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CpuExceptionHandlerLib: Add comments to make code more readable

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Today's implementation of handling HOOK_BEFORE and HOOK_AFTER is
a bit complex. More comments is better.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Ruiyu Ni <ruiyu.ni@intel.com>
Cc: Fan Jeff <vanjeff_919@hotmail.com>
Reviewed-by: Jian J Wang <jian.j.wang@intel.com>
This commit is contained in:
Ruiyu Ni
2018-08-31 15:30:26 +08:00
parent 4cf022f2f1
commit 87a9dd0d15
3 changed files with 18 additions and 10 deletions
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8
UefiCpuPkg/Library/CpuExceptionHandlerLib/Ia32/ArchExceptionHandler.c
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@@ -1,7 +1,7 @@
/** @file
IA32 CPU Exception Handler functons.
Copyright (c) 2012 - 2017, Intel Corporation. All rights reserved.<BR>
Copyright (c) 2012 - 2018, Intel Corporation. All rights reserved.<BR>
This program and the accompanying materials
are licensed and made available under the terms and conditions of the BSD License
which accompanies this distribution. The full text of the license may be found at
@@ -66,7 +66,9 @@ ArchSaveExceptionContext (
ReservedVectors = ExceptionHandlerData->ReservedVectors;
//
// Save Exception context in global variable
// Save Exception context in global variable in first entry of the exception handler.
// So when original exception handler returns to the new exception handler (second entry),
// the Eflags/Cs/Eip/ExceptionData can be used.
//
ReservedVectors[ExceptionType].OldFlags = SystemContext.SystemContextIa32->Eflags;
ReservedVectors[ExceptionType].OldCs = SystemContext.SystemContextIa32->Cs;
@@ -79,7 +81,7 @@ ArchSaveExceptionContext (
Eflags.Bits.IF = 0;
SystemContext.SystemContextIa32->Eflags = Eflags.UintN;
//
// Modify the EIP in stack, then old IDT handler will return to the stub code
// Modify the EIP in stack, then old IDT handler will return to HookAfterStubBegin.
//
SystemContext.SystemContextIa32->Eip = (UINTN) ReservedVectors[ExceptionType].HookAfterStubHeaderCode;
}