descriptor.h

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/*
 *  Copyright (C) 2003 Bregmasoft
 * 
 * This program is free software; you can redistribute it and/or modify it under
 * the terms of the GNU General Public License as published by the Free Software
 * Foundation; either version 2 of the License, or (at your option) any later
 * version.
 * 
 * This program is distributed in the hope that it will be useful, but WITHOUT ANY
 * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
 * PARTICULAR PURPOSE. See the GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License along with
 * this program; if not, write to the Free Software Foundation, Inc., 59 Temple
 * Place, Suite 330, Boston, MA 02111-1307 USA
 */
#ifndef ZYGOMA_IA32_DESCRIPTOR_H_ 
#define ZYGOMA_IA32_DESCRIPTOR_H_ 

#include <config.h>

namespace Zygoma
{
  namespace ia32
  {
    class Descriptor
    {
    public:
      enum Type
      {
        kTYPE_RESERVED_0    = 0,
        kTYPE_TSS_AVAILABLE = 1,
        kTYPE_LDT           = 2,
        kTYPE_TSS_BUSY      = 3,
        kTYPE_CALL_GATE     = 4,
        kTYPE_TASK_GATE     = 5,
        kTYPE_INT_GATE      = 6,
        kTYPE_TRAP_GATE     = 7
      };

      enum Granularity
      {
        kGRANULARITY_BYTE = 0,  
        kGRANULARITY_4K   = 1   
      };

      enum OperationSize
      {
        kOP_SIZE_16 = 0,
        kOP_SIZE_32 = 1
      };

    public:
      Type
      type() const
      { return static_cast<Type>(m_type); }

      bool
      isSystemDescriptor() const
      { return m_flags1.m_system.m_isSystemDescriptor; }

      int
      privilegeLevel() const
      { return m_flags1.m_code.m_privilegeLevel; }

      u32
      base() const
      {
        return (m_base24_31 & 0xfe) << 24
             +  m_base16_23 << 16
             +  m_base00_15;
      }

      u32
      limit() const
      {
        return (m_flags2 & 0x0f) << 16
             +  m_limit00_15;
      }

      Granularity
      granularity() const
      { return static_cast<Granularity>(m_granularity); }

      OperationSize
      operationSize() const
      { return static_cast<OperationSIze>(m_operationSize); }

      bool
      isPresent() const
      { return m_flags1.m_code.m_segmentIsPresent; }

      int
      limit() const
      { return m_segmentLimit; }

    private:
      struct DataSegment
      {
        u08 m_accessed:1;
        u08 m_write:1;
        u08 m_read:1;
        u08 m_selector:1;
        u08 m_isSystemDescriptor:1;
        u08 m_privilegeLevel:2;
        u08 m_segmentIsPresent:1;
      };

      struct CodeSegment
      {
        u08 m_accessed:1;
        u08 m_execute:1;
        u08 m_conforming:1;
        u08 m_selector:1;
        u08 m_isSystemDescriptor:1;
        u08 m_privilegeLevel:2;
        u08 m_segmentIsPresent:1;
      };

      struct SystemSegment
      {
        u08 m_type:3;
        u08 m_size:1;
        u08 m_isSystemDescriptor:1;
        u08 m_privilegeLevel:2;
        u08 m_segmentIsPresent:1;
      };

      union TypeUnion {
        CodeSegment   m_code;
        DataSegment   m_data;
        SystemSegment m_system;
      };

    protected:
      u16       m_limit00_15;
      u16       m_base00_15;
      u08       m_base16_23;
      TypeUnion m_flags1;
      u08       m_segmentLimit:4;
      u08       m_useMe:1;
      u08       m_reserved:1;
      u08       m_operationSize:1;
      u08       m_granularity:1;
      u08       m_base24_31;
    } ZYGOMA_PACKED;

    class TaskGate
    {
    public:
      u16 m_unused1;
      u16 m_segmentSelector;
      u08 m_unused2;
      u08 m_type:3;               /* 5 */
      u08 m_size:1;               /* 0 */
      u08 m_isSystemDescriptor:1; /* 0 */
      u08 m_privilegeLevel:2;
      u08 m_segmentIsPresent:1;
      u16 m_unused3
    };

    class InterruptGate
    {
    public:
      u16 m_offset00_15;      
      u16 m_segmentSelector;
      u08 m_unused2;
      u08 m_type:3;               /* 6 */
      u08 m_size:1;               /* 0 */
      u08 m_isSystemDescriptor:1; /* 0 */
      u08 m_privilegeLevel:2;
      u08 m_segmentIsPresent:1;   /* 1 */
      u16 m_offset16_31;
    };

    class TrapGate
    {
    public:
      u16 m_offset00_15;
      u16 m_segmentSelector;
      u08 m_unused2;
      u08 m_type:3;               /* 7 */
      u08 m_size:1;               /* 0 */
      u08 m_isSystemDescriptor:1; /* 0 */
      u08 m_privilegeLevel:2;
      u08 m_segmentIsPresent:1;   /* 1 */
      u16 m_offset16_31;
    };
  } // namespace ia32
} // namespace Zygoma

#endif // ZYGOMA_IA32_DESCRIPTOR_H_ 

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