clang supports arbitrary length ints using the _ExtInt extension. This can be useful to hold very large values, e.g. 256 bit or 512 bit types.
Larger types (e.g. 1024 bits) are possible but I am unaware of a use case for these. This requires the _ExtInt extension enabled in clang, which is under review. Link: https://clang.llvm.org/docs/LanguageExtensions.html#extended-integer-types Link: https://reviews.llvm.org/D93103 Signed-off-by: Sean Young <s...@mess.org> --- Documentation/bpf/btf.rst | 4 +-- include/uapi/linux/btf.h | 2 +- kernel/bpf/btf.c | 54 ++++++++++++++++++++++++++++------ tools/include/uapi/linux/btf.h | 2 +- 4 files changed, 49 insertions(+), 13 deletions(-) diff --git a/Documentation/bpf/btf.rst b/Documentation/bpf/btf.rst index 44dc789de2b4..784f1743dbc7 100644 --- a/Documentation/bpf/btf.rst +++ b/Documentation/bpf/btf.rst @@ -132,7 +132,7 @@ The following sections detail encoding of each kind. #define BTF_INT_ENCODING(VAL) (((VAL) & 0x0f000000) >> 24) #define BTF_INT_OFFSET(VAL) (((VAL) & 0x00ff0000) >> 16) - #define BTF_INT_BITS(VAL) ((VAL) & 0x000000ff) + #define BTF_INT_BITS(VAL) ((VAL) & 0x000003ff) The ``BTF_INT_ENCODING`` has the following attributes:: @@ -147,7 +147,7 @@ pretty print. At most one encoding can be specified for the int type. The ``BTF_INT_BITS()`` specifies the number of actual bits held by this int type. For example, a 4-bit bitfield encodes ``BTF_INT_BITS()`` equals to 4. The ``btf_type.size * 8`` must be equal to or greater than ``BTF_INT_BITS()`` -for the type. The maximum value of ``BTF_INT_BITS()`` is 128. +for the type. The maximum value of ``BTF_INT_BITS()`` is 512. The ``BTF_INT_OFFSET()`` specifies the starting bit offset to calculate values for this int. For example, a bitfield struct member has: diff --git a/include/uapi/linux/btf.h b/include/uapi/linux/btf.h index 5a667107ad2c..1696fd02b302 100644 --- a/include/uapi/linux/btf.h +++ b/include/uapi/linux/btf.h @@ -84,7 +84,7 @@ 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) & 0x000000ff) +#define BTF_INT_BITS(VAL) ((VAL) & 0x000003ff) /* Attributes stored in the BTF_INT_ENCODING */ #define BTF_INT_SIGNED (1 << 0) diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index 8d6bdb4f4d61..44bc17207e9b 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -166,7 +166,8 @@ * */ -#define BITS_PER_U128 (sizeof(u64) * BITS_PER_BYTE * 2) +#define BITS_PER_U128 128 +#define BITS_PER_U512 512 #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) @@ -1907,9 +1908,9 @@ 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_U128) { + if (nr_copy_bits > BITS_PER_U512) { btf_verifier_log_member(env, struct_type, member, - "nr_copy_bits exceeds 128"); + "nr_copy_bits exceeds 512"); return -EINVAL; } @@ -1963,9 +1964,9 @@ 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_U128) { + if (nr_copy_bits > BITS_PER_U512) { btf_verifier_log_member(env, struct_type, member, - "nr_copy_bits exceeds 128"); + "nr_copy_bits exceeds 512"); return -EINVAL; } @@ -2012,9 +2013,9 @@ 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_U128) { - btf_verifier_log_type(env, t, "nr_bits exceeds %zu", - BITS_PER_U128); + if (nr_bits > BITS_PER_U512) { + btf_verifier_log_type(env, t, "nr_bits exceeds %u", + BITS_PER_U512); return -EINVAL; } @@ -2080,6 +2081,37 @@ static void btf_int128_print(struct btf_show *show, void *data) lower_num); } +static void btf_bigint_print(struct btf_show *show, void *data, u16 nr_bits) +{ + /* data points to 256 or 512 bit int type */ + char buf[129]; + int last_u64 = nr_bits / 64 - 1; + bool seen_nonzero = false; + int i; + + for (i = 0; i <= last_u64; i++) { +#ifdef __BIG_ENDIAN_BITFIELD + u64 v = ((u64 *)data)[i]; +#else + u64 v = ((u64 *)data)[last_u64 - i]; +#endif + if (!seen_nonzero) { + if (!v && i != last_u64) + continue; + + snprintf(buf, sizeof(buf), "%llx", v); + + seen_nonzero = true; + } else { + size_t off = strlen(buf); + + snprintf(buf + off, sizeof(buf) - off, "%016llx", v); + } + } + + btf_show_type_value(show, "0x%s", buf); +} + static void btf_int128_shift(u64 *print_num, u16 left_shift_bits, u16 right_shift_bits) { @@ -2172,7 +2204,7 @@ static void btf_int_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; - u8 nr_bits = BTF_INT_BITS(int_data); + u16 nr_bits = BTF_INT_BITS(int_data); void *safe_data; safe_data = btf_show_start_type(show, t, type_id, data); @@ -2186,6 +2218,10 @@ static void btf_int_show(const struct btf *btf, const struct btf_type *t, } switch (nr_bits) { + case 512: + case 256: + btf_bigint_print(show, safe_data, nr_bits); + break; case 128: btf_int128_print(show, safe_data); break; diff --git a/tools/include/uapi/linux/btf.h b/tools/include/uapi/linux/btf.h index 5a667107ad2c..1696fd02b302 100644 --- a/tools/include/uapi/linux/btf.h +++ b/tools/include/uapi/linux/btf.h @@ -84,7 +84,7 @@ 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) & 0x000000ff) +#define BTF_INT_BITS(VAL) ((VAL) & 0x000003ff) /* Attributes stored in the BTF_INT_ENCODING */ #define BTF_INT_SIGNED (1 << 0) -- 2.29.2
