root/arch/arm/lib/csumpartial.S

   1 /* SPDX-License-Identifier: GPL-2.0-only */
   2 /*
   3  *  linux/arch/arm/lib/csumpartial.S
   4  *
   5  *  Copyright (C) 1995-1998 Russell King
   6  */
   7 #include <linux/linkage.h>
   8 #include <asm/assembler.h>
   9 
  10                 .text
  11 
  12 /*
  13  * Function: __u32 csum_partial(const char *src, int len, __u32 sum)
  14  * Params  : r0 = buffer, r1 = len, r2 = checksum
  15  * Returns : r0 = new checksum
  16  */
  17 
  18 buf     .req    r0
  19 len     .req    r1
  20 sum     .req    r2
  21 td0     .req    r3
  22 td1     .req    r4      @ save before use
  23 td2     .req    r5      @ save before use
  24 td3     .req    lr
  25 
  26 .Lzero:         mov     r0, sum
  27                 add     sp, sp, #4
  28                 ldr     pc, [sp], #4
  29 
  30                 /*
  31                  * Handle 0 to 7 bytes, with any alignment of source and
  32                  * destination pointers.  Note that when we get here, C = 0
  33                  */
  34 .Lless8:                teq     len, #0                 @ check for zero count
  35                 beq     .Lzero
  36 
  37                 /* we must have at least one byte. */
  38                 tst     buf, #1                 @ odd address?
  39                 movne   sum, sum, ror #8
  40                 ldrbne  td0, [buf], #1
  41                 subne   len, len, #1
  42                 adcsne  sum, sum, td0, put_byte_1
  43 
  44 .Lless4:                tst     len, #6
  45                 beq     .Lless8_byte
  46 
  47                 /* we are now half-word aligned */
  48 
  49 .Lless8_wordlp:
  50 #if __LINUX_ARM_ARCH__ >= 4
  51                 ldrh    td0, [buf], #2
  52                 sub     len, len, #2
  53 #else
  54                 ldrb    td0, [buf], #1
  55                 ldrb    td3, [buf], #1
  56                 sub     len, len, #2
  57 #ifndef __ARMEB__
  58                 orr     td0, td0, td3, lsl #8
  59 #else
  60                 orr     td0, td3, td0, lsl #8
  61 #endif
  62 #endif
  63                 adcs    sum, sum, td0
  64                 tst     len, #6
  65                 bne     .Lless8_wordlp
  66 
  67 .Lless8_byte:   tst     len, #1                 @ odd number of bytes
  68                 ldrbne  td0, [buf], #1          @ include last byte
  69                 adcsne  sum, sum, td0, put_byte_0       @ update checksum
  70 
  71 .Ldone:         adc     r0, sum, #0             @ collect up the last carry
  72                 ldr     td0, [sp], #4
  73                 tst     td0, #1                 @ check buffer alignment
  74                 movne   r0, r0, ror #8          @ rotate checksum by 8 bits
  75                 ldr     pc, [sp], #4            @ return
  76 
  77 .Lnot_aligned:  tst     buf, #1                 @ odd address
  78                 ldrbne  td0, [buf], #1          @ make even
  79                 subne   len, len, #1
  80                 adcsne  sum, sum, td0, put_byte_1       @ update checksum
  81 
  82                 tst     buf, #2                 @ 32-bit aligned?
  83 #if __LINUX_ARM_ARCH__ >= 4
  84                 ldrhne  td0, [buf], #2          @ make 32-bit aligned
  85                 subne   len, len, #2
  86 #else
  87                 ldrbne  td0, [buf], #1
  88                 ldrbne  ip, [buf], #1
  89                 subne   len, len, #2
  90 #ifndef __ARMEB__
  91                 orrne   td0, td0, ip, lsl #8
  92 #else
  93                 orrne   td0, ip, td0, lsl #8
  94 #endif
  95 #endif
  96                 adcsne  sum, sum, td0           @ update checksum
  97                 ret     lr
  98 
  99 ENTRY(csum_partial)
 100                 stmfd   sp!, {buf, lr}
 101                 cmp     len, #8                 @ Ensure that we have at least
 102                 blo     .Lless8                 @ 8 bytes to copy.
 103 
 104                 tst     buf, #1
 105                 movne   sum, sum, ror #8
 106 
 107                 adds    sum, sum, #0            @ C = 0
 108                 tst     buf, #3                 @ Test destination alignment
 109                 blne    .Lnot_aligned           @ align destination, return here
 110 
 111 1:              bics    ip, len, #31
 112                 beq     3f
 113 
 114                 stmfd   sp!, {r4 - r5}
 115 2:              ldmia   buf!, {td0, td1, td2, td3}
 116                 adcs    sum, sum, td0
 117                 adcs    sum, sum, td1
 118                 adcs    sum, sum, td2
 119                 adcs    sum, sum, td3
 120                 ldmia   buf!, {td0, td1, td2, td3}
 121                 adcs    sum, sum, td0
 122                 adcs    sum, sum, td1
 123                 adcs    sum, sum, td2
 124                 adcs    sum, sum, td3
 125                 sub     ip, ip, #32
 126                 teq     ip, #0
 127                 bne     2b
 128                 ldmfd   sp!, {r4 - r5}
 129 
 130 3:              tst     len, #0x1c              @ should not change C
 131                 beq     .Lless4
 132 
 133 4:              ldr     td0, [buf], #4
 134                 sub     len, len, #4
 135                 adcs    sum, sum, td0
 136                 tst     len, #0x1c
 137                 bne     4b
 138                 b       .Lless4
 139 ENDPROC(csum_partial)