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
  44     InterruptHandler                = (UINTN)&Exception0Handle + Index * ExceptionStubHeaderSize;
  45     IdtEntry[Index].Bits.OffsetLow  = (UINT16)(UINTN)InterruptHandler;
  46     IdtEntry[Index].Bits.OffsetHigh = (UINT16)((UINTN)InterruptHandler >> 16);
  47     IdtEntry[Index].Bits.Selector   = CodeSegment;
  48     IdtEntry[Index].Bits.GateType   = IA32_IDT_GATE_TYPE_INTERRUPT_32;
  49   }
  50
  51   InterruptHandler                             = (UINTN)&TimerInterruptHandle;
  52   IdtEntry[DEBUG_TIMER_VECTOR].Bits.OffsetLow  = (UINT16)(UINTN)InterruptHandler;
  53   IdtEntry[DEBUG_TIMER_VECTOR].Bits.OffsetHigh = (UINT16)((UINTN)InterruptHandler >> 16);
  54   IdtEntry[DEBUG_TIMER_VECTOR].Bits.Selector   = CodeSegment;
  55   IdtEntry[DEBUG_TIMER_VECTOR].Bits.GateType   = IA32_IDT_GATE_TYPE_INTERRUPT_32;
  56
  57   //
  58   // If the CPU supports Debug Extensions(CPUID:01 EDX:BIT2), then
  59   // Set DE flag in CR4 to enable IO breakpoint
  60   //
  61   AsmCpuid (1, NULL, NULL, NULL, &RegEdx);
  62   if ((RegEdx & BIT2) != 0) {
  63     AsmWriteCr4 (AsmReadCr4 () | BIT3);
  64   }
  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 }