1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
| ;------------------------------------------------------------------------------
| ;
| ; Copyright (c) 2016, Intel Corporation. All rights reserved.<BR>
| ; SPDX-License-Identifier: BSD-2-Clause-Patent
| ;
| ; Module Name:
| ;
| ; IsZeroBuffer.nasm
| ;
| ; Abstract:
| ;
| ; IsZeroBuffer function
| ;
| ; Notes:
| ;
| ;------------------------------------------------------------------------------
|
| SECTION .text
|
| ;------------------------------------------------------------------------------
| ; BOOLEAN
| ; EFIAPI
| ; InternalMemIsZeroBuffer (
| ; IN CONST VOID *Buffer,
| ; IN UINTN Length
| ; );
| ;------------------------------------------------------------------------------
| global ASM_PFX(InternalMemIsZeroBuffer)
| ASM_PFX(InternalMemIsZeroBuffer):
| push edi
| mov edi, [esp + 8] ; edi <- Buffer
| mov edx, [esp + 12] ; edx <- Length
| xor ecx, ecx ; ecx <- 0
| sub ecx, edi
| and ecx, 15 ; ecx + edi aligns on 16-byte boundary
| jz @Is16BytesZero
| cmp ecx, edx
| cmova ecx, edx ; bytes before the 16-byte boundary
| sub edx, ecx
| xor eax, eax ; eax <- 0, also set ZF
| repe scasb
| jnz @ReturnFalse ; ZF=0 means non-zero element found
| @Is16BytesZero:
| mov ecx, edx
| and edx, 15
| shr ecx, 4
| jz @IsBytesZero
| .0:
| pxor xmm0, xmm0 ; xmm0 <- 0
| pcmpeqb xmm0, [edi] ; check zero for 16 bytes
| pmovmskb eax, xmm0 ; eax <- compare results
| cmp eax, 0xffff
| jnz @ReturnFalse
| add edi, 16
| loop .0
| @IsBytesZero:
| mov ecx, edx
| xor eax, eax ; eax <- 0, also set ZF
| repe scasb
| jnz @ReturnFalse ; ZF=0 means non-zero element found
| pop edi
| mov eax, 1 ; return TRUE
| ret
| @ReturnFalse:
| pop edi
| xor eax, eax
| ret ; return FALSE
|
|
|
