projects / mirror_edk2.git / blame
| Commit | Line | Data |
|---|---|---|
| 9da59186 JY |
1 | ;; @file\r |
| 2 | ; This is the code that goes from real-mode to protected mode.\r | |
| 3 | ; It consumes the reset vector, configures the stack.\r | |
| 4 | ;\r | |
| 5 | ; Copyright (c) 2015, Intel Corporation. All rights reserved.<BR>\r | |
| 16a16ea6 | 6 | ; SPDX-License-Identifier: BSD-2-Clause-Patent\r |
| 9da59186 JY |
7 | ;;\r |
| 8 | \r | |
| 9 | ;\r | |
| 10 | ; Define assembler characteristics\r | |
| 11 | ;\r | |
| 12 | .586p\r | |
| 13 | .xmm\r | |
| 14 | .model flat, c\r | |
| 15 | \r | |
| 16 | EXTRN TempRamInitApi:NEAR\r | |
| 17 | EXTRN FspInitApi:NEAR\r | |
| 18 | \r | |
| 19 | ;\r | |
| 20 | ; Contrary to the name, this file contains 16 bit code as well.\r | |
| 21 | ;\r | |
| 22 | _TEXT_REALMODE SEGMENT PARA PUBLIC USE16 'CODE'\r | |
| 23 | ASSUME CS:_TEXT_REALMODE, DS:_TEXT_REALMODE\r | |
| 24 | \r | |
| 25 | ;----------------------------------------------------------------------------\r | |
| 26 | ;\r | |
| 27 | ; Procedure: _ModuleEntryPoint\r | |
| 28 | ;\r | |
| 29 | ; Input: None\r | |
| 30 | ;\r | |
| 31 | ; Output: None\r | |
| 32 | ;\r | |
| 33 | ; Destroys: Assume all registers\r | |
| 34 | ;\r | |
| 35 | ; Description:\r | |
| 36 | ;\r | |
| 37 | ; Transition to non-paged flat-model protected mode from a\r | |
| 38 | ; hard-coded GDT that provides exactly two descriptors.\r | |
| 39 | ; This is a bare bones transition to protected mode only\r | |
| 40 | ; used for a while in PEI and possibly DXE.\r | |
| 41 | ;\r | |
| 42 | ; After enabling protected mode, a far jump is executed to\r | |
| 43 | ; transfer to PEI using the newly loaded GDT.\r | |
| 44 | ;\r | |
| 45 | ; Return: None\r | |
| 46 | ;\r | |
| 47 | ;----------------------------------------------------------------------------\r | |
| 48 | align 16\r | |
| 49 | _ModuleEntryPoint PROC C PUBLIC\r | |
| 50 | ;\r | |
| 51 | ; Load the GDT table in GdtDesc\r | |
| 52 | ;\r | |
| 53 | mov esi, OFFSET GdtDesc\r | |
| 54 | db 66h\r | |
| 55 | lgdt fword ptr cs:[si]\r | |
| 56 | \r | |
| 57 | ;\r | |
| 58 | ; Transition to 16 bit protected mode\r | |
| 59 | ;\r | |
| 60 | mov eax, cr0 ; Get control register 0\r | |
| 61 | or eax, 00000003h ; Set PE bit (bit #0) & MP bit (bit #1)\r | |
| 62 | mov cr0, eax ; Activate protected mode\r | |
| 63 | \r | |
| 64 | ;\r | |
| 65 | ; Now we're in 16 bit protected mode\r | |
| 66 | ; Set up the selectors for 32 bit protected mode entry\r | |
| 67 | ; \r | |
| 68 | mov ax, SYS_DATA_SEL\r | |
| 69 | mov ds, ax\r | |
| 70 | mov es, ax\r | |
| 71 | mov fs, ax\r | |
| 72 | mov gs, ax\r | |
| 73 | mov ss, ax\r | |
| 74 | \r | |
| 75 | ;\r | |
| 76 | ; Transition to Flat 32 bit protected mode\r | |
| 77 | ; The jump to a far pointer causes the transition to 32 bit mode\r | |
| 78 | ;\r | |
| 79 | mov esi, offset ProtectedModeEntryLinearAddress\r | |
| 80 | jmp fword ptr cs:[si]\r | |
| 81 | \r | |
| 82 | _ModuleEntryPoint ENDP\r | |
| 83 | \r | |
| 84 | _TEXT_REALMODE ENDS\r | |
| 85 | \r | |
| 86 | .code \r | |
| 87 | ;\r | |
| 88 | ; Protected mode portion initializes stack, configures cache, and calls C entry point\r | |
| 89 | ;\r | |
| 90 | \r | |
| 91 | ;----------------------------------------------------------------------------\r | |
| 92 | ;\r | |
| 93 | ; Procedure: ProtectedModeEntryPoint\r | |
| 94 | ;\r | |
| 95 | ; Input: Executing in 32 Bit Protected (flat) mode\r | |
| 96 | ; cs: 0-4GB\r | |
| 97 | ; ds: 0-4GB\r | |
| 98 | ; es: 0-4GB\r | |
| 99 | ; fs: 0-4GB\r | |
| 100 | ; gs: 0-4GB\r | |
| 101 | ; ss: 0-4GB\r | |
| 102 | ;\r | |
| 103 | ; Output: This function never returns\r | |
| 104 | ;\r | |
| 105 | ; Destroys:\r | |
| 106 | ; ecx\r | |
| 107 | ; edi\r | |
| 108 | ; esi\r | |
| 109 | ; esp\r | |
| 110 | ;\r | |
| 111 | ; Description:\r | |
| 112 | ; Perform any essential early platform initilaisation\r | |
| 113 | ; Setup a stack\r | |
| 114 | ;\r | |
| 115 | ;----------------------------------------------------------------------------\r | |
| 116 | \r | |
| 117 | ProtectedModeEntryPoint PROC NEAR C PUBLIC\r | |
| 118 | ;\r | |
| 119 | ; Dummy function. Consume 2 API to make sure they can be linked.\r | |
| 120 | ;\r | |
| 121 | mov eax, TempRamInitApi\r | |
| 122 | mov eax, FspInitApi\r | |
| 123 | \r | |
| 124 | ; Should never return\r | |
| 125 | jmp $\r | |
| 126 | \r | |
| 127 | ProtectedModeEntryPoint ENDP\r | |
| 128 | \r | |
| 129 | ;\r | |
| 130 | ; ROM-based Global-Descriptor Table for the PEI Phase\r | |
| 131 | ;\r | |
| 132 | align 16\r | |
| 133 | PUBLIC BootGdtTable\r | |
| 134 | \r | |
| 135 | ;\r | |
| 136 | ; GDT[0]: 0x00: Null entry, never used.\r | |
| 137 | ;\r | |
| 138 | NULL_SEL equ $ - GDT_BASE ; Selector [0]\r | |
| 139 | GDT_BASE:\r | |
| 140 | BootGdtTable DD 0\r | |
| 141 | DD 0\r | |
| 142 | ;\r | |
| 143 | ; Linear code segment descriptor\r | |
| 144 | ;\r | |
| 145 | LINEAR_CODE_SEL equ $ - GDT_BASE ; Selector [0x8]\r | |
| 146 | DW 0FFFFh ; limit 0xFFFF\r | |
| 147 | DW 0 ; base 0\r | |
| 148 | DB 0\r | |
| 149 | DB 09Bh ; present, ring 0, data, expand-up, not-writable\r | |
| 150 | DB 0CFh ; page-granular, 32-bit\r | |
| 151 | DB 0\r | |
| 152 | ;\r | |
| 153 | ; System data segment descriptor\r | |
| 154 | ;\r | |
| 155 | SYS_DATA_SEL equ $ - GDT_BASE ; Selector [0x10]\r | |
| 156 | DW 0FFFFh ; limit 0xFFFF\r | |
| 157 | DW 0 ; base 0\r | |
| 158 | DB 0\r | |
| 159 | DB 093h ; present, ring 0, data, expand-up, not-writable\r | |
| 160 | DB 0CFh ; page-granular, 32-bit\r | |
| 161 | DB 0\r | |
| 162 | \r | |
| 163 | GDT_SIZE EQU $ - BootGDTtable ; Size, in bytes\r | |
| 164 | \r | |
| 165 | ;\r | |
| 166 | ; GDT Descriptor\r | |
| 167 | ;\r | |
| 168 | GdtDesc: ; GDT descriptor\r | |
| 169 | DW GDT_SIZE - 1 ; GDT limit\r | |
| 170 | DD OFFSET BootGdtTable ; GDT base address\r | |
| 171 | \r | |
| 172 | ProtectedModeEntryLinearAddress LABEL FWORD\r | |
| 173 | ProtectedModeEntryLinearOffset LABEL DWORD\r | |
| 174 | DD OFFSET ProtectedModeEntryPoint ; Offset of our 32 bit code\r | |
| 175 | DW LINEAR_CODE_SEL\r | |
| 176 | \r | |
| 177 | END\r |