audk/MdePkg/Library/BaseLib/CpuDeadLoop.c
Ray Ni d3b32dca06 MdePkg/BaseLib: Let CpuDeadLoop() be breakable in debugger
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>
2024-06-12 07:18:12 +00:00

35 lines
768 B
C

/** @file
Base Library CPU Functions for all architectures.
Copyright (c) 2006 - 2024, Intel Corporation. All rights reserved.<BR>
SPDX-License-Identifier: BSD-2-Clause-Patent
**/
#include <Base.h>
#include <Library/BaseLib.h>
static volatile UINTN mDeadLoopComparator = 0;
/**
Executes an infinite loop.
Forces the CPU to execute an infinite loop. A debugger may be used to skip
past the loop and the code that follows the loop must execute properly. This
implies that the infinite loop must not cause the code that follow it to be
optimized away.
**/
VOID
EFIAPI
CpuDeadLoop (
VOID
)
{
volatile UINTN Index;
for (Index = mDeadLoopComparator; Index == mDeadLoopComparator;) {
CpuPause ();
}
}