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1 | /** @file\r | |
2 | Real Mode Thunk Functions for IA32 and X64.\r | |
3 | \r | |
4 | Copyright (c) 2006, Intel Corporation<BR>\r | |
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 | |
13 | Module Name: x86Thunk.c\r | |
14 | \r | |
15 | **/\r | |
16 | \r | |
17 | //\r | |
18 | // Include common header file for this module.\r | |
19 | //\r | |
20 | #include <BaseLibInternals.h>\r | |
21 | \r | |
22 | \r | |
23 | //\r | |
24 | // Byte packed structure for a segment descriptor in a GDT/LDT\r | |
25 | //\r | |
26 | typedef union {\r | |
27 | struct {\r | |
28 | UINT32 LimitLow:16;\r | |
29 | UINT32 BaseLow:16;\r | |
30 | UINT32 BaseMid:8;\r | |
31 | UINT32 Type:4;\r | |
32 | UINT32 S:1;\r | |
33 | UINT32 DPL:2;\r | |
34 | UINT32 P:1;\r | |
35 | UINT32 LimitHigh:4;\r | |
36 | UINT32 AVL:1;\r | |
37 | UINT32 L:1;\r | |
38 | UINT32 DB:1;\r | |
39 | UINT32 G:1;\r | |
40 | UINT32 BaseHigh:8;\r | |
41 | } Bits;\r | |
42 | UINT64 Uint64;\r | |
43 | } IA32_SEGMENT_DESCRIPTOR;\r | |
44 | \r | |
45 | extern CONST UINT8 m16Start;\r | |
46 | extern CONST UINT16 m16Size;\r | |
47 | extern CONST UINT16 mThunk16Attr;\r | |
48 | extern CONST UINT16 m16Gdt;\r | |
49 | extern CONST UINT16 m16GdtrBase;\r | |
50 | extern CONST UINT16 mTransition;\r | |
51 | \r | |
52 | /**\r | |
53 | Invokes 16-bit code in big real mode and returns the updated register set.\r | |
54 | \r | |
55 | This function transfers control to the 16-bit code specified by CS:EIP using\r | |
56 | the stack specified by SS:ESP in RegisterSet. The updated registers are saved\r | |
57 | on the real mode stack and the starting address of the save area is returned.\r | |
58 | \r | |
59 | @param RegisterSet Values of registers before invocation of 16-bit code.\r | |
60 | @param Transition Pointer to the transition code under 1MB.\r | |
61 | \r | |
62 | @return The pointer to a IA32_REGISTER_SET structure containing the updated\r | |
63 | register values.\r | |
64 | \r | |
65 | **/\r | |
66 | IA32_REGISTER_SET *\r | |
67 | EFIAPI\r | |
68 | InternalAsmThunk16 (\r | |
69 | IN IA32_REGISTER_SET *RegisterSet,\r | |
70 | IN OUT VOID *Transition\r | |
71 | );\r | |
72 | \r | |
73 | /**\r | |
74 | Retrieves the properties for 16-bit thunk functions.\r | |
75 | \r | |
76 | Computes the size of the buffer and stack below 1MB required to use the\r | |
77 | AsmPrepareThunk16(), AsmThunk16() and AsmPrepareAndThunk16() functions. This\r | |
78 | buffer size is returned in RealModeBufferSize, and the stack size is returned\r | |
79 | in ExtraStackSize. If parameters are passed to the 16-bit real mode code,\r | |
80 | then the actual minimum stack size is ExtraStackSize plus the maximum number\r | |
81 | of bytes that need to be passed to the 16-bit real mode code.\r | |
82 | \r | |
83 | If RealModeBufferSize is NULL, then ASSERT().\r | |
84 | If ExtraStackSize is NULL, then ASSERT().\r | |
85 | \r | |
86 | @param RealModeBufferSize A pointer to the size of the buffer below 1MB\r | |
87 | required to use the 16-bit thunk functions.\r | |
88 | @param ExtraStackSize A pointer to the extra size of stack below 1MB\r | |
89 | that the 16-bit thunk functions require for\r | |
90 | temporary storage in the transition to and from\r | |
91 | 16-bit real mode.\r | |
92 | \r | |
93 | **/\r | |
94 | VOID\r | |
95 | EFIAPI\r | |
96 | AsmGetThunk16Properties (\r | |
97 | OUT UINT32 *RealModeBufferSize,\r | |
98 | OUT UINT32 *ExtraStackSize\r | |
99 | )\r | |
100 | {\r | |
101 | ASSERT (RealModeBufferSize != NULL);\r | |
102 | ASSERT (ExtraStackSize != NULL);\r | |
103 | \r | |
104 | *RealModeBufferSize = m16Size;\r | |
105 | \r | |
106 | //\r | |
107 | // Extra 4 bytes for return address, and another 4 bytes for mode transition\r | |
108 | //\r | |
109 | *ExtraStackSize = sizeof (IA32_DWORD_REGS) + 8;\r | |
110 | }\r | |
111 | \r | |
112 | /**\r | |
113 | Prepares all structures a code required to use AsmThunk16().\r | |
114 | \r | |
115 | Prepares all structures and code required to use AsmThunk16().\r | |
116 | \r | |
117 | If ThunkContext is NULL, then ASSERT().\r | |
118 | \r | |
119 | @param ThunkContext A pointer to the context structure that describes the\r | |
120 | 16-bit real mode code to call.\r | |
121 | \r | |
122 | **/\r | |
123 | VOID\r | |
124 | EFIAPI\r | |
125 | AsmPrepareThunk16 (\r | |
126 | OUT THUNK_CONTEXT *ThunkContext\r | |
127 | )\r | |
128 | {\r | |
129 | IA32_SEGMENT_DESCRIPTOR *RealModeGdt;\r | |
130 | \r | |
131 | ASSERT (ThunkContext != NULL);\r | |
132 | ASSERT ((UINTN)ThunkContext->RealModeBuffer < 0x100000);\r | |
133 | ASSERT (ThunkContext->RealModeBufferSize >= m16Size);\r | |
134 | ASSERT ((UINTN)ThunkContext->RealModeBuffer + m16Size <= 0x100000);\r | |
135 | \r | |
136 | CopyMem (ThunkContext->RealModeBuffer, &m16Start, m16Size);\r | |
137 | \r | |
138 | //\r | |
139 | // Point RealModeGdt to the GDT to be used in transition\r | |
140 | //\r | |
141 | // RealModeGdt[0]: Reserved as NULL descriptor\r | |
142 | // RealModeGdt[1]: Code Segment\r | |
143 | // RealModeGdt[2]: Data Segment\r | |
144 | // RealModeGdt[3]: Call Gate\r | |
145 | //\r | |
146 | RealModeGdt = (IA32_SEGMENT_DESCRIPTOR*)(\r | |
147 | (UINTN)ThunkContext->RealModeBuffer + m16Gdt);\r | |
148 | \r | |
149 | //\r | |
150 | // Update Code & Data Segment Descriptor\r | |
151 | //\r | |
152 | RealModeGdt[1].Bits.BaseLow =\r | |
153 | (UINT32)(UINTN)ThunkContext->RealModeBuffer & ~0xf;\r | |
154 | RealModeGdt[1].Bits.BaseMid =\r | |
155 | (UINT32)(UINTN)ThunkContext->RealModeBuffer >> 16;\r | |
156 | \r | |
157 | //\r | |
158 | // Update transition code entry point offset\r | |
159 | //\r | |
160 | *(UINT32*)((UINTN)ThunkContext->RealModeBuffer + mTransition) +=\r | |
161 | (UINT32)(UINTN)ThunkContext->RealModeBuffer & 0xf;\r | |
162 | \r | |
163 | //\r | |
164 | // Update Segment Limits for both Code and Data Segment Descriptors\r | |
165 | //\r | |
166 | if ((ThunkContext->ThunkAttributes & THUNK_ATTRIBUTE_BIG_REAL_MODE) == 0) {\r | |
167 | //\r | |
168 | // Set segment limits to 64KB\r | |
169 | //\r | |
170 | RealModeGdt[1].Bits.LimitHigh = 0;\r | |
171 | RealModeGdt[1].Bits.G = 0;\r | |
172 | RealModeGdt[2].Bits.LimitHigh = 0;\r | |
173 | RealModeGdt[2].Bits.G = 0;\r | |
174 | }\r | |
175 | \r | |
176 | //\r | |
177 | // Update GDTBASE for this thunk context\r | |
178 | //\r | |
179 | *(VOID**)((UINTN)ThunkContext->RealModeBuffer + m16GdtrBase) = RealModeGdt;\r | |
180 | \r | |
181 | //\r | |
182 | // Update Thunk Attributes\r | |
183 | //\r | |
184 | *(UINT32*)((UINTN)ThunkContext->RealModeBuffer + mThunk16Attr) =\r | |
185 | ThunkContext->ThunkAttributes;\r | |
186 | }\r | |
187 | \r | |
188 | /**\r | |
189 | Transfers control to a 16-bit real mode entry point and returns the results.\r | |
190 | \r | |
191 | Transfers control to a 16-bit real mode entry point and returns the results.\r | |
192 | AsmPrepareThunk16() must be called with ThunkContext before this function is\r | |
193 | used. This function must be called with interrupts disabled.\r | |
194 | \r | |
195 | If ThunkContext is NULL, then ASSERT().\r | |
196 | If AsmPrepareThunk16() was not previously called with ThunkContext, then ASSERT().\r | |
197 | \r | |
198 | @param ThunkContext A pointer to the context structure that describes the\r | |
199 | 16-bit real mode code to call.\r | |
200 | \r | |
201 | **/\r | |
202 | VOID\r | |
203 | EFIAPI\r | |
204 | AsmThunk16 (\r | |
205 | IN OUT THUNK_CONTEXT *ThunkContext\r | |
206 | )\r | |
207 | {\r | |
208 | IA32_REGISTER_SET *UpdatedRegs;\r | |
209 | \r | |
210 | ASSERT (ThunkContext != NULL);\r | |
211 | ASSERT ((UINTN)ThunkContext->RealModeBuffer < 0x100000);\r | |
212 | ASSERT (ThunkContext->RealModeBufferSize >= m16Size);\r | |
213 | ASSERT ((UINTN)ThunkContext->RealModeBuffer + m16Size <= 0x100000);\r | |
214 | \r | |
215 | UpdatedRegs = InternalAsmThunk16 (\r | |
216 | ThunkContext->RealModeState,\r | |
217 | ThunkContext->RealModeBuffer\r | |
218 | );\r | |
219 | \r | |
220 | CopyMem (ThunkContext->RealModeState, UpdatedRegs, sizeof (*UpdatedRegs));\r | |
221 | }\r | |
222 | \r | |
223 | /**\r | |
224 | Prepares all structures and code for a 16-bit real mode thunk, transfers\r | |
225 | control to a 16-bit real mode entry point, and returns the results.\r | |
226 | \r | |
227 | Prepares all structures and code for a 16-bit real mode thunk, transfers\r | |
228 | control to a 16-bit real mode entry point, and returns the results. If the\r | |
229 | caller only need to perform a single 16-bit real mode thunk, then this\r | |
230 | service should be used. If the caller intends to make more than one 16-bit\r | |
231 | real mode thunk, then it is more efficient if AsmPrepareThunk16() is called\r | |
232 | once and AsmThunk16() can be called for each 16-bit real mode thunk. This\r | |
233 | function must be called with interrupts disabled.\r | |
234 | \r | |
235 | If ThunkContext is NULL, then ASSERT().\r | |
236 | \r | |
237 | @param ThunkContext A pointer to the context structure that describes the\r | |
238 | 16-bit real mode code to call.\r | |
239 | \r | |
240 | **/\r | |
241 | VOID\r | |
242 | EFIAPI\r | |
243 | AsmPrepareAndThunk16 (\r | |
244 | IN OUT THUNK_CONTEXT *ThunkContext\r | |
245 | )\r | |
246 | {\r | |
247 | AsmPrepareThunk16 (ThunkContext);\r | |
248 | AsmThunk16 (ThunkContext);\r | |
249 | }\r |