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/RawData.h>
22 // Sometimes we compile libjava without libstdc++-v3. Therefore make
23 // sure we use stdlib.h's abort().
24 #define gcc_unreachable() ::abort ()
27 struct alignment_test_struct
30 char end[0] __attribute__((aligned));
33 struct java_exception_header
35 /* Cache handler details between Phase 1 and Phase 2. */
36 _Unwind_Ptr landingPad;
37 int handlerSwitchValue;
39 /* The object being thrown. Compiled code expects this to be immediately
40 before the generic exception header. Which is complicated by the fact
41 that _Unwind_Exception is ((aligned)). */
43 char pad[sizeof(jthrowable) < sizeof(alignment_test_struct)
44 ? sizeof(alignment_test_struct) - sizeof(jthrowable) : 0]
45 __attribute__((aligned));
49 /* The generic exception header. */
50 _Unwind_Exception unwindHeader;
53 // This is the exception class we report -- "GNUCJAVA".
54 const _Unwind_Exception_Class __gcj_exception_class
55 = ((((((((_Unwind_Exception_Class) 'G'
56 << 8 | (_Unwind_Exception_Class) 'N')
57 << 8 | (_Unwind_Exception_Class) 'U')
58 << 8 | (_Unwind_Exception_Class) 'C')
59 << 8 | (_Unwind_Exception_Class) 'J')
60 << 8 | (_Unwind_Exception_Class) 'A')
61 << 8 | (_Unwind_Exception_Class) 'V')
62 << 8 | (_Unwind_Exception_Class) 'A');
65 static inline java_exception_header *
66 get_exception_header_from_ue (_Unwind_Exception *exc)
68 return reinterpret_cast<java_exception_header *>(exc + 1) - 1;
71 /* Perform a throw, Java style. Throw will unwind through this call,
72 so there better not be any handlers or exception thrown here. */
75 _Jv_Throw (jthrowable value)
77 java_exception_header *xh
78 = static_cast<java_exception_header *>(_Jv_AllocRawObj (sizeof (*xh)));
81 value = new java::lang::NullPointerException ();
84 xh->unwindHeader.exception_class = __gcj_exception_class;
85 xh->unwindHeader.exception_cleanup = NULL;
87 /* We're happy with setjmp/longjmp exceptions or region-based
88 exception handlers: entry points are provided here for both. */
89 _Unwind_Reason_Code code;
90 #ifdef SJLJ_EXCEPTIONS
91 code = _Unwind_SjLj_RaiseException (&xh->unwindHeader);
93 code = _Unwind_RaiseException (&xh->unwindHeader);
96 /* If code == _URC_END_OF_STACK, then we reached top of stack without
97 finding a handler for the exception. Since each thread is run in
98 a try/catch, this oughtn't happen. If code is something else, we
99 encountered some sort of heinous lossage from which we could not
100 recover. As is the way of such things, almost certainly we will have
101 crashed before now, rather than actually being able to diagnose the
107 #include "unwind-pe.h"
109 struct lsda_header_info
113 const unsigned char *TType;
114 const unsigned char *action_table;
115 unsigned char ttype_encoding;
116 unsigned char call_site_encoding;
119 static const unsigned char *
120 parse_lsda_header (_Unwind_Context *context, const unsigned char *p,
121 lsda_header_info *info)
124 unsigned char lpstart_encoding;
126 info->Start = (context ? _Unwind_GetRegionStart (context) : 0);
128 // Find @LPStart, the base to which landing pad offsets are relative.
129 lpstart_encoding = *p++;
130 if (lpstart_encoding != DW_EH_PE_omit)
131 p = read_encoded_value (context, lpstart_encoding, p, &info->LPStart);
133 info->LPStart = info->Start;
135 // Find @TType, the base of the handler and exception spec type data.
136 info->ttype_encoding = *p++;
137 if (info->ttype_encoding != DW_EH_PE_omit)
139 p = read_uleb128 (p, &tmp);
140 info->TType = p + tmp;
145 // The encoding and length of the call-site table; the action table
146 // immediately follows.
147 info->call_site_encoding = *p++;
148 p = read_uleb128 (p, &tmp);
149 info->action_table = p + tmp;
155 get_ttype_entry (_Unwind_Context *context, lsda_header_info *info, long i)
159 i *= size_of_encoded_value (info->ttype_encoding);
160 read_encoded_value (context, info->ttype_encoding, info->TType - i, &ptr);
162 return reinterpret_cast<void **>(ptr);
166 // Using a different personality function name causes link failures
167 // when trying to mix code using different exception handling models.
168 #ifdef SJLJ_EXCEPTIONS
169 #define PERSONALITY_FUNCTION __gcj_personality_sj0
170 #define __builtin_eh_return_data_regno(x) x
172 #define PERSONALITY_FUNCTION __gcj_personality_v0
175 extern "C" _Unwind_Reason_Code
176 PERSONALITY_FUNCTION (int version,
177 _Unwind_Action actions,
178 _Unwind_Exception_Class exception_class,
179 struct _Unwind_Exception *ue_header,
180 struct _Unwind_Context *context)
182 java_exception_header *xh = get_exception_header_from_ue (ue_header);
184 lsda_header_info info;
185 const unsigned char *language_specific_data;
186 const unsigned char *action_record;
187 const unsigned char *p;
188 _Unwind_Ptr landing_pad, ip;
189 int handler_switch_value;
194 // Interface version check.
196 return _URC_FATAL_PHASE1_ERROR;
198 // Shortcut for phase 2 found handler for domestic exception.
199 if (actions == (_UA_CLEANUP_PHASE | _UA_HANDLER_FRAME)
200 && exception_class == __gcj_exception_class)
202 handler_switch_value = xh->handlerSwitchValue;
203 landing_pad = xh->landingPad;
204 goto install_context;
207 // FIXME: In Phase 1, record _Unwind_GetIP in xh->obj as a part of
208 // the stack trace for this exception. This will only collect Java
209 // frames, but perhaps that is acceptable.
210 // FIXME2: _Unwind_GetIP is nonsensical for SJLJ, being a call-site
211 // index instead of a PC value. We could perhaps arrange for
212 // _Unwind_GetRegionStart to return context->fc->jbuf[1], which
213 // is the address of the handler label for __builtin_longjmp, but
214 // there is no solution for DONT_USE_BUILTIN_SETJMP.
216 language_specific_data = (const unsigned char *)
217 _Unwind_GetLanguageSpecificData (context);
219 // If no LSDA, then there are no handlers or cleanups.
220 if (! language_specific_data)
221 return _URC_CONTINUE_UNWIND;
223 // Parse the LSDA header.
224 p = parse_lsda_header (context, language_specific_data, &info);
225 ip = _Unwind_GetIP (context) - 1;
228 handler_switch_value = 0;
230 #ifdef SJLJ_EXCEPTIONS
231 // The given "IP" is an index into the call-site table, with two
232 // exceptions -- -1 means no-action, and 0 means terminate. But
233 // since we're using uleb128 values, we've not got random access
236 return _URC_CONTINUE_UNWIND;
239 _Unwind_Word cs_lp, cs_action;
242 p = read_uleb128 (p, &cs_lp);
243 p = read_uleb128 (p, &cs_action);
247 // Can never have null landing pad for sjlj -- that would have
248 // been indicated by a -1 call site index.
249 landing_pad = cs_lp + 1;
251 action_record = info.action_table + cs_action - 1;
252 goto found_something;
255 // Search the call-site table for the action associated with this IP.
256 while (p < info.action_table)
258 _Unwind_Ptr cs_start, cs_len, cs_lp;
259 _Unwind_Word cs_action;
261 // Note that all call-site encodings are "absolute" displacements.
262 p = read_encoded_value (0, info.call_site_encoding, p, &cs_start);
263 p = read_encoded_value (0, info.call_site_encoding, p, &cs_len);
264 p = read_encoded_value (0, info.call_site_encoding, p, &cs_lp);
265 p = read_uleb128 (p, &cs_action);
267 // The table is sorted, so if we've passed the ip, stop.
268 if (ip < info.Start + cs_start)
269 p = info.action_table;
270 else if (ip < info.Start + cs_start + cs_len)
273 landing_pad = info.LPStart + cs_lp;
275 action_record = info.action_table + cs_action - 1;
276 goto found_something;
279 #endif // SJLJ_EXCEPTIONS
281 // If ip is not present in the table, C++ would call terminate.
282 // ??? It is perhaps better to tweek the LSDA so that no-action
283 // is mapped to no-entry for Java.
284 return _URC_CONTINUE_UNWIND;
290 if (landing_pad == 0)
292 // If ip is present, and has a null landing pad, there are
293 // no cleanups or handlers to be run.
295 else if (action_record == 0)
297 // If ip is present, has a non-null landing pad, and a null
298 // action table offset, then there are only cleanups present.
299 // Cleanups use a zero switch value, as set above.
304 // Otherwise we have a catch handler.
305 _Unwind_Sword ar_filter, ar_disp;
310 p = read_sleb128 (p, &ar_filter);
311 read_sleb128 (p, &ar_disp);
315 // Zero filter values are cleanups.
319 // During forced unwinding, we only run cleanups. With a
320 // foreign exception class, we have no class info to match.
321 else if ((actions & _UA_FORCE_UNWIND)
322 || exception_class != __gcj_exception_class)
325 else if (ar_filter > 0)
327 // Positive filter values are handlers.
329 void **catch_word = get_ttype_entry (context, &info, ar_filter);
330 jclass catch_type = (jclass)*catch_word;
332 // FIXME: This line is a kludge to work around exception
333 // handlers written in C++, which don't yet use indirect
335 if (catch_type == *(void **)&java::lang::Class::class$)
336 catch_type = (jclass)catch_word;
338 if (_Jv_IsInstanceOf (xh->value, catch_type))
340 handler_switch_value = ar_filter;
347 // Negative filter values are exception specifications,
348 // which Java does not use.
349 // ??? Perhaps better to make them an index into a table
350 // of null-terminated strings instead of playing games
351 // with Utf8Const+1 as above.
357 action_record = p + ar_disp;
361 if (! saw_handler && ! saw_cleanup)
362 return _URC_CONTINUE_UNWIND;
364 if (actions & _UA_SEARCH_PHASE)
367 return _URC_CONTINUE_UNWIND;
369 // For domestic exceptions, we cache data from phase 1 for phase 2.
370 if (exception_class == __gcj_exception_class)
372 xh->handlerSwitchValue = handler_switch_value;
373 xh->landingPad = landing_pad;
375 return _URC_HANDLER_FOUND;
379 _Unwind_SetGR (context, __builtin_eh_return_data_regno (0),
380 (_Unwind_Ptr) &xh->unwindHeader);
381 _Unwind_SetGR (context, __builtin_eh_return_data_regno (1),
382 handler_switch_value);
383 _Unwind_SetIP (context, landing_pad);
384 return _URC_INSTALL_CONTEXT;