MdePkg/Library/BaseLib/X86DisablePaging32.c

   1 /** @file
   2   IA-32/x64 AsmDisablePaging32()
   3
   4   Copyright (c) 2006 - 2008, Intel Corporation. All rights reserved.<BR>
   5   SPDX-License-Identifier: BSD-2-Clause-Patent
   6
   7 **/
   8
   9
  10
  11
  12 #include "BaseLibInternals.h"
  13
  14 /**
  15   Disables the 32-bit paging mode on the CPU.
  16
  17   Disables the 32-bit paging mode on the CPU and returns to 32-bit protected
  18   mode. This function assumes the current execution mode is 32-paged protected
  19   mode. This function is only available on IA-32. After the 32-bit paging mode
  20   is disabled, control is transferred to the function specified by EntryPoint
  21   using the new stack specified by NewStack and passing in the parameters
  22   specified by Context1 and Context2. Context1 and Context2 are optional and
  23   may be NULL. The function EntryPoint must never return.
  24
  25   If the current execution mode is not 32-bit paged mode, then ASSERT().
  26   If EntryPoint is NULL, then ASSERT().
  27   If NewStack is NULL, then ASSERT().
  28
  29   There are a number of constraints that must be followed before calling this
  30   function:
  31   1)  Interrupts must be disabled.
  32   2)  The caller must be in 32-bit paged mode.
  33   3)  CR0, CR3, and CR4 must be compatible with 32-bit paged mode.
  34   4)  CR3 must point to valid page tables that guarantee that the pages for
  35       this function and the stack are identity mapped.
  36
  37   @param  EntryPoint  A pointer to function to call with the new stack after
  38                       paging is disabled.
  39   @param  Context1    A pointer to the context to pass into the EntryPoint
  40                       function as the first parameter after paging is disabled.
  41   @param  Context2    A pointer to the context to pass into the EntryPoint
  42                       function as the second parameter after paging is
  43                       disabled.
  44   @param  NewStack    A pointer to the new stack to use for the EntryPoint
  45                       function after paging is disabled.
  46
  47 **/
  48 VOID
  49 EFIAPI
  50 AsmDisablePaging32 (
  51   IN      SWITCH_STACK_ENTRY_POINT  EntryPoint,
  52   IN      VOID                      *Context1,  OPTIONAL
  53   IN      VOID                      *Context2,  OPTIONAL
  54   IN      VOID                      *NewStack
  55   )
  56 {
  57   ASSERT (EntryPoint != NULL);
  58   ASSERT (NewStack != NULL);
  59   InternalX86DisablePaging32 (EntryPoint, Context1, Context2, NewStack);
  60 }