IntelFspWrapperPkg/Library/BaseFspApiLib/X64/DispatchExecute.c

   1 /** @file
   2   Execute 32-bit code in Long Mode.
   3   Provide a thunk function to transition from long mode to compatibility mode to execute 32-bit code and then transit
   4   back to long mode.
   5
   6   Copyright (c) 2014 - 2015, Intel Corporation. All rights reserved.<BR>
   7   SPDX-License-Identifier: BSD-2-Clause-Patent
   8
   9 **/
  10
  11 #include <Uefi.h>
  12 #include <Library/BaseLib.h>
  13 #include <FspApi.h>
  14
  15 #pragma pack(1)
  16 typedef union {
  17   struct {
  18     UINT32  LimitLow    : 16;
  19     UINT32  BaseLow     : 16;
  20     UINT32  BaseMid     : 8;
  21     UINT32  Type        : 4;
  22     UINT32  System      : 1;
  23     UINT32  Dpl         : 2;
  24     UINT32  Present     : 1;
  25     UINT32  LimitHigh   : 4;
  26     UINT32  Software    : 1;
  27     UINT32  Reserved    : 1;
  28     UINT32  DefaultSize : 1;
  29     UINT32  Granularity : 1;
  30     UINT32  BaseHigh    : 8;
  31   } Bits;
  32   UINT64  Uint64;
  33 } IA32_GDT;
  34 #pragma pack()
  35
  36 GLOBAL_REMOVE_IF_UNREFERENCED IA32_GDT mGdtEntries[] = {
  37   {{0,      0,  0,  0,    0,  0,  0,  0,    0,  0, 0,  0,  0}}, /* 0x0:  reserve */
  38   {{0xFFFF, 0,  0,  0xB,  1,  0,  1,  0xF,  0,  0, 1,  1,  0}}, /* 0x8:  compatibility mode */
  39   {{0xFFFF, 0,  0,  0xB,  1,  0,  1,  0xF,  0,  1, 0,  1,  0}}, /* 0x10: for long mode */
  40   {{0xFFFF, 0,  0,  0x3,  1,  0,  1,  0xF,  0,  0, 1,  1,  0}}, /* 0x18: data */
  41   {{0,      0,  0,  0,    0,  0,  0,  0,    0,  0, 0,  0,  0}}, /* 0x20: reserve */
  42 };
  43
  44 //
  45 // IA32 Gdt register
  46 //
  47 GLOBAL_REMOVE_IF_UNREFERENCED IA32_DESCRIPTOR mGdt = {
  48   sizeof (mGdtEntries) - 1,
  49   (UINTN) mGdtEntries
  50   };
  51
  52 /**
  53   Assembly function to transition from long mode to compatibility mode to execute 32-bit code and then transit back to
  54   long mode.
  55
  56   @param[in] Function     The 32bit code entry to be executed.
  57   @param[in] Param1       The first parameter to pass to 32bit code
  58   @param[in] Param2       The second parameter to pass to 32bit code
  59   @param[in] InternalGdtr The GDT and GDT descriptor used by this library
  60
  61   @return status.
  62 **/
  63 UINT32
  64 AsmExecute32BitCode (
  65   IN UINT64           Function,
  66   IN UINT64           Param1,
  67   IN UINT64           Param2,
  68   IN IA32_DESCRIPTOR  *InternalGdtr
  69   );
  70
  71 /**
  72   Wrapper for a thunk  to transition from long mode to compatibility mode to execute 32-bit code and then transit back to
  73   long mode.
  74
  75   @param[in] Function     The 32bit code entry to be executed.
  76   @param[in] Param1       The first parameter to pass to 32bit code.
  77
  78   @return EFI_STATUS.
  79 **/
  80 EFI_STATUS
  81 Execute32BitCode (
  82   IN UINT64      Function,
  83   IN UINT64      Param1
  84   )
  85 {
  86   EFI_STATUS       Status;
  87   IA32_DESCRIPTOR  Idtr;
  88
  89   //
  90   // Idtr might be changed inside of FSP. 32bit FSP only knows the <4G address.
  91   // If IDTR.Base is >4G, FSP can not handle. So we need save/restore IDTR here for X64 only.
  92   // Interrupt is already disabled here, so it is safety to update IDTR.
  93   //
  94   AsmReadIdtr (&Idtr);
  95   Status = AsmExecute32BitCode (Function, Param1, 0, &mGdt);
  96   AsmWriteIdtr (&Idtr);
  97
  98   return Status;
  99 }
 100