Fix MASM build break
[mirror_edk2.git] / MdePkg / Library / BaseLib / x86Thunk.c
CommitLineData
878ddf1f 1/** @file\r
2 Real Mode Thunk Functions for IA32 and X64.\r
3\r
4 Copyright (c) 2006, Intel Corporation<BR>\r
5 All rights reserved. This program and the accompanying materials\r
6 are licensed and made available under the terms and conditions of the BSD License\r
7 which accompanies this distribution. The full text of the license may be found at\r
8 http://opensource.org/licenses/bsd-license.php\r
9\r
10 THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,\r
11 WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.\r
12\r
13 Module Name: x86Thunk.c\r
14\r
15**/\r
16\r
17/**\r
18 Invokes 16-bit code in big real mode and returns the updated register set.\r
19\r
20 This function transfers control to the 16-bit code specified by CS:EIP using\r
21 the stack specified by SS:ESP in RegisterSet. The updated registers are saved\r
22 on the real mode stack and the starting address of the save area is returned.\r
23\r
24 @param RegisterSet Values of registers before invocation of 16-bit code.\r
25 @param Patch Pointer to the area following the 16-bit code.\r
26\r
27 @return The pointer to a IA32_REGISTER_SET structure containing the updated\r
28 register values.\r
29\r
30**/\r
31IA32_REGISTER_SET *\r
32InternalAsmThunk16 (\r
33 IN IA32_REGISTER_SET *RegisterSet,\r
34 IN OUT VOID *Patch\r
35 );\r
36\r
37/**\r
38 Prepares all structures a code required to use AsmThunk16().\r
39\r
40 Prepares all structures and code required to use AsmThunk16().\r
41\r
42 If ThunkContext is NULL, then ASSERT().\r
43\r
44 @param ThunkContext A pointer to the context structure that describes the\r
45 16-bit real mode code to call.\r
46\r
47**/\r
48VOID\r
49EFIAPI\r
50AsmPrepareThunk16 (\r
51 OUT THUNK_CONTEXT *ThunkContext\r
52 )\r
53{\r
54 ASSERT (ThunkContext != NULL);\r
55}\r
56\r
57/**\r
58 Transfers control to a 16-bit real mode entry point and returns the results.\r
59\r
60 Transfers control to a 16-bit real mode entry point and returns the results.\r
61 AsmPrepareThunk16() must be called with ThunkContext before this function is\r
62 used. This function must be called with interrupts disabled.\r
63\r
64 If ThunkContext is NULL, then ASSERT().\r
65 If AsmPrepareThunk16() was not previously called with ThunkContext, then ASSERT().\r
66\r
67 @param ThunkContext A pointer to the context structure that describes the\r
68 16-bit real mode code to call.\r
69\r
70**/\r
71VOID\r
72EFIAPI\r
73AsmThunk16 (\r
74 IN OUT THUNK_CONTEXT *ThunkContext\r
75 )\r
76{\r
77 UINT16 *Patch;\r
78\r
79 ASSERT (ThunkContext != NULL);\r
80\r
81 Patch = (UINT16*)(\r
82 (UINTN)ThunkContext->RealModeCode +\r
83 ThunkContext->RealModeCodeSize\r
84 );\r
85\r
86 //\r
87 // 0x9a66 is the OpCode of far call with an operand size override.\r
88 //\r
89 *Patch = 0x9a66;\r
90\r
91 //\r
92 // CopyMem() here copies the updated register values back to RealModeState\r
93 //\r
94 CopyMem (\r
95 &ThunkContext->RealModeState,\r
96 InternalAsmThunk16 (&ThunkContext->RealModeState, Patch + 1),\r
97 sizeof (ThunkContext->RealModeState)\r
98 );\r
99}\r
100\r
101/**\r
102 Prepares all structures and code for a 16-bit real mode thunk, transfers\r
103 control to a 16-bit real mode entry point, and returns the results.\r
104\r
105 Prepares all structures and code for a 16-bit real mode thunk, transfers\r
106 control to a 16-bit real mode entry point, and returns the results. If the\r
107 caller only need to perform a single 16-bit real mode thunk, then this\r
108 service should be used. If the caller intends to make more than one 16-bit\r
109 real mode thunk, then it is more efficient if AsmPrepareThunk16() is called\r
110 once and AsmThunk16() can be called for each 16-bit real mode thunk. This\r
111 function must be called with interrupts disabled.\r
112\r
113 If ThunkContext is NULL, then ASSERT().\r
114\r
115 @param ThunkContext A pointer to the context structure that describes the\r
116 16-bit real mode code to call.\r
117\r
118**/\r
119VOID\r
120EFIAPI\r
121AsmPrepareAndThunk16 (\r
122 IN OUT THUNK_CONTEXT *ThunkContext\r
123 )\r
124{\r
125 AsmPrepareThunk16 (ThunkContext);\r
126 AsmThunk16 (ThunkContext);\r
127}\r