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 This program and the accompanying materials
8 are licensed and made available under the terms and conditions of the BSD License
9 which accompanies this distribution. The full text of the license may be found at
10 http://opensource.org/licenses/bsd-license.php.
11
12 THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
13 WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
14
15 **/
16
17 #include <Uefi.h>
18 #include <Library/BaseLib.h>
19 #include <FspApi.h>
20
21 #pragma pack(1)
22 typedef union {
23 struct {
24 UINT32 LimitLow : 16;
25 UINT32 BaseLow : 16;
26 UINT32 BaseMid : 8;
27 UINT32 Type : 4;
28 UINT32 System : 1;
29 UINT32 Dpl : 2;
30 UINT32 Present : 1;
31 UINT32 LimitHigh : 4;
32 UINT32 Software : 1;
33 UINT32 Reserved : 1;
34 UINT32 DefaultSize : 1;
35 UINT32 Granularity : 1;
36 UINT32 BaseHigh : 8;
37 } Bits;
38 UINT64 Uint64;
39 } IA32_GDT;
40 #pragma pack()
41
42 GLOBAL_REMOVE_IF_UNREFERENCED IA32_GDT mGdtEntries[] = {
43 {{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}}, /* 0x0: reserve */
44 {{0xFFFF, 0, 0, 0xB, 1, 0, 1, 0xF, 0, 0, 1, 1, 0}}, /* 0x8: compatibility mode */
45 {{0xFFFF, 0, 0, 0xB, 1, 0, 1, 0xF, 0, 1, 0, 1, 0}}, /* 0x10: for long mode */
46 {{0xFFFF, 0, 0, 0x3, 1, 0, 1, 0xF, 0, 0, 1, 1, 0}}, /* 0x18: data */
47 {{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}}, /* 0x20: reserve */
48 };
49
50 //
51 // IA32 Gdt register
52 //
53 GLOBAL_REMOVE_IF_UNREFERENCED IA32_DESCRIPTOR mGdt = {
54 sizeof (mGdtEntries) - 1,
55 (UINTN) mGdtEntries
56 };
57
58 /**
59 Assembly function to transition from long mode to compatibility mode to execute 32-bit code and then transit back to
60 long mode.
61
62 @param[in] Function The 32bit code entry to be executed.
63 @param[in] Param1 The first parameter to pass to 32bit code
64 @param[in] Param2 The second parameter to pass to 32bit code
65 @param[in] InternalGdtr The GDT and GDT descriptor used by this library
66
67 @return status.
68 **/
69 UINT32
70 AsmExecute32BitCode (
71 IN UINT64 Function,
72 IN UINT64 Param1,
73 IN UINT64 Param2,
74 IN IA32_DESCRIPTOR *InternalGdtr
75 );
76
77 /**
78 Wrapper for a thunk to transition from long mode to compatibility mode to execute 32-bit code and then transit back to
79 long mode.
80
81 @param[in] Function The 32bit code entry to be executed.
82 @param[in] Param1 The first parameter to pass to 32bit code.
83
84 @return EFI_STATUS.
85 **/
86 EFI_STATUS
Execute32BitCode(IN UINT64 Function,IN UINT64 Param1)87 Execute32BitCode (
88 IN UINT64 Function,
89 IN UINT64 Param1
90 )
91 {
92 EFI_STATUS Status;
93 IA32_DESCRIPTOR Idtr;
94
95 //
96 // Idtr might be changed inside of FSP. 32bit FSP only knows the <4G address.
97 // If IDTR.Base is >4G, FSP can not handle. So we need save/restore IDTR here for X64 only.
98 // Interrupt is already disabled here, so it is safety to update IDTR.
99 //
100 AsmReadIdtr (&Idtr);
101 Status = AsmExecute32BitCode (Function, Param1, 0, &mGdt);
102 AsmWriteIdtr (&Idtr);
103
104 return Status;
105 }
106
107