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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 - 2012, Intel Corporation. All rights reserved.<BR>\r |
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5 | This program and the accompanying materials\r |
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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 |
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8 | http://opensource.org/licenses/bsd-license.php.\r |
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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 | extern CONST UINT8 m16Start;\r |
| 19 | extern CONST UINT16 m16Size;\r |
| 20 | extern CONST UINT16 mThunk16Attr;\r |
| 21 | extern CONST UINT16 m16Gdt;\r |
| 22 | extern CONST UINT16 m16GdtrBase;\r |
| 23 | extern CONST UINT16 mTransition;\r |
| 24 | \r |
| 25 | /**\r |
| 26 | Invokes 16-bit code in big real mode and returns the updated register set.\r |
| 27 | \r |
| 28 | This function transfers control to the 16-bit code specified by CS:EIP using\r |
| 29 | the stack specified by SS:ESP in RegisterSet. The updated registers are saved\r |
| 30 | on the real mode stack and the starting address of the save area is returned.\r |
| 31 | \r |
| 32 | @param RegisterSet Values of registers before invocation of 16-bit code.\r |
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33 | @param Transition The pointer to the transition code under 1MB.\r |
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34 | \r |
| 35 | @return The pointer to a IA32_REGISTER_SET structure containing the updated\r |
| 36 | register values.\r |
| 37 | \r |
| 38 | **/\r |
| 39 | IA32_REGISTER_SET *\r |
| 40 | EFIAPI\r |
| 41 | InternalAsmThunk16 (\r |
| 42 | IN IA32_REGISTER_SET *RegisterSet,\r |
| 43 | IN OUT VOID *Transition\r |
| 44 | );\r |
| 45 | \r |
| 46 | /**\r |
| 47 | Retrieves the properties for 16-bit thunk functions.\r |
| 48 | \r |
| 49 | Computes the size of the buffer and stack below 1MB required to use the\r |
| 50 | AsmPrepareThunk16(), AsmThunk16() and AsmPrepareAndThunk16() functions. This\r |
| 51 | buffer size is returned in RealModeBufferSize, and the stack size is returned\r |
| 52 | in ExtraStackSize. If parameters are passed to the 16-bit real mode code,\r |
| 53 | then the actual minimum stack size is ExtraStackSize plus the maximum number\r |
| 54 | of bytes that need to be passed to the 16-bit real mode code.\r |
| 55 | \r |
| 56 | If RealModeBufferSize is NULL, then ASSERT().\r |
| 57 | If ExtraStackSize is NULL, then ASSERT().\r |
| 58 | \r |
| 59 | @param RealModeBufferSize A pointer to the size of the buffer below 1MB\r |
| 60 | required to use the 16-bit thunk functions.\r |
| 61 | @param ExtraStackSize A pointer to the extra size of stack below 1MB\r |
| 62 | that the 16-bit thunk functions require for\r |
| 63 | temporary storage in the transition to and from\r |
| 64 | 16-bit real mode.\r |
| 65 | \r |
| 66 | **/\r |
| 67 | VOID\r |
| 68 | EFIAPI\r |
| 69 | AsmGetThunk16Properties (\r |
| 70 | OUT UINT32 *RealModeBufferSize,\r |
| 71 | OUT UINT32 *ExtraStackSize\r |
| 72 | )\r |
| 73 | {\r |
| 74 | ASSERT (RealModeBufferSize != NULL);\r |
| 75 | ASSERT (ExtraStackSize != NULL);\r |
| 76 | \r |
| 77 | *RealModeBufferSize = m16Size;\r |
| 78 | \r |
| 79 | //\r |
| 80 | // Extra 4 bytes for return address, and another 4 bytes for mode transition\r |
| 81 | //\r |
| 82 | *ExtraStackSize = sizeof (IA32_DWORD_REGS) + 8;\r |
| 83 | }\r |
| 84 | \r |
| 85 | /**\r |
| 86 | Prepares all structures a code required to use AsmThunk16().\r |
| 87 | \r |
| 88 | Prepares all structures and code required to use AsmThunk16().\r |
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89 | \r |
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90 | This interface is limited to be used in either physical mode or virtual modes with paging enabled where the\r |
| 91 | virtual to physical mappings for ThunkContext.RealModeBuffer is mapped 1:1.\r |
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92 | \r |
| 93 | If ThunkContext is NULL, then ASSERT().\r |
| 94 | \r |
| 95 | @param ThunkContext A pointer to the context structure that describes the\r |
| 96 | 16-bit real mode code to call.\r |
| 97 | \r |
| 98 | **/\r |
| 99 | VOID\r |
| 100 | EFIAPI\r |
| 101 | AsmPrepareThunk16 (\r |
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102 | IN OUT THUNK_CONTEXT *ThunkContext\r |
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103 | )\r |
| 104 | {\r |
| 105 | IA32_SEGMENT_DESCRIPTOR *RealModeGdt;\r |
| 106 | \r |
| 107 | ASSERT (ThunkContext != NULL);\r |
| 108 | ASSERT ((UINTN)ThunkContext->RealModeBuffer < 0x100000);\r |
| 109 | ASSERT (ThunkContext->RealModeBufferSize >= m16Size);\r |
| 110 | ASSERT ((UINTN)ThunkContext->RealModeBuffer + m16Size <= 0x100000);\r |
| 111 | \r |
| 112 | CopyMem (ThunkContext->RealModeBuffer, &m16Start, m16Size);\r |
| 113 | \r |
| 114 | //\r |
| 115 | // Point RealModeGdt to the GDT to be used in transition\r |
| 116 | //\r |
| 117 | // RealModeGdt[0]: Reserved as NULL descriptor\r |
| 118 | // RealModeGdt[1]: Code Segment\r |
| 119 | // RealModeGdt[2]: Data Segment\r |
| 120 | // RealModeGdt[3]: Call Gate\r |
| 121 | //\r |
| 122 | RealModeGdt = (IA32_SEGMENT_DESCRIPTOR*)(\r |
| 123 | (UINTN)ThunkContext->RealModeBuffer + m16Gdt);\r |
| 124 | \r |
| 125 | //\r |
| 126 | // Update Code & Data Segment Descriptor\r |
| 127 | //\r |
| 128 | RealModeGdt[1].Bits.BaseLow =\r |
| 129 | (UINT32)(UINTN)ThunkContext->RealModeBuffer & ~0xf;\r |
| 130 | RealModeGdt[1].Bits.BaseMid =\r |
| 131 | (UINT32)(UINTN)ThunkContext->RealModeBuffer >> 16;\r |
| 132 | \r |
| 133 | //\r |
| 134 | // Update transition code entry point offset\r |
| 135 | //\r |
| 136 | *(UINT32*)((UINTN)ThunkContext->RealModeBuffer + mTransition) +=\r |
| 137 | (UINT32)(UINTN)ThunkContext->RealModeBuffer & 0xf;\r |
| 138 | \r |
| 139 | //\r |
| 140 | // Update Segment Limits for both Code and Data Segment Descriptors\r |
| 141 | //\r |
| 142 | if ((ThunkContext->ThunkAttributes & THUNK_ATTRIBUTE_BIG_REAL_MODE) == 0) {\r |
| 143 | //\r |
| 144 | // Set segment limits to 64KB\r |
| 145 | //\r |
| 146 | RealModeGdt[1].Bits.LimitHigh = 0;\r |
| 147 | RealModeGdt[1].Bits.G = 0;\r |
| 148 | RealModeGdt[2].Bits.LimitHigh = 0;\r |
| 149 | RealModeGdt[2].Bits.G = 0;\r |
| 150 | }\r |
| 151 | \r |
| 152 | //\r |
| 153 | // Update GDTBASE for this thunk context\r |
| 154 | //\r |
| 155 | *(VOID**)((UINTN)ThunkContext->RealModeBuffer + m16GdtrBase) = RealModeGdt;\r |
| 156 | \r |
| 157 | //\r |
| 158 | // Update Thunk Attributes\r |
| 159 | //\r |
| 160 | *(UINT32*)((UINTN)ThunkContext->RealModeBuffer + mThunk16Attr) =\r |
| 161 | ThunkContext->ThunkAttributes;\r |
| 162 | }\r |
| 163 | \r |
| 164 | /**\r |
| 165 | Transfers control to a 16-bit real mode entry point and returns the results.\r |
| 166 | \r |
| 167 | Transfers control to a 16-bit real mode entry point and returns the results.\r |
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168 | AsmPrepareThunk16() must be called with ThunkContext before this function is used.\r |
| 169 | This function must be called with interrupts disabled.\r |
| 170 | \r |
| 171 | The register state from the RealModeState field of ThunkContext is restored just prior \r |
| 172 | to calling the 16-bit real mode entry point. This includes the EFLAGS field of RealModeState, \r |
| 173 | which is used to set the interrupt state when a 16-bit real mode entry point is called.\r |
| 174 | Control is transferred to the 16-bit real mode entry point specified by the CS and Eip fields of RealModeState.\r |
| 175 | The stack is initialized to the SS and ESP fields of RealModeState. Any parameters passed to \r |
| 176 | the 16-bit real mode code must be populated by the caller at SS:ESP prior to calling this function. \r |
| 177 | The 16-bit real mode entry point is invoked with a 16-bit CALL FAR instruction,\r |
| 178 | so when accessing stack contents, the 16-bit real mode code must account for the 16-bit segment \r |
| 179 | and 16-bit offset of the return address that were pushed onto the stack. The 16-bit real mode entry \r |
| 180 | point must exit with a RETF instruction. The register state is captured into RealModeState immediately \r |
| 181 | after the RETF instruction is executed.\r |
| 182 | \r |
| 183 | If EFLAGS specifies interrupts enabled, or any of the 16-bit real mode code enables interrupts, \r |
| 184 | or any of the 16-bit real mode code makes a SW interrupt, then the caller is responsible for making sure \r |
| 185 | the IDT at address 0 is initialized to handle any HW or SW interrupts that may occur while in 16-bit real mode. \r |
| 186 | \r |
| 187 | If EFLAGS specifies interrupts enabled, or any of the 16-bit real mode code enables interrupts, \r |
| 188 | then the caller is responsible for making sure the 8259 PIC is in a state compatible with 16-bit real mode. \r |
| 189 | This includes the base vectors, the interrupt masks, and the edge/level trigger mode.\r |
| 190 | \r |
| 191 | If THUNK_ATTRIBUTE_BIG_REAL_MODE is set in the ThunkAttributes field of ThunkContext, then the user code \r |
| 192 | is invoked in big real mode. Otherwise, the user code is invoked in 16-bit real mode with 64KB segment limits.\r |
| 193 | \r |
| 194 | If neither THUNK_ATTRIBUTE_DISABLE_A20_MASK_INT_15 nor THUNK_ATTRIBUTE_DISABLE_A20_MASK_KBD_CTRL are set in \r |
| 195 | ThunkAttributes, then it is assumed that the user code did not enable the A20 mask, and no attempt is made to \r |
| 196 | disable the A20 mask.\r |
| 197 | \r |
| 198 | If THUNK_ATTRIBUTE_DISABLE_A20_MASK_INT_15 is set and THUNK_ATTRIBUTE_DISABLE_A20_MASK_KBD_CTRL is clear in \r |
| 199 | ThunkAttributes, then attempt to use the INT 15 service to disable the A20 mask. If this INT 15 call fails, \r |
| 200 | then attempt to disable the A20 mask by directly accessing the 8042 keyboard controller I/O ports.\r |
| 201 | \r |
| 202 | If THUNK_ATTRIBUTE_DISABLE_A20_MASK_INT_15 is clear and THUNK_ATTRIBUTE_DISABLE_A20_MASK_KBD_CTRL is set in \r |
| 203 | ThunkAttributes, then attempt to disable the A20 mask by directly accessing the 8042 keyboard controller I/O ports.\r |
| 204 | \r |
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205 | If ThunkContext is NULL, then ASSERT().\r |
| 206 | If AsmPrepareThunk16() was not previously called with ThunkContext, then ASSERT().\r |
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207 | If both THUNK_ATTRIBUTE_DISABLE_A20_MASK_INT_15 and THUNK_ATTRIBUTE_DISABLE_A20_MASK_KBD_CTRL are set in \r |
| 208 | ThunkAttributes, then ASSERT().\r |
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209 | \r |
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210 | This interface is limited to be used in either physical mode or virtual modes with paging enabled where the\r |
| 211 | virtual to physical mappings for ThunkContext.RealModeBuffer is mapped 1:1.\r |
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212 | \r |
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213 | @param ThunkContext A pointer to the context structure that describes the\r |
| 214 | 16-bit real mode code to call.\r |
| 215 | \r |
| 216 | **/\r |
| 217 | VOID\r |
| 218 | EFIAPI\r |
| 219 | AsmThunk16 (\r |
| 220 | IN OUT THUNK_CONTEXT *ThunkContext\r |
| 221 | )\r |
| 222 | {\r |
| 223 | IA32_REGISTER_SET *UpdatedRegs;\r |
| 224 | \r |
| 225 | ASSERT (ThunkContext != NULL);\r |
| 226 | ASSERT ((UINTN)ThunkContext->RealModeBuffer < 0x100000);\r |
| 227 | ASSERT (ThunkContext->RealModeBufferSize >= m16Size);\r |
| 228 | ASSERT ((UINTN)ThunkContext->RealModeBuffer + m16Size <= 0x100000);\r |
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229 | ASSERT (((ThunkContext->ThunkAttributes & (THUNK_ATTRIBUTE_DISABLE_A20_MASK_INT_15 | THUNK_ATTRIBUTE_DISABLE_A20_MASK_KBD_CTRL)) != \\r |
| 230 | (THUNK_ATTRIBUTE_DISABLE_A20_MASK_INT_15 | THUNK_ATTRIBUTE_DISABLE_A20_MASK_KBD_CTRL)));\r |
| 231 | \r |
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232 | UpdatedRegs = InternalAsmThunk16 (\r |
| 233 | ThunkContext->RealModeState,\r |
| 234 | ThunkContext->RealModeBuffer\r |
| 235 | );\r |
| 236 | \r |
| 237 | CopyMem (ThunkContext->RealModeState, UpdatedRegs, sizeof (*UpdatedRegs));\r |
| 238 | }\r |
| 239 | \r |
| 240 | /**\r |
| 241 | Prepares all structures and code for a 16-bit real mode thunk, transfers\r |
| 242 | control to a 16-bit real mode entry point, and returns the results.\r |
| 243 | \r |
| 244 | Prepares all structures and code for a 16-bit real mode thunk, transfers\r |
| 245 | control to a 16-bit real mode entry point, and returns the results. If the\r |
| 246 | caller only need to perform a single 16-bit real mode thunk, then this\r |
| 247 | service should be used. If the caller intends to make more than one 16-bit\r |
| 248 | real mode thunk, then it is more efficient if AsmPrepareThunk16() is called\r |
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249 | once and AsmThunk16() can be called for each 16-bit real mode thunk.\r |
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250 | \r |
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251 | This interface is limited to be used in either physical mode or virtual modes with paging enabled where the\r |
| 252 | virtual to physical mappings for ThunkContext.RealModeBuffer is mapped 1:1.\r |
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253 | \r |
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254 | See AsmPrepareThunk16() and AsmThunk16() for the detailed description and ASSERT() conditions.\r |
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255 | \r |
| 256 | @param ThunkContext A pointer to the context structure that describes the\r |
| 257 | 16-bit real mode code to call.\r |
| 258 | \r |
| 259 | **/\r |
| 260 | VOID\r |
| 261 | EFIAPI\r |
| 262 | AsmPrepareAndThunk16 (\r |
| 263 | IN OUT THUNK_CONTEXT *ThunkContext\r |
| 264 | )\r |
| 265 | {\r |
| 266 | AsmPrepareThunk16 (ThunkContext);\r |
| 267 | AsmThunk16 (ThunkContext);\r |
| 268 | }\r |
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