1 #------------------------------------------------------------------------------ 2 # 3 # Copyright (c) 2015, Intel Corporation. All rights reserved.<BR> 4 # This program and the accompanying materials 5 # are licensed and made available under the terms and conditions of the BSD License 6 # which accompanies this distribution. The full text of the license may be found at 7 # http://opensource.org/licenses/bsd-license.php. 8 # 9 # THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS, 10 # WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED. 11 # 12 # Abstract: 13 # 14 # This is the code that goes from real-mode to protected mode. 15 # It consumes the reset vector, configures the stack. 16 # 17 #------------------------------------------------------------------------------ 18 19 20 # 21 # Contrary to the name, this file contains 16 bit code as well. 22 # 23 .text 24 #---------------------------------------------------------------------------- 25 # 26 # Procedure: _ModuleEntryPoint 27 # 28 # Input: None 29 # 30 # Output: None 31 # 32 # Destroys: Assume all registers 33 # 34 # Description: 35 # 36 # Transition to non-paged flat-model protected mode from a 37 # hard-coded GDT that provides exactly two descriptors. 38 # This is a bare bones transition to protected mode only 39 # used for a while in PEI and possibly DXE. 40 # 41 # After enabling protected mode, a far jump is executed to 42 # transfer to PEI using the newly loaded GDT. 43 # 44 # Return: None 45 # 46 #---------------------------------------------------------------------------- 47 ASM_GLOBAL ASM_PFX(_ModuleEntryPoint) 48 ASM_PFX(_ModuleEntryPoint): 49 50 # 51 # Load the GDT table in GdtDesc 52 # 53 .byte 0x66,0xbe #movl $GdtDesc, %esi 54 .long GdtDesc 55 56 .byte 0x66,0x2e,0x0f,0x01,0x14 #lgdt %cs:(%si) 57 58 # 59 # Transition to 16 bit protected mode 60 # 61 .byte 0x0f,0x20,0xc0 #movl %cr0, %eax # Get control register 0 62 .byte 0x66,0x83,0xc8,0x03 #orl $0x0000003, %eax # Set PE bit (bit #0) & MP bit (bit #1) 63 .byte 0x0f,0x22,0xc0 #movl %eax, %cr0 # Activate protected mode 64 65 # 66 # Now we're in 16 bit protected mode 67 # Set up the selectors for 32 bit protected mode entry 68 # 69 .byte 0xb8 #movw SYS_DATA_SEL, %ax 70 .word SYS_DATA_SEL 71 72 .byte 0x8e,0xd8 #movw %ax, %ds 73 .byte 0x8e,0xc0 #movw %ax, %es 74 .byte 0x8e,0xe0 #movw %ax, %fs 75 .byte 0x8e,0xe8 #movw %ax, %gs 76 .byte 0x8e,0xd0 #movw %ax, %ss 77 78 # 79 # Transition to Flat 32 bit protected mode 80 # The jump to a far pointer causes the transition to 32 bit mode 81 # 82 .byte 0x66,0xbe #movl ProtectedModeEntryLinearAddress, %esi 83 .long ProtectedModeEntryLinearAddress 84 .byte 0x66,0x2e,0xff,0x2c #jmp %cs:(%esi) 85 86 # 87 # Protected mode portion initializes stack, configures cache, and calls C entry point 88 # 89 90 #---------------------------------------------------------------------------- 91 # 92 # Procedure: ProtectedModeEntryPoint 93 # 94 # Input: Executing in 32 Bit Protected (flat) mode 95 # cs: 0-4GB 96 # ds: 0-4GB 97 # es: 0-4GB 98 # fs: 0-4GB 99 # gs: 0-4GB 100 # ss: 0-4GB 101 # 102 # Output: This function never returns 103 # 104 # Destroys: 105 # ecx 106 # edi 107 # esi 108 # esp 109 # 110 # Description: 111 # Perform any essential early platform initilaisation 112 # Setup a stack 113 # 114 #---------------------------------------------------------------------------- 115 ProtectedModeEntryPoint: 116 # 117 # Dummy function. Consume 2 API to make sure they can be linked. 118 # 119 movl ASM_PFX(TempRamInitApi), %eax 120 movl ASM_PFX(FspInitApi), %eax 121 # 122 # Should never return 123 # 124 jmp . #'$' 125 126 # 127 # ROM-based Global-Descriptor Table for the PEI Phase 128 # 129 .align 16 130 # 131 # GDT[0]: 000h: Null entry, never used. 132 # 133 .equ NULL_SEL, . - GDT_BASE # Selector [0] 134 GDT_BASE: 135 BootGdtTable: 136 .long 0 137 .long 0 138 # 139 # Linear code segment descriptor 140 # 141 .equ LINEAR_CODE_SEL, . - GDT_BASE # Selector [08h] 142 .word 0xFFFF # limit 0FFFFh 143 .word 0 # base 0 144 .byte 0 145 .byte 0x9B # present, ring 0, data, expand-up, not-writable 146 .byte 0xCF # page-granular, 32-bit 147 .byte 0 148 # 149 # System data segment descriptor 150 # 151 .equ SYS_DATA_SEL, . - GDT_BASE # Selector [010h] 152 .word 0xFFFF # limit 0FFFFh 153 .word 0 # base 0 154 .byte 0 155 .byte 0x93 # present, ring 0, data, expand-up, not-writable 156 .byte 0xCF # page-granular, 32-bit 157 .byte 0 158 159 .equ GDT_SIZE, . - BootGdtTable # Size, in bytes 160 161 # 162 # GDT Descriptor 163 # 164 GdtDesc: # GDT descriptor 165 .word GDT_SIZE - 1 166 .long BootGdtTable 167 168 ProtectedModeEntryLinearAddress: 169 ProtectedModeEntryLinearOffset: 170 .long ProtectedModeEntryPoint 171 .word LINEAR_CODE_SEL 172
