/uapi/linux/btf.h
View File

@ -76,7 +76,7 @@ struct btf_type {
*/
#define BTF_INT_ENCODING(VAL) (((VAL) & 0x0f000000) >> 24)
#define BTF_INT_OFFSET(VAL) (((VAL & 0x00ff0000)) >> 16)
#define BTF_INT_BITS(VAL) ((VAL) & 0x0000ffff)
#define BTF_INT_BITS(VAL) ((VAL) & 0x000000ff)
/* Attributes stored in the BTF_INT_ENCODING */
#define BTF_INT_SIGNED (1 << 0)

16
kernel/bpf/btf.c
View File

@ -450,7 +450,7 @@ static const struct btf_type *btf_type_by_id(const struct btf *btf, u32 type_id)
*/
static bool btf_type_int_is_regular(const struct btf_type *t)
{
u16 nr_bits, nr_bytes;
u8 nr_bits, nr_bytes;
u32 int_data;
int_data = btf_type_int(t);
@ -993,12 +993,16 @@ static void btf_int_bits_seq_show(const struct btf *btf,
{
u16 left_shift_bits, right_shift_bits;
u32 int_data = btf_type_int(t);
u16 nr_bits = BTF_INT_BITS(int_data);
u16 total_bits_offset;
u16 nr_copy_bytes;
u16 nr_copy_bits;
u8 nr_bits = BTF_INT_BITS(int_data);
u8 total_bits_offset;
u8 nr_copy_bytes;
u8 nr_copy_bits;
u64 print_num;
/*
* bits_offset is at most 7.
* BTF_INT_OFFSET() cannot exceed 64 bits.
*/
total_bits_offset = bits_offset + BTF_INT_OFFSET(int_data);
data += BITS_ROUNDDOWN_BYTES(total_bits_offset);
bits_offset = BITS_PER_BYTE_MASKED(total_bits_offset);
@ -1028,7 +1032,7 @@ static void btf_int_seq_show(const struct btf *btf, const struct btf_type *t,
u32 int_data = btf_type_int(t);
u8 encoding = BTF_INT_ENCODING(int_data);
bool sign = encoding & BTF_INT_SIGNED;
u32 nr_bits = BTF_INT_BITS(int_data);
u8 nr_bits = BTF_INT_BITS(int_data);
if (bits_offset || BTF_INT_OFFSET(int_data) ||
BITS_PER_BYTE_MASKED(nr_bits)) {