1 /** @file
2 AsmEnablePaging32 function
3
4 Copyright (c) 2006 - 2008, Intel Corporation. All rights reserved.<BR>
5 This program and the accompanying materials
6 are licensed and made available under the terms and conditions of the BSD License
7 which accompanies this distribution. The full text of the license may be found at
8 http://opensource.org/licenses/bsd-license.php.
9
10 THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
11 WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
12
13 **/
14
15 #include "BaseLibInternals.h"
16
17 /**
18 Enables the 32-bit paging mode on the CPU.
19
20 Enables the 32-bit paging mode on the CPU. CR0, CR3, CR4, and the page tables
21 must be properly initialized prior to calling this service. This function
22 assumes the current execution mode is 32-bit protected mode. This function is
23 only available on IA-32. After the 32-bit paging mode is enabled, control is
24 transferred to the function specified by EntryPoint using the new stack
25 specified by NewStack and passing in the parameters specified by Context1 and
26 Context2. Context1 and Context2 are optional and may be NULL. The function
27 EntryPoint must never return.
28
29 There are a number of constraints that must be followed before calling this
30 function:
31 1) Interrupts must be disabled.
32 2) The caller must be in 32-bit protected mode with flat descriptors. This
33 means all descriptors must have a base of 0 and a limit of 4GB.
34 3) CR0 and CR4 must be compatible with 32-bit protected mode with flat
35 descriptors.
36 4) CR3 must point to valid page tables that will be used once the transition
37 is complete, and those page tables must guarantee that the pages for this
38 function and the stack are identity mapped.
39
40 @param EntryPoint A pointer to function to call with the new stack after
41 paging is enabled.
42 @param Context1 A pointer to the context to pass into the EntryPoint
43 function as the first parameter after paging is enabled.
44 @param Context2 A pointer to the context to pass into the EntryPoint
45 function as the second parameter after paging is enabled.
46 @param NewStack A pointer to the new stack to use for the EntryPoint
47 function after paging is enabled.
48
49 **/
50 __declspec (naked)
51 VOID
52 EFIAPI
InternalX86EnablePaging32(IN SWITCH_STACK_ENTRY_POINT EntryPoint,IN VOID * Context1,OPTIONAL IN VOID * Context2,OPTIONAL IN VOID * NewStack)53 InternalX86EnablePaging32 (
54 IN SWITCH_STACK_ENTRY_POINT EntryPoint,
55 IN VOID *Context1, OPTIONAL
56 IN VOID *Context2, OPTIONAL
57 IN VOID *NewStack
58 )
59 {
60 _asm {
61 push ebp
62 mov ebp, esp
63 mov ebx, EntryPoint
64 mov ecx, Context1
65 mov edx, Context2
66 pushfd
67 pop edi
68 cli
69 mov eax, cr0
70 bts eax, 31
71 mov esp, NewStack
72 mov cr0, eax
73 push edi
74 popfd
75 push edx
76 push ecx
77 call ebx
78 jmp $
79 }
80 }
81
82