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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 |
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17 | //\r |
18 | // Byte packed structure for a segment descriptor in a GDT/LDT\r |
19 | //\r |
20 | typedef union {\r |
21 | struct {\r |
22 | UINT32 LimitLow:16;\r |
23 | UINT32 BaseLow:16;\r |
24 | UINT32 BaseMid:8;\r |
25 | UINT32 Type:4;\r |
26 | UINT32 S:1;\r |
27 | UINT32 DPL:2;\r |
28 | UINT32 P:1;\r |
29 | UINT32 LimitHigh:4;\r |
30 | UINT32 AVL:1;\r |
31 | UINT32 L:1;\r |
32 | UINT32 DB:1;\r |
33 | UINT32 G:1;\r |
34 | UINT32 BaseHigh:8;\r |
35 | } Bits;\r |
36 | UINT64 Uint64;\r |
37 | } IA32_SEGMENT_DESCRIPTOR;\r |
38 | \r |
39 | extern CONST UINT8 m16Start;\r |
40 | extern CONST UINT16 m16Size;\r |
41 | extern CONST UINT16 mThunk16Attr;\r |
42 | extern CONST UINT16 m16Gdt;\r |
43 | extern CONST UINT16 m16GdtrBase;\r |
44 | extern CONST UINT16 mTransition;\r |
45 | \r |
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46 | /**\r |
47 | Invokes 16-bit code in big real mode and returns the updated register set.\r |
48 | \r |
49 | This function transfers control to the 16-bit code specified by CS:EIP using\r |
50 | the stack specified by SS:ESP in RegisterSet. The updated registers are saved\r |
51 | on the real mode stack and the starting address of the save area is returned.\r |
52 | \r |
53 | @param RegisterSet Values of registers before invocation of 16-bit code.\r |
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54 | @param Transition Pointer to the transition code under 1MB.\r |
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55 | \r |
56 | @return The pointer to a IA32_REGISTER_SET structure containing the updated\r |
57 | register values.\r |
58 | \r |
59 | **/\r |
60 | IA32_REGISTER_SET *\r |
61 | InternalAsmThunk16 (\r |
62 | IN IA32_REGISTER_SET *RegisterSet,\r |
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63 | IN OUT VOID *Transition\r |
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64 | );\r |
65 | \r |
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66 | /**\r |
67 | Retrieves the properties for 16-bit thunk functions.\r |
68 | \r |
69 | Computes the size of the buffer and stack below 1MB required to use the\r |
70 | AsmPrepareThunk16(), AsmThunk16() and AsmPrepareAndThunk16() functions. This\r |
71 | buffer size is returned in RealModeBufferSize, and the stack size is returned\r |
72 | in ExtraStackSize. If parameters are passed to the 16-bit real mode code,\r |
73 | then the actual minimum stack size is ExtraStackSize plus the maximum number\r |
74 | of bytes that need to be passed to the 16-bit real mode code.\r |
75 | \r |
76 | If RealModeBufferSize is NULL, then ASSERT().\r |
77 | If ExtraStackSize is NULL, then ASSERT().\r |
78 | \r |
79 | @param RealModeBufferSize A pointer to the size of the buffer below 1MB\r |
80 | required to use the 16-bit thunk functions.\r |
81 | @param ExtraStackSize A pointer to the extra size of stack below 1MB\r |
82 | that the 16-bit thunk functions require for\r |
83 | temporary storage in the transition to and from\r |
84 | 16-bit real mode.\r |
85 | \r |
86 | **/\r |
87 | VOID\r |
88 | EFIAPI\r |
89 | AsmGetThunk16Properties (\r |
90 | OUT UINT32 *RealModeBufferSize,\r |
91 | OUT UINT32 *ExtraStackSize\r |
92 | )\r |
93 | {\r |
94 | ASSERT (RealModeBufferSize != NULL);\r |
95 | ASSERT (ExtraStackSize != NULL);\r |
96 | \r |
97 | *RealModeBufferSize = m16Size;\r |
98 | *ExtraStackSize = sizeof (IA32_DWORD_REGS) + 8;\r |
99 | }\r |
100 | \r |
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101 | /**\r |
102 | Prepares all structures a code required to use AsmThunk16().\r |
103 | \r |
104 | Prepares all structures and code required to use AsmThunk16().\r |
105 | \r |
106 | If ThunkContext is NULL, then ASSERT().\r |
107 | \r |
108 | @param ThunkContext A pointer to the context structure that describes the\r |
109 | 16-bit real mode code to call.\r |
110 | \r |
111 | **/\r |
112 | VOID\r |
113 | EFIAPI\r |
114 | AsmPrepareThunk16 (\r |
115 | OUT THUNK_CONTEXT *ThunkContext\r |
116 | )\r |
117 | {\r |
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118 | IA32_SEGMENT_DESCRIPTOR *RealModeGdt;\r |
119 | \r |
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120 | ASSERT (ThunkContext != NULL);\r |
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121 | ASSERT ((UINTN)ThunkContext->RealModeBuffer < 0x100000);\r |
122 | ASSERT (ThunkContext->RealModeBufferSize >= m16Size);\r |
123 | ASSERT ((UINTN)ThunkContext->RealModeBuffer + m16Size <= 0x100000);\r |
124 | ASSERT (((UINTN)ThunkContext->RealModeBuffer & 0x0f) == 0);\r |
125 | \r |
126 | CopyMem (ThunkContext->RealModeBuffer, &m16Start, m16Size);\r |
127 | \r |
128 | //\r |
129 | // Point RealModeGdt to the GDT to be used in transition\r |
130 | //\r |
131 | // RealModeGdt[0]: Reserved as NULL descriptor\r |
132 | // RealModeGdt[1]: Code Segment\r |
133 | // RealModeGdt[2]: Data Segment\r |
134 | // RealModeGdt[3]: Call Gate\r |
135 | //\r |
136 | RealModeGdt = (IA32_SEGMENT_DESCRIPTOR*)(\r |
137 | (UINTN)ThunkContext->RealModeBuffer + m16Gdt);\r |
138 | \r |
139 | //\r |
140 | // Update Code & Data Segment Descriptor\r |
141 | //\r |
142 | RealModeGdt[1].Bits.BaseLow =\r |
143 | (UINT32)(UINTN)ThunkContext->RealModeBuffer & ~0xf;\r |
144 | RealModeGdt[1].Bits.BaseMid =\r |
145 | (UINT32)(UINTN)ThunkContext->RealModeBuffer >> 16;\r |
146 | \r |
147 | //\r |
148 | // Update transition code entry point offset\r |
149 | //\r |
150 | *(UINT32*)((UINTN)ThunkContext->RealModeBuffer + mTransition) +=\r |
151 | (UINT32)(UINTN)ThunkContext->RealModeBuffer & 0xf;\r |
152 | \r |
153 | //\r |
154 | // Update Segment Limits for both Code and Data Segment Descriptors\r |
155 | //\r |
156 | if ((ThunkContext->ThunkAttributes & THUNK_ATTRIBUTE_BIG_REAL_MODE) == 0) {\r |
157 | //\r |
158 | // Set segment limits to 64KB\r |
159 | //\r |
160 | RealModeGdt[1].Bits.LimitHigh = 0;\r |
161 | RealModeGdt[1].Bits.G = 0;\r |
162 | RealModeGdt[2].Bits.LimitHigh = 0;\r |
163 | RealModeGdt[2].Bits.G = 0;\r |
164 | }\r |
165 | \r |
166 | //\r |
167 | // Update GDTBASE for this thunk context\r |
168 | //\r |
169 | *(VOID**)((UINTN)ThunkContext->RealModeBuffer + m16GdtrBase) = RealModeGdt;\r |
170 | \r |
171 | //\r |
172 | // Update Thunk Attributes\r |
173 | //\r |
174 | *(UINT32*)((UINTN)ThunkContext->RealModeBuffer + mThunk16Attr) =\r |
175 | ThunkContext->ThunkAttributes;\r |
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176 | }\r |
177 | \r |
178 | /**\r |
179 | Transfers control to a 16-bit real mode entry point and returns the results.\r |
180 | \r |
181 | Transfers control to a 16-bit real mode entry point and returns the results.\r |
182 | AsmPrepareThunk16() must be called with ThunkContext before this function is\r |
183 | used. This function must be called with interrupts disabled.\r |
184 | \r |
185 | If ThunkContext is NULL, then ASSERT().\r |
186 | If AsmPrepareThunk16() was not previously called with ThunkContext, then ASSERT().\r |
187 | \r |
188 | @param ThunkContext A pointer to the context structure that describes the\r |
189 | 16-bit real mode code to call.\r |
190 | \r |
191 | **/\r |
192 | VOID\r |
193 | EFIAPI\r |
194 | AsmThunk16 (\r |
195 | IN OUT THUNK_CONTEXT *ThunkContext\r |
196 | )\r |
197 | {\r |
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198 | IA32_REGISTER_SET *UpdatedRegs;\r |
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199 | \r |
200 | ASSERT (ThunkContext != NULL);\r |
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201 | ASSERT ((UINTN)ThunkContext->RealModeBuffer < 0x100000);\r |
202 | ASSERT (ThunkContext->RealModeBufferSize >= m16Size);\r |
203 | ASSERT ((UINTN)ThunkContext->RealModeBuffer + m16Size <= 0x100000);\r |
204 | ASSERT (((UINTN)ThunkContext->RealModeBuffer & 0x0f) == 0);\r |
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205 | \r |
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206 | UpdatedRegs = InternalAsmThunk16 (\r |
207 | ThunkContext->RealModeState,\r |
208 | ThunkContext->RealModeBuffer\r |
209 | );\r |
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210 | \r |
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211 | CopyMem (ThunkContext->RealModeState, UpdatedRegs, sizeof (*UpdatedRegs));\r |
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212 | }\r |
213 | \r |
214 | /**\r |
215 | Prepares all structures and code for a 16-bit real mode thunk, transfers\r |
216 | control to a 16-bit real mode entry point, and returns the results.\r |
217 | \r |
218 | Prepares all structures and code for a 16-bit real mode thunk, transfers\r |
219 | control to a 16-bit real mode entry point, and returns the results. If the\r |
220 | caller only need to perform a single 16-bit real mode thunk, then this\r |
221 | service should be used. If the caller intends to make more than one 16-bit\r |
222 | real mode thunk, then it is more efficient if AsmPrepareThunk16() is called\r |
223 | once and AsmThunk16() can be called for each 16-bit real mode thunk. This\r |
224 | function must be called with interrupts disabled.\r |
225 | \r |
226 | If ThunkContext is NULL, then ASSERT().\r |
227 | \r |
228 | @param ThunkContext A pointer to the context structure that describes the\r |
229 | 16-bit real mode code to call.\r |
230 | \r |
231 | **/\r |
232 | VOID\r |
233 | EFIAPI\r |
234 | AsmPrepareAndThunk16 (\r |
235 | IN OUT THUNK_CONTEXT *ThunkContext\r |
236 | )\r |
237 | {\r |
238 | AsmPrepareThunk16 (ThunkContext);\r |
239 | AsmThunk16 (ThunkContext);\r |
240 | }\r |