root/arch/x86/um/checksum_32.S

   1 /* SPDX-License-Identifier: GPL-2.0-or-later */
   2 /*
   3  * INET         An implementation of the TCP/IP protocol suite for the LINUX
   4  *              operating system.  INET is implemented using the  BSD Socket
   5  *              interface as the means of communication with the user level.
   6  *
   7  *              IP/TCP/UDP checksumming routines
   8  *
   9  * Authors:     Jorge Cwik, <jorge@laser.satlink.net>
  10  *              Arnt Gulbrandsen, <agulbra@nvg.unit.no>
  11  *              Tom May, <ftom@netcom.com>
  12  *              Pentium Pro/II routines:
  13  *              Alexander Kjeldaas <astor@guardian.no>
  14  *              Finn Arne Gangstad <finnag@guardian.no>
  15  *              Lots of code moved from tcp.c and ip.c; see those files
  16  *              for more names.
  17  *
  18  * Changes:     Ingo Molnar, converted csum_partial_copy() to 2.1 exception
  19  *                           handling.
  20  *              Andi Kleen,  add zeroing on error
  21  *                   converted to pure assembler
  22  */
  23 
  24 #include <asm/errno.h>
  25 #include <asm/asm.h>
  26 #include <asm/export.h>
  27                                 
  28 /*
  29  * computes a partial checksum, e.g. for TCP/UDP fragments
  30  */
  31 
  32 /*      
  33 unsigned int csum_partial(const unsigned char * buff, int len, unsigned int sum)
  34  */
  35                 
  36 .text
  37 .align 4
  38 .globl csum_partial
  39                 
  40 #ifndef CONFIG_X86_USE_PPRO_CHECKSUM
  41 
  42           /*            
  43            * Experiments with Ethernet and SLIP connections show that buff
  44            * is aligned on either a 2-byte or 4-byte boundary.  We get at
  45            * least a twofold speedup on 486 and Pentium if it is 4-byte aligned.
  46            * Fortunately, it is easy to convert 2-byte alignment to 4-byte
  47            * alignment for the unrolled loop.
  48            */           
  49 csum_partial:
  50         pushl %esi
  51         pushl %ebx
  52         movl 20(%esp),%eax      # Function arg: unsigned int sum
  53         movl 16(%esp),%ecx      # Function arg: int len
  54         movl 12(%esp),%esi      # Function arg: unsigned char *buff
  55         testl $2, %esi          # Check alignment.
  56         jz 2f                   # Jump if alignment is ok.
  57         subl $2, %ecx           # Alignment uses up two bytes.
  58         jae 1f                  # Jump if we had at least two bytes.
  59         addl $2, %ecx           # ecx was < 2.  Deal with it.
  60         jmp 4f
  61 1:      movw (%esi), %bx
  62         addl $2, %esi
  63         addw %bx, %ax
  64         adcl $0, %eax
  65 2:
  66         movl %ecx, %edx
  67         shrl $5, %ecx
  68         jz 2f
  69         testl %esi, %esi
  70 1:      movl (%esi), %ebx
  71         adcl %ebx, %eax
  72         movl 4(%esi), %ebx
  73         adcl %ebx, %eax
  74         movl 8(%esi), %ebx
  75         adcl %ebx, %eax
  76         movl 12(%esi), %ebx
  77         adcl %ebx, %eax
  78         movl 16(%esi), %ebx
  79         adcl %ebx, %eax
  80         movl 20(%esi), %ebx
  81         adcl %ebx, %eax
  82         movl 24(%esi), %ebx
  83         adcl %ebx, %eax
  84         movl 28(%esi), %ebx
  85         adcl %ebx, %eax
  86         lea 32(%esi), %esi
  87         dec %ecx
  88         jne 1b
  89         adcl $0, %eax
  90 2:      movl %edx, %ecx
  91         andl $0x1c, %edx
  92         je 4f
  93         shrl $2, %edx           # This clears CF
  94 3:      adcl (%esi), %eax
  95         lea 4(%esi), %esi
  96         dec %edx
  97         jne 3b
  98         adcl $0, %eax
  99 4:      andl $3, %ecx
 100         jz 7f
 101         cmpl $2, %ecx
 102         jb 5f
 103         movw (%esi),%cx
 104         leal 2(%esi),%esi
 105         je 6f
 106         shll $16,%ecx
 107 5:      movb (%esi),%cl
 108 6:      addl %ecx,%eax
 109         adcl $0, %eax 
 110 7:      
 111         popl %ebx
 112         popl %esi
 113         ret
 114 
 115 #else
 116 
 117 /* Version for PentiumII/PPro */
 118 
 119 csum_partial:
 120         pushl %esi
 121         pushl %ebx
 122         movl 20(%esp),%eax      # Function arg: unsigned int sum
 123         movl 16(%esp),%ecx      # Function arg: int len
 124         movl 12(%esp),%esi      # Function arg: const unsigned char *buf
 125 
 126         testl $2, %esi         
 127         jnz 30f                 
 128 10:
 129         movl %ecx, %edx
 130         movl %ecx, %ebx
 131         andl $0x7c, %ebx
 132         shrl $7, %ecx
 133         addl %ebx,%esi
 134         shrl $2, %ebx  
 135         negl %ebx
 136         lea 45f(%ebx,%ebx,2), %ebx
 137         testl %esi, %esi
 138         jmp *%ebx
 139 
 140         # Handle 2-byte-aligned regions
 141 20:     addw (%esi), %ax
 142         lea 2(%esi), %esi
 143         adcl $0, %eax
 144         jmp 10b
 145 
 146 30:     subl $2, %ecx          
 147         ja 20b                 
 148         je 32f
 149         movzbl (%esi),%ebx      # csumming 1 byte, 2-aligned
 150         addl %ebx, %eax
 151         adcl $0, %eax
 152         jmp 80f
 153 32:
 154         addw (%esi), %ax        # csumming 2 bytes, 2-aligned
 155         adcl $0, %eax
 156         jmp 80f
 157 
 158 40: 
 159         addl -128(%esi), %eax
 160         adcl -124(%esi), %eax
 161         adcl -120(%esi), %eax
 162         adcl -116(%esi), %eax   
 163         adcl -112(%esi), %eax   
 164         adcl -108(%esi), %eax
 165         adcl -104(%esi), %eax
 166         adcl -100(%esi), %eax
 167         adcl -96(%esi), %eax
 168         adcl -92(%esi), %eax
 169         adcl -88(%esi), %eax
 170         adcl -84(%esi), %eax
 171         adcl -80(%esi), %eax
 172         adcl -76(%esi), %eax
 173         adcl -72(%esi), %eax
 174         adcl -68(%esi), %eax
 175         adcl -64(%esi), %eax     
 176         adcl -60(%esi), %eax     
 177         adcl -56(%esi), %eax     
 178         adcl -52(%esi), %eax   
 179         adcl -48(%esi), %eax   
 180         adcl -44(%esi), %eax
 181         adcl -40(%esi), %eax
 182         adcl -36(%esi), %eax
 183         adcl -32(%esi), %eax
 184         adcl -28(%esi), %eax
 185         adcl -24(%esi), %eax
 186         adcl -20(%esi), %eax
 187         adcl -16(%esi), %eax
 188         adcl -12(%esi), %eax
 189         adcl -8(%esi), %eax
 190         adcl -4(%esi), %eax
 191 45:
 192         lea 128(%esi), %esi
 193         adcl $0, %eax
 194         dec %ecx
 195         jge 40b
 196         movl %edx, %ecx
 197 50:     andl $3, %ecx
 198         jz 80f
 199 
 200         # Handle the last 1-3 bytes without jumping
 201         notl %ecx               # 1->2, 2->1, 3->0, higher bits are masked
 202         movl $0xffffff,%ebx     # by the shll and shrl instructions
 203         shll $3,%ecx
 204         shrl %cl,%ebx
 205         andl -128(%esi),%ebx    # esi is 4-aligned so should be ok
 206         addl %ebx,%eax
 207         adcl $0,%eax
 208 80: 
 209         popl %ebx
 210         popl %esi
 211         ret
 212                                 
 213 #endif
 214         EXPORT_SYMBOL(csum_partial)