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

   1 /** @file
   2   Supporting functions for IA32 architecture.
   3
   4   Copyright (c) 2010 - 2018, 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   UINT32                     RegEdx;
  32
  33   AsmReadIdtr (&IdtDescriptor);
  34
  35   //
  36   // Use current CS as the segment selector of interrupt gate in IDT
  37   //
  38   CodeSegment = AsmReadCs ();
  39
  40   IdtEntry = (IA32_IDT_GATE_DESCRIPTOR *) IdtDescriptor.Base;
  41
  42   for (Index = 0; Index < 20; Index ++) {
  43     if (((PcdGet32 (PcdExceptionsIgnoredByDebugger) & ~(BIT1 | BIT3)) & (1 << Index)) != 0) {
  44       //
  45       // If the exception is masked to be reserved except for INT1 and INT3, skip it
  46       //
  47       continue;
  48     }
  49     InterruptHandler = (UINTN)&Exception0Handle + Index * ExceptionStubHeaderSize;
  50     IdtEntry[Index].Bits.OffsetLow  = (UINT16)(UINTN)InterruptHandler;
  51     IdtEntry[Index].Bits.OffsetHigh = (UINT16)((UINTN)InterruptHandler >> 16);
  52     IdtEntry[Index].Bits.Selector   = CodeSegment;
  53     IdtEntry[Index].Bits.GateType   = IA32_IDT_GATE_TYPE_INTERRUPT_32;
  54   }
  55
  56   InterruptHandler = (UINTN) &TimerInterruptHandle;
  57   IdtEntry[DEBUG_TIMER_VECTOR].Bits.OffsetLow  = (UINT16)(UINTN)InterruptHandler;
  58   IdtEntry[DEBUG_TIMER_VECTOR].Bits.OffsetHigh = (UINT16)((UINTN)InterruptHandler >> 16);
  59   IdtEntry[DEBUG_TIMER_VECTOR].Bits.Selector   = CodeSegment;
  60   IdtEntry[DEBUG_TIMER_VECTOR].Bits.GateType   = IA32_IDT_GATE_TYPE_INTERRUPT_32;
  61
  62   //
  63   // If the CPU supports Debug Extensions(CPUID:01 EDX:BIT2), then
  64   // Set DE flag in CR4 to enable IO breakpoint
  65   //
  66   AsmCpuid (1, NULL, NULL, NULL, &RegEdx);
  67   if ((RegEdx & BIT2) != 0) {
  68     AsmWriteCr4 (AsmReadCr4 () | BIT3);
  69   }
  70 }
  71
  72 /**
  73   Retrieve exception handler from IDT table by ExceptionNum.
  74
  75   @param[in]  ExceptionNum    Exception number
  76
  77   @return Exception handler
  78
  79 **/
  80 VOID *
  81 GetExceptionHandlerInIdtEntry (
  82   IN UINTN             ExceptionNum
  83   )
  84 {
  85   IA32_IDT_GATE_DESCRIPTOR   *IdtEntry;
  86   IA32_DESCRIPTOR            IdtDescriptor;
  87
  88   AsmReadIdtr (&IdtDescriptor);
  89   IdtEntry = (IA32_IDT_GATE_DESCRIPTOR *) IdtDescriptor.Base;
  90
  91   return (VOID *) (((UINTN)IdtEntry[ExceptionNum].Bits.OffsetLow) |
  92                   (((UINTN)IdtEntry[ExceptionNum].Bits.OffsetHigh) << 16));
  93 }
  94
  95 /**
  96   Set exception handler in IDT table by ExceptionNum.
  97
  98   @param[in]  ExceptionNum      Exception number
  99   @param[in]  ExceptionHandler  Exception Handler to be set
 100
 101 **/
 102 VOID
 103 SetExceptionHandlerInIdtEntry (
 104   IN UINTN             ExceptionNum,
 105   IN VOID              *ExceptionHandler
 106   )
 107 {
 108   IA32_IDT_GATE_DESCRIPTOR   *IdtEntry;
 109   IA32_DESCRIPTOR            IdtDescriptor;
 110
 111   AsmReadIdtr (&IdtDescriptor);
 112   IdtEntry = (IA32_IDT_GATE_DESCRIPTOR *) IdtDescriptor.Base;
 113
 114   IdtEntry[ExceptionNum].Bits.OffsetLow   = (UINT16)(UINTN)ExceptionHandler;
 115   IdtEntry[ExceptionNum].Bits.OffsetHigh  = (UINT16)((UINTN)ExceptionHandler >> 16);
 116 }