1;------------------------------------------------------------------------------ 2; @file 3; Transition from 16 bit real mode into 32 bit flat protected mode 4; 5; Copyright (c) 2008 - 2010, Intel Corporation. All rights reserved.<BR> 6; This program and the accompanying materials 7; are licensed and made available under the terms and conditions of the BSD License 8; which accompanies this distribution. The full text of the license may be found at 9; http://opensource.org/licenses/bsd-license.php 10; 11; THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS, 12; WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED. 13; 14;------------------------------------------------------------------------------ 15 16%define SEC_DEFAULT_CR0 0x40000023 17%define SEC_DEFAULT_CR4 0x640 18 19BITS 16 20 21; 22; Modified: EAX, EBX 23; 24TransitionFromReal16To32BitFlat: 25 26 debugShowPostCode POSTCODE_16BIT_MODE 27 28 cli 29 30 mov bx, 0xf000 31 mov ds, bx 32 33 mov bx, ADDR16_OF(gdtr) 34 35o32 lgdt [cs:bx] 36 37 mov eax, SEC_DEFAULT_CR0 38 mov cr0, eax 39 40 jmp LINEAR_CODE_SEL:dword ADDR_OF(jumpTo32BitAndLandHere) 41BITS 32 42jumpTo32BitAndLandHere: 43 44 mov eax, SEC_DEFAULT_CR4 45 mov cr4, eax 46 47 debugShowPostCode POSTCODE_32BIT_MODE 48 49 mov ax, LINEAR_SEL 50 mov ds, ax 51 mov es, ax 52 mov fs, ax 53 mov gs, ax 54 mov ss, ax 55 56 OneTimeCallRet TransitionFromReal16To32BitFlat 57 58ALIGN 2 59 60gdtr: 61 dw GDT_END - GDT_BASE - 1 ; GDT limit 62 dd ADDR_OF(GDT_BASE) 63 64ALIGN 16 65 66; 67; Macros for GDT entries 68; 69 70%define PRESENT_FLAG(p) (p << 7) 71%define DPL(dpl) (dpl << 5) 72%define SYSTEM_FLAG(s) (s << 4) 73%define DESC_TYPE(t) (t) 74 75; Type: data, expand-up, writable, accessed 76%define DATA32_TYPE 3 77 78; Type: execute, readable, expand-up, accessed 79%define CODE32_TYPE 0xb 80 81; Type: execute, readable, expand-up, accessed 82%define CODE64_TYPE 0xb 83 84%define GRANULARITY_FLAG(g) (g << 7) 85%define DEFAULT_SIZE32(d) (d << 6) 86%define CODE64_FLAG(l) (l << 5) 87%define UPPER_LIMIT(l) (l) 88 89; 90; The Global Descriptor Table (GDT) 91; 92 93GDT_BASE: 94; null descriptor 95NULL_SEL equ $-GDT_BASE 96 DW 0 ; limit 15:0 97 DW 0 ; base 15:0 98 DB 0 ; base 23:16 99 DB 0 ; sys flag, dpl, type 100 DB 0 ; limit 19:16, flags 101 DB 0 ; base 31:24 102 103; linear data segment descriptor 104LINEAR_SEL equ $-GDT_BASE 105 DW 0xffff ; limit 15:0 106 DW 0 ; base 15:0 107 DB 0 ; base 23:16 108 DB PRESENT_FLAG(1)|DPL(0)|SYSTEM_FLAG(1)|DESC_TYPE(DATA32_TYPE) 109 DB GRANULARITY_FLAG(1)|DEFAULT_SIZE32(1)|CODE64_FLAG(0)|UPPER_LIMIT(0xf) 110 DB 0 ; base 31:24 111 112; linear code segment descriptor 113LINEAR_CODE_SEL equ $-GDT_BASE 114 DW 0xffff ; limit 15:0 115 DW 0 ; base 15:0 116 DB 0 ; base 23:16 117 DB PRESENT_FLAG(1)|DPL(0)|SYSTEM_FLAG(1)|DESC_TYPE(CODE32_TYPE) 118 DB GRANULARITY_FLAG(1)|DEFAULT_SIZE32(1)|CODE64_FLAG(0)|UPPER_LIMIT(0xf) 119 DB 0 ; base 31:24 120 121%ifdef ARCH_X64 122; linear code (64-bit) segment descriptor 123LINEAR_CODE64_SEL equ $-GDT_BASE 124 DW 0xffff ; limit 15:0 125 DW 0 ; base 15:0 126 DB 0 ; base 23:16 127 DB PRESENT_FLAG(1)|DPL(0)|SYSTEM_FLAG(1)|DESC_TYPE(CODE64_TYPE) 128 DB GRANULARITY_FLAG(1)|DEFAULT_SIZE32(0)|CODE64_FLAG(1)|UPPER_LIMIT(0xf) 129 DB 0 ; base 31:24 130%endif 131 132GDT_END: 133 134