Commit 36fc3c8c authored by Martin KaFai Lau's avatar Martin KaFai Lau Committed by Daniel Borkmann
Browse files

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



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: 69b693f0 ("bpf: btf: Introduce BPF Type Format (BTF)")
Signed-off-by: default avatarMartin KaFai Lau <kafai@fb.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
parent 759b94a0

include/uapi/linux/btf.h

+1 −1
Original line number Diff line number Diff line
@@ -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)

kernel/bpf/btf.c

+10 −6
Original line number Diff line number Diff line
@@ -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)) {

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