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Commit | Line | Data |
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24498828 | 1 | ;\r |
c45f4c5e | 2 | ; Copyright (c) 2016 - 2018, Intel Corporation. All rights reserved.<BR>\r |
512e23a3 | 3 | ; SPDX-License-Identifier: BSD-2-Clause-Patent\r |
24498828 LG |
4 | ;\r |
5 | ;\r | |
6 | ; Module Name:\r | |
7 | ;\r | |
8 | ; Thunk64To32.nasm\r | |
9 | ;\r | |
10 | ; Abstract:\r | |
11 | ;\r | |
12 | ; This is the assembly code to transition from long mode to compatibility mode to execute 32-bit code and then\r | |
13 | ; transit back to long mode.\r | |
14 | ;\r | |
15 | ;-------------------------------------------------------------------------------\r | |
16 | DEFAULT REL\r | |
17 | SECTION .text\r | |
18 | ;----------------------------------------------------------------------------\r | |
19 | ; Procedure: AsmExecute32BitCode\r | |
20 | ;\r | |
21 | ; Input: None\r | |
22 | ;\r | |
23 | ; Output: None\r | |
24 | ;\r | |
25 | ; Prototype: UINT32\r | |
26 | ; AsmExecute32BitCode (\r | |
27 | ; IN UINT64 Function,\r | |
28 | ; IN UINT64 Param1,\r | |
29 | ; IN UINT64 Param2,\r | |
30 | ; IN IA32_DESCRIPTOR *InternalGdtr\r | |
31 | ; );\r | |
32 | ;\r | |
33 | ;\r | |
34 | ; Description: A thunk function to execute 32-bit code in long mode.\r | |
35 | ;\r | |
36 | ;----------------------------------------------------------------------------\r | |
37 | global ASM_PFX(AsmExecute32BitCode)\r | |
38 | ASM_PFX(AsmExecute32BitCode):\r | |
39 | ;\r | |
40 | ; save IFLAG and disable it\r | |
41 | ;\r | |
42 | pushfq\r | |
43 | cli\r | |
44 | \r | |
45 | ;\r | |
46 | ; save orignal GDTR and CS\r | |
47 | ;\r | |
48 | mov rax, ds\r | |
49 | push rax\r | |
50 | mov rax, cs\r | |
51 | push rax\r | |
52 | sub rsp, 0x10\r | |
53 | sgdt [rsp]\r | |
54 | ;\r | |
55 | ; load internal GDT\r | |
56 | ;\r | |
57 | lgdt [r9]\r | |
58 | ;\r | |
59 | ; Save general purpose register and rflag register\r | |
60 | ;\r | |
61 | pushfq\r | |
62 | push rdi\r | |
63 | push rsi\r | |
64 | push rbp\r | |
65 | push rbx\r | |
66 | \r | |
67 | ;\r | |
68 | ; save CR3\r | |
69 | ;\r | |
70 | mov rax, cr3\r | |
71 | mov rbp, rax\r | |
72 | \r | |
73 | ;\r | |
74 | ; Prepare the CS and return address for the transition from 32-bit to 64-bit mode\r | |
75 | ;\r | |
76 | mov rax, dword 0x10 ; load long mode selector\r | |
77 | shl rax, 32\r | |
c45f4c5e | 78 | lea r9, [ReloadCS] ;Assume the ReloadCS is under 4G\r |
24498828 LG |
79 | or rax, r9\r |
80 | push rax\r | |
81 | ;\r | |
82 | ; Save parameters for 32-bit function call\r | |
83 | ;\r | |
84 | mov rax, r8\r | |
85 | shl rax, 32\r | |
86 | or rax, rdx\r | |
87 | push rax\r | |
88 | ;\r | |
89 | ; save the 32-bit function entry and the return address into stack which will be\r | |
90 | ; retrieve in compatibility mode.\r | |
91 | ;\r | |
c45f4c5e | 92 | lea rax, [ReturnBack] ;Assume the ReloadCS is under 4G\r |
24498828 LG |
93 | shl rax, 32\r |
94 | or rax, rcx\r | |
95 | push rax\r | |
96 | \r | |
97 | ;\r | |
98 | ; let rax save DS\r | |
99 | ;\r | |
100 | mov rax, dword 0x18\r | |
101 | \r | |
102 | ;\r | |
103 | ; Change to Compatible Segment\r | |
104 | ;\r | |
105 | mov rcx, dword 0x8 ; load compatible mode selector\r | |
106 | shl rcx, 32\r | |
c45f4c5e | 107 | lea rdx, [Compatible] ; assume address < 4G\r |
24498828 LG |
108 | or rcx, rdx\r |
109 | push rcx\r | |
110 | retf\r | |
111 | \r | |
112 | Compatible:\r | |
113 | ; reload DS/ES/SS to make sure they are correct referred to current GDT\r | |
114 | mov ds, ax\r | |
115 | mov es, ax\r | |
116 | mov ss, ax\r | |
117 | \r | |
118 | ;\r | |
119 | ; Disable paging\r | |
120 | ;\r | |
121 | mov rcx, cr0\r | |
122 | btc ecx, 31\r | |
123 | mov cr0, rcx\r | |
124 | ;\r | |
125 | ; Clear EFER.LME\r | |
126 | ;\r | |
127 | mov ecx, 0xC0000080\r | |
128 | rdmsr\r | |
129 | btc eax, 8\r | |
130 | wrmsr\r | |
131 | \r | |
132 | ; Now we are in protected mode\r | |
133 | ;\r | |
134 | ; Call 32-bit function. Assume the function entry address and parameter value is less than 4G\r | |
135 | ;\r | |
136 | pop rax ; Here is the function entry\r | |
137 | ;\r | |
138 | ; Now the parameter is at the bottom of the stack, then call in to IA32 function.\r | |
139 | ;\r | |
140 | jmp rax\r | |
141 | ReturnBack:\r | |
142 | mov ebx, eax ; save return status\r | |
143 | pop rcx ; drop param1\r | |
144 | pop rcx ; drop param2\r | |
145 | \r | |
146 | ;\r | |
147 | ; restore CR4\r | |
148 | ;\r | |
149 | mov rax, cr4\r | |
150 | bts eax, 5\r | |
151 | mov cr4, rax\r | |
152 | \r | |
153 | ;\r | |
154 | ; restore CR3\r | |
155 | ;\r | |
156 | mov eax, ebp\r | |
157 | mov cr3, rax\r | |
158 | \r | |
159 | ;\r | |
160 | ; Set EFER.LME to re-enable ia32-e\r | |
161 | ;\r | |
162 | mov ecx, 0xC0000080\r | |
163 | rdmsr\r | |
164 | bts eax, 8\r | |
165 | wrmsr\r | |
166 | ;\r | |
167 | ; Enable paging\r | |
168 | ;\r | |
169 | mov rax, cr0\r | |
170 | bts eax, 31\r | |
171 | mov cr0, rax\r | |
172 | ; Now we are in compatible mode\r | |
173 | \r | |
174 | ;\r | |
175 | ; Reload cs register\r | |
176 | ;\r | |
177 | retf\r | |
178 | ReloadCS:\r | |
179 | ;\r | |
180 | ; Now we're in Long Mode\r | |
181 | ;\r | |
182 | ;\r | |
183 | ; Restore C register and eax hold the return status from 32-bit function.\r | |
184 | ; Note: Do not touch rax from now which hold the return value from IA32 function\r | |
185 | ;\r | |
186 | mov eax, ebx ; put return status to EAX\r | |
187 | pop rbx\r | |
188 | pop rbp\r | |
189 | pop rsi\r | |
190 | pop rdi\r | |
191 | popfq\r | |
192 | ;\r | |
193 | ; Switch to orignal GDT and CS. here rsp is pointer to the orignal GDT descriptor.\r | |
194 | ;\r | |
195 | lgdt [rsp]\r | |
196 | ;\r | |
197 | ; drop GDT descriptor in stack\r | |
198 | ;\r | |
199 | add rsp, 0x10\r | |
200 | ;\r | |
201 | ; switch to orignal CS and GDTR\r | |
202 | ;\r | |
203 | pop r9 ; get CS\r | |
204 | shl r9, 32 ; rcx[32..47] <- Cs\r | |
c45f4c5e | 205 | lea rcx, [.0]\r |
24498828 LG |
206 | or rcx, r9\r |
207 | push rcx\r | |
208 | retf\r | |
209 | .0:\r | |
210 | ;\r | |
211 | ; Reload original DS/ES/SS\r | |
212 | ;\r | |
213 | pop rcx\r | |
214 | mov ds, rcx\r | |
215 | mov es, rcx\r | |
216 | mov ss, rcx\r | |
217 | \r | |
218 | ;\r | |
219 | ; Restore IFLAG\r | |
220 | ;\r | |
221 | popfq\r | |
222 | \r | |
223 | ret\r | |
224 | \r |