MdePkg/Library/BaseLib/X86EnablePaging32.c

/** @file
  IA-32/x64 AsmEnablePaging32()

  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.

  If the current execution mode is not 32-bit protected mode, then ASSERT().
  If EntryPoint is NULL, then ASSERT().
  If NewStack is NULL, then ASSERT().

  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.

**/
VOID
EFIAPI
AsmEnablePaging32 (
  IN      SWITCH_STACK_ENTRY_POINT  EntryPoint,
  IN      VOID                      *Context1   OPTIONAL,
  IN      VOID                      *Context2   OPTIONAL,
  IN      VOID                      *NewStack
  )
{
  ASSERT (EntryPoint != NULL);
  ASSERT (NewStack != NULL);
  InternalX86EnablePaging32 (EntryPoint, Context1, Context2, NewStack);
}