1 /** @file 2 IA-32/x64 AsmEnablePaging32() 3 4 Copyright (c) 2006 - 2008, Intel Corporation. All rights reserved.<BR> 5 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 17 18 #include "BaseLibInternals.h" 19 20 /** 21 Enables the 32-bit paging mode on the CPU. 22 23 Enables the 32-bit paging mode on the CPU. CR0, CR3, CR4, and the page tables 24 must be properly initialized prior to calling this service. This function 25 assumes the current execution mode is 32-bit protected mode. This function is 26 only available on IA-32. After the 32-bit paging mode is enabled, control is 27 transferred to the function specified by EntryPoint using the new stack 28 specified by NewStack and passing in the parameters specified by Context1 and 29 Context2. Context1 and Context2 are optional and may be NULL. The function 30 EntryPoint must never return. 31 32 If the current execution mode is not 32-bit protected mode, then ASSERT(). 33 If EntryPoint is NULL, then ASSERT(). 34 If NewStack is NULL, then ASSERT(). 35 36 There are a number of constraints that must be followed before calling this 37 function: 38 1) Interrupts must be disabled. 39 2) The caller must be in 32-bit protected mode with flat descriptors. This 40 means all descriptors must have a base of 0 and a limit of 4GB. 41 3) CR0 and CR4 must be compatible with 32-bit protected mode with flat 42 descriptors. 43 4) CR3 must point to valid page tables that will be used once the transition 44 is complete, and those page tables must guarantee that the pages for this 45 function and the stack are identity mapped. 46 47 @param EntryPoint A pointer to function to call with the new stack after 48 paging is enabled. 49 @param Context1 A pointer to the context to pass into the EntryPoint 50 function as the first parameter after paging is enabled. 51 @param Context2 A pointer to the context to pass into the EntryPoint 52 function as the second parameter after paging is enabled. 53 @param NewStack A pointer to the new stack to use for the EntryPoint 54 function after paging is enabled. 55 56 **/ 57 VOID 58 EFIAPI 59 AsmEnablePaging32 ( 60 IN SWITCH_STACK_ENTRY_POINT EntryPoint, 61 IN VOID *Context1, OPTIONAL 62 IN VOID *Context2, OPTIONAL 63 IN VOID *NewStack 64 ) 65 { 66 ASSERT (EntryPoint != NULL); 67 ASSERT (NewStack != NULL); 68 InternalX86EnablePaging32 (EntryPoint, Context1, Context2, NewStack); 69 } 70
