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https://github.com/CloverHackyColor/CloverBootloader.git
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69 lines
2.2 KiB
NASM
69 lines
2.2 KiB
NASM
;------------------------------------------------------------------------------
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;
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; Copyright (c) 2016, Intel Corporation. All rights reserved.<BR>
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; SPDX-License-Identifier: BSD-2-Clause-Patent
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;
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; Module Name:
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;
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; IsZeroBuffer.nasm
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;
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; Abstract:
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;
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; IsZeroBuffer function
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;
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; Notes:
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;
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;------------------------------------------------------------------------------
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SECTION .text
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;------------------------------------------------------------------------------
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; BOOLEAN
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; EFIAPI
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; InternalMemIsZeroBuffer (
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; IN CONST VOID *Buffer,
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; IN UINTN Length
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; );
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;------------------------------------------------------------------------------
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global ASM_PFX(InternalMemIsZeroBuffer)
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ASM_PFX(InternalMemIsZeroBuffer):
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push edi
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mov edi, [esp + 8] ; edi <- Buffer
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mov edx, [esp + 12] ; edx <- Length
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xor ecx, ecx ; ecx <- 0
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sub ecx, edi
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and ecx, 15 ; ecx + edi aligns on 16-byte boundary
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jz @Is16BytesZero
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cmp ecx, edx
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cmova ecx, edx ; bytes before the 16-byte boundary
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sub edx, ecx
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xor eax, eax ; eax <- 0, also set ZF
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repe scasb
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jnz @ReturnFalse ; ZF=0 means non-zero element found
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@Is16BytesZero:
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mov ecx, edx
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and edx, 15
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shr ecx, 4
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jz @IsBytesZero
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.0:
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pxor xmm0, xmm0 ; xmm0 <- 0
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pcmpeqb xmm0, [edi] ; check zero for 16 bytes
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pmovmskb eax, xmm0 ; eax <- compare results
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cmp eax, 0xffff
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jnz @ReturnFalse
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add edi, 16
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loop .0
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@IsBytesZero:
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mov ecx, edx
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xor eax, eax ; eax <- 0, also set ZF
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repe scasb
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jnz @ReturnFalse ; ZF=0 means non-zero element found
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pop edi
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mov eax, 1 ; return TRUE
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ret
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@ReturnFalse:
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pop edi
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xor eax, eax
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ret ; return FALSE
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