OvmfPkg/Library/LoadLinuxLib/LinuxGdt.c

   1 /** @file
   2   Initialize GDT for Linux.
   3
   4   Copyright (c) 2006 - 2012, 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 "LoadLinuxLib.h"
  16
  17
  18 //
  19 // Local structure definitions
  20 //
  21
  22 #pragma pack (1)
  23
  24 //
  25 // Global Descriptor Entry structures
  26 //
  27
  28 typedef struct _GDT_ENTRY {
  29   UINT16 Limit15_0;
  30   UINT16 Base15_0;
  31   UINT8  Base23_16;
  32   UINT8  Type;
  33   UINT8  Limit19_16_and_flags;
  34   UINT8  Base31_24;
  35 } GDT_ENTRY;
  36
  37 typedef
  38 struct _GDT_ENTRIES {
  39   GDT_ENTRY Null;
  40   GDT_ENTRY Null2;
  41   GDT_ENTRY Linear;
  42   GDT_ENTRY LinearCode;
  43   GDT_ENTRY TaskSegment;
  44   GDT_ENTRY Spare4;
  45   GDT_ENTRY Spare5;
  46 } GDT_ENTRIES;
  47
  48 #pragma pack ()
  49
  50 STATIC GDT_ENTRIES *mGdt = NULL;
  51
  52 //
  53 // Global descriptor table (GDT) Template
  54 //
  55 STATIC GDT_ENTRIES GdtTemplate = {
  56   //
  57   // Null
  58   //
  59   {
  60     0x0,            // limit 15:0
  61     0x0,            // base 15:0
  62     0x0,            // base 23:16
  63     0x0,            // type
  64     0x0,            // limit 19:16, flags
  65     0x0,            // base 31:24
  66   },
  67   //
  68   // Null2
  69   //
  70   {
  71     0x0,            // limit 15:0
  72     0x0,            // base 15:0
  73     0x0,            // base 23:16
  74     0x0,            // type
  75     0x0,            // limit 19:16, flags
  76     0x0,            // base 31:24
  77   },
  78   //
  79   // Linear
  80   //
  81   {
  82     0x0FFFF,        // limit 0xFFFFF
  83     0x0,            // base 0
  84     0x0,
  85     0x09A,          // present, ring 0, data, expand-up, writable
  86     0x0CF,          // page-granular, 32-bit
  87     0x0,
  88   },
  89   //
  90   // LinearCode
  91   //
  92   {
  93     0x0FFFF,        // limit 0xFFFFF
  94     0x0,            // base 0
  95     0x0,
  96     0x092,          // present, ring 0, data, expand-up, writable
  97     0x0CF,          // page-granular, 32-bit
  98     0x0,
  99   },
 100   //
 101   // TaskSegment
 102   //
 103   {
 104     0x0,            // limit 0
 105     0x0,            // base 0
 106     0x0,
 107     0x089,          // ?
 108     0x080,          // ?
 109     0x0,
 110   },
 111   //
 112   // Spare4
 113   //
 114   {
 115     0x0,            // limit 0
 116     0x0,            // base 0
 117     0x0,
 118     0x0,            // present, ring 0, data, expand-up, writable
 119     0x0,            // page-granular, 32-bit
 120     0x0,
 121   },
 122   //
 123   // Spare5
 124   //
 125   {
 126     0x0,            // limit 0
 127     0x0,            // base 0
 128     0x0,
 129     0x0,            // present, ring 0, data, expand-up, writable
 130     0x0,            // page-granular, 32-bit
 131     0x0,
 132   },
 133 };
 134
 135 /**
 136   Initialize Global Descriptor Table.
 137
 138 **/
 139 VOID
 140 InitLinuxDescriptorTables (
 141   VOID
 142   )
 143 {
 144   //
 145   // Allocate Runtime Data for the GDT
 146   //
 147   mGdt = AllocateRuntimePool (sizeof (GdtTemplate) + 8);
 148   ASSERT (mGdt != NULL);
 149   mGdt = ALIGN_POINTER (mGdt, 8);
 150
 151   //
 152   // Initialize all GDT entries
 153   //
 154   CopyMem (mGdt, &GdtTemplate, sizeof (GdtTemplate));
 155
 156 }
 157
 158 /**
 159   Initialize Global Descriptor Table.
 160
 161 **/
 162 VOID
 163 SetLinuxDescriptorTables (
 164   VOID
 165   )
 166 {
 167   IA32_DESCRIPTOR GdtPtr;
 168   IA32_DESCRIPTOR IdtPtr;
 169
 170   //
 171   // Write GDT register
 172   //
 173   GdtPtr.Base = (UINT32)(UINTN)(VOID*) mGdt;
 174   GdtPtr.Limit = (UINT16) (sizeof (GdtTemplate) - 1);
 175   AsmWriteGdtr (&GdtPtr);
 176
 177   IdtPtr.Base = (UINT32) 0;
 178   IdtPtr.Limit = (UINT16) 0;
 179   AsmWriteIdtr (&IdtPtr);
 180 }
 181