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   SPDX-License-Identifier: BSD-2-Clause-Patent
   6
   7 **/
   8
   9 #include "DebugAgent.h"
  10
  11 /**
  12   Initialize IDT entries to support source level debug.
  13
  14 **/
  15 VOID
  16 InitializeDebugIdt (
  17   VOID
  18   )
  19 {
  20   IA32_IDT_GATE_DESCRIPTOR   *IdtEntry;
  21   UINTN                      InterruptHandler;
  22   IA32_DESCRIPTOR            IdtDescriptor;
  23   UINTN                      Index;
  24   UINT16                     CodeSegment;
  25   UINT32                     RegEdx;
  26
  27   AsmReadIdtr (&IdtDescriptor);
  28
  29   //
  30   // Use current CS as the segment selector of interrupt gate in IDT
  31   //
  32   CodeSegment = AsmReadCs ();
  33
  34   IdtEntry = (IA32_IDT_GATE_DESCRIPTOR *) IdtDescriptor.Base;
  35
  36   for (Index = 0; Index < 20; Index ++) {
  37     if (((PcdGet32 (PcdExceptionsIgnoredByDebugger) & ~(BIT1 | BIT3)) & (1 << Index)) != 0) {
  38       //
  39       // If the exception is masked to be reserved except for INT1 and INT3, skip it
  40       //
  41       continue;
  42     }
  43     InterruptHandler = (UINTN)&Exception0Handle + Index * ExceptionStubHeaderSize;
  44     IdtEntry[Index].Bits.OffsetLow  = (UINT16)(UINTN)InterruptHandler;
  45     IdtEntry[Index].Bits.OffsetHigh = (UINT16)((UINTN)InterruptHandler >> 16);
  46     IdtEntry[Index].Bits.Selector   = CodeSegment;
  47     IdtEntry[Index].Bits.GateType   = IA32_IDT_GATE_TYPE_INTERRUPT_32;
  48   }
  49
  50   InterruptHandler = (UINTN) &TimerInterruptHandle;
  51   IdtEntry[DEBUG_TIMER_VECTOR].Bits.OffsetLow  = (UINT16)(UINTN)InterruptHandler;
  52   IdtEntry[DEBUG_TIMER_VECTOR].Bits.OffsetHigh = (UINT16)((UINTN)InterruptHandler >> 16);
  53   IdtEntry[DEBUG_TIMER_VECTOR].Bits.Selector   = CodeSegment;
  54   IdtEntry[DEBUG_TIMER_VECTOR].Bits.GateType   = IA32_IDT_GATE_TYPE_INTERRUPT_32;
  55
  56   //
  57   // If the CPU supports Debug Extensions(CPUID:01 EDX:BIT2), then
  58   // Set DE flag in CR4 to enable IO breakpoint
  59   //
  60   AsmCpuid (1, NULL, NULL, NULL, &RegEdx);
  61   if ((RegEdx & BIT2) != 0) {
  62     AsmWriteCr4 (AsmReadCr4 () | BIT3);
  63   }
  64 }
  65
  66 /**
  67   Retrieve exception handler from IDT table by ExceptionNum.
  68
  69   @param[in]  ExceptionNum    Exception number
  70
  71   @return Exception handler
  72
  73 **/
  74 VOID *
  75 GetExceptionHandlerInIdtEntry (
  76   IN UINTN             ExceptionNum
  77   )
  78 {
  79   IA32_IDT_GATE_DESCRIPTOR   *IdtEntry;
  80   IA32_DESCRIPTOR            IdtDescriptor;
  81
  82   AsmReadIdtr (&IdtDescriptor);
  83   IdtEntry = (IA32_IDT_GATE_DESCRIPTOR *) IdtDescriptor.Base;
  84
  85   return (VOID *) (((UINTN)IdtEntry[ExceptionNum].Bits.OffsetLow) |
  86                   (((UINTN)IdtEntry[ExceptionNum].Bits.OffsetHigh) << 16));
  87 }
  88
  89 /**
  90   Set exception handler in IDT table by ExceptionNum.
  91
  92   @param[in]  ExceptionNum      Exception number
  93   @param[in]  ExceptionHandler  Exception Handler to be set
  94
  95 **/
  96 VOID
  97 SetExceptionHandlerInIdtEntry (
  98   IN UINTN             ExceptionNum,
  99   IN VOID              *ExceptionHandler
 100   )
 101 {
 102   IA32_IDT_GATE_DESCRIPTOR   *IdtEntry;
 103   IA32_DESCRIPTOR            IdtDescriptor;
 104
 105   AsmReadIdtr (&IdtDescriptor);
 106   IdtEntry = (IA32_IDT_GATE_DESCRIPTOR *) IdtDescriptor.Base;
 107
 108   IdtEntry[ExceptionNum].Bits.OffsetLow   = (UINT16)(UINTN)ExceptionHandler;
 109   IdtEntry[ExceptionNum].Bits.OffsetHigh  = (UINT16)((UINTN)ExceptionHandler >> 16);
 110 }