MdePkg/Library/BaseLib/Ia32/EnablePaging32.c

   1 /** @file
   2   AsmEnablePaging32 function
   3
   4   Copyright (c) 2006 - 2007, Intel Corporation<BR>
   5   All rights reserved. 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 //
  16 // Include common header file for this module.
  17 //
  18 #include <BaseLibInternals.h>
  19
  20 #if _MSC_EXTENSIONS
  21
  22 /**
  23   Enables the 32-bit paging mode on the CPU.
  24
  25   Enables the 32-bit paging mode on the CPU. CR0, CR3, CR4, and the page tables
  26   must be properly initialized prior to calling this service. This function
  27   assumes the current execution mode is 32-bit protected mode. This function is
  28   only available on IA-32. After the 32-bit paging mode is enabled, control is
  29   transferred to the function specified by EntryPoint using the new stack
  30   specified by NewStack and passing in the parameters specified by Context1 and
  31   Context2. Context1 and Context2 are optional and may be NULL. The function
  32   EntryPoint must never return.
  33
  34   There are a number of constraints that must be followed before calling this
  35   function:
  36   1)  Interrupts must be disabled.
  37   2)  The caller must be in 32-bit protected mode with flat descriptors. This
  38       means all descriptors must have a base of 0 and a limit of 4GB.
  39   3)  CR0 and CR4 must be compatible with 32-bit protected mode with flat
  40       descriptors.
  41   4)  CR3 must point to valid page tables that will be used once the transition
  42       is complete, and those page tables must guarantee that the pages for this
  43       function and the stack are identity mapped.
  44
  45   @param  EntryPoint  A pointer to function to call with the new stack after
  46                       paging is enabled.
  47   @param  Context1    A pointer to the context to pass into the EntryPoint
  48                       function as the first parameter after paging is enabled.
  49   @param  Context2    A pointer to the context to pass into the EntryPoint
  50                       function as the second parameter after paging is enabled.
  51   @param  NewStack    A pointer to the new stack to use for the EntryPoint
  52                       function after paging is enabled.
  53
  54 **/
  55 __declspec (naked)
  56 VOID
  57 EFIAPI
  58 InternalX86EnablePaging32 (
  59   IN      SWITCH_STACK_ENTRY_POINT  EntryPoint,
  60   IN      VOID                      *Context1,    OPTIONAL
  61   IN      VOID                      *Context2,    OPTIONAL
  62   IN      VOID                      *NewStack
  63   )
  64 {
  65   _asm {
  66     push    ebp
  67     mov     ebp, esp
  68     mov     ebx, EntryPoint
  69     mov     ecx, Context1
  70     mov     edx, Context2
  71     pushfd
  72     pop     edi
  73     cli
  74     mov     eax, cr0
  75     bts     eax, 31
  76     mov     esp, NewStack
  77     mov     cr0, eax
  78     push    edi
  79     popfd
  80     push    edx
  81     push    ecx
  82     call    ebx
  83     jmp     $
  84   }
  85 }
  86
  87 #endif