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1 | /* Definitions for Dwarf2 EH unwind support for Windows32 targets |
2 | Copyright (C) 2007, 2009, 2010 | |
76f5e200 DS |
3 | Free Software Foundation, Inc. |
4 | Contributed by Pascal Obry <obry@adacore.com> | |
5 | ||
6 | This file is part of GCC. | |
7 | ||
8 | GCC is free software; you can redistribute it and/or modify it under | |
9 | the terms of the GNU General Public License as published by the Free | |
748086b7 | 10 | Software Foundation; either version 3, or (at your option) any later |
76f5e200 DS |
11 | version. |
12 | ||
76f5e200 DS |
13 | GCC is distributed in the hope that it will be useful, but WITHOUT ANY |
14 | WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
15 | FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
16 | for more details. | |
17 | ||
748086b7 JJ |
18 | Under Section 7 of GPL version 3, you are granted additional |
19 | permissions described in the GCC Runtime Library Exception, version | |
20 | 3.1, as published by the Free Software Foundation. | |
21 | ||
22 | You should have received a copy of the GNU General Public License and | |
23 | a copy of the GCC Runtime Library Exception along with this program; | |
24 | see the files COPYING3 and COPYING.RUNTIME respectively. If not, see | |
25 | <http://www.gnu.org/licenses/>. */ | |
26 | ||
76f5e200 DS |
27 | |
28 | /* This file implements the md_fallback_frame_state_for routine for | |
29 | Windows, triggered when the GCC table based unwinding process hits a | |
30 | frame for which no unwind info has been registered. This typically | |
31 | occurs when raising an exception from a signal handler, because the | |
32 | handler is actually called from the OS kernel. | |
33 | ||
34 | The basic idea is to detect that we are indeed trying to unwind past a | |
35 | signal handler and to fill out the GCC internal unwinding structures for | |
36 | the OS kernel frame as if it had been directly called from the | |
37 | interrupted context. | |
38 | ||
39 | This is all assuming that the code to set the handler asked the kernel | |
40 | to pass a pointer to such context information. | |
41 | ||
42 | There is three main parts. | |
43 | ||
44 | 1) The first thing to do is to check if we are in a signal context. If | |
45 | not we can just return as there is nothing to do. We are probably on | |
46 | some foreign code for which no unwind frame can be found. If this is | |
47 | a call from the Windows signal handler, then: | |
48 | ||
49 | 2) We must get the signal context information. | |
50 | ||
51 | * With the standard exception filter: | |
52 | ||
53 | This is on Windows pointed to by an EXCEPTION_POINTERS. We know that | |
54 | the signal handle will call an UnhandledExceptionFilter with this | |
55 | parameter. The spec for this routine is: | |
56 | ||
57 | LONG WINAPI UnhandledExceptionFilter(struct _EXCEPTION_POINTERS*); | |
58 | ||
59 | So the pointer to struct _EXCEPTION_POINTERS must be somewhere on the | |
60 | stack. | |
61 | ||
62 | This was found experimentally to always be at offset 0 of the context | |
63 | frame in all cases handled by this implementation. | |
64 | ||
65 | * With the SEH exception handler: | |
66 | ||
67 | In this case the signal context is directly on the stack as the SEH | |
68 | exception handler has the following prototype: | |
69 | ||
70 | DWORD | |
71 | SEH_error_handler (PEXCEPTION_RECORD ExceptionRecord, | |
72 | PVOID EstablisherFrame, | |
73 | PCONTEXT ContextRecord, | |
74 | PVOID DispatcherContext) | |
75 | ||
76 | This was found experimentally to always be at offset 56 of the | |
77 | context frame in all cases handled by this implementation. | |
78 | ||
79 | 3) When we have the signal context we just have to save some registers | |
80 | and set the return address based on the program counter (Eip). | |
81 | ||
82 | Note that this implementation follows closely the same principles as the | |
83 | GNU/Linux and OSF ones. */ | |
84 | ||
85 | #define WIN32_MEAN_AND_LEAN | |
86 | #include <windows.h> | |
87 | /* Patterns found experimentally to be on a Windows signal handler */ | |
88 | ||
89 | /* In a standard exception filter */ | |
90 | ||
91 | #define SIG_PAT1 \ | |
92 | (pc_[-2] == 0xff && pc_[-1] == 0xd0 /* call %eax */ \ | |
93 | && pc_[0] == 0x83 && pc_[1] == 0xf8) /* cmp 0xdepl,%eax */ | |
94 | ||
95 | #define SIG_PAT2 \ | |
96 | (pc_[-5] == 0xe8 && pc_[-4] == 0x68 /* call (depl16) */ \ | |
97 | && pc_[0] == 0xc3) /* ret */ | |
98 | ||
99 | /* In a Win32 SEH handler */ | |
100 | ||
101 | #define SIG_SEH1 \ | |
102 | (pc_[-5] == 0xe8 /* call addr */ \ | |
103 | && pc_[0] == 0x83 && pc_[1] == 0xc4 /* add 0xval,%esp */ \ | |
104 | && pc_[3] == 0xb8) /* mov 0xval,%eax */ | |
105 | ||
106 | #define SIG_SEH2 \ | |
107 | (pc_[-5] == 0x8b && pc_[-4] == 0x4d /* mov depl(%ebp),%ecx */ \ | |
108 | && pc_[0] == 0x64 && pc_[1] == 0x8b) /* mov %fs:(0),<reg> */ \ | |
109 | ||
110 | /* In the GCC alloca (stack probing) */ | |
111 | ||
112 | #define SIG_ALLOCA \ | |
113 | (pc_[-1] == 0x83 /* orl $0x0,(%ecx) */ \ | |
114 | && pc_[0] == 0x9 && pc_[1] == 0 \ | |
115 | && pc_[2] == 0x2d && pc_[3] == 0 /* subl $0x1000,%eax */ \ | |
116 | && pc_[4] == 0x10 && pc_[5] == 0) | |
117 | ||
118 | ||
119 | #define MD_FALLBACK_FRAME_STATE_FOR i386_w32_fallback_frame_state | |
120 | ||
121 | static _Unwind_Reason_Code | |
122 | i386_w32_fallback_frame_state (struct _Unwind_Context *context, | |
123 | _Unwind_FrameState *fs) | |
124 | ||
125 | { | |
126 | void * ctx_ra_ = (void *)(context->ra); /* return address */ | |
127 | void * ctx_cfa_ = (void *)(context->cfa); /* context frame address */ | |
128 | unsigned char * pc_ = (unsigned char *) ctx_ra_; | |
129 | ||
130 | /* In the test below we look for two specific patterns found | |
131 | experimentally to be in the Windows signal handler. */ | |
76f5e200 DS |
132 | if (SIG_PAT1 || SIG_PAT2 || SIG_SEH1 || SIG_SEH2) |
133 | { | |
134 | PEXCEPTION_POINTERS weinfo_; | |
135 | PCONTEXT proc_ctx_; | |
136 | long new_cfa_; | |
137 | ||
138 | if (SIG_SEH1) | |
139 | proc_ctx_ = (PCONTEXT) (*(int*)(ctx_cfa_ + 56)); | |
140 | else if (SIG_SEH2) | |
141 | proc_ctx_ = (PCONTEXT) (*(int*)(ctx_cfa_ + 8)); | |
142 | else | |
143 | { | |
144 | weinfo_ = (PEXCEPTION_POINTERS) (*(int*)ctx_cfa_); | |
145 | proc_ctx_ = weinfo_->ContextRecord; | |
146 | } | |
147 | ||
148 | /* The new context frame address is the stack pointer. */ | |
76f5e200 DS |
149 | new_cfa_ = proc_ctx_->Esp; |
150 | fs->regs.cfa_how = CFA_REG_OFFSET; | |
151 | fs->regs.cfa_reg = __builtin_dwarf_sp_column(); | |
152 | fs->regs.cfa_offset = new_cfa_ - (long) ctx_cfa_; | |
153 | ||
5d0d1564 | 154 | /* Restore registers. */ |
76f5e200 DS |
155 | fs->regs.reg[0].how = REG_SAVED_OFFSET; |
156 | fs->regs.reg[0].loc.offset = (long)&proc_ctx_->Eax - new_cfa_; | |
157 | fs->regs.reg[3].how = REG_SAVED_OFFSET; | |
158 | fs->regs.reg[3].loc.offset = (long)&proc_ctx_->Ebx - new_cfa_; | |
159 | fs->regs.reg[1].how = REG_SAVED_OFFSET; | |
160 | fs->regs.reg[1].loc.offset = (long)&proc_ctx_->Ecx - new_cfa_; | |
161 | fs->regs.reg[2].how = REG_SAVED_OFFSET; | |
162 | fs->regs.reg[2].loc.offset = (long)&proc_ctx_->Edx - new_cfa_; | |
163 | fs->regs.reg[6].how = REG_SAVED_OFFSET; | |
164 | fs->regs.reg[6].loc.offset = (long)&proc_ctx_->Esi - new_cfa_; | |
165 | fs->regs.reg[7].how = REG_SAVED_OFFSET; | |
166 | fs->regs.reg[7].loc.offset = (long)&proc_ctx_->Edi - new_cfa_; | |
5d0d1564 EB |
167 | fs->regs.reg[5].how = REG_SAVED_OFFSET; |
168 | fs->regs.reg[5].loc.offset = (long)&proc_ctx_->Ebp - new_cfa_; | |
76f5e200 | 169 | fs->regs.reg[8].how = REG_SAVED_OFFSET; |
5d0d1564 | 170 | fs->regs.reg[8].loc.offset = (long)&proc_ctx_->Eip - new_cfa_; |
76f5e200 | 171 | fs->retaddr_column = 8; |
5d0d1564 EB |
172 | fs->signal_frame = 1; |
173 | ||
76f5e200 DS |
174 | return _URC_NO_REASON; |
175 | } | |
176 | ||
177 | /* Unwinding through _alloca, propagating from a trap triggered by | |
178 | one of it's probes prior to the real SP adjustment. The only | |
179 | operations of interest performed is "pushl %ecx", followed by | |
180 | ecx clobbering. */ | |
76f5e200 DS |
181 | else if (SIG_ALLOCA) |
182 | { | |
183 | /* Only one push between entry in _alloca and the probe trap. */ | |
184 | long new_cfa_ = (long) ctx_cfa_ + 4; | |
185 | ||
186 | fs->regs.cfa_how = CFA_REG_OFFSET; | |
187 | fs->regs.cfa_reg = __builtin_dwarf_sp_column(); | |
188 | fs->regs.cfa_offset = new_cfa_ - (long) ctx_cfa_; | |
189 | ||
190 | /* The saved value of %ecx is at CFA - 4 */ | |
191 | fs->regs.reg[1].how = REG_SAVED_OFFSET; | |
192 | fs->regs.reg[1].loc.offset = -4; | |
193 | ||
194 | /* and what is stored at the CFA is the return address. */ | |
195 | fs->retaddr_column = 8; | |
196 | fs->regs.reg[8].how = REG_SAVED_OFFSET; | |
197 | fs->regs.reg[8].loc.offset = 0; | |
5d0d1564 EB |
198 | fs->signal_frame = 1; |
199 | ||
76f5e200 DS |
200 | return _URC_NO_REASON; |
201 | } | |
202 | else | |
203 | return _URC_END_OF_STACK; | |
204 | } |