projects / mirror_ubuntu-bionic-kernel.git / blame
| Commit | Line | Data |
|---|---|---|
| b2441318 | 1 | /* SPDX-License-Identifier: GPL-2.0 */ |
| ab59284e | 2 | /* |
| 1da177e4 LT |
3 | * A fast checksum+copy routine using movem |
| 4 | * Copyright (c) 1998, 2001 Axis Communications AB | |
| 5 | * | |
| 6 | * Authors: Bjorn Wesen | |
| 7 | * | |
| 8 | * csum_partial_copy_nocheck(const char *src, char *dst, | |
| 9 | * int len, unsigned int sum) | |
| 10 | */ | |
| 11 | ||
| 12 | .globl csum_partial_copy_nocheck | |
| 13 | csum_partial_copy_nocheck: | |
| 14 | ||
| 15 | ;; r10 - src | |
| 16 | ;; r11 - dst | |
| 17 | ;; r12 - length | |
| 18 | ;; r13 - checksum | |
| 19 | ||
| 20 | ;; check for breakeven length between movem and normal word looping versions | |
| 21 | ;; we also do _NOT_ want to compute a checksum over more than the | |
| 22 | ;; actual length when length < 40 | |
| 23 | ||
| 24 | cmpu.w 80, $r12 | |
| 25 | blo _word_loop | |
| 26 | nop | |
| 27 | ||
| 28 | ;; need to save the registers we use below in the movem loop | |
| 29 | ;; this overhead is why we have a check above for breakeven length | |
| 30 | ;; only r0 - r8 have to be saved, the other ones are clobber-able | |
| 31 | ;; according to the ABI | |
| 32 | ||
| 33 | subq 9*4, $sp | |
| 34 | movem $r8, [$sp] | |
| 35 | ||
| 36 | ;; do a movem copy and checksum | |
| 37 | ||
| 38 | subq 10*4, $r12 ; update length for the first loop | |
| 39 | ||
| 40 | _mloop: movem [$r10+],$r9 ; read 10 longwords | |
| 41 | 1: ;; A failing userspace access will have this as PC. | |
| 42 | movem $r9,[$r11+] ; write 10 longwords | |
| 43 | ||
| 44 | ;; perform dword checksumming on the 10 longwords | |
| 45 | ||
| 46 | add.d $r0,$r13 | |
| 47 | ax | |
| 48 | add.d $r1,$r13 | |
| 49 | ax | |
| 50 | add.d $r2,$r13 | |
| 51 | ax | |
| 52 | add.d $r3,$r13 | |
| 53 | ax | |
| 54 | add.d $r4,$r13 | |
| 55 | ax | |
| 56 | add.d $r5,$r13 | |
| 57 | ax | |
| 58 | add.d $r6,$r13 | |
| 59 | ax | |
| 60 | add.d $r7,$r13 | |
| 61 | ax | |
| 62 | add.d $r8,$r13 | |
| 63 | ax | |
| 64 | add.d $r9,$r13 | |
| 65 | ||
| 66 | ;; fold the carry into the checksum, to avoid having to loop the carry | |
| 67 | ;; back into the top | |
| 68 | ||
| 69 | ax | |
| 70 | addq 0,$r13 | |
| 1da177e4 LT |
71 | |
| 72 | subq 10*4,$r12 | |
| 73 | bge _mloop | |
| 74 | nop | |
| 75 | ||
| 76 | addq 10*4,$r12 ; compensate for last loop underflowing length | |
| 77 | ||
| 78 | movem [$sp+],$r8 ; restore regs | |
| 79 | ||
| 80 | _word_loop: | |
| 81 | ;; only fold if there is anything to fold. | |
| 82 | ||
| 83 | cmpq 0,$r13 | |
| 84 | beq _no_fold | |
| 85 | ||
| 86 | ;; fold 32-bit checksum into a 16-bit checksum, to avoid carries below | |
| 87 | ;; r9 can be used as temporary. | |
| 88 | ||
| 89 | move.d $r13,$r9 | |
| 90 | lsrq 16,$r9 ; r0 = checksum >> 16 | |
| 91 | and.d 0xffff,$r13 ; checksum = checksum & 0xffff | |
| 92 | add.d $r9,$r13 ; checksum += r0 | |
| 1da177e4 LT |
93 | |
| 94 | _no_fold: | |
| 95 | cmpq 2,$r12 | |
| 96 | blt _no_words | |
| 97 | nop | |
| 98 | ||
| 99 | ;; copy and checksum the rest of the words | |
| 100 | ||
| 101 | subq 2,$r12 | |
| 102 | ||
| 103 | _wloop: move.w [$r10+],$r9 | |
| 104 | 2: ;; A failing userspace access will have this as PC. | |
| 105 | addu.w $r9,$r13 | |
| 106 | subq 2,$r12 | |
| 107 | bge _wloop | |
| 108 | move.w $r9,[$r11+] | |
| 109 | ||
| 110 | addq 2,$r12 | |
| 111 | ||
| 112 | _no_words: | |
| 113 | ;; see if we have one odd byte more | |
| 114 | cmpq 1,$r12 | |
| 115 | beq _do_byte | |
| 116 | nop | |
| 117 | ret | |
| 118 | move.d $r13, $r10 | |
| 119 | ||
| 120 | _do_byte: | |
| 121 | ;; copy and checksum the last byte | |
| 122 | move.b [$r10],$r9 | |
| 123 | 3: ;; A failing userspace access will have this as PC. | |
| 124 | addu.b $r9,$r13 | |
| 125 | move.b $r9,[$r11] | |
| 126 | ret | |
| 127 | move.d $r13, $r10 |