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| -rw-r--r-- | Documentation/bpf/standardization/instruction-set.rst | 82 |
1 files changed, 74 insertions, 8 deletions
diff --git a/Documentation/bpf/standardization/instruction-set.rst b/Documentation/bpf/standardization/instruction-set.rst index 655494ac7af6..25be958130dc 100644 --- a/Documentation/bpf/standardization/instruction-set.rst +++ b/Documentation/bpf/standardization/instruction-set.rst @@ -10,9 +10,71 @@ This document specifies version 1.0 of the eBPF instruction set. Documentation conventions ========================= -For brevity, this document uses the type notion "u64", "u32", etc. -to mean an unsigned integer whose width is the specified number of bits, -and "s32", etc. to mean a signed integer of the specified number of bits. +For brevity and consistency, this document refers to families +of types using a shorthand syntax and refers to several expository, +mnemonic functions when describing the semantics of instructions. +The range of valid values for those types and the semantics of those +functions are defined in the following subsections. + +Types +----- +This document refers to integer types with the notation `SN` to specify +a type's signedness (`S`) and bit width (`N`), respectively. + +.. table:: Meaning of signedness notation. + + ==== ========= + `S` Meaning + ==== ========= + `u` unsigned + `s` signed + ==== ========= + +.. table:: Meaning of bit-width notation. + + ===== ========= + `N` Bit width + ===== ========= + `8` 8 bits + `16` 16 bits + `32` 32 bits + `64` 64 bits + `128` 128 bits + ===== ========= + +For example, `u32` is a type whose valid values are all the 32-bit unsigned +numbers and `s16` is a types whose valid values are all the 16-bit signed +numbers. + +Functions +--------- +* `htobe16`: Takes an unsigned 16-bit number in host-endian format and + returns the equivalent number as an unsigned 16-bit number in big-endian + format. +* `htobe32`: Takes an unsigned 32-bit number in host-endian format and + returns the equivalent number as an unsigned 32-bit number in big-endian + format. +* `htobe64`: Takes an unsigned 64-bit number in host-endian format and + returns the equivalent number as an unsigned 64-bit number in big-endian + format. +* `htole16`: Takes an unsigned 16-bit number in host-endian format and + returns the equivalent number as an unsigned 16-bit number in little-endian + format. +* `htole32`: Takes an unsigned 32-bit number in host-endian format and + returns the equivalent number as an unsigned 32-bit number in little-endian + format. +* `htole64`: Takes an unsigned 64-bit number in host-endian format and + returns the equivalent number as an unsigned 64-bit number in little-endian + format. +* `bswap16`: Takes an unsigned 16-bit number in either big- or little-endian + format and returns the equivalent number with the same bit width but + opposite endianness. +* `bswap32`: Takes an unsigned 32-bit number in either big- or little-endian + format and returns the equivalent number with the same bit width but + opposite endianness. +* `bswap64`: Takes an unsigned 64-bit number in either big- or little-endian + format and returns the equivalent number with the same bit width but + opposite endianness. Registers and calling convention ================================ @@ -252,19 +314,23 @@ are supported: 16, 32 and 64. Examples: -``BPF_ALU | BPF_TO_LE | BPF_END`` with imm = 16 means:: +``BPF_ALU | BPF_TO_LE | BPF_END`` with imm = 16/32/64 means:: dst = htole16(dst) + dst = htole32(dst) + dst = htole64(dst) -``BPF_ALU | BPF_TO_BE | BPF_END`` with imm = 64 means:: +``BPF_ALU | BPF_TO_BE | BPF_END`` with imm = 16/32/64 means:: + dst = htobe16(dst) + dst = htobe32(dst) dst = htobe64(dst) ``BPF_ALU64 | BPF_TO_LE | BPF_END`` with imm = 16/32/64 means:: - dst = bswap16 dst - dst = bswap32 dst - dst = bswap64 dst + dst = bswap16(dst) + dst = bswap32(dst) + dst = bswap64(dst) Jump instructions ----------------- |