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      1 /** @file
      2   Supporting functions for IA32 architecture.
      3 
      4   Copyright (c) 2010 - 2015, 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 }
    117