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Starting from certain version of Visual Studio C compiler (I don’t have the exact version. I am using VS2019), CpuDeadLoop is optimized quite well by compiler. The compiler does not generate instructions that jump out of the loop when the "Index" is non-zero. It becomes harder/impossible for developers to break out of the dead-loop in debugger. The new version of CpuDeadLoop() compares a volatile global to a volatile local. This forces 2 reads and a comparison on every loop iteration. The local variable can be set to 1 to exit the loop without modifying the global variable. Using VS2019 with max opt enabled, The dead-loop can be exit by setting Index to 1 in a debugger. Signed-off-by: Michael D Kinney <michael.d.kinney@intel.com>
35 lines
768 B
C
35 lines
768 B
C
/** @file
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Base Library CPU Functions for all architectures.
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Copyright (c) 2006 - 2024, 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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#include <Base.h>
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#include <Library/BaseLib.h>
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static volatile UINTN mDeadLoopComparator = 0;
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/**
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Executes an infinite loop.
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Forces the CPU to execute an infinite loop. A debugger may be used to skip
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past the loop and the code that follows the loop must execute properly. This
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implies that the infinite loop must not cause the code that follow it to be
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optimized away.
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**/
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VOID
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EFIAPI
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CpuDeadLoop (
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VOID
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)
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{
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volatile UINTN Index;
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for (Index = mDeadLoopComparator; Index == mDeadLoopComparator;) {
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CpuPause ();
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}
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}
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