arch/loongarch/lib/csum.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 // Copyright (C) 2019-2020 Arm Ltd.
   3
   4 #include <linux/compiler.h>
   5 #include <linux/kasan-checks.h>
   6 #include <linux/kernel.h>
   7
   8 #include <net/checksum.h>
   9
  10 static u64 accumulate(u64 sum, u64 data)
  11 {
  12         sum += data;
  13         if (sum < data)
  14                 sum += 1;
  15         return sum;
  16 }
  17
  18 /*
  19  * We over-read the buffer and this makes KASAN unhappy. Instead, disable
  20  * instrumentation and call kasan explicitly.
  21  */
  22 unsigned int __no_sanitize_address do_csum(const unsigned char *buff, int len)
  23 {
  24         unsigned int offset, shift, sum;
  25         const u64 *ptr;
  26         u64 data, sum64 = 0;
  27
  28         if (unlikely(len == 0))
  29                 return 0;
  30
  31         offset = (unsigned long)buff & 7;
  32         /*
  33          * This is to all intents and purposes safe, since rounding down cannot
  34          * result in a different page or cache line being accessed, and @buff
  35          * should absolutely not be pointing to anything read-sensitive. We do,
  36          * however, have to be careful not to piss off KASAN, which means using
  37          * unchecked reads to accommodate the head and tail, for which we'll
  38          * compensate with an explicit check up-front.
  39          */
  40         kasan_check_read(buff, len);
  41         ptr = (u64 *)(buff - offset);
  42         len = len + offset - 8;
  43
  44         /*
  45          * Head: zero out any excess leading bytes. Shifting back by the same
  46          * amount should be at least as fast as any other way of handling the
  47          * odd/even alignment, and means we can ignore it until the very end.
  48          */
  49         shift = offset * 8;
  50         data = *ptr++;
  51         data = (data >> shift) << shift;
  52
  53         /*
  54          * Body: straightforward aligned loads from here on (the paired loads
  55          * underlying the quadword type still only need dword alignment). The
  56          * main loop strictly excludes the tail, so the second loop will always
  57          * run at least once.
  58          */
  59         while (unlikely(len > 64)) {
  60                 __uint128_t tmp1, tmp2, tmp3, tmp4;
  61
  62                 tmp1 = *(__uint128_t *)ptr;
  63                 tmp2 = *(__uint128_t *)(ptr + 2);
  64                 tmp3 = *(__uint128_t *)(ptr + 4);
  65                 tmp4 = *(__uint128_t *)(ptr + 6);
  66
  67                 len -= 64;
  68                 ptr += 8;
  69
  70                 /* This is the "don't dump the carry flag into a GPR" idiom */
  71                 tmp1 += (tmp1 >> 64) | (tmp1 << 64);
  72                 tmp2 += (tmp2 >> 64) | (tmp2 << 64);
  73                 tmp3 += (tmp3 >> 64) | (tmp3 << 64);
  74                 tmp4 += (tmp4 >> 64) | (tmp4 << 64);
  75                 tmp1 = ((tmp1 >> 64) << 64) | (tmp2 >> 64);
  76                 tmp1 += (tmp1 >> 64) | (tmp1 << 64);
  77                 tmp3 = ((tmp3 >> 64) << 64) | (tmp4 >> 64);
  78                 tmp3 += (tmp3 >> 64) | (tmp3 << 64);
  79                 tmp1 = ((tmp1 >> 64) << 64) | (tmp3 >> 64);
  80                 tmp1 += (tmp1 >> 64) | (tmp1 << 64);
  81                 tmp1 = ((tmp1 >> 64) << 64) | sum64;
  82                 tmp1 += (tmp1 >> 64) | (tmp1 << 64);
  83                 sum64 = tmp1 >> 64;
  84         }
  85         while (len > 8) {
  86                 __uint128_t tmp;
  87
  88                 sum64 = accumulate(sum64, data);
  89                 tmp = *(__uint128_t *)ptr;
  90
  91                 len -= 16;
  92                 ptr += 2;
  93
  94                 data = tmp >> 64;
  95                 sum64 = accumulate(sum64, tmp);
  96         }
  97         if (len > 0) {
  98                 sum64 = accumulate(sum64, data);
  99                 data = *ptr;
 100                 len -= 8;
 101         }
 102         /*
 103          * Tail: zero any over-read bytes similarly to the head, again
 104          * preserving odd/even alignment.
 105          */
 106         shift = len * -8;
 107         data = (data << shift) >> shift;
 108         sum64 = accumulate(sum64, data);
 109
 110         /* Finally, folding */
 111         sum64 += (sum64 >> 32) | (sum64 << 32);
 112         sum = sum64 >> 32;
 113         sum += (sum >> 16) | (sum << 16);
 114         if (offset & 1)
 115                 return (u16)swab32(sum);
 116
 117         return sum >> 16;
 118 }
 119
 120 __sum16 csum_ipv6_magic(const struct in6_addr *saddr,
 121                         const struct in6_addr *daddr,
 122                         __u32 len, __u8 proto, __wsum csum)
 123 {
 124         __uint128_t src, dst;
 125         u64 sum = (__force u64)csum;
 126
 127         src = *(const __uint128_t *)saddr->s6_addr;
 128         dst = *(const __uint128_t *)daddr->s6_addr;
 129
 130         sum += (__force u32)htonl(len);
 131         sum += (u32)proto << 24;
 132         src += (src >> 64) | (src << 64);
 133         dst += (dst >> 64) | (dst << 64);
 134
 135         sum = accumulate(sum, src >> 64);
 136         sum = accumulate(sum, dst >> 64);
 137
 138         sum += ((sum >> 32) | (sum << 32));
 139         return csum_fold((__force __wsum)(sum >> 32));
 140 }
 141 EXPORT_SYMBOL(csum_ipv6_magic);