bpf_endian.h

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// Copyright (c) Microsoft Corporation
// SPDX-License-Identifier: MIT
#pragma once
 
#include <stdint.h>
 
// copied from linux kernel v6.1 tools/lib/bpf/bpf_endian.h
// https://github.com/torvalds/linux/blob/v6.1/tools/lib/bpf/bpf_endian.h
// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
 
/*
 * Isolate byte #n and put it into byte #m, for __u##b type.
 * E.g., moving byte #6 (nnnnnnnn) into byte #1 (mmmmmmmm) for __u64:
 * 1) xxxxxxxx nnnnnnnn xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx mmmmmmmm xxxxxxxx
 * 2) nnnnnnnn xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx mmmmmmmm xxxxxxxx 00000000
 * 3) 00000000 00000000 00000000 00000000 00000000 00000000 00000000 nnnnnnnn
 * 4) 00000000 00000000 00000000 00000000 00000000 00000000 nnnnnnnn 00000000
 */
 
#define ___bpf_mvb(x, b, n, m) ((__u##b)(x) << (b - (n + 1) * 8) >> (b - 8) << (m * 8))
 
#define ___bpf_swab16(x) ((__u16)(___bpf_mvb(x, 16, 0, 1) | ___bpf_mvb(x, 16, 1, 0)))
 
#define ___bpf_swab32(x) \
    ((__u32)(___bpf_mvb(x, 32, 0, 3) | ___bpf_mvb(x, 32, 1, 2) | ___bpf_mvb(x, 32, 2, 1) | ___bpf_mvb(x, 32, 3, 0)))
 
#define ___bpf_swab64(x)                                                                                        \
    ((__u64)(                                                                                                   \
        ___bpf_mvb(x, 64, 0, 7) | ___bpf_mvb(x, 64, 1, 6) | ___bpf_mvb(x, 64, 2, 5) | ___bpf_mvb(x, 64, 3, 4) | \
        ___bpf_mvb(x, 64, 4, 3) | ___bpf_mvb(x, 64, 5, 2) | ___bpf_mvb(x, 64, 6, 1) | ___bpf_mvb(x, 64, 7, 0)))
 
/* LLVM's BPF target selects the endianness of the CPU
 * it compiles on, or the user specifies (bpfel/bpfeb),
 * respectively. The used __BYTE_ORDER__ is defined by
 * the compiler, we cannot rely on __BYTE_ORDER from
 * libc headers, since it doesn't reflect the actual
 * requested byte order.
 *
 * Note, LLVM's BPF target has different __builtin_bswapX()
 * semantics. It does map to BPF_ALU | BPF_END | BPF_TO_BE
 * in bpfel and bpfeb case, which means below, that we map
 * to cpu_to_be16(). We could use it unconditionally in BPF
 * case, but better not rely on it, so that this header here
 * can be used from application and BPF program side, which
 * use different targets.
 */
#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
#define __bpf_ntohs(x) __builtin_bswap16(x)
#define __bpf_htons(x) __builtin_bswap16(x)
#define __bpf_constant_ntohs(x) ___bpf_swab16(x)
#define __bpf_constant_htons(x) ___bpf_swab16(x)
#define __bpf_ntohl(x) __builtin_bswap32(x)
#define __bpf_htonl(x) __builtin_bswap32(x)
#define __bpf_constant_ntohl(x) ___bpf_swab32(x)
#define __bpf_constant_htonl(x) ___bpf_swab32(x)
#define __bpf_be64_to_cpu(x) __builtin_bswap64(x)
#define __bpf_cpu_to_be64(x) __builtin_bswap64(x)
#define __bpf_constant_be64_to_cpu(x) ___bpf_swab64(x)
#define __bpf_constant_cpu_to_be64(x) ___bpf_swab64(x)
#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
#define __bpf_ntohs(x) (x)
#define __bpf_htons(x) (x)
#define __bpf_constant_ntohs(x) (x)
#define __bpf_constant_htons(x) (x)
#define __bpf_ntohl(x) (x)
#define __bpf_htonl(x) (x)
#define __bpf_constant_ntohl(x) (x)
#define __bpf_constant_htonl(x) (x)
#define __bpf_be64_to_cpu(x) (x)
#define __bpf_cpu_to_be64(x) (x)
#define __bpf_constant_be64_to_cpu(x) (x)
#define __bpf_constant_cpu_to_be64(x) (x)
#else
#error "Fix your compiler's __BYTE_ORDER__?!"
#endif
 
#define bpf_htons(x) (__builtin_constant_p(x) ? __bpf_constant_htons(x) : __bpf_htons(x))
#define bpf_ntohs(x) (__builtin_constant_p(x) ? __bpf_constant_ntohs(x) : __bpf_ntohs(x))
#define bpf_htonl(x) (__builtin_constant_p(x) ? __bpf_constant_htonl(x) : __bpf_htonl(x))
#define bpf_ntohl(x) (__builtin_constant_p(x) ? __bpf_constant_ntohl(x) : __bpf_ntohl(x))
#define bpf_cpu_to_be64(x) (__builtin_constant_p(x) ? __bpf_constant_cpu_to_be64(x) : __bpf_cpu_to_be64(x))
#define bpf_be64_to_cpu(x) (__builtin_constant_p(x) ? __bpf_constant_be64_to_cpu(x) : __bpf_be64_to_cpu(x))
 
#ifndef ntohs
#define ntohs bpf_ntohs
#endif
#ifndef htons
#define htons bpf_htons
#endif
 
#ifndef ntohl
#define ntohl bpf_ntohl
#endif
#ifndef htonl
#define htonl bpf_htonl
#endif