1 ;------------------------------------------------------------------------------ 2 ; 3 ; Copyright (c) 2016, 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 ; IsZeroBuffer.nasm 15 ; 16 ; Abstract: 17 ; 18 ; IsZeroBuffer function 19 ; 20 ; Notes: 21 ; 22 ;------------------------------------------------------------------------------ 23 24 DEFAULT REL 25 SECTION .text 26 27 ;------------------------------------------------------------------------------ 28 ; BOOLEAN 29 ; EFIAPI 30 ; InternalMemIsZeroBuffer ( 31 ; IN CONST VOID *Buffer, 32 ; IN UINTN Length 33 ; ); 34 ;------------------------------------------------------------------------------ 35 global ASM_PFX(InternalMemIsZeroBuffer) 36 ASM_PFX(InternalMemIsZeroBuffer): 37 push rdi 38 mov rdi, rcx ; rdi <- Buffer 39 mov rcx, rdx ; rcx <- Length 40 shr rcx, 3 ; rcx <- number of qwords 41 and rdx, 7 ; rdx <- number of trailing bytes 42 xor rax, rax ; rax <- 0, also set ZF 43 repe scasq 44 jnz @ReturnFalse ; ZF=0 means non-zero element found 45 mov rcx, rdx 46 repe scasb 47 jnz @ReturnFalse 48 pop rdi 49 mov rax, 1 ; return TRUE 50 ret 51 @ReturnFalse: 52 pop rdi 53 xor rax, rax 54 ret ; return FALSE 55 56
