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Last change
on this file since 80924 was 80721, checked in by vboxsync, 5 years ago |
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Devices/EFI/FirmwareNew: Start upgrade process to edk2-stable201908 (compiles on Windows and works to some extent), bugref:4643
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File size:
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| 1 | /** @file
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| 2 | Implementation of TestAndClearBit using compare-exchange primitive
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| 3 |
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| 4 | Copyright (C) 2015, Linaro Ltd.
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| 5 | Copyright (c) 2015, Intel Corporation. All rights reserved.<BR>
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| 6 |
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| 7 | SPDX-License-Identifier: BSD-2-Clause-Patent
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| 8 |
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| 9 | **/
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| 10 |
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| 11 | #include <Base.h>
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| 12 | #include <Library/SynchronizationLib.h>
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| 13 |
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| 14 | INT32
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| 15 | EFIAPI
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| 16 | TestAndClearBit (
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| 17 | IN INT32 Bit,
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| 18 | IN VOID *Address
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| 19 | )
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| 20 | {
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| 21 | UINT16 Word, Read;
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| 22 | UINT16 Mask;
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| 23 |
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| 24 | //
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| 25 | // Calculate the effective address relative to 'Address' based on the
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| 26 | // higher order bits of 'Bit'. Use signed shift instead of division to
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| 27 | // ensure we round towards -Inf, and end up with a positive shift in
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| 28 | // 'Bit', even if 'Bit' itself is negative.
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| 29 | //
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| 30 | Address = (VOID*)((UINT8*) Address + ((Bit >> 4) * sizeof(UINT16)));
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| 31 | Mask = 1U << (Bit & 15);
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| 32 |
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| 33 | for (Word = *(UINT16 *) Address; Word & Mask; Word = Read) {
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| 34 | Read = InterlockedCompareExchange16 (Address, Word, Word & ~Mask);
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| 35 | if (Read == Word) {
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| 36 | return 1;
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| 37 | }
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| 38 | }
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| 39 | return 0;
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| 40 | }
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