1;/*++ 2; 3;Copyright (c) 2006, Intel Corporation. All rights reserved.<BR> 4;This program and the accompanying materials 5;are licensed and made available under the terms and conditions of the BSD License 6;which accompanies this distribution. The full text of the license may be found at 7;http://opensource.org/licenses/bsd-license.php 8; 9;THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS, 10;WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED. 11; 12;Module Name: 13; 14; EfiZeroMem.c 15; 16;Abstract: 17; 18; This is the code that supports IA32-optimized ZeroMem service 19; 20;--*/ 21;--------------------------------------------------------------------------- 22 .686 23 .model flat,C 24 .mmx 25 .code 26 27;--------------------------------------------------------------------------- 28;VOID 29;EfiCommonLibZeroMem ( 30; IN VOID *Buffer, 31; IN UINTN Count 32; ) 33;/*++ 34; 35;Input: VOID *Buffer - Pointer to buffer to clear 36; UINTN Count - Number of bytes to clear 37; 38;Output: None. 39; 40;Saves: 41; 42;Modifies: 43; 44;Description: This function is an optimized zero-memory function. 45; 46;Notes: This function tries to zero memory 8 bytes at a time. As a result, 47; it first picks up any misaligned bytes, then words, before getting 48; in the main loop that does the 8-byte clears. 49; 50;--*/ 51EfiCommonLibZeroMem PROC 52; UINT64 MmxSave; 53 push ebp 54 mov ebp, esp 55 push ecx ; Reserve space for local variable MmxSave 56 push ecx 57 push edi 58 59 mov ecx, [ebp + 0Ch] ; Count 60 mov edi, [ebp + 8]; Buffer 61 62 ; Pick up misaligned start bytes (get pointer 4-byte aligned) 63_StartByteZero: 64 mov eax, edi 65 and al, 3 ; check lower 2 bits of address 66 test al, al 67 je _ZeroBlocks ; already aligned? 68 cmp ecx, 0 69 je _ZeroMemDone 70 71 ; Clear the byte memory location 72 mov BYTE PTR [edi], 0 73 inc edi 74 75 ; Decrement our count 76 dec ecx 77 jmp _StartByteZero ; back to top of loop 78 79_ZeroBlocks: 80 81 ; Compute how many 64-byte blocks we can clear 82 mov edx, ecx 83 shr ecx, 6 ; convert to 64-byte count 84 shl ecx, 6 ; convert back to bytes 85 sub edx, ecx ; subtract from the original count 86 shr ecx, 6 ; and this is how many 64-byte blocks 87 88 ; If no 64-byte blocks, then skip 89 cmp ecx, 0 90 je _ZeroRemaining 91 92 ; Save mm0 93 movq [ebp - 8], mm0 ; Save mm0 to MmxSave 94 95 pxor mm0, mm0 ; Clear mm0 96 97_B: 98 movq QWORD PTR ds:[edi], mm0 99 movq QWORD PTR ds:[edi+8], mm0 100 movq QWORD PTR ds:[edi+16], mm0 101 movq QWORD PTR ds:[edi+24], mm0 102 movq QWORD PTR ds:[edi+32], mm0 103 movq QWORD PTR ds:[edi+40], mm0 104 movq QWORD PTR ds:[edi+48], mm0 105 movq QWORD PTR ds:[edi+56], mm0 106 107 add edi, 64 108 dec ecx 109 jnz _B 110 111; Restore mm0 112 movq mm0, [ebp - 8] ; Restore mm0 from MmxSave 113 emms ; Exit MMX Instruction 114 115_ZeroRemaining: 116 ; Zero out as many DWORDS as possible 117 mov ecx, edx 118 shr ecx, 2 119 xor eax, eax 120 121 rep stosd 122 123 ; Zero out remaining as bytes 124 mov ecx, edx 125 and ecx, 03 126 127 rep stosb 128 129_ZeroMemDone: 130 131 pop edi 132 leave 133 ret 134EfiCommonLibZeroMem ENDP 135 END 136