1 // Functions for Exception Support for Java.
3 /* Copyright (C) 1998, 1999, 2001 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>
24 // More nastiness: the GC wants to define TRUE and FALSE. We don't
25 // need the Java definitions (themselves a hack), so we undefine them.
33 #include <include/gc_gcj.h>
37 struct alignment_test_struct
40 char end[0] __attribute__((aligned));
43 struct java_exception_header
45 /* Cache handler details between Phase 1 and Phase 2. */
46 _Unwind_Ptr landingPad;
47 int handlerSwitchValue;
49 /* The object being thrown. Compiled code expects this to be immediately
50 before the generic exception header. Which is complicated by the fact
51 that _Unwind_Exception is ((aligned)). */
53 char pad[sizeof(jthrowable) < sizeof(alignment_test_struct)
54 ? sizeof(alignment_test_struct) - sizeof(jthrowable) : 0]
55 __attribute__((aligned));
59 /* The generic exception header. */
60 _Unwind_Exception unwindHeader;
63 // This is the exception class we report -- "GNUCJAVA".
64 const _Unwind_Exception_Class __gcj_exception_class
65 = ((((((((_Unwind_Exception_Class) 'G'
66 << 8 | (_Unwind_Exception_Class) 'N')
67 << 8 | (_Unwind_Exception_Class) 'U')
68 << 8 | (_Unwind_Exception_Class) 'C')
69 << 8 | (_Unwind_Exception_Class) 'J')
70 << 8 | (_Unwind_Exception_Class) 'A')
71 << 8 | (_Unwind_Exception_Class) 'V')
72 << 8 | (_Unwind_Exception_Class) 'A');
75 static inline java_exception_header *
76 get_exception_header_from_ue (_Unwind_Exception *exc)
78 return reinterpret_cast<java_exception_header *>(exc + 1) - 1;
81 /* Perform a throw, Java style. Throw will unwind through this call,
82 so there better not be any handlers or exception thrown here. */
85 _Jv_Throw (jthrowable value)
87 /* FIXME: Use the proper API to the collector. */
88 java_exception_header *xh
89 = static_cast<java_exception_header *>(GC_malloc (sizeof (*xh)));
92 value = new java::lang::NullPointerException ();
95 xh->unwindHeader.exception_class = __gcj_exception_class;
96 xh->unwindHeader.exception_cleanup = NULL;
98 /* We're happy with setjmp/longjmp exceptions or region-based
99 exception handlers: entry points are provided here for both. */
100 _Unwind_Reason_Code code;
101 #ifdef SJLJ_EXCEPTIONS
102 code = _Unwind_SjLj_RaiseException (&xh->unwindHeader);
104 code = _Unwind_RaiseException (&xh->unwindHeader);
107 /* FIXME: If code == _URC_END_OF_STACK, then we reached top of
108 stack without finding a handler for the exception. I seem to
109 recall that Java has specific rules to handle this.
111 If code is something else, we encountered some sort of heinous
112 lossage, from which we could not recover. As is the way of such
113 things we'll almost certainly have crashed before now, rather
114 than actually being able to diagnose the problem. */
119 // ??? These ought to go somewhere else dwarf2 or dwarf2eh related.
121 // Pointer encodings.
122 #define DW_EH_PE_absptr 0x00
123 #define DW_EH_PE_omit 0xff
125 #define DW_EH_PE_uleb128 0x01
126 #define DW_EH_PE_udata2 0x02
127 #define DW_EH_PE_udata4 0x03
128 #define DW_EH_PE_udata8 0x04
129 #define DW_EH_PE_sleb128 0x09
130 #define DW_EH_PE_sdata2 0x0A
131 #define DW_EH_PE_sdata4 0x0B
132 #define DW_EH_PE_sdata8 0x0C
133 #define DW_EH_PE_signed 0x08
135 #define DW_EH_PE_pcrel 0x10
136 #define DW_EH_PE_textrel 0x20
137 #define DW_EH_PE_datarel 0x30
138 #define DW_EH_PE_funcrel 0x40
141 size_of_encoded_value (unsigned char encoding)
143 switch (encoding & 0x07)
145 case DW_EH_PE_absptr:
146 return sizeof (void *);
147 case DW_EH_PE_udata2:
149 case DW_EH_PE_udata4:
151 case DW_EH_PE_udata8:
157 static const unsigned char *
158 read_encoded_value (_Unwind_Context *context, unsigned char encoding,
159 const unsigned char *p, _Unwind_Ptr *val)
164 unsigned u2 __attribute__ ((mode (HI)));
165 unsigned u4 __attribute__ ((mode (SI)));
166 unsigned u8 __attribute__ ((mode (DI)));
167 signed s2 __attribute__ ((mode (HI)));
168 signed s4 __attribute__ ((mode (SI)));
169 signed s8 __attribute__ ((mode (DI)));
170 } __attribute__((__packed__));
172 union unaligned *u = (union unaligned *) p;
175 switch (encoding & 0x0f)
177 case DW_EH_PE_absptr:
178 result = (_Unwind_Ptr) u->ptr;
179 p += sizeof (void *);
182 case DW_EH_PE_uleb128:
184 unsigned int shift = 0;
191 result |= (_Unwind_Ptr)(byte & 0x7f) << shift;
198 case DW_EH_PE_sleb128:
200 unsigned int shift = 0;
207 result |= (_Unwind_Ptr)(byte & 0x7f) << shift;
212 if (shift < 8 * sizeof(result) && (byte & 0x40) != 0)
213 result |= -(1L << shift);
217 case DW_EH_PE_udata2:
221 case DW_EH_PE_udata4:
225 case DW_EH_PE_udata8:
230 case DW_EH_PE_sdata2:
234 case DW_EH_PE_sdata4:
238 case DW_EH_PE_sdata8:
248 switch (encoding & 0xf0)
250 case DW_EH_PE_absptr:
254 // Define as relative to the beginning of the pointer.
255 result += (_Unwind_Ptr) u;
258 case DW_EH_PE_textrel:
259 case DW_EH_PE_datarel:
263 case DW_EH_PE_funcrel:
264 result += _Unwind_GetRegionStart (context);
275 static inline const unsigned char *
276 read_uleb128 (const unsigned char *p, _Unwind_Ptr *val)
278 return read_encoded_value (0, DW_EH_PE_uleb128, p, val);
281 static inline const unsigned char *
282 read_sleb128 (const unsigned char *p, _Unwind_Ptr *val)
284 return read_encoded_value (0, DW_EH_PE_sleb128, p, val);
288 struct lsda_header_info
292 const unsigned char *TType;
293 const unsigned char *action_table;
294 unsigned char ttype_encoding;
295 unsigned char call_site_encoding;
298 static const unsigned char *
299 parse_lsda_header (_Unwind_Context *context, const unsigned char *p,
300 lsda_header_info *info)
303 unsigned char lpstart_encoding;
305 info->Start = (context ? _Unwind_GetRegionStart (context) : 0);
307 // Find @LPStart, the base to which landing pad offsets are relative.
308 lpstart_encoding = *p++;
309 if (lpstart_encoding != DW_EH_PE_omit)
310 p = read_encoded_value (context, lpstart_encoding, p, &info->LPStart);
312 info->LPStart = info->Start;
314 // Find @TType, the base of the handler and exception spec type data.
315 info->ttype_encoding = *p++;
316 if (info->ttype_encoding != DW_EH_PE_omit)
318 p = read_uleb128 (p, &tmp);
319 info->TType = p + tmp;
324 // The encoding and length of the call-site table; the action table
325 // immediately follows.
326 info->call_site_encoding = *p++;
327 p = read_uleb128 (p, &tmp);
328 info->action_table = p + tmp;
334 get_ttype_entry (_Unwind_Context *context, lsda_header_info *info, long i)
338 i *= size_of_encoded_value (info->ttype_encoding);
339 read_encoded_value (context, info->ttype_encoding, info->TType - i, &ptr);
341 return reinterpret_cast<jclass>(ptr);
345 // Using a different personality function name causes link failures
346 // when trying to mix code using different exception handling models.
347 #ifdef SJLJ_EXCEPTIONS
348 #define PERSONALITY_FUNCTION __gcj_personality_sj0
349 #define __builtin_eh_return_data_regno(x) x
351 #define PERSONALITY_FUNCTION __gcj_personality_v0
354 extern "C" _Unwind_Reason_Code
355 PERSONALITY_FUNCTION (int version,
356 _Unwind_Action actions,
357 _Unwind_Exception_Class exception_class,
358 struct _Unwind_Exception *ue_header,
359 struct _Unwind_Context *context)
361 java_exception_header *xh = get_exception_header_from_ue (ue_header);
363 lsda_header_info info;
364 const unsigned char *language_specific_data;
365 const unsigned char *action_record;
366 const unsigned char *p;
367 _Unwind_Ptr landing_pad, ip;
368 int handler_switch_value;
373 // Interface version check.
375 return _URC_FATAL_PHASE1_ERROR;
377 // Shortcut for phase 2 found handler for domestic exception.
378 if (actions == (_UA_CLEANUP_PHASE | _UA_HANDLER_FRAME)
379 && exception_class == __gcj_exception_class)
381 handler_switch_value = xh->handlerSwitchValue;
382 landing_pad = xh->landingPad;
383 goto install_context;
386 // FIXME: In Phase 1, record _Unwind_GetIP in xh->obj as a part of
387 // the stack trace for this exception. This will only collect Java
388 // frames, but perhaps that is acceptable.
389 // FIXME2: _Unwind_GetIP is nonsensical for SJLJ, being a call-site
390 // index instead of a PC value. We could perhaps arrange for
391 // _Unwind_GetRegionStart to return context->fc->jbuf[1], which
392 // is the address of the handler label for __builtin_longjmp, but
393 // there is no solution for DONT_USE_BUILTIN_SETJMP.
395 language_specific_data = (const unsigned char *)
396 _Unwind_GetLanguageSpecificData (context);
398 // If no LSDA, then there are no handlers or cleanups.
399 if (! language_specific_data)
400 return _URC_CONTINUE_UNWIND;
402 // Parse the LSDA header.
403 p = parse_lsda_header (context, language_specific_data, &info);
404 ip = _Unwind_GetIP (context) - 1;
407 handler_switch_value = 0;
409 #ifdef SJLJ_EXCEPTIONS
410 // The given "IP" is an index into the call-site table, with two
411 // exceptions -- -1 means no-action, and 0 means terminate. But
412 // since we're using uleb128 values, we've not got random access
415 return _URC_CONTINUE_UNWIND;
418 _Unwind_Ptr cs_lp, cs_action;
421 p = read_uleb128 (p, &cs_lp);
422 p = read_uleb128 (p, &cs_action);
426 // Can never have null landing pad for sjlj -- that would have
427 // been indicated by a -1 call site index.
428 landing_pad = cs_lp + 1;
430 action_record = info.action_table + cs_action - 1;
431 goto found_something;
434 // Search the call-site table for the action associated with this IP.
435 while (p < info.action_table)
437 _Unwind_Ptr cs_start, cs_len, cs_lp, cs_action;
439 // Note that all call-site encodings are "absolute" displacements.
440 p = read_encoded_value (0, info.call_site_encoding, p, &cs_start);
441 p = read_encoded_value (0, info.call_site_encoding, p, &cs_len);
442 p = read_encoded_value (0, info.call_site_encoding, p, &cs_lp);
443 p = read_uleb128 (p, &cs_action);
445 // The table is sorted, so if we've passed the ip, stop.
446 if (ip < info.Start + cs_start)
447 p = info.action_table;
448 else if (ip < info.Start + cs_start + cs_len)
451 landing_pad = info.LPStart + cs_lp;
453 action_record = info.action_table + cs_action - 1;
454 goto found_something;
457 #endif // SJLJ_EXCEPTIONS
459 // If ip is not present in the table, C++ would call terminate.
460 // ??? It is perhaps better to tweek the LSDA so that no-action
461 // is mapped to no-entry for Java.
462 return _URC_CONTINUE_UNWIND;
468 if (landing_pad == 0)
470 // If ip is present, and has a null landing pad, there are
471 // no cleanups or handlers to be run.
473 else if (action_record == 0)
475 // If ip is present, has a non-null landing pad, and a null
476 // action table offset, then there are only cleanups present.
477 // Cleanups use a zero switch value, as set above.
482 // Otherwise we have a catch handler.
483 signed long ar_filter, ar_disp;
490 p = read_sleb128 (p, &tmp); ar_filter = tmp;
491 read_sleb128 (p, &tmp); ar_disp = tmp;
495 // Zero filter values are cleanups.
499 // During forced unwinding, we only run cleanups. With a
500 // foreign exception class, we have no class info to match.
501 else if ((actions & _UA_FORCE_UNWIND)
502 || exception_class != __gcj_exception_class)
505 else if (ar_filter > 0)
507 // Positive filter values are handlers.
509 jclass catch_type = get_ttype_entry (context, &info, ar_filter);
511 // The catch_type is either a (java::lang::Class*) or
512 // is one more than a (Utf8Const*).
513 if ((size_t)catch_type & 1)
514 catch_type = _Jv_FindClass ((Utf8Const*)catch_type - 1, NULL);
516 if (_Jv_IsInstanceOf (xh->value, catch_type))
518 handler_switch_value = ar_filter;
525 // Negative filter values are exception specifications,
526 // which Java does not use.
527 // ??? Perhaps better to make them an index into a table
528 // of null-terminated strings instead of playing games
529 // with Utf8Const+1 as above.
535 action_record = p + ar_disp;
539 if (! saw_handler && ! saw_cleanup)
540 return _URC_CONTINUE_UNWIND;
542 if (actions & _UA_SEARCH_PHASE)
545 return _URC_CONTINUE_UNWIND;
547 // For domestic exceptions, we cache data from phase 1 for phase 2.
548 if (exception_class == __gcj_exception_class)
550 xh->handlerSwitchValue = handler_switch_value;
551 xh->landingPad = landing_pad;
553 return _URC_HANDLER_FOUND;
557 _Unwind_SetGR (context, __builtin_eh_return_data_regno (0),
558 (_Unwind_Ptr) &xh->unwindHeader);
559 _Unwind_SetGR (context, __builtin_eh_return_data_regno (1),
560 handler_switch_value);
561 _Unwind_SetIP (context, landing_pad);
562 return _URC_INSTALL_CONTEXT;