MdePkg/Library/BaseLib/x86DisablePaging32.c

   1 /** @file
   2   IA-32/x64 AsmDisablePaging32()
   3
   4   Copyright (c) 2006, 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
  19
  20 #include "BaseLibInternals.h"
  21
  22 /**
  23   Disables the 32-bit paging mode on the CPU.
  24
  25   Disables the 32-bit paging mode on the CPU and returns to 32-bit protected
  26   mode. This function assumes the current execution mode is 32-paged protected
  27   mode. This function is only available on IA-32. After the 32-bit paging mode
  28   is disabled, control is transferred to the function specified by EntryPoint
  29   using the new stack specified by NewStack and passing in the parameters
  30   specified by Context1 and Context2. Context1 and Context2 are optional and
  31   may be NULL. The function EntryPoint must never return.
  32
  33   If the current execution mode is not 32-bit paged mode, then ASSERT().
  34   If EntryPoint is NULL, then ASSERT().
  35   If NewStack is NULL, then ASSERT().
  36
  37   There are a number of constraints that must be followed before calling this
  38   function:
  39   1)  Interrupts must be disabled.
  40   2)  The caller must be in 32-bit paged mode.
  41   3)  CR0, CR3, and CR4 must be compatible with 32-bit paged mode.
  42   4)  CR3 must point to valid page tables that guarantee that the pages for
  43       this 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 disabled.
  47   @param  Context1    A pointer to the context to pass into the EntryPoint
  48                       function as the first parameter after paging is disabled.
  49   @param  Context2    A pointer to the context to pass into the EntryPoint
  50                       function as the second parameter after paging is
  51                       disabled.
  52   @param  NewStack    A pointer to the new stack to use for the EntryPoint
  53                       function after paging is disabled.
  54
  55 **/
  56 VOID
  57 EFIAPI
  58 AsmDisablePaging32 (
  59   IN      SWITCH_STACK_ENTRY_POINT  EntryPoint,
  60   IN      VOID                      *Context1,  OPTIONAL
  61   IN      VOID                      *Context2,  OPTIONAL
  62   IN      VOID                      *NewStack
  63   )
  64 {
  65   ASSERT (EntryPoint != NULL);
  66   ASSERT (NewStack != NULL);
  67   InternalX86DisablePaging32 (EntryPoint, Context1, Context2, NewStack);
  68 }