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76 lines
2.6 KiB
C
76 lines
2.6 KiB
C
/** @file
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AsmEnablePaging32 function
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Copyright (c) 2006 - 2008, Intel Corporation. All rights reserved.<BR>
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SPDX-License-Identifier: BSD-2-Clause-Patent
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**/
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#include "BaseLibInternals.h"
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/**
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Enables the 32-bit paging mode on the CPU.
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Enables the 32-bit paging mode on the CPU. CR0, CR3, CR4, and the page tables
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must be properly initialized prior to calling this service. This function
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assumes the current execution mode is 32-bit protected mode. This function is
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only available on IA-32. After the 32-bit paging mode is enabled, control is
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transferred to the function specified by EntryPoint using the new stack
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specified by NewStack and passing in the parameters specified by Context1 and
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Context2. Context1 and Context2 are optional and may be NULL. The function
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EntryPoint must never return.
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There are a number of constraints that must be followed before calling this
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function:
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1) Interrupts must be disabled.
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2) The caller must be in 32-bit protected mode with flat descriptors. This
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means all descriptors must have a base of 0 and a limit of 4GB.
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3) CR0 and CR4 must be compatible with 32-bit protected mode with flat
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descriptors.
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4) CR3 must point to valid page tables that will be used once the transition
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is complete, and those page tables must guarantee that the pages for this
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function and the stack are identity mapped.
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@param EntryPoint A pointer to function to call with the new stack after
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paging is enabled.
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@param Context1 A pointer to the context to pass into the EntryPoint
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function as the first parameter after paging is enabled.
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@param Context2 A pointer to the context to pass into the EntryPoint
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function as the second parameter after paging is enabled.
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@param NewStack A pointer to the new stack to use for the EntryPoint
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function after paging is enabled.
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**/
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__declspec (naked)
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VOID
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EFIAPI
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InternalX86EnablePaging32 (
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IN SWITCH_STACK_ENTRY_POINT EntryPoint,
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IN VOID *Context1, OPTIONAL
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IN VOID *Context2, OPTIONAL
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IN VOID *NewStack
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)
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{
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_asm {
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push ebp
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mov ebp, esp
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mov ebx, EntryPoint
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mov ecx, Context1
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mov edx, Context2
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pushfd
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pop edi
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cli
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mov eax, cr0
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bts eax, 31
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mov esp, NewStack
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mov cr0, eax
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push edi
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popfd
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push edx
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push ecx
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call ebx
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jmp $
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}
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}
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