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 #include <asm/export.h>
  31
  32 /*
  33  * computes a partial checksum, e.g. for TCP/UDP fragments
  34  */
  35
  36 /*
  37 unsigned int csum_partial(const unsigned char * buff, int len, unsigned int sum)
  38  */
  39
  40 .text
  41 .align 4
  42 .globl csum_partial
  43
  44 #ifndef CONFIG_X86_USE_PPRO_CHECKSUM
  45
  46           /*
  47            * Experiments with Ethernet and SLIP connections show that buff
  48            * is aligned on either a 2-byte or 4-byte boundary.  We get at
  49            * least a twofold speedup on 486 and Pentium if it is 4-byte aligned.
  50            * Fortunately, it is easy to convert 2-byte alignment to 4-byte
  51            * alignment for the unrolled loop.
  52            */
  53 csum_partial:
  54         pushl %esi
  55         pushl %ebx
  56         movl 20(%esp),%eax      # Function arg: unsigned int sum
  57         movl 16(%esp),%ecx      # Function arg: int len
  58         movl 12(%esp),%esi      # Function arg: unsigned char *buff
  59         testl $2, %esi          # Check alignment.
  60         jz 2f                   # Jump if alignment is ok.
  61         subl $2, %ecx           # Alignment uses up two bytes.
  62         jae 1f                  # Jump if we had at least two bytes.
  63         addl $2, %ecx           # ecx was < 2.  Deal with it.
  64         jmp 4f
  65 1:      movw (%esi), %bx
  66         addl $2, %esi
  67         addw %bx, %ax
  68         adcl $0, %eax
  69 2:
  70         movl %ecx, %edx
  71         shrl $5, %ecx
  72         jz 2f
  73         testl %esi, %esi
  74 1:      movl (%esi), %ebx
  75         adcl %ebx, %eax
  76         movl 4(%esi), %ebx
  77         adcl %ebx, %eax
  78         movl 8(%esi), %ebx
  79         adcl %ebx, %eax
  80         movl 12(%esi), %ebx
  81         adcl %ebx, %eax
  82         movl 16(%esi), %ebx
  83         adcl %ebx, %eax
  84         movl 20(%esi), %ebx
  85         adcl %ebx, %eax
  86         movl 24(%esi), %ebx
  87         adcl %ebx, %eax
  88         movl 28(%esi), %ebx
  89         adcl %ebx, %eax
  90         lea 32(%esi), %esi
  91         dec %ecx
  92         jne 1b
  93         adcl $0, %eax
  94 2:      movl %edx, %ecx
  95         andl $0x1c, %edx
  96         je 4f
  97         shrl $2, %edx           # This clears CF
  98 3:      adcl (%esi), %eax
  99         lea 4(%esi), %esi
 100         dec %edx
 101         jne 3b
 102         adcl $0, %eax
 103 4:      andl $3, %ecx
 104         jz 7f
 105         cmpl $2, %ecx
 106         jb 5f
 107         movw (%esi),%cx
 108         leal 2(%esi),%esi
 109         je 6f
 110         shll $16,%ecx
 111 5:      movb (%esi),%cl
 112 6:      addl %ecx,%eax
 113         adcl $0, %eax
 114 7:
 115         popl %ebx
 116         popl %esi
 117         ret
 118
 119 #else
 120
 121 /* Version for PentiumII/PPro */
 122
 123 csum_partial:
 124         pushl %esi
 125         pushl %ebx
 126         movl 20(%esp),%eax      # Function arg: unsigned int sum
 127         movl 16(%esp),%ecx      # Function arg: int len
 128         movl 12(%esp),%esi      # Function arg: const unsigned char *buf
 129
 130         testl $2, %esi
 131         jnz 30f
 132 10:
 133         movl %ecx, %edx
 134         movl %ecx, %ebx
 135         andl $0x7c, %ebx
 136         shrl $7, %ecx
 137         addl %ebx,%esi
 138         shrl $2, %ebx
 139         negl %ebx
 140         lea 45f(%ebx,%ebx,2), %ebx
 141         testl %esi, %esi
 142         jmp *%ebx
 143
 144         # Handle 2-byte-aligned regions
 145 20:     addw (%esi), %ax
 146         lea 2(%esi), %esi
 147         adcl $0, %eax
 148         jmp 10b
 149
 150 30:     subl $2, %ecx
 151         ja 20b
 152         je 32f
 153         movzbl (%esi),%ebx      # csumming 1 byte, 2-aligned
 154         addl %ebx, %eax
 155         adcl $0, %eax
 156         jmp 80f
 157 32:
 158         addw (%esi), %ax        # csumming 2 bytes, 2-aligned
 159         adcl $0, %eax
 160         jmp 80f
 161
 162 40:
 163         addl -128(%esi), %eax
 164         adcl -124(%esi), %eax
 165         adcl -120(%esi), %eax
 166         adcl -116(%esi), %eax
 167         adcl -112(%esi), %eax
 168         adcl -108(%esi), %eax
 169         adcl -104(%esi), %eax
 170         adcl -100(%esi), %eax
 171         adcl -96(%esi), %eax
 172         adcl -92(%esi), %eax
 173         adcl -88(%esi), %eax
 174         adcl -84(%esi), %eax
 175         adcl -80(%esi), %eax
 176         adcl -76(%esi), %eax
 177         adcl -72(%esi), %eax
 178         adcl -68(%esi), %eax
 179         adcl -64(%esi), %eax
 180         adcl -60(%esi), %eax
 181         adcl -56(%esi), %eax
 182         adcl -52(%esi), %eax
 183         adcl -48(%esi), %eax
 184         adcl -44(%esi), %eax
 185         adcl -40(%esi), %eax
 186         adcl -36(%esi), %eax
 187         adcl -32(%esi), %eax
 188         adcl -28(%esi), %eax
 189         adcl -24(%esi), %eax
 190         adcl -20(%esi), %eax
 191         adcl -16(%esi), %eax
 192         adcl -12(%esi), %eax
 193         adcl -8(%esi), %eax
 194         adcl -4(%esi), %eax
 195 45:
 196         lea 128(%esi), %esi
 197         adcl $0, %eax
 198         dec %ecx
 199         jge 40b
 200         movl %edx, %ecx
 201 50:     andl $3, %ecx
 202         jz 80f
 203
 204         # Handle the last 1-3 bytes without jumping
 205         notl %ecx               # 1->2, 2->1, 3->0, higher bits are masked
 206         movl $0xffffff,%ebx     # by the shll and shrl instructions
 207         shll $3,%ecx
 208         shrl %cl,%ebx
 209         andl -128(%esi),%ebx    # esi is 4-aligned so should be ok
 210         addl %ebx,%eax
 211         adcl $0,%eax
 212 80:
 213         popl %ebx
 214         popl %esi
 215         ret
 216
 217 #endif
 218         EXPORT_SYMBOL(csum_partial)