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 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
