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bpf: btf: support 128 bit integer type

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Currently, btf only supports up to 64-bit integer.
On the other hand, 128bit support for gcc and clang
has existed for a long time. For example, both gcc 4.8
and llvm 3.7 supports types "__int128" and
"unsigned __int128" for virtually all 64bit architectures
including bpf.

The requirement for __int128 support comes from two areas:
  . bpf program may use __int128. For example, some bcc tools
    (https://github.com/iovisor/bcc/tree/master/tools),
    mostly tcp v6 related, tcpstates.py, tcpaccept.py, etc.,
    are using __int128 to represent the ipv6 addresses.
  . linux itself is using __int128 types. Hence supporting
    __int128 type in BTF is required for vmlinux BTF,
    which will be used by "compile once and run everywhere"
    and other projects.

For 128bit integer, instead of base-10, hex numbers are pretty
printed out as large decimal number is hard to decipher, e.g.,
for ipv6 addresses.

Acked-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This commit is contained in:
Yonghong Song 2019-01-15 17:07:47 -08:00 committed by Daniel Borkmann
parent eeedd3527d
commit b1e8818cab
1 changed files with 85 additions and 19 deletions
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104
kernel/bpf/btf.c
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@ -157,7 +157,7 @@
*
*/
#define BITS_PER_U64 (sizeof(u64) * BITS_PER_BYTE)
#define BITS_PER_U128 (sizeof(u64) * BITS_PER_BYTE * 2)
#define BITS_PER_BYTE_MASK (BITS_PER_BYTE - 1)
#define BITS_PER_BYTE_MASKED(bits) ((bits) & BITS_PER_BYTE_MASK)
#define BITS_ROUNDDOWN_BYTES(bits) ((bits) >> 3)
@ -525,7 +525,7 @@ const struct btf_type *btf_type_by_id(const struct btf *btf, u32 type_id)
/*
* Regular int is not a bit field and it must be either
* u8/u16/u32/u64.
* u8/u16/u32/u64 or __int128.
*/
static bool btf_type_int_is_regular(const struct btf_type *t)
{
@ -538,7 +538,8 @@ static bool btf_type_int_is_regular(const struct btf_type *t)
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 != sizeof(u32) && nr_bytes != sizeof(u64) &&
nr_bytes != (2 * sizeof(u64)))) {
return false;
}
@ -1063,9 +1064,9 @@ static int btf_int_check_member(struct btf_verifier_env *env,
nr_copy_bits = BTF_INT_BITS(int_data) +
BITS_PER_BYTE_MASKED(struct_bits_off);
if (nr_copy_bits > BITS_PER_U64) {
if (nr_copy_bits > BITS_PER_U128) {
btf_verifier_log_member(env, struct_type, member,
"nr_copy_bits exceeds 64");
"nr_copy_bits exceeds 128");
return -EINVAL;
}
@ -1119,9 +1120,9 @@ static int btf_int_check_kflag_member(struct btf_verifier_env *env,
bytes_offset = BITS_ROUNDDOWN_BYTES(struct_bits_off);
nr_copy_bits = nr_bits + BITS_PER_BYTE_MASKED(struct_bits_off);
if (nr_copy_bits > BITS_PER_U64) {
if (nr_copy_bits > BITS_PER_U128) {
btf_verifier_log_member(env, struct_type, member,
"nr_copy_bits exceeds 64");
"nr_copy_bits exceeds 128");
return -EINVAL;
}
@ -1168,9 +1169,9 @@ static s32 btf_int_check_meta(struct btf_verifier_env *env,
nr_bits = BTF_INT_BITS(int_data) + BTF_INT_OFFSET(int_data);
if (nr_bits > BITS_PER_U64) {
if (nr_bits > BITS_PER_U128) {
btf_verifier_log_type(env, t, "nr_bits exceeds %zu",
BITS_PER_U64);
BITS_PER_U128);
return -EINVAL;
}
@ -1211,31 +1212,93 @@ static void btf_int_log(struct btf_verifier_env *env,
btf_int_encoding_str(BTF_INT_ENCODING(int_data)));
}
static void btf_int128_print(struct seq_file *m, void *data)
{
/* data points to a __int128 number.
* Suppose
* int128_num = *(__int128 *)data;
* The below formulas shows what upper_num and lower_num represents:
* upper_num = int128_num >> 64;
* lower_num = int128_num & 0xffffffffFFFFFFFFULL;
*/
u64 upper_num, lower_num;
#ifdef __BIG_ENDIAN_BITFIELD
upper_num = *(u64 *)data;
lower_num = *(u64 *)(data + 8);
#else
upper_num = *(u64 *)(data + 8);
lower_num = *(u64 *)data;
#endif
if (upper_num == 0)
seq_printf(m, "0x%llx", lower_num);
else
seq_printf(m, "0x%llx%016llx", upper_num, lower_num);
}
static void btf_int128_shift(u64 *print_num, u16 left_shift_bits,
u16 right_shift_bits)
{
u64 upper_num, lower_num;
#ifdef __BIG_ENDIAN_BITFIELD
upper_num = print_num[0];
lower_num = print_num[1];
#else
upper_num = print_num[1];
lower_num = print_num[0];
#endif
/* shake out un-needed bits by shift/or operations */
if (left_shift_bits >= 64) {
upper_num = lower_num << (left_shift_bits - 64);
lower_num = 0;
} else {
upper_num = (upper_num << left_shift_bits) |
(lower_num >> (64 - left_shift_bits));
lower_num = lower_num << left_shift_bits;
}
if (right_shift_bits >= 64) {
lower_num = upper_num >> (right_shift_bits - 64);
upper_num = 0;
} else {
lower_num = (lower_num >> right_shift_bits) |
(upper_num << (64 - right_shift_bits));
upper_num = upper_num >> right_shift_bits;
}
#ifdef __BIG_ENDIAN_BITFIELD
print_num[0] = upper_num;
print_num[1] = lower_num;
#else
print_num[0] = lower_num;
print_num[1] = upper_num;
#endif
}
static void btf_bitfield_seq_show(void *data, u8 bits_offset,
u8 nr_bits, struct seq_file *m)
{
u16 left_shift_bits, right_shift_bits;
u8 nr_copy_bytes;
u8 nr_copy_bits;
u64 print_num;
u64 print_num[2] = {};
nr_copy_bits = nr_bits + bits_offset;
nr_copy_bytes = BITS_ROUNDUP_BYTES(nr_copy_bits);
print_num = 0;
memcpy(&print_num, data, nr_copy_bytes);
memcpy(print_num, data, nr_copy_bytes);
#ifdef __BIG_ENDIAN_BITFIELD
left_shift_bits = bits_offset;
#else
left_shift_bits = BITS_PER_U64 - nr_copy_bits;
left_shift_bits = BITS_PER_U128 - nr_copy_bits;
#endif
right_shift_bits = BITS_PER_U64 - nr_bits;
right_shift_bits = BITS_PER_U128 - nr_bits;
print_num <<= left_shift_bits;
print_num >>= right_shift_bits;
seq_printf(m, "0x%llx", print_num);
btf_int128_shift(print_num, left_shift_bits, right_shift_bits);
btf_int128_print(m, print_num);
}
@ -1250,7 +1313,7 @@ static void btf_int_bits_seq_show(const struct btf *btf,
/*
* bits_offset is at most 7.
* BTF_INT_OFFSET() cannot exceed 64 bits.
* BTF_INT_OFFSET() cannot exceed 128 bits.
*/
total_bits_offset = bits_offset + BTF_INT_OFFSET(int_data);
data += BITS_ROUNDDOWN_BYTES(total_bits_offset);
@ -1274,6 +1337,9 @@ static void btf_int_seq_show(const struct btf *btf, const struct btf_type *t,
}
switch (nr_bits) {
case 128:
btf_int128_print(m, data);
break;
case 64:
if (sign)
seq_printf(m, "%lld", *(s64 *)data);