1/* 2 * A fast checksum+copy routine using movem 3 * Copyright (c) 1998-2007 Axis Communications AB 4 * 5 * Authors: Bjorn Wesen 6 * 7 * csum_partial_copy_nocheck(const char *src, char *dst, 8 * int len, unsigned int sum) 9 */ 10 11 .globl csum_partial_copy_nocheck 12 .type csum_partial_copy_nocheck,@function 13csum_partial_copy_nocheck: 14 15 ;; r10 - src 16 ;; r11 - dst 17 ;; r12 - length 18 ;; r13 - checksum 19 20 ;; Optimized for large packets 21 subq 10*4, $r12 22 blt _word_loop 23 move.d $r12, $acr 24 25 subq 9*4,$sp 26 clearf c 27 movem $r8,[$sp] 28 29 ;; do a movem copy and checksum 301: ;; A failing userspace access (the read) will have this as PC. 31_mloop: movem [$r10+],$r9 ; read 10 longwords 32 addoq -10*4, $acr, $acr ; loop counter in latency cycle 33 movem $r9,[$r11+] ; write 10 longwords 34 35 ;; perform dword checksumming on the 10 longwords 36 addc $r0,$r13 37 addc $r1,$r13 38 addc $r2,$r13 39 addc $r3,$r13 40 addc $r4,$r13 41 addc $r5,$r13 42 addc $r6,$r13 43 addc $r7,$r13 44 addc $r8,$r13 45 addc $r9,$r13 46 47 ;; test $acr, without trashing carry. 48 move.d $acr, $acr 49 bpl _mloop 50 ;; r12 <= acr is needed after mloop and in the exception handlers. 51 move.d $acr, $r12 52 53 ;; fold the last carry into r13 54 addc 0, $r13 55 movem [$sp+],$r8 ; restore regs 56 57_word_loop: 58 addq 10*4,$r12 ; compensate for last loop underflowing length 59 60 ;; fold 32-bit checksum into a 16-bit checksum, to avoid carries below 61 ;; r9 can be used as temporary. 62 move.d $r13,$r9 63 lsrq 16,$r9 ; r0 = checksum >> 16 64 and.d 0xffff,$r13 ; checksum = checksum & 0xffff 65 66 subq 2, $r12 67 blt _no_words 68 add.d $r9,$r13 ; checksum += r0 69 70 ;; copy and checksum the rest of the words 712: ;; A failing userspace access for the read below will have this as PC. 72_wloop: move.w [$r10+],$r9 73 addu.w $r9,$r13 74 subq 2,$r12 75 bge _wloop 76 move.w $r9,[$r11+] 77 78_no_words: 79 addq 2,$r12 80 bne _do_byte 81 nop 82 ret 83 move.d $r13,$r10 84 85_do_byte: 86 ;; copy and checksum the last byte 873: ;; A failing userspace access for the read below will have this as PC. 88 move.b [$r10],$r9 89 addu.b $r9,$r13 90 move.b $r9,[$r11] 91 ret 92 move.d $r13,$r10 93 94 .size csum_partial_copy_nocheck, . - csum_partial_copy_nocheck 95