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/** @file
AsmEnablePaging32 function
Copyright (c) 2006 - 2008, Intel Corporation. All rights reserved.<BR>
SPDX-License-Identifier: BSD-2-Clause-Patent
**/
#include "BaseLibInternals.h"
/**
Enables the 32-bit paging mode on the CPU.
Enables the 32-bit paging mode on the CPU. CR0, CR3, CR4, and the page tables
must be properly initialized prior to calling this service. This function
assumes the current execution mode is 32-bit protected mode. This function is
only available on IA-32. After the 32-bit paging mode is enabled, 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 protected mode with flat descriptors. This
means all descriptors must have a base of 0 and a limit of 4GB.
3) CR0 and CR4 must be compatible with 32-bit protected mode with flat
descriptors.
4) CR3 must point to valid page tables that will be used once the transition
is complete, and those page tables must 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 enabled.
@param Context1 A pointer to the context to pass into the EntryPoint
function as the first parameter after paging is enabled.
@param Context2 A pointer to the context to pass into the EntryPoint
function as the second parameter after paging is enabled.
@param NewStack A pointer to the new stack to use for the EntryPoint
function after paging is enabled.
**/
__declspec (naked)
VOID
EFIAPI
InternalX86EnablePaging32 (
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
cli
mov eax, cr0
bts eax, 31
mov esp, NewStack
mov cr0, eax
push edi
popfd
push edx
push ecx
call ebx
jmp $
}
}
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