1 /* SJLJ exception handling and frame unwind runtime interface routines.
2    Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2006,
3    2009, 2011 Free Software Foundation, Inc.
4 
5    This file is part of GCC.
6 
7    GCC is free software; you can redistribute it and/or modify it
8    under the terms of the GNU General Public License as published by
9    the Free Software Foundation; either version 3, or (at your option)
10    any later version.
11 
12    GCC is distributed in the hope that it will be useful, but WITHOUT
13    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
14    or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
15    License for more details.
16 
17    Under Section 7 of GPL version 3, you are granted additional
18    permissions described in the GCC Runtime Library Exception, version
19    3.1, as published by the Free Software Foundation.
20 
21    You should have received a copy of the GNU General Public License and
22    a copy of the GCC Runtime Library Exception along with this program;
23    see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
24    <http://www.gnu.org/licenses/>.  */
25 
26 #include "tconfig.h"
27 #include "tsystem.h"
28 #include "coretypes.h"
29 #include "tm.h"
30 #include "libgcc_tm.h"
31 #include "unwind.h"
32 #include "gthr.h"
33 
34 #ifdef __USING_SJLJ_EXCEPTIONS__
35 
36 #ifdef DONT_USE_BUILTIN_SETJMP
37 #ifndef inhibit_libc
38 #include <setjmp.h>
39 #else
40 typedef void *jmp_buf[JMP_BUF_SIZE];
41 extern void longjmp(jmp_buf, int) __attribute__((noreturn));
42 #endif
43 #else
44 #define longjmp __builtin_longjmp
45 #endif
46 
47 /* The setjmp side is dealt with in the except.c file.  */
48 #undef setjmp
49 #define setjmp setjmp_should_not_be_used_in_this_file
50 
51 
52 /* This structure is allocated on the stack of the target function.
53    This must match the definition created in except.c:init_eh.  */
54 struct SjLj_Function_Context
55 {
56   /* This is the chain through all registered contexts.  It is
57      filled in by _Unwind_SjLj_Register.  */
58   struct SjLj_Function_Context *prev;
59 
60   /* This is assigned in by the target function before every call
61      to the index of the call site in the lsda.  It is assigned by
62      the personality routine to the landing pad index.  */
63   int call_site;
64 
65   /* This is how data is returned from the personality routine to
66      the target function's handler.  */
67   _Unwind_Word data[4];
68 
69   /* These are filled in once by the target function before any
70      exceptions are expected to be handled.  */
71   _Unwind_Personality_Fn personality;
72   void *lsda;
73 
74 #ifdef DONT_USE_BUILTIN_SETJMP
75   /* We don't know what sort of alignment requirements the system
76      jmp_buf has.  We over estimated in except.c, and now we have
77      to match that here just in case the system *didn't* have more
78      restrictive requirements.  */
79   jmp_buf jbuf __attribute__((aligned));
80 #else
81   void *jbuf[];
82 #endif
83 };
84 
85 struct _Unwind_Context
86 {
87   struct SjLj_Function_Context *fc;
88 };
89 
90 typedef struct
91 {
92   _Unwind_Personality_Fn personality;
93 } _Unwind_FrameState;
94 
95 
96 /* Manage the chain of registered function contexts.  */
97 
98 /* Single threaded fallback chain.  */
99 static struct SjLj_Function_Context *fc_static;
100 
101 #if __GTHREADS
102 static __gthread_key_t fc_key;
103 static int use_fc_key = -1;
104 
105 static void
106 fc_key_init (void)
107 {
108   use_fc_key = __gthread_key_create (&fc_key, 0) == 0;
109 }
110 
111 static void
112 fc_key_init_once (void)
113 {
114   static __gthread_once_t once = __GTHREAD_ONCE_INIT;
115   if (__gthread_once (&once, fc_key_init) != 0 || use_fc_key < 0)
116     use_fc_key = 0;
117 }
118 #endif
119 
120 void
121 _Unwind_SjLj_Register (struct SjLj_Function_Context *fc)
122 {
123 #if __GTHREADS
124   if (use_fc_key < 0)
125     fc_key_init_once ();
126 
127   if (use_fc_key)
128     {
129       fc->prev = __gthread_getspecific (fc_key);
130       __gthread_setspecific (fc_key, fc);
131     }
132   else
133 #endif
134     {
135       fc->prev = fc_static;
136       fc_static = fc;
137     }
138 }
139 
140 static inline struct SjLj_Function_Context *
141 _Unwind_SjLj_GetContext (void)
142 {
143 #if __GTHREADS
144   if (use_fc_key < 0)
145     fc_key_init_once ();
146 
147   if (use_fc_key)
148     return __gthread_getspecific (fc_key);
149 #endif
150   return fc_static;
151 }
152 
153 static inline void
154 _Unwind_SjLj_SetContext (struct SjLj_Function_Context *fc)
155 {
156 #if __GTHREADS
157   if (use_fc_key < 0)
158     fc_key_init_once ();
159 
160   if (use_fc_key)
161     __gthread_setspecific (fc_key, fc);
162   else
163 #endif
164     fc_static = fc;
165 }
166 
167 void
168 _Unwind_SjLj_Unregister (struct SjLj_Function_Context *fc)
169 {
170   _Unwind_SjLj_SetContext (fc->prev);
171 }
172 
173 
174 /* Get/set the return data value at INDEX in CONTEXT.  */
175 
176 _Unwind_Word
177 _Unwind_GetGR (struct _Unwind_Context *context, int index)
178 {
179   return context->fc->data[index];
180 }
181 
182 /* Get the value of the CFA as saved in CONTEXT.  */
183 
184 _Unwind_Word
185 _Unwind_GetCFA (struct _Unwind_Context *context __attribute__((unused)))
186 {
187   /* ??? Ideally __builtin_setjmp places the CFA in the jmpbuf.  */
188 
189 #ifndef DONT_USE_BUILTIN_SETJMP
190   /* This is a crude imitation of the CFA: the saved stack pointer.
191      This is roughly the CFA of the frame before CONTEXT.  When using the
192      DWARF-2 unwinder _Unwind_GetCFA returns the CFA of the frame described
193      by CONTEXT instead; but for DWARF-2 the cleanups associated with
194      CONTEXT have already been run, and for SJLJ they have not yet been.  */
195   if (context->fc != NULL)
196     return (_Unwind_Word) context->fc->jbuf[2];
197 #endif
198 
199   /* Otherwise we're out of luck for now.  */
200   return (_Unwind_Word) 0;
201 }
202 
203 void
204 _Unwind_SetGR (struct _Unwind_Context *context, int index, _Unwind_Word val)
205 {
206   context->fc->data[index] = val;
207 }
208 
209 /* Get the call-site index as saved in CONTEXT.  */
210 
211 _Unwind_Ptr
212 _Unwind_GetIP (struct _Unwind_Context *context)
213 {
214   return context->fc->call_site + 1;
215 }
216 
217 _Unwind_Ptr
218 _Unwind_GetIPInfo (struct _Unwind_Context *context, int *ip_before_insn)
219 {
220   *ip_before_insn = 0;
221   if (context->fc != NULL)
222     return context->fc->call_site + 1;
223   else
224     return 0;
225 }
226 
227 /* Set the return landing pad index in CONTEXT.  */
228 
229 void
230 _Unwind_SetIP (struct _Unwind_Context *context, _Unwind_Ptr val)
231 {
232   context->fc->call_site = val - 1;
233 }
234 
235 void *
236 _Unwind_GetLanguageSpecificData (struct _Unwind_Context *context)
237 {
238   return context->fc->lsda;
239 }
240 
241 _Unwind_Ptr
242 _Unwind_GetRegionStart (struct _Unwind_Context *context __attribute__((unused)) )
243 {
244   return 0;
245 }
246 
247 void *
248 _Unwind_FindEnclosingFunction (void *pc __attribute__((unused)))
249 {
250   return NULL;
251 }
252 
253 #ifndef __ia64__
254 _Unwind_Ptr
255 _Unwind_GetDataRelBase (struct _Unwind_Context *context __attribute__((unused)) )
256 {
257   return 0;
258 }
259 
260 _Unwind_Ptr
261 _Unwind_GetTextRelBase (struct _Unwind_Context *context __attribute__((unused)) )
262 {
263   return 0;
264 }
265 #endif
266 
267 static inline _Unwind_Reason_Code
268 uw_frame_state_for (struct _Unwind_Context *context, _Unwind_FrameState *fs)
269 {
270   if (context->fc == NULL)
271     {
272       fs->personality = NULL;
273       return _URC_END_OF_STACK;
274     }
275   else
276     {
277       fs->personality = context->fc->personality;
278       return _URC_NO_REASON;
279     }
280 }
281 
282 static inline void
283 uw_update_context (struct _Unwind_Context *context,
284 		   _Unwind_FrameState *fs __attribute__((unused)) )
285 {
286   context->fc = context->fc->prev;
287 }
288 
289 static void
290 uw_advance_context (struct _Unwind_Context *context, _Unwind_FrameState *fs)
291 {
292   _Unwind_SjLj_Unregister (context->fc);
293   uw_update_context (context, fs);
294 }
295 
296 static inline void
297 uw_init_context (struct _Unwind_Context *context)
298 {
299   context->fc = _Unwind_SjLj_GetContext ();
300 }
301 
302 static void __attribute__((noreturn))
303 uw_install_context (struct _Unwind_Context *current __attribute__((unused)),
304                     struct _Unwind_Context *target)
305 {
306   _Unwind_SjLj_SetContext (target->fc);
307   longjmp (target->fc->jbuf, 1);
308 }
309 
310 static inline _Unwind_Ptr
311 uw_identify_context (struct _Unwind_Context *context)
312 {
313   return (_Unwind_Ptr) context->fc;
314 }
315 
316 
317 /* Play games with unwind symbols so that we can have call frame
318    and sjlj symbols in the same shared library.  Not that you can
319    use them simultaneously...  */
320 #define _Unwind_RaiseException		_Unwind_SjLj_RaiseException
321 #define _Unwind_ForcedUnwind		_Unwind_SjLj_ForcedUnwind
322 #define _Unwind_Resume			_Unwind_SjLj_Resume
323 #define _Unwind_Resume_or_Rethrow	_Unwind_SjLj_Resume_or_Rethrow
324 
325 #include "unwind.inc"
326 
327 #endif /* USING_SJLJ_EXCEPTIONS */
328