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 } 181 182
