1 // Functions for Exception Support for Java.
3 /* Copyright (C) 1998, 1999, 2001, 2002 Free Software Foundation
5 This file is part of libgcj.
7 This software is copyrighted work licensed under the terms of the
8 Libgcj License. Please consult the file "LIBGCJ_LICENSE" for
16 #include <java/lang/Class.h>
17 #include <java/lang/NullPointerException.h>
18 #include <gnu/gcj/runtime/MethodRef.h>
19 #include <gnu/gcj/RawData.h>
23 // unwind-pe.h uses std::abort(), but sometimes we compile libjava
24 // without libstdc++-v3. The following hack forces it to use
25 // stdlib.h's abort().
28 static __attribute__ ((__noreturn__)) void
36 struct alignment_test_struct
39 char end[0] __attribute__((aligned));
42 struct java_exception_header
44 /* Cache handler details between Phase 1 and Phase 2. */
45 _Unwind_Ptr landingPad;
46 int handlerSwitchValue;
48 /* The object being thrown. Compiled code expects this to be immediately
49 before the generic exception header. Which is complicated by the fact
50 that _Unwind_Exception is ((aligned)). */
52 char pad[sizeof(jthrowable) < sizeof(alignment_test_struct)
53 ? sizeof(alignment_test_struct) - sizeof(jthrowable) : 0]
54 __attribute__((aligned));
58 /* The generic exception header. */
59 _Unwind_Exception unwindHeader;
62 // This is the exception class we report -- "GNUCJAVA".
63 const _Unwind_Exception_Class __gcj_exception_class
64 = ((((((((_Unwind_Exception_Class) 'G'
65 << 8 | (_Unwind_Exception_Class) 'N')
66 << 8 | (_Unwind_Exception_Class) 'U')
67 << 8 | (_Unwind_Exception_Class) 'C')
68 << 8 | (_Unwind_Exception_Class) 'J')
69 << 8 | (_Unwind_Exception_Class) 'A')
70 << 8 | (_Unwind_Exception_Class) 'V')
71 << 8 | (_Unwind_Exception_Class) 'A');
74 static inline java_exception_header *
75 get_exception_header_from_ue (_Unwind_Exception *exc)
77 return reinterpret_cast<java_exception_header *>(exc + 1) - 1;
80 /* Perform a throw, Java style. Throw will unwind through this call,
81 so there better not be any handlers or exception thrown here. */
84 _Jv_Throw (jthrowable value)
86 java_exception_header *xh
87 = static_cast<java_exception_header *>(_Jv_AllocRawObj (sizeof (*xh)));
90 value = new java::lang::NullPointerException ();
93 xh->unwindHeader.exception_class = __gcj_exception_class;
94 xh->unwindHeader.exception_cleanup = NULL;
96 /* We're happy with setjmp/longjmp exceptions or region-based
97 exception handlers: entry points are provided here for both. */
98 _Unwind_Reason_Code code;
99 #ifdef SJLJ_EXCEPTIONS
100 code = _Unwind_SjLj_RaiseException (&xh->unwindHeader);
102 code = _Unwind_RaiseException (&xh->unwindHeader);
105 /* If code == _URC_END_OF_STACK, then we reached top of stack without
106 finding a handler for the exception. Since each thread is run in
107 a try/catch, this oughtn't happen. If code is something else, we
108 encountered some sort of heinous lossage from which we could not
109 recover. As is the way of such things, almost certainly we will have
110 crashed before now, rather than actually being able to diagnose the
116 #include "unwind-pe.h"
118 struct lsda_header_info
122 const unsigned char *TType;
123 const unsigned char *action_table;
124 unsigned char ttype_encoding;
125 unsigned char call_site_encoding;
128 static const unsigned char *
129 parse_lsda_header (_Unwind_Context *context, const unsigned char *p,
130 lsda_header_info *info)
133 unsigned char lpstart_encoding;
135 info->Start = (context ? _Unwind_GetRegionStart (context) : 0);
137 // Find @LPStart, the base to which landing pad offsets are relative.
138 lpstart_encoding = *p++;
139 if (lpstart_encoding != DW_EH_PE_omit)
140 p = read_encoded_value (context, lpstart_encoding, p, &info->LPStart);
142 info->LPStart = info->Start;
144 // Find @TType, the base of the handler and exception spec type data.
145 info->ttype_encoding = *p++;
146 if (info->ttype_encoding != DW_EH_PE_omit)
148 p = read_uleb128 (p, &tmp);
149 info->TType = p + tmp;
154 // The encoding and length of the call-site table; the action table
155 // immediately follows.
156 info->call_site_encoding = *p++;
157 p = read_uleb128 (p, &tmp);
158 info->action_table = p + tmp;
164 get_ttype_entry (_Unwind_Context *context, lsda_header_info *info, long i)
168 i *= size_of_encoded_value (info->ttype_encoding);
169 read_encoded_value (context, info->ttype_encoding, info->TType - i, &ptr);
171 return reinterpret_cast<void **>(ptr);
175 // Using a different personality function name causes link failures
176 // when trying to mix code using different exception handling models.
177 #ifdef SJLJ_EXCEPTIONS
178 #define PERSONALITY_FUNCTION __gcj_personality_sj0
179 #define __builtin_eh_return_data_regno(x) x
181 #define PERSONALITY_FUNCTION __gcj_personality_v0
184 extern "C" _Unwind_Reason_Code
185 PERSONALITY_FUNCTION (int version,
186 _Unwind_Action actions,
187 _Unwind_Exception_Class exception_class,
188 struct _Unwind_Exception *ue_header,
189 struct _Unwind_Context *context)
191 java_exception_header *xh = get_exception_header_from_ue (ue_header);
193 lsda_header_info info;
194 const unsigned char *language_specific_data;
195 const unsigned char *action_record;
196 const unsigned char *p;
197 _Unwind_Ptr landing_pad, ip;
198 int handler_switch_value;
203 // Interface version check.
205 return _URC_FATAL_PHASE1_ERROR;
207 // Shortcut for phase 2 found handler for domestic exception.
208 if (actions == (_UA_CLEANUP_PHASE | _UA_HANDLER_FRAME)
209 && exception_class == __gcj_exception_class)
211 handler_switch_value = xh->handlerSwitchValue;
212 landing_pad = xh->landingPad;
213 goto install_context;
216 // FIXME: In Phase 1, record _Unwind_GetIP in xh->obj as a part of
217 // the stack trace for this exception. This will only collect Java
218 // frames, but perhaps that is acceptable.
219 // FIXME2: _Unwind_GetIP is nonsensical for SJLJ, being a call-site
220 // index instead of a PC value. We could perhaps arrange for
221 // _Unwind_GetRegionStart to return context->fc->jbuf[1], which
222 // is the address of the handler label for __builtin_longjmp, but
223 // there is no solution for DONT_USE_BUILTIN_SETJMP.
225 language_specific_data = (const unsigned char *)
226 _Unwind_GetLanguageSpecificData (context);
228 // If no LSDA, then there are no handlers or cleanups.
229 if (! language_specific_data)
230 return _URC_CONTINUE_UNWIND;
232 // Parse the LSDA header.
233 p = parse_lsda_header (context, language_specific_data, &info);
234 ip = _Unwind_GetIP (context) - 1;
237 handler_switch_value = 0;
239 #ifdef SJLJ_EXCEPTIONS
240 // The given "IP" is an index into the call-site table, with two
241 // exceptions -- -1 means no-action, and 0 means terminate. But
242 // since we're using uleb128 values, we've not got random access
245 return _URC_CONTINUE_UNWIND;
248 _Unwind_Word cs_lp, cs_action;
251 p = read_uleb128 (p, &cs_lp);
252 p = read_uleb128 (p, &cs_action);
256 // Can never have null landing pad for sjlj -- that would have
257 // been indicated by a -1 call site index.
258 landing_pad = cs_lp + 1;
260 action_record = info.action_table + cs_action - 1;
261 goto found_something;
264 // Search the call-site table for the action associated with this IP.
265 while (p < info.action_table)
267 _Unwind_Ptr cs_start, cs_len, cs_lp;
268 _Unwind_Word cs_action;
270 // Note that all call-site encodings are "absolute" displacements.
271 p = read_encoded_value (0, info.call_site_encoding, p, &cs_start);
272 p = read_encoded_value (0, info.call_site_encoding, p, &cs_len);
273 p = read_encoded_value (0, info.call_site_encoding, p, &cs_lp);
274 p = read_uleb128 (p, &cs_action);
276 // The table is sorted, so if we've passed the ip, stop.
277 if (ip < info.Start + cs_start)
278 p = info.action_table;
279 else if (ip < info.Start + cs_start + cs_len)
282 landing_pad = info.LPStart + cs_lp;
284 action_record = info.action_table + cs_action - 1;
285 goto found_something;
288 #endif // SJLJ_EXCEPTIONS
290 // If ip is not present in the table, C++ would call terminate.
291 // ??? It is perhaps better to tweek the LSDA so that no-action
292 // is mapped to no-entry for Java.
293 return _URC_CONTINUE_UNWIND;
299 if (landing_pad == 0)
301 // If ip is present, and has a null landing pad, there are
302 // no cleanups or handlers to be run.
304 else if (action_record == 0)
306 // If ip is present, has a non-null landing pad, and a null
307 // action table offset, then there are only cleanups present.
308 // Cleanups use a zero switch value, as set above.
313 // Otherwise we have a catch handler.
314 _Unwind_Sword ar_filter, ar_disp;
319 p = read_sleb128 (p, &ar_filter);
320 read_sleb128 (p, &ar_disp);
324 // Zero filter values are cleanups.
328 // During forced unwinding, we only run cleanups. With a
329 // foreign exception class, we have no class info to match.
330 else if ((actions & _UA_FORCE_UNWIND)
331 || exception_class != __gcj_exception_class)
334 else if (ar_filter > 0)
336 // Positive filter values are handlers.
338 void **catch_word = get_ttype_entry (context, &info, ar_filter);
339 jclass catch_type = (jclass)*catch_word;
341 // FIXME: This line is a kludge to work around exception
342 // handlers written in C++, which don't yet use indirect
344 if (catch_type == *(void **)&java::lang::Class::class$)
345 catch_type = (jclass)catch_word;
347 if (_Jv_IsInstanceOf (xh->value, catch_type))
349 handler_switch_value = ar_filter;
356 // Negative filter values are exception specifications,
357 // which Java does not use.
358 // ??? Perhaps better to make them an index into a table
359 // of null-terminated strings instead of playing games
360 // with Utf8Const+1 as above.
366 action_record = p + ar_disp;
370 if (! saw_handler && ! saw_cleanup)
371 return _URC_CONTINUE_UNWIND;
373 if (actions & _UA_SEARCH_PHASE)
376 return _URC_CONTINUE_UNWIND;
378 // For domestic exceptions, we cache data from phase 1 for phase 2.
379 if (exception_class == __gcj_exception_class)
381 xh->handlerSwitchValue = handler_switch_value;
382 xh->landingPad = landing_pad;
384 return _URC_HANDLER_FOUND;
388 _Unwind_SetGR (context, __builtin_eh_return_data_regno (0),
389 (_Unwind_Ptr) &xh->unwindHeader);
390 _Unwind_SetGR (context, __builtin_eh_return_data_regno (1),
391 handler_switch_value);
392 _Unwind_SetIP (context, landing_pad);
393 return _URC_INSTALL_CONTEXT;