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 to enabled for BPF 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 +- tools/bpf/bpftool/btf_dumper.c | 39 ++++++++++++++++++++++++++++++++++ tools/include/uapi/linux/btf.h | 2 +- 4 files changed, 43 insertions(+), 4 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/tools/bpf/bpftool/btf_dumper.c b/tools/bpf/bpftool/btf_dumper.c index 0e9310727281..45ed45ea9962 100644 --- a/tools/bpf/bpftool/btf_dumper.c +++ b/tools/bpf/bpftool/btf_dumper.c @@ -271,6 +271,40 @@ static void btf_int128_print(json_writer_t *jw, const void *data, } } +static void btf_bigint_print(json_writer_t *jw, const void *data, int nr_bits, + bool is_plain_text) +{ + char buf[nr_bits / 4 + 1]; + bool first = true; + int i; + +#ifdef __BIG_ENDIAN_BITFIELD + for (i = 0; i < nr_bits / 64; i++) { +#else + for (i = nr_bits / 64 - 1; i >= 0; i++) { +#endif + __u64 v = ((__u64 *)data)[i]; + + if (first) { + if (!v) + continue; + + snprintf(buf, sizeof(buf), "%llx", v); + + first = false; + } else { + size_t off = strlen(buf); + + snprintf(buf + off, sizeof(buf) - off, "%016llx", v); + } + } + + if (is_plain_text) + jsonw_printf(jw, "0x%s", buf); + else + jsonw_printf(jw, "\"0x%s\"", buf); +} + static void btf_int128_shift(__u64 *print_num, __u16 left_shift_bits, __u16 right_shift_bits) { @@ -373,6 +407,11 @@ static int btf_dumper_int(const struct btf_type *t, __u8 bit_offset, return 0; } + if (nr_bits > 128) { + btf_bigint_print(jw, data, nr_bits, is_plain_text); + return 0; + } + if (nr_bits == 128) { btf_int128_print(jw, data, is_plain_text); return 0; 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
