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e1f414b6 | 1 | /** @file\r |
2 | AsmDisablePaging32 function.\r | |
3 | \r | |
373ade0e | 4 | Copyright (c) 2006 - 2008, Intel Corporation<BR>\r |
e1f414b6 | 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 | **/\r | |
14 | \r | |
47fc17d8 | 15 | #include "BaseLibInternals.h"\r |
f734a10a | 16 | \r |
42eedea9 | 17 | /**\r |
18 | Disables the 32-bit paging mode on the CPU.\r | |
19 | \r | |
20 | Disables the 32-bit paging mode on the CPU and returns to 32-bit protected\r | |
21 | mode. This function assumes the current execution mode is 32-paged protected\r | |
22 | mode. This function is only available on IA-32. After the 32-bit paging mode\r | |
23 | is disabled, control is transferred to the function specified by EntryPoint\r | |
24 | using the new stack specified by NewStack and passing in the parameters\r | |
25 | specified by Context1 and Context2. Context1 and Context2 are optional and\r | |
26 | may be NULL. The function EntryPoint must never return.\r | |
27 | \r | |
28 | There are a number of constraints that must be followed before calling this\r | |
29 | function:\r | |
30 | 1) Interrupts must be disabled.\r | |
31 | 2) The caller must be in 32-bit paged mode.\r | |
32 | 3) CR0, CR3, and CR4 must be compatible with 32-bit paged mode.\r | |
33 | 4) CR3 must point to valid page tables that guarantee that the pages for\r | |
34 | this function and the stack are identity mapped.\r | |
35 | \r | |
36 | @param EntryPoint A pointer to function to call with the new stack after\r | |
37 | paging is disabled.\r | |
38 | @param Context1 A pointer to the context to pass into the EntryPoint\r | |
39 | function as the first parameter after paging is disabled.\r | |
40 | @param Context2 A pointer to the context to pass into the EntryPoint\r | |
41 | function as the second parameter after paging is\r | |
42 | disabled.\r | |
43 | @param NewStack A pointer to the new stack to use for the EntryPoint\r | |
44 | function after paging is disabled.\r | |
45 | \r | |
46 | **/\r | |
e1f414b6 | 47 | __declspec (naked)\r |
48 | VOID\r | |
49 | EFIAPI\r | |
50 | InternalX86DisablePaging32 (\r | |
51 | IN SWITCH_STACK_ENTRY_POINT EntryPoint,\r | |
52 | IN VOID *Context1, OPTIONAL\r | |
53 | IN VOID *Context2, OPTIONAL\r | |
54 | IN VOID *NewStack\r | |
55 | )\r | |
56 | {\r | |
57 | _asm {\r | |
58 | push ebp\r | |
59 | mov ebp, esp\r | |
60 | mov ebx, EntryPoint\r | |
61 | mov ecx, Context1\r | |
62 | mov edx, Context2\r | |
63 | pushfd\r | |
64 | pop edi // save EFLAGS to edi\r | |
65 | cli\r | |
66 | mov eax, cr0\r | |
67 | btr eax, 31\r | |
68 | mov esp, NewStack\r | |
69 | mov cr0, eax\r | |
70 | push edi\r | |
71 | popfd // restore EFLAGS from edi\r | |
72 | push edx\r | |
73 | push ecx\r | |
74 | call ebx\r | |
75 | jmp $ // EntryPoint() should not return\r | |
76 | }\r | |
77 | }\r |