1 /* 2 * linux/arch/arm/lib/memset.S 3 * 4 * Copyright (C) 1995-2000 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 * ASM optimised string functions 11 */ 12 #include <linux/linkage.h> 13 #include <asm/assembler.h> 14 15 .text 16 .align 5 17 18 .syntax unified 19 #if CONFIG_IS_ENABLED(SYS_THUMB_BUILD) && !defined(MEMSET_NO_THUMB_BUILD) 20 .thumb 21 .thumb_func 22 #endif 23 ENTRY(memset) 24 ands r3, r0, #3 @ 1 unaligned? 25 mov ip, r0 @ preserve r0 as return value 26 bne 6f @ 1 27 /* 28 * we know that the pointer in ip is aligned to a word boundary. 29 */ 30 1: orr r1, r1, r1, lsl #8 31 orr r1, r1, r1, lsl #16 32 mov r3, r1 33 cmp r2, #16 34 blt 4f 35 36 #if ! CALGN(1)+0 37 38 /* 39 * We need 2 extra registers for this loop - use r8 and the LR 40 */ 41 stmfd sp!, {r8, lr} 42 mov r8, r1 43 mov lr, r1 44 45 2: subs r2, r2, #64 46 stmiage ip!, {r1, r3, r8, lr} @ 64 bytes at a time. 47 stmiage ip!, {r1, r3, r8, lr} 48 stmiage ip!, {r1, r3, r8, lr} 49 stmiage ip!, {r1, r3, r8, lr} 50 bgt 2b 51 ldmfdeq sp!, {r8, pc} @ Now <64 bytes to go. 52 /* 53 * No need to correct the count; we're only testing bits from now on 54 */ 55 tst r2, #32 56 stmiane ip!, {r1, r3, r8, lr} 57 stmiane ip!, {r1, r3, r8, lr} 58 tst r2, #16 59 stmiane ip!, {r1, r3, r8, lr} 60 ldmfd sp!, {r8, lr} 61 62 #else 63 64 /* 65 * This version aligns the destination pointer in order to write 66 * whole cache lines at once. 67 */ 68 69 stmfd sp!, {r4-r8, lr} 70 mov r4, r1 71 mov r5, r1 72 mov r6, r1 73 mov r7, r1 74 mov r8, r1 75 mov lr, r1 76 77 cmp r2, #96 78 tstgt ip, #31 79 ble 3f 80 81 and r8, ip, #31 82 rsb r8, r8, #32 83 sub r2, r2, r8 84 movs r8, r8, lsl #(32 - 4) 85 stmiacs ip!, {r4, r5, r6, r7} 86 stmiami ip!, {r4, r5} 87 tst r8, #(1 << 30) 88 mov r8, r1 89 strne r1, [ip], #4 90 91 3: subs r2, r2, #64 92 stmiage ip!, {r1, r3-r8, lr} 93 stmiage ip!, {r1, r3-r8, lr} 94 bgt 3b 95 ldmfdeq sp!, {r4-r8, pc} 96 97 tst r2, #32 98 stmiane ip!, {r1, r3-r8, lr} 99 tst r2, #16 100 stmiane ip!, {r4-r7} 101 ldmfd sp!, {r4-r8, lr} 102 103 #endif 104 105 4: tst r2, #8 106 stmiane ip!, {r1, r3} 107 tst r2, #4 108 strne r1, [ip], #4 109 /* 110 * When we get here, we've got less than 4 bytes to zero. We 111 * may have an unaligned pointer as well. 112 */ 113 5: tst r2, #2 114 strbne r1, [ip], #1 115 strbne r1, [ip], #1 116 tst r2, #1 117 strbne r1, [ip], #1 118 ret lr 119 120 6: subs r2, r2, #4 @ 1 do we have enough 121 blt 5b @ 1 bytes to align with? 122 cmp r3, #2 @ 1 123 strblt r1, [ip], #1 @ 1 124 strble r1, [ip], #1 @ 1 125 strb r1, [ip], #1 @ 1 126 add r2, r2, r3 @ 1 (r2 = r2 - (4 - r3)) 127 b 1b 128 ENDPROC(memset) 129