/** @file | |
AsmDisablePaging32 function. | |
Copyright (c) 2006 - 2008, Intel Corporation. All rights reserved.<BR> | |
This program and the accompanying materials | |
are licensed and made available under the terms and conditions of the BSD License | |
which accompanies this distribution. The full text of the license may be found at | |
http://opensource.org/licenses/bsd-license.php. | |
THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS, | |
WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED. | |
**/ | |
#include "BaseLibInternals.h" | |
/** | |
Disables the 32-bit paging mode on the CPU. | |
Disables the 32-bit paging mode on the CPU and returns to 32-bit protected | |
mode. This function assumes the current execution mode is 32-paged protected | |
mode. This function is only available on IA-32. After the 32-bit paging mode | |
is disabled, control is transferred to the function specified by EntryPoint | |
using the new stack specified by NewStack and passing in the parameters | |
specified by Context1 and Context2. Context1 and Context2 are optional and | |
may be NULL. The function EntryPoint must never return. | |
There are a number of constraints that must be followed before calling this | |
function: | |
1) Interrupts must be disabled. | |
2) The caller must be in 32-bit paged mode. | |
3) CR0, CR3, and CR4 must be compatible with 32-bit paged mode. | |
4) CR3 must point to valid page tables that guarantee that the pages for | |
this function and the stack are identity mapped. | |
@param EntryPoint A pointer to function to call with the new stack after | |
paging is disabled. | |
@param Context1 A pointer to the context to pass into the EntryPoint | |
function as the first parameter after paging is disabled. | |
@param Context2 A pointer to the context to pass into the EntryPoint | |
function as the second parameter after paging is | |
disabled. | |
@param NewStack A pointer to the new stack to use for the EntryPoint | |
function after paging is disabled. | |
**/ | |
__declspec (naked) | |
VOID | |
EFIAPI | |
InternalX86DisablePaging32 ( | |
IN SWITCH_STACK_ENTRY_POINT EntryPoint, | |
IN VOID *Context1, OPTIONAL | |
IN VOID *Context2, OPTIONAL | |
IN VOID *NewStack | |
) | |
{ | |
_asm { | |
push ebp | |
mov ebp, esp | |
mov ebx, EntryPoint | |
mov ecx, Context1 | |
mov edx, Context2 | |
pushfd | |
pop edi // save EFLAGS to edi | |
cli | |
mov eax, cr0 | |
btr eax, 31 | |
mov esp, NewStack | |
mov cr0, eax | |
push edi | |
popfd // restore EFLAGS from edi | |
push edx | |
push ecx | |
call ebx | |
jmp $ // EntryPoint() should not return | |
} | |
} |