| Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1 | /* |
| 2 | * linux/arch/arm/lib/memzero.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 | #include <linux/linkage.h> |
| 11 | #include <asm/assembler.h> |
| 12 | |
| 13 | .text |
| 14 | .align 5 |
| 15 | .word 0 |
| 16 | /* |
| 17 | * Align the pointer in r0. r3 contains the number of bytes that we are |
| 18 | * mis-aligned by, and r1 is the number of bytes. If r1 < 4, then we |
| 19 | * don't bother; we use byte stores instead. |
| 20 | */ |
| 21 | 1: subs r1, r1, #4 @ 1 do we have enough |
| 22 | blt 5f @ 1 bytes to align with? |
| 23 | cmp r3, #2 @ 1 |
| 24 | strltb r2, [r0], #1 @ 1 |
| 25 | strleb r2, [r0], #1 @ 1 |
| 26 | strb r2, [r0], #1 @ 1 |
| 27 | add r1, r1, r3 @ 1 (r1 = r1 - (4 - r3)) |
| 28 | /* |
| 29 | * The pointer is now aligned and the length is adjusted. Try doing the |
| 30 | * memzero again. |
| 31 | */ |
| 32 | |
| 33 | ENTRY(__memzero) |
| 34 | mov r2, #0 @ 1 |
| 35 | ands r3, r0, #3 @ 1 unaligned? |
| 36 | bne 1b @ 1 |
| 37 | /* |
| 38 | * r3 = 0, and we know that the pointer in r0 is aligned to a word boundary. |
| 39 | */ |
| 40 | cmp r1, #16 @ 1 we can skip this chunk if we |
| 41 | blt 4f @ 1 have < 16 bytes |
| 42 | /* |
| 43 | * We need an extra register for this loop - save the return address and |
| 44 | * use the LR |
| 45 | */ |
| 46 | str lr, [sp, #-4]! @ 1 |
| 47 | mov ip, r2 @ 1 |
| 48 | mov lr, r2 @ 1 |
| 49 | |
| 50 | 3: subs r1, r1, #64 @ 1 write 32 bytes out per loop |
| 51 | stmgeia r0!, {r2, r3, ip, lr} @ 4 |
| 52 | stmgeia r0!, {r2, r3, ip, lr} @ 4 |
| 53 | stmgeia r0!, {r2, r3, ip, lr} @ 4 |
| 54 | stmgeia r0!, {r2, r3, ip, lr} @ 4 |
| 55 | bgt 3b @ 1 |
| 56 | LOADREGS(eqfd, sp!, {pc}) @ 1/2 quick exit |
| 57 | /* |
| 58 | * No need to correct the count; we're only testing bits from now on |
| 59 | */ |
| 60 | tst r1, #32 @ 1 |
| 61 | stmneia r0!, {r2, r3, ip, lr} @ 4 |
| 62 | stmneia r0!, {r2, r3, ip, lr} @ 4 |
| 63 | tst r1, #16 @ 1 16 bytes or more? |
| 64 | stmneia r0!, {r2, r3, ip, lr} @ 4 |
| 65 | ldr lr, [sp], #4 @ 1 |
| 66 | |
| 67 | 4: tst r1, #8 @ 1 8 bytes or more? |
| 68 | stmneia r0!, {r2, r3} @ 2 |
| 69 | tst r1, #4 @ 1 4 bytes or more? |
| 70 | strne r2, [r0], #4 @ 1 |
| 71 | /* |
| 72 | * When we get here, we've got less than 4 bytes to zero. We |
| 73 | * may have an unaligned pointer as well. |
| 74 | */ |
| 75 | 5: tst r1, #2 @ 1 2 bytes or more? |
| 76 | strneb r2, [r0], #1 @ 1 |
| 77 | strneb r2, [r0], #1 @ 1 |
| 78 | tst r1, #1 @ 1 a byte left over |
| 79 | strneb r2, [r0], #1 @ 1 |
| 80 | RETINSTR(mov,pc,lr) @ 1 |