arch/arm/lib/csumpartial.S

   1 /*
   2  *  linux/arch/arm/lib/csumpartial.S
   3  *
   4  *  Copyright (C) 1995-1998 Russell King
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 as
   8  * published by the Free Software Foundation.
   9  */
  10 #include <linux/linkage.h>
  11 #include <asm/assembler.h>
  12
  13                 .text
  14
  15 /*
  16  * Function: __u32 csum_partial(const char *src, int len, __u32 sum)
  17  * Params  : r0 = buffer, r1 = len, r2 = checksum
  18  * Returns : r0 = new checksum
  19  */
  20
  21 buf     .req    r0
  22 len     .req    r1
  23 sum     .req    r2
  24 td0     .req    r3
  25 td1     .req    r4      @ save before use
  26 td2     .req    r5      @ save before use
  27 td3     .req    lr
  28
  29 .Lzero:         mov     r0, sum
  30                 add     sp, sp, #4
  31                 ldr     pc, [sp], #4
  32
  33                 /*
  34                  * Handle 0 to 7 bytes, with any alignment of source and
  35                  * destination pointers.  Note that when we get here, C = 0
  36                  */
  37 .Lless8:                teq     len, #0                 @ check for zero count
  38                 beq     .Lzero
  39
  40                 /* we must have at least one byte. */
  41                 tst     buf, #1                 @ odd address?
  42                 movne   sum, sum, ror #8
  43                 ldrneb  td0, [buf], #1
  44                 subne   len, len, #1
  45                 adcnes  sum, sum, td0, put_byte_1
  46
  47 .Lless4:                tst     len, #6
  48                 beq     .Lless8_byte
  49
  50                 /* we are now half-word aligned */
  51
  52 .Lless8_wordlp:
  53 #if __LINUX_ARM_ARCH__ >= 4
  54                 ldrh    td0, [buf], #2
  55                 sub     len, len, #2
  56 #else
  57                 ldrb    td0, [buf], #1
  58                 ldrb    td3, [buf], #1
  59                 sub     len, len, #2
  60 #ifndef __ARMEB__
  61                 orr     td0, td0, td3, lsl #8
  62 #else
  63                 orr     td0, td3, td0, lsl #8
  64 #endif
  65 #endif
  66                 adcs    sum, sum, td0
  67                 tst     len, #6
  68                 bne     .Lless8_wordlp
  69
  70 .Lless8_byte:   tst     len, #1                 @ odd number of bytes
  71                 ldrneb  td0, [buf], #1          @ include last byte
  72                 adcnes  sum, sum, td0, put_byte_0       @ update checksum
  73
  74 .Ldone:         adc     r0, sum, #0             @ collect up the last carry
  75                 ldr     td0, [sp], #4
  76                 tst     td0, #1                 @ check buffer alignment
  77                 movne   r0, r0, ror #8          @ rotate checksum by 8 bits
  78                 ldr     pc, [sp], #4            @ return
  79
  80 .Lnot_aligned:  tst     buf, #1                 @ odd address
  81                 ldrneb  td0, [buf], #1          @ make even
  82                 subne   len, len, #1
  83                 adcnes  sum, sum, td0, put_byte_1       @ update checksum
  84
  85                 tst     buf, #2                 @ 32-bit aligned?
  86 #if __LINUX_ARM_ARCH__ >= 4
  87                 ldrneh  td0, [buf], #2          @ make 32-bit aligned
  88                 subne   len, len, #2
  89 #else
  90                 ldrneb  td0, [buf], #1
  91                 ldrneb  ip, [buf], #1
  92                 subne   len, len, #2
  93 #ifndef __ARMEB__
  94                 orrne   td0, td0, ip, lsl #8
  95 #else
  96                 orrne   td0, ip, td0, lsl #8
  97 #endif
  98 #endif
  99                 adcnes  sum, sum, td0           @ update checksum
 100                 ret     lr
 101
 102 ENTRY(csum_partial)
 103                 stmfd   sp!, {buf, lr}
 104                 cmp     len, #8                 @ Ensure that we have at least
 105                 blo     .Lless8                 @ 8 bytes to copy.
 106
 107                 tst     buf, #1
 108                 movne   sum, sum, ror #8
 109
 110                 adds    sum, sum, #0            @ C = 0
 111                 tst     buf, #3                 @ Test destination alignment
 112                 blne    .Lnot_aligned           @ align destination, return here
 113
 114 1:              bics    ip, len, #31
 115                 beq     3f
 116
 117                 stmfd   sp!, {r4 - r5}
 118 2:              ldmia   buf!, {td0, td1, td2, td3}
 119                 adcs    sum, sum, td0
 120                 adcs    sum, sum, td1
 121                 adcs    sum, sum, td2
 122                 adcs    sum, sum, td3
 123                 ldmia   buf!, {td0, td1, td2, td3}
 124                 adcs    sum, sum, td0
 125                 adcs    sum, sum, td1
 126                 adcs    sum, sum, td2
 127                 adcs    sum, sum, td3
 128                 sub     ip, ip, #32
 129                 teq     ip, #0
 130                 bne     2b
 131                 ldmfd   sp!, {r4 - r5}
 132
 133 3:              tst     len, #0x1c              @ should not change C
 134                 beq     .Lless4
 135
 136 4:              ldr     td0, [buf], #4
 137                 sub     len, len, #4
 138                 adcs    sum, sum, td0
 139                 tst     len, #0x1c
 140                 bne     4b
 141                 b       .Lless4
 142 ENDPROC(csum_partial)