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MdePkg/BaseLib: Let CpuDeadLoop() be breakable in debugger

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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>
This commit is contained in:
Ray Ni 2024-06-11 15:00:41 +08:00 committed by mergify[bot]
parent 0982da4f50
commit d3b32dca06
1 changed files with 4 additions and 2 deletions
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6
MdePkg/Library/BaseLib/CpuDeadLoop.c
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@ -1,7 +1,7 @@
/** @file
Base Library CPU Functions for all architectures.
Copyright (c) 2006 - 2008, Intel Corporation. All rights reserved.<BR>
Copyright (c) 2006 - 2024, Intel Corporation. All rights reserved.<BR>
SPDX-License-Identifier: BSD-2-Clause-Patent
**/
@ -9,6 +9,8 @@
#include <Base.h>
#include <Library/BaseLib.h>
static volatile UINTN mDeadLoopComparator = 0;
/**
Executes an infinite loop.
@ -26,7 +28,7 @@ CpuDeadLoop (
{
volatile UINTN Index;
for (Index = 0; Index == 0;) {
for (Index = mDeadLoopComparator; Index == mDeadLoopComparator;) {
CpuPause ();
}
}