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   SPDX-License-Identifier: BSD-2-Clause-Patent
   6
   7 **/
   8
   9 #include "LoadLinuxLib.h"
  10
  11
  12 //
  13 // Local structure definitions
  14 //
  15
  16 #pragma pack (1)
  17
  18 //
  19 // Global Descriptor Entry structures
  20 //
  21
  22 typedef struct _GDT_ENTRY {
  23   UINT16 Limit15_0;
  24   UINT16 Base15_0;
  25   UINT8  Base23_16;
  26   UINT8  Type;
  27   UINT8  Limit19_16_and_flags;
  28   UINT8  Base31_24;
  29 } GDT_ENTRY;
  30
  31 typedef
  32 struct _GDT_ENTRIES {
  33   GDT_ENTRY Null;
  34   GDT_ENTRY Null2;
  35   GDT_ENTRY Linear;
  36   GDT_ENTRY LinearCode;
  37   GDT_ENTRY TaskSegment;
  38   GDT_ENTRY Spare4;
  39   GDT_ENTRY Spare5;
  40 } GDT_ENTRIES;
  41
  42 #pragma pack ()
  43
  44 STATIC GDT_ENTRIES *mGdt = NULL;
  45
  46 //
  47 // Global descriptor table (GDT) Template
  48 //
  49 STATIC GDT_ENTRIES GdtTemplate = {
  50   //
  51   // Null
  52   //
  53   {
  54     0x0,            // limit 15:0
  55     0x0,            // base 15:0
  56     0x0,            // base 23:16
  57     0x0,            // type
  58     0x0,            // limit 19:16, flags
  59     0x0,            // base 31:24
  60   },
  61   //
  62   // Null2
  63   //
  64   {
  65     0x0,            // limit 15:0
  66     0x0,            // base 15:0
  67     0x0,            // base 23:16
  68     0x0,            // type
  69     0x0,            // limit 19:16, flags
  70     0x0,            // base 31:24
  71   },
  72   //
  73   // Linear
  74   //
  75   {
  76     0x0FFFF,        // limit 0xFFFFF
  77     0x0,            // base 0
  78     0x0,
  79     0x09A,          // present, ring 0, data, expand-up, writable
  80     0x0CF,          // page-granular, 32-bit
  81     0x0,
  82   },
  83   //
  84   // LinearCode
  85   //
  86   {
  87     0x0FFFF,        // limit 0xFFFFF
  88     0x0,            // base 0
  89     0x0,
  90     0x092,          // present, ring 0, data, expand-up, writable
  91     0x0CF,          // page-granular, 32-bit
  92     0x0,
  93   },
  94   //
  95   // TaskSegment
  96   //
  97   {
  98     0x0,            // limit 0
  99     0x0,            // base 0
 100     0x0,
 101     0x089,          // ?
 102     0x080,          // ?
 103     0x0,
 104   },
 105   //
 106   // Spare4
 107   //
 108   {
 109     0x0,            // limit 0
 110     0x0,            // base 0
 111     0x0,
 112     0x0,            // present, ring 0, data, expand-up, writable
 113     0x0,            // page-granular, 32-bit
 114     0x0,
 115   },
 116   //
 117   // Spare5
 118   //
 119   {
 120     0x0,            // limit 0
 121     0x0,            // base 0
 122     0x0,
 123     0x0,            // present, ring 0, data, expand-up, writable
 124     0x0,            // page-granular, 32-bit
 125     0x0,
 126   },
 127 };
 128
 129 /**
 130   Initialize Global Descriptor Table.
 131
 132 **/
 133 VOID
 134 InitLinuxDescriptorTables (
 135   VOID
 136   )
 137 {
 138   //
 139   // Allocate Runtime Data for the GDT
 140   //
 141   mGdt = AllocateRuntimePool (sizeof (GdtTemplate) + 8);
 142   ASSERT (mGdt != NULL);
 143   mGdt = ALIGN_POINTER (mGdt, 8);
 144
 145   //
 146   // Initialize all GDT entries
 147   //
 148   CopyMem (mGdt, &GdtTemplate, sizeof (GdtTemplate));
 149
 150 }
 151
 152 /**
 153   Initialize Global Descriptor Table.
 154
 155 **/
 156 VOID
 157 SetLinuxDescriptorTables (
 158   VOID
 159   )
 160 {
 161   IA32_DESCRIPTOR GdtPtr;
 162   IA32_DESCRIPTOR IdtPtr;
 163
 164   //
 165   // Write GDT register
 166   //
 167   GdtPtr.Base = (UINT32)(UINTN)(VOID*) mGdt;
 168   GdtPtr.Limit = (UINT16) (sizeof (GdtTemplate) - 1);
 169   AsmWriteGdtr (&GdtPtr);
 170
 171   IdtPtr.Base = (UINT32) 0;
 172   IdtPtr.Limit = (UINT16) 0;
 173   AsmWriteIdtr (&IdtPtr);
 174 }
 175