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1 // Copyright (c) 2010 The Chromium Authors. All rights reserved. | |
2 // Use of this source code is governed by a BSD-style license that can be | |
3 // found in the LICENSE file. | |
4 | |
5 | |
6 #ifndef CHROME_FRAME_FUNCTION_STUB_H_ | |
7 #define CHROME_FRAME_FUNCTION_STUB_H_ | |
8 | |
9 #include <windows.h> | |
10 | |
11 #include "base/basictypes.h" | |
12 | |
13 // IMPORTANT: The struct below must be byte aligned. | |
14 #pragma pack(push) | |
15 #pragma pack(1) | |
16 | |
17 struct FunctionStubAsm { | |
18 // The stub always starts with an indirect jump, which starts out jumping | |
19 // to the remainder of the stub. This means we can bypass the stub by | |
20 // rewriting the jump destination, which is data, in a manner that does | |
21 // not involve writing code, only writing data at a natural word boundary. | |
22 uint16 jump_to_bypass_; // indirect jump | |
23 uintptr_t bypass_target_addr_; // to the bypass target. | |
24 uint8 pop_return_addr_; // pop eax | |
25 uint16 push_; // push [arg] ; push... | |
26 uintptr_t arg_addr_; // ; extra argument | |
27 uint8 push_return_addr_; // push eax ; push the return address | |
28 uint16 jump_to_target; // jmp [target] ; jump... | |
29 uintptr_t target_addr_; // ; to the hook function | |
30 }; | |
31 | |
32 #pragma pack(pop) | |
33 | |
34 | |
35 #ifndef _M_IX86 | |
36 #error Only x86 supported right now. | |
37 #endif | |
38 | |
39 // This struct is assembly code + signature. The purpose of the struct is to be | |
40 // able to hook an existing function with our own and store information such | |
41 // as the original function pointer with the code stub. Typically this is used | |
42 // for patching entries of a vtable or e.g. a globally registered wndproc | |
43 // for a class as opposed to a window. | |
44 // When unhooking, you can just call the BypassStub() function and leave the | |
45 // stub in memory. This unhooks your function while leaving the (potential) | |
46 // chain of patches intact. | |
47 // | |
48 // @note: This class is meant for __stdcall calling convention and | |
49 // it uses eax as a temporary variable. The struct can | |
50 // be improved in the future to save eax before the | |
51 // operation and then restore it. | |
52 // | |
53 // For instance if the function prototype is: | |
54 // | |
55 // @code | |
56 // LRESULT WndProc(HWND hwnd, UINT msg, WPARAM wparam, LPARAM lparam); | |
57 // @endcode | |
58 // | |
59 // and we would like to add one static argument to make it, say: | |
60 // | |
61 // @code | |
62 // LRESULT MyNewWndProc(WNDPROC original, HWND hwnd, UINT msg, | |
63 // WPARAM wparam, LPARAM lparam); | |
64 // @endcode | |
65 // | |
66 // That can be achieved by wrapping the function up with a FunctionStub: | |
67 // | |
68 // @code | |
69 // FunctionStub* stub = FunctionStub::Create(original_wndproc, MyNewWndProc); | |
70 // SetClassLongPtr(wnd, GCLP_WNDPROC, stub->code()); | |
71 // @endcode | |
72 struct FunctionStub { | |
73 public: | |
74 // Neutralizes this stub and converts it to a direct jump to a new target. | |
75 void BypassStub(void* new_target); | |
76 | |
77 inline bool is_bypassed() const { | |
78 return bypass_address_ != | |
79 reinterpret_cast<uintptr_t>(&stub_.pop_return_addr_); | |
80 } | |
81 | |
82 // Returns true if the stub is valid and enabled. | |
83 // Don't call this method after bypassing the stub. | |
84 bool is_valid() const; | |
85 | |
86 inline PROC code() const { | |
87 return reinterpret_cast<PROC>(const_cast<FunctionStubAsm*>(&stub_)); | |
88 } | |
89 | |
90 // Use to create a new function stub as shown above. | |
91 // @param extra_argument The static argument to pass to the function. | |
92 // @param dest Target function to which the stub applies. | |
93 // @returns NULL if an error occurs, otherwise a pointer to the | |
94 // function stub. | |
95 static FunctionStub* Create(uintptr_t extra_argument, void* dest); | |
96 | |
97 // Test whether address (likely) points to an existing function stub. | |
98 // @returns NULL if address does not point to a function stub. | |
99 // @note likely means approximately 1/2^48 here. | |
100 static FunctionStub* FromCode(void* address); | |
101 | |
102 // Deallocates a FunctionStub. | |
103 // The stub must not be in use on any thread! | |
104 static bool Destroy(FunctionStub* stub); | |
105 | |
106 // Accessors. | |
107 uintptr_t argument() const { return argument_; } | |
108 void set_argument(uintptr_t argument) { argument_ = argument; } | |
109 | |
110 uintptr_t bypass_address() const { return bypass_address_; } | |
111 void set_bypass_address(uintptr_t bypass_address) { | |
112 bypass_address_ = bypass_address; | |
113 } | |
114 | |
115 uintptr_t destination_function() const { return destination_function_; } | |
116 void set_destination_function(uintptr_t destination_function) { | |
117 destination_function_ = destination_function; | |
118 } | |
119 | |
120 protected: | |
121 // Protected for testing only. | |
122 FunctionStub(uintptr_t extra_argument, void* dest); | |
123 ~FunctionStub(); | |
124 | |
125 void Init(FunctionStubAsm* stub); | |
126 | |
127 FunctionStubAsm stub_; | |
128 | |
129 // Used to identify function stubs that belong to this module. | |
130 HMODULE signature_; | |
131 | |
132 // This is the argument value that gets passed to the destination_function_. | |
133 uintptr_t argument_; | |
134 // Bypass address, if this is the address of the pop_return_addr_, the | |
135 // function stub is not bypassed. | |
136 uintptr_t bypass_address_; | |
137 // The destination function we dispatch to, not used if the stub | |
138 // is bypassed. | |
139 uintptr_t destination_function_; | |
140 }; | |
141 | |
142 #endif // CHROME_FRAME_FUNCTION_STUB_H_ | |
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