LXR linux/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
  21buf     .req    r0
  22len     .req    r1
  23sum     .req    r2
  24td0     .req    r3
  25td1     .req    r4      @ save before use
  26td2     .req    r5      @ save before use
  27td3     .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                mov     pc, lr
 101
 102ENTRY(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
 1141:              bics    ip, len, #31
 115                beq     3f
 116
 117                stmfd   sp!, {r4 - r5}
 1182:              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
 1333:              tst     len, #0x1c              @ should not change C
 134                beq     .Lless4
 135
 1364:              ldr     td0, [buf], #4
 137                sub     len, len, #4
 138                adcs    sum, sum, td0
 139                tst     len, #0x1c
 140                bne     4b
 141                b       .Lless4
 142ENDPROC(csum_partial)
 143