arch/x86/um/checksum_32.S

   1 /*
   2  * INET         An implementation of the TCP/IP protocol suite for the LINUX
   3  *              operating system.  INET is implemented using the  BSD Socket
   4  *              interface as the means of communication with the user level.
   5  *
   6  *              IP/TCP/UDP checksumming routines
   7  *
   8  * Authors:     Jorge Cwik, <jorge@laser.satlink.net>
   9  *              Arnt Gulbrandsen, <agulbra@nvg.unit.no>
  10  *              Tom May, <ftom@netcom.com>
  11  *              Pentium Pro/II routines:
  12  *              Alexander Kjeldaas <astor@guardian.no>
  13  *              Finn Arne Gangstad <finnag@guardian.no>
  14  *              Lots of code moved from tcp.c and ip.c; see those files
  15  *              for more names.
  16  *
  17  * Changes:     Ingo Molnar, converted csum_partial_copy() to 2.1 exception
  18  *                           handling.
  19  *              Andi Kleen,  add zeroing on error
  20  *                   converted to pure assembler
  21  *
  22  *              This program is free software; you can redistribute it and/or
  23  *              modify it under the terms of the GNU General Public License
  24  *              as published by the Free Software Foundation; either version
  25  *              2 of the License, or (at your option) any later version.
  26  */
  27
  28 #include <asm/errno.h>
  29 #include <asm/asm.h>
  30
  31 /*
  32  * computes a partial checksum, e.g. for TCP/UDP fragments
  33  */
  34
  35 /*
  36 unsigned int csum_partial(const unsigned char * buff, int len, unsigned int sum)
  37  */
  38
  39 .text
  40 .align 4
  41 .globl csum_partial
  42
  43 #ifndef CONFIG_X86_USE_PPRO_CHECKSUM
  44
  45           /*
  46            * Experiments with Ethernet and SLIP connections show that buff
  47            * is aligned on either a 2-byte or 4-byte boundary.  We get at
  48            * least a twofold speedup on 486 and Pentium if it is 4-byte aligned.
  49            * Fortunately, it is easy to convert 2-byte alignment to 4-byte
  50            * alignment for the unrolled loop.
  51            */
  52 csum_partial:
  53         pushl %esi
  54         pushl %ebx
  55         movl 20(%esp),%eax      # Function arg: unsigned int sum
  56         movl 16(%esp),%ecx      # Function arg: int len
  57         movl 12(%esp),%esi      # Function arg: unsigned char *buff
  58         testl $2, %esi          # Check alignment.
  59         jz 2f                   # Jump if alignment is ok.
  60         subl $2, %ecx           # Alignment uses up two bytes.
  61         jae 1f                  # Jump if we had at least two bytes.
  62         addl $2, %ecx           # ecx was < 2.  Deal with it.
  63         jmp 4f
  64 1:      movw (%esi), %bx
  65         addl $2, %esi
  66         addw %bx, %ax
  67         adcl $0, %eax
  68 2:
  69         movl %ecx, %edx
  70         shrl $5, %ecx
  71         jz 2f
  72         testl %esi, %esi
  73 1:      movl (%esi), %ebx
  74         adcl %ebx, %eax
  75         movl 4(%esi), %ebx
  76         adcl %ebx, %eax
  77         movl 8(%esi), %ebx
  78         adcl %ebx, %eax
  79         movl 12(%esi), %ebx
  80         adcl %ebx, %eax
  81         movl 16(%esi), %ebx
  82         adcl %ebx, %eax
  83         movl 20(%esi), %ebx
  84         adcl %ebx, %eax
  85         movl 24(%esi), %ebx
  86         adcl %ebx, %eax
  87         movl 28(%esi), %ebx
  88         adcl %ebx, %eax
  89         lea 32(%esi), %esi
  90         dec %ecx
  91         jne 1b
  92         adcl $0, %eax
  93 2:      movl %edx, %ecx
  94         andl $0x1c, %edx
  95         je 4f
  96         shrl $2, %edx           # This clears CF
  97 3:      adcl (%esi), %eax
  98         lea 4(%esi), %esi
  99         dec %edx
 100         jne 3b
 101         adcl $0, %eax
 102 4:      andl $3, %ecx
 103         jz 7f
 104         cmpl $2, %ecx
 105         jb 5f
 106         movw (%esi),%cx
 107         leal 2(%esi),%esi
 108         je 6f
 109         shll $16,%ecx
 110 5:      movb (%esi),%cl
 111 6:      addl %ecx,%eax
 112         adcl $0, %eax
 113 7:
 114         popl %ebx
 115         popl %esi
 116         ret
 117
 118 #else
 119
 120 /* Version for PentiumII/PPro */
 121
 122 csum_partial:
 123         pushl %esi
 124         pushl %ebx
 125         movl 20(%esp),%eax      # Function arg: unsigned int sum
 126         movl 16(%esp),%ecx      # Function arg: int len
 127         movl 12(%esp),%esi      # Function arg: const unsigned char *buf
 128
 129         testl $2, %esi
 130         jnz 30f
 131 10:
 132         movl %ecx, %edx
 133         movl %ecx, %ebx
 134         andl $0x7c, %ebx
 135         shrl $7, %ecx
 136         addl %ebx,%esi
 137         shrl $2, %ebx
 138         negl %ebx
 139         lea 45f(%ebx,%ebx,2), %ebx
 140         testl %esi, %esi
 141         jmp *%ebx
 142
 143         # Handle 2-byte-aligned regions
 144 20:     addw (%esi), %ax
 145         lea 2(%esi), %esi
 146         adcl $0, %eax
 147         jmp 10b
 148
 149 30:     subl $2, %ecx
 150         ja 20b
 151         je 32f
 152         movzbl (%esi),%ebx      # csumming 1 byte, 2-aligned
 153         addl %ebx, %eax
 154         adcl $0, %eax
 155         jmp 80f
 156 32:
 157         addw (%esi), %ax        # csumming 2 bytes, 2-aligned
 158         adcl $0, %eax
 159         jmp 80f
 160
 161 40:
 162         addl -128(%esi), %eax
 163         adcl -124(%esi), %eax
 164         adcl -120(%esi), %eax
 165         adcl -116(%esi), %eax
 166         adcl -112(%esi), %eax
 167         adcl -108(%esi), %eax
 168         adcl -104(%esi), %eax
 169         adcl -100(%esi), %eax
 170         adcl -96(%esi), %eax
 171         adcl -92(%esi), %eax
 172         adcl -88(%esi), %eax
 173         adcl -84(%esi), %eax
 174         adcl -80(%esi), %eax
 175         adcl -76(%esi), %eax
 176         adcl -72(%esi), %eax
 177         adcl -68(%esi), %eax
 178         adcl -64(%esi), %eax
 179         adcl -60(%esi), %eax
 180         adcl -56(%esi), %eax
 181         adcl -52(%esi), %eax
 182         adcl -48(%esi), %eax
 183         adcl -44(%esi), %eax
 184         adcl -40(%esi), %eax
 185         adcl -36(%esi), %eax
 186         adcl -32(%esi), %eax
 187         adcl -28(%esi), %eax
 188         adcl -24(%esi), %eax
 189         adcl -20(%esi), %eax
 190         adcl -16(%esi), %eax
 191         adcl -12(%esi), %eax
 192         adcl -8(%esi), %eax
 193         adcl -4(%esi), %eax
 194 45:
 195         lea 128(%esi), %esi
 196         adcl $0, %eax
 197         dec %ecx
 198         jge 40b
 199         movl %edx, %ecx
 200 50:     andl $3, %ecx
 201         jz 80f
 202
 203         # Handle the last 1-3 bytes without jumping
 204         notl %ecx               # 1->2, 2->1, 3->0, higher bits are masked
 205         movl $0xffffff,%ebx     # by the shll and shrl instructions
 206         shll $3,%ecx
 207         shrl %cl,%ebx
 208         andl -128(%esi),%ebx    # esi is 4-aligned so should be ok
 209         addl %ebx,%eax
 210         adcl $0,%eax
 211 80:
 212         popl %ebx
 213         popl %esi
 214         ret
 215
 216 #endif