SourceLevelDebugPkg/Library/DebugAgent/DebugAgentCommon/Ia32/ArchDebugSupport.c

   1 /** @file
   2   Supporting functions for IA32 architecture.
   3
   4   Copyright (c) 2010 - 2013, Intel Corporation. All rights reserved.<BR>
   5   This program and the accompanying materials
   6   are licensed and made available under the terms and conditions of the BSD License
   7   which accompanies this distribution.  The full text of the license may be found at
   8   http://opensource.org/licenses/bsd-license.php.
   9
  10   THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
  11   WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
  12
  13 **/
  14
  15 #include "DebugAgent.h"
  16
  17 /**
  18   Initialize IDT entries to support source level debug.
  19
  20 **/
  21 VOID
  22 InitializeDebugIdt (
  23   VOID
  24   )
  25 {
  26   IA32_IDT_GATE_DESCRIPTOR   *IdtEntry;
  27   UINTN                      InterruptHandler;
  28   IA32_DESCRIPTOR            IdtDescriptor;
  29   UINTN                      Index;
  30   UINT16                     CodeSegment;
  31
  32   AsmReadIdtr (&IdtDescriptor);
  33
  34   //
  35   // Use current CS as the segment selector of interrupt gate in IDT
  36   //
  37   CodeSegment = AsmReadCs ();
  38
  39   IdtEntry = (IA32_IDT_GATE_DESCRIPTOR *) IdtDescriptor.Base;
  40
  41   for (Index = 0; Index < 20; Index ++) {
  42     if (((PcdGet32 (PcdExceptionsIgnoredByDebugger) & ~(BIT1 | BIT3)) & (1 << Index)) != 0) {
  43       //
  44       // If the exception is masked to be reserved except for INT1 and INT3, skip it
  45       //
  46       continue;
  47     }
  48     InterruptHandler = (UINTN)&Exception0Handle + Index * ExceptionStubHeaderSize;
  49     IdtEntry[Index].Bits.OffsetLow  = (UINT16)(UINTN)InterruptHandler;
  50     IdtEntry[Index].Bits.OffsetHigh = (UINT16)((UINTN)InterruptHandler >> 16);
  51     IdtEntry[Index].Bits.Selector   = CodeSegment;
  52     IdtEntry[Index].Bits.GateType   = IA32_IDT_GATE_TYPE_INTERRUPT_32;
  53   }
  54
  55   InterruptHandler = (UINTN) &TimerInterruptHandle;
  56   IdtEntry[DEBUG_TIMER_VECTOR].Bits.OffsetLow  = (UINT16)(UINTN)InterruptHandler;
  57   IdtEntry[DEBUG_TIMER_VECTOR].Bits.OffsetHigh = (UINT16)((UINTN)InterruptHandler >> 16);
  58   IdtEntry[DEBUG_TIMER_VECTOR].Bits.Selector   = CodeSegment;
  59   IdtEntry[DEBUG_TIMER_VECTOR].Bits.GateType   = IA32_IDT_GATE_TYPE_INTERRUPT_32;
  60
  61   //
  62   // Set DE flag in CR4 to enable IO breakpoint
  63   //
  64   AsmWriteCr4 (AsmReadCr4 () | BIT3);
  65 }
  66
  67 /**
  68   Retrieve exception handler from IDT table by ExceptionNum.
  69
  70   @param[in]  ExceptionNum    Exception number
  71
  72   @return Exception handler
  73
  74 **/
  75 VOID *
  76 GetExceptionHandlerInIdtEntry (
  77   IN UINTN             ExceptionNum
  78   )
  79 {
  80   IA32_IDT_GATE_DESCRIPTOR   *IdtEntry;
  81   IA32_DESCRIPTOR            IdtDescriptor;
  82
  83   AsmReadIdtr (&IdtDescriptor);
  84   IdtEntry = (IA32_IDT_GATE_DESCRIPTOR *) IdtDescriptor.Base;
  85
  86   return (VOID *) (((UINTN)IdtEntry[ExceptionNum].Bits.OffsetLow) |
  87                   (((UINTN)IdtEntry[ExceptionNum].Bits.OffsetHigh) << 16));
  88 }
  89
  90 /**
  91   Set exception handler in IDT table by ExceptionNum.
  92
  93   @param[in]  ExceptionNum      Exception number
  94   @param[in]  ExceptionHandler  Exception Handler to be set
  95
  96 **/
  97 VOID
  98 SetExceptionHandlerInIdtEntry (
  99   IN UINTN             ExceptionNum,
 100   IN VOID              *ExceptionHandler
 101   )
 102 {
 103   IA32_IDT_GATE_DESCRIPTOR   *IdtEntry;
 104   IA32_DESCRIPTOR            IdtDescriptor;
 105
 106   AsmReadIdtr (&IdtDescriptor);
 107   IdtEntry = (IA32_IDT_GATE_DESCRIPTOR *) IdtDescriptor.Base;
 108
 109   IdtEntry[ExceptionNum].Bits.OffsetLow   = (UINT16)(UINTN)ExceptionHandler;
 110   IdtEntry[ExceptionNum].Bits.OffsetHigh  = (UINT16)((UINTN)ExceptionHandler >> 16);
 111 }