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1 | /** @file\r |
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2 | Real Mode Thunk Functions for IA32 and x64.\r |
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3 | \r |
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4 | Copyright (c) 2006 - 2008, Intel Corporation<BR>\r |
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5 | All rights reserved. This program and the accompanying materials\r |
| 6 | are licensed and made available under the terms and conditions of the BSD License\r |
| 7 | which accompanies this distribution. The full text of the license may be found at\r |
| 8 | http://opensource.org/licenses/bsd-license.php\r |
| 9 | \r |
| 10 | THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,\r |
| 11 | WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.\r |
| 12 | \r |
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13 | **/\r |
| 14 | \r |
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15 | \r |
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16 | #include "BaseLibInternals.h"\r |
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17 | \r |
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18 | \r |
| 19 | //\r |
| 20 | // Byte packed structure for a segment descriptor in a GDT/LDT\r |
| 21 | //\r |
| 22 | typedef union {\r |
| 23 | struct {\r |
| 24 | UINT32 LimitLow:16;\r |
| 25 | UINT32 BaseLow:16;\r |
| 26 | UINT32 BaseMid:8;\r |
| 27 | UINT32 Type:4;\r |
| 28 | UINT32 S:1;\r |
| 29 | UINT32 DPL:2;\r |
| 30 | UINT32 P:1;\r |
| 31 | UINT32 LimitHigh:4;\r |
| 32 | UINT32 AVL:1;\r |
| 33 | UINT32 L:1;\r |
| 34 | UINT32 DB:1;\r |
| 35 | UINT32 G:1;\r |
| 36 | UINT32 BaseHigh:8;\r |
| 37 | } Bits;\r |
| 38 | UINT64 Uint64;\r |
| 39 | } IA32_SEGMENT_DESCRIPTOR;\r |
| 40 | \r |
| 41 | extern CONST UINT8 m16Start;\r |
| 42 | extern CONST UINT16 m16Size;\r |
| 43 | extern CONST UINT16 mThunk16Attr;\r |
| 44 | extern CONST UINT16 m16Gdt;\r |
| 45 | extern CONST UINT16 m16GdtrBase;\r |
| 46 | extern CONST UINT16 mTransition;\r |
| 47 | \r |
| 48 | /**\r |
| 49 | Invokes 16-bit code in big real mode and returns the updated register set.\r |
| 50 | \r |
| 51 | This function transfers control to the 16-bit code specified by CS:EIP using\r |
| 52 | the stack specified by SS:ESP in RegisterSet. The updated registers are saved\r |
| 53 | on the real mode stack and the starting address of the save area is returned.\r |
| 54 | \r |
| 55 | @param RegisterSet Values of registers before invocation of 16-bit code.\r |
| 56 | @param Transition Pointer to the transition code under 1MB.\r |
| 57 | \r |
| 58 | @return The pointer to a IA32_REGISTER_SET structure containing the updated\r |
| 59 | register values.\r |
| 60 | \r |
| 61 | **/\r |
| 62 | IA32_REGISTER_SET *\r |
| 63 | EFIAPI\r |
| 64 | InternalAsmThunk16 (\r |
| 65 | IN IA32_REGISTER_SET *RegisterSet,\r |
| 66 | IN OUT VOID *Transition\r |
| 67 | );\r |
| 68 | \r |
| 69 | /**\r |
| 70 | Retrieves the properties for 16-bit thunk functions.\r |
| 71 | \r |
| 72 | Computes the size of the buffer and stack below 1MB required to use the\r |
| 73 | AsmPrepareThunk16(), AsmThunk16() and AsmPrepareAndThunk16() functions. This\r |
| 74 | buffer size is returned in RealModeBufferSize, and the stack size is returned\r |
| 75 | in ExtraStackSize. If parameters are passed to the 16-bit real mode code,\r |
| 76 | then the actual minimum stack size is ExtraStackSize plus the maximum number\r |
| 77 | of bytes that need to be passed to the 16-bit real mode code.\r |
| 78 | \r |
| 79 | If RealModeBufferSize is NULL, then ASSERT().\r |
| 80 | If ExtraStackSize is NULL, then ASSERT().\r |
| 81 | \r |
| 82 | @param RealModeBufferSize A pointer to the size of the buffer below 1MB\r |
| 83 | required to use the 16-bit thunk functions.\r |
| 84 | @param ExtraStackSize A pointer to the extra size of stack below 1MB\r |
| 85 | that the 16-bit thunk functions require for\r |
| 86 | temporary storage in the transition to and from\r |
| 87 | 16-bit real mode.\r |
| 88 | \r |
| 89 | **/\r |
| 90 | VOID\r |
| 91 | EFIAPI\r |
| 92 | AsmGetThunk16Properties (\r |
| 93 | OUT UINT32 *RealModeBufferSize,\r |
| 94 | OUT UINT32 *ExtraStackSize\r |
| 95 | )\r |
| 96 | {\r |
| 97 | ASSERT (RealModeBufferSize != NULL);\r |
| 98 | ASSERT (ExtraStackSize != NULL);\r |
| 99 | \r |
| 100 | *RealModeBufferSize = m16Size;\r |
| 101 | \r |
| 102 | //\r |
| 103 | // Extra 4 bytes for return address, and another 4 bytes for mode transition\r |
| 104 | //\r |
| 105 | *ExtraStackSize = sizeof (IA32_DWORD_REGS) + 8;\r |
| 106 | }\r |
| 107 | \r |
| 108 | /**\r |
| 109 | Prepares all structures a code required to use AsmThunk16().\r |
| 110 | \r |
| 111 | Prepares all structures and code required to use AsmThunk16().\r |
| 112 | \r |
| 113 | If ThunkContext is NULL, then ASSERT().\r |
| 114 | \r |
| 115 | @param ThunkContext A pointer to the context structure that describes the\r |
| 116 | 16-bit real mode code to call.\r |
| 117 | \r |
| 118 | **/\r |
| 119 | VOID\r |
| 120 | EFIAPI\r |
| 121 | AsmPrepareThunk16 (\r |
| 122 | OUT THUNK_CONTEXT *ThunkContext\r |
| 123 | )\r |
| 124 | {\r |
| 125 | IA32_SEGMENT_DESCRIPTOR *RealModeGdt;\r |
| 126 | \r |
| 127 | ASSERT (ThunkContext != NULL);\r |
| 128 | ASSERT ((UINTN)ThunkContext->RealModeBuffer < 0x100000);\r |
| 129 | ASSERT (ThunkContext->RealModeBufferSize >= m16Size);\r |
| 130 | ASSERT ((UINTN)ThunkContext->RealModeBuffer + m16Size <= 0x100000);\r |
| 131 | \r |
| 132 | CopyMem (ThunkContext->RealModeBuffer, &m16Start, m16Size);\r |
| 133 | \r |
| 134 | //\r |
| 135 | // Point RealModeGdt to the GDT to be used in transition\r |
| 136 | //\r |
| 137 | // RealModeGdt[0]: Reserved as NULL descriptor\r |
| 138 | // RealModeGdt[1]: Code Segment\r |
| 139 | // RealModeGdt[2]: Data Segment\r |
| 140 | // RealModeGdt[3]: Call Gate\r |
| 141 | //\r |
| 142 | RealModeGdt = (IA32_SEGMENT_DESCRIPTOR*)(\r |
| 143 | (UINTN)ThunkContext->RealModeBuffer + m16Gdt);\r |
| 144 | \r |
| 145 | //\r |
| 146 | // Update Code & Data Segment Descriptor\r |
| 147 | //\r |
| 148 | RealModeGdt[1].Bits.BaseLow =\r |
| 149 | (UINT32)(UINTN)ThunkContext->RealModeBuffer & ~0xf;\r |
| 150 | RealModeGdt[1].Bits.BaseMid =\r |
| 151 | (UINT32)(UINTN)ThunkContext->RealModeBuffer >> 16;\r |
| 152 | \r |
| 153 | //\r |
| 154 | // Update transition code entry point offset\r |
| 155 | //\r |
| 156 | *(UINT32*)((UINTN)ThunkContext->RealModeBuffer + mTransition) +=\r |
| 157 | (UINT32)(UINTN)ThunkContext->RealModeBuffer & 0xf;\r |
| 158 | \r |
| 159 | //\r |
| 160 | // Update Segment Limits for both Code and Data Segment Descriptors\r |
| 161 | //\r |
| 162 | if ((ThunkContext->ThunkAttributes & THUNK_ATTRIBUTE_BIG_REAL_MODE) == 0) {\r |
| 163 | //\r |
| 164 | // Set segment limits to 64KB\r |
| 165 | //\r |
| 166 | RealModeGdt[1].Bits.LimitHigh = 0;\r |
| 167 | RealModeGdt[1].Bits.G = 0;\r |
| 168 | RealModeGdt[2].Bits.LimitHigh = 0;\r |
| 169 | RealModeGdt[2].Bits.G = 0;\r |
| 170 | }\r |
| 171 | \r |
| 172 | //\r |
| 173 | // Update GDTBASE for this thunk context\r |
| 174 | //\r |
| 175 | *(VOID**)((UINTN)ThunkContext->RealModeBuffer + m16GdtrBase) = RealModeGdt;\r |
| 176 | \r |
| 177 | //\r |
| 178 | // Update Thunk Attributes\r |
| 179 | //\r |
| 180 | *(UINT32*)((UINTN)ThunkContext->RealModeBuffer + mThunk16Attr) =\r |
| 181 | ThunkContext->ThunkAttributes;\r |
| 182 | }\r |
| 183 | \r |
| 184 | /**\r |
| 185 | Transfers control to a 16-bit real mode entry point and returns the results.\r |
| 186 | \r |
| 187 | Transfers control to a 16-bit real mode entry point and returns the results.\r |
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188 | AsmPrepareThunk16() must be called with ThunkContext before this function is used.\r |
| 189 | This function must be called with interrupts disabled.\r |
| 190 | \r |
| 191 | The register state from the RealModeState field of ThunkContext is restored just prior \r |
| 192 | to calling the 16-bit real mode entry point. This includes the EFLAGS field of RealModeState, \r |
| 193 | which is used to set the interrupt state when a 16-bit real mode entry point is called.\r |
| 194 | Control is transferred to the 16-bit real mode entry point specified by the CS and Eip fields of RealModeState.\r |
| 195 | The stack is initialized to the SS and ESP fields of RealModeState. Any parameters passed to \r |
| 196 | the 16-bit real mode code must be populated by the caller at SS:ESP prior to calling this function. \r |
| 197 | The 16-bit real mode entry point is invoked with a 16-bit CALL FAR instruction,\r |
| 198 | so when accessing stack contents, the 16-bit real mode code must account for the 16-bit segment \r |
| 199 | and 16-bit offset of the return address that were pushed onto the stack. The 16-bit real mode entry \r |
| 200 | point must exit with a RETF instruction. The register state is captured into RealModeState immediately \r |
| 201 | after the RETF instruction is executed.\r |
| 202 | \r |
| 203 | If EFLAGS specifies interrupts enabled, or any of the 16-bit real mode code enables interrupts, \r |
| 204 | or any of the 16-bit real mode code makes a SW interrupt, then the caller is responsible for making sure \r |
| 205 | the IDT at address 0 is initialized to handle any HW or SW interrupts that may occur while in 16-bit real mode. \r |
| 206 | \r |
| 207 | If EFLAGS specifies interrupts enabled, or any of the 16-bit real mode code enables interrupts, \r |
| 208 | then the caller is responsible for making sure the 8259 PIC is in a state compatible with 16-bit real mode. \r |
| 209 | This includes the base vectors, the interrupt masks, and the edge/level trigger mode.\r |
| 210 | \r |
| 211 | If THUNK_ATTRIBUTE_BIG_REAL_MODE is set in the ThunkAttributes field of ThunkContext, then the user code \r |
| 212 | is invoked in big real mode. Otherwise, the user code is invoked in 16-bit real mode with 64KB segment limits.\r |
| 213 | \r |
| 214 | If neither THUNK_ATTRIBUTE_DISABLE_A20_MASK_INT_15 nor THUNK_ATTRIBUTE_DISABLE_A20_MASK_KBD_CTRL are set in \r |
| 215 | ThunkAttributes, then it is assumed that the user code did not enable the A20 mask, and no attempt is made to \r |
| 216 | disable the A20 mask.\r |
| 217 | \r |
| 218 | If THUNK_ATTRIBUTE_DISABLE_A20_MASK_INT_15 is set and THUNK_ATTRIBUTE_DISABLE_A20_MASK_KBD_CTRL is clear in \r |
| 219 | ThunkAttributes, then attempt to use the INT 15 service to disable the A20 mask. If this INT 15 call fails, \r |
| 220 | then attempt to disable the A20 mask by directly accessing the 8042 keyboard controller I/O ports.\r |
| 221 | \r |
| 222 | If THUNK_ATTRIBUTE_DISABLE_A20_MASK_INT_15 is clear and THUNK_ATTRIBUTE_DISABLE_A20_MASK_KBD_CTRL is set in \r |
| 223 | ThunkAttributes, then attempt to disable the A20 mask by directly accessing the 8042 keyboard controller I/O ports.\r |
| 224 | \r |
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225 | If ThunkContext is NULL, then ASSERT().\r |
| 226 | If AsmPrepareThunk16() was not previously called with ThunkContext, then ASSERT().\r |
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227 | If both THUNK_ATTRIBUTE_DISABLE_A20_MASK_INT_15 and THUNK_ATTRIBUTE_DISABLE_A20_MASK_KBD_CTRL are set in \r |
| 228 | ThunkAttributes, then ASSERT().\r |
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229 | \r |
| 230 | @param ThunkContext A pointer to the context structure that describes the\r |
| 231 | 16-bit real mode code to call.\r |
| 232 | \r |
| 233 | **/\r |
| 234 | VOID\r |
| 235 | EFIAPI\r |
| 236 | AsmThunk16 (\r |
| 237 | IN OUT THUNK_CONTEXT *ThunkContext\r |
| 238 | )\r |
| 239 | {\r |
| 240 | IA32_REGISTER_SET *UpdatedRegs;\r |
| 241 | \r |
| 242 | ASSERT (ThunkContext != NULL);\r |
| 243 | ASSERT ((UINTN)ThunkContext->RealModeBuffer < 0x100000);\r |
| 244 | ASSERT (ThunkContext->RealModeBufferSize >= m16Size);\r |
| 245 | ASSERT ((UINTN)ThunkContext->RealModeBuffer + m16Size <= 0x100000);\r |
| 246 | \r |
| 247 | UpdatedRegs = InternalAsmThunk16 (\r |
| 248 | ThunkContext->RealModeState,\r |
| 249 | ThunkContext->RealModeBuffer\r |
| 250 | );\r |
| 251 | \r |
| 252 | CopyMem (ThunkContext->RealModeState, UpdatedRegs, sizeof (*UpdatedRegs));\r |
| 253 | }\r |
| 254 | \r |
| 255 | /**\r |
| 256 | Prepares all structures and code for a 16-bit real mode thunk, transfers\r |
| 257 | control to a 16-bit real mode entry point, and returns the results.\r |
| 258 | \r |
| 259 | Prepares all structures and code for a 16-bit real mode thunk, transfers\r |
| 260 | control to a 16-bit real mode entry point, and returns the results. If the\r |
| 261 | caller only need to perform a single 16-bit real mode thunk, then this\r |
| 262 | service should be used. If the caller intends to make more than one 16-bit\r |
| 263 | real mode thunk, then it is more efficient if AsmPrepareThunk16() is called\r |
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264 | once and AsmThunk16() can be called for each 16-bit real mode thunk.\r |
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265 | \r |
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266 | See AsmPrepareThunk16() and AsmThunk16() for the detailed description and ASSERT() conditions.\r |
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267 | \r |
| 268 | @param ThunkContext A pointer to the context structure that describes the\r |
| 269 | 16-bit real mode code to call.\r |
| 270 | \r |
| 271 | **/\r |
| 272 | VOID\r |
| 273 | EFIAPI\r |
| 274 | AsmPrepareAndThunk16 (\r |
| 275 | IN OUT THUNK_CONTEXT *ThunkContext\r |
| 276 | )\r |
| 277 | {\r |
| 278 | AsmPrepareThunk16 (ThunkContext);\r |
| 279 | AsmThunk16 (ThunkContext);\r |
| 280 | }\r |
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