libjava/exception.cc

   1 // Functions for Exception Support for Java.
   2
   3 /* Copyright (C) 1998, 1999, 2001, 2002, 2006  Free Software Foundation
   4
   5    This file is part of libgcj.
   6
   7 This software is copyrighted work licensed under the terms of the
   8 Libgcj License.  Please consult the file "LIBGCJ_LICENSE" for
   9 details.  */
  10
  11 #include <config.h>
  12
  13 #include <stddef.h>
  14 #include <stdlib.h>
  15
  16 #include <java/lang/Class.h>
  17 #include <java/lang/NullPointerException.h>
  18 #include <gnu/gcj/RawData.h>
  19 #include <gcj/cni.h>
  20 #include <jvm.h>
  21
  22 // unwind-pe.h uses std::abort(), but sometimes we compile libjava
  23 // without libstdc++-v3. The following hack forces it to use
  24 // stdlib.h's abort().
  25 namespace std
  26 {
  27   static __attribute__ ((__noreturn__)) void
  28   abort ()
  29   {
  30     ::abort ();
  31   }
  32 }
  33 #include "unwind.h"
  34
  35 struct alignment_test_struct
  36 {
  37   char space;
  38   char end[0] __attribute__((aligned));
  39 };
  40
  41 struct java_exception_header
  42 {
  43   /* Cache handler details between Phase 1 and Phase 2.  */
  44   _Unwind_Ptr landingPad;
  45   int handlerSwitchValue;
  46
  47   /* The object being thrown.  Compiled code expects this to be immediately
  48      before the generic exception header.  Which is complicated by the fact
  49      that _Unwind_Exception is ((aligned)).  */
  50
  51   char pad[sizeof(jthrowable) < sizeof(alignment_test_struct)
  52            ? sizeof(alignment_test_struct) - sizeof(jthrowable) : 0]
  53     __attribute__((aligned));
  54
  55   jthrowable value;
  56
  57   /* The generic exception header.  */
  58   _Unwind_Exception unwindHeader;
  59 };
  60
  61 #ifdef __ARM_EABI_UNWINDER__
  62 // This is the exception class we report -- "GNUCJAVA".
  63
  64 const _Unwind_Exception_Class __gcj_exception_class
  65   = {'G', 'N', 'U', 'C', 'J', 'A', 'V', 'A'};
  66
  67 static inline java_exception_header *
  68 get_exception_header_from_ue (_Unwind_Exception *exc)
  69 {
  70   return reinterpret_cast<java_exception_header *>(exc + 1) - 1;
  71 }
  72
  73 extern "C" void __cxa_begin_cleanup (_Unwind_Exception*);
  74
  75 #else // !__ARM_EABI_UNWINDER__
  76 // This is the exception class we report -- "GNUCJAVA".
  77 const _Unwind_Exception_Class __gcj_exception_class
  78 = ((((((((_Unwind_Exception_Class) 'G'
  79          << 8 | (_Unwind_Exception_Class) 'N')
  80         << 8 | (_Unwind_Exception_Class) 'U')
  81        << 8 | (_Unwind_Exception_Class) 'C')
  82       << 8 | (_Unwind_Exception_Class) 'J')
  83      << 8 | (_Unwind_Exception_Class) 'A')
  84     << 8 | (_Unwind_Exception_Class) 'V')
  85    << 8 | (_Unwind_Exception_Class) 'A');
  86
  87
  88 static inline java_exception_header *
  89 get_exception_header_from_ue (_Unwind_Exception *exc)
  90 {
  91   return reinterpret_cast<java_exception_header *>(exc + 1) - 1;
  92 }
  93 #endif // !__ARM_EABI_UNWINDER__
  94
  95 /* Perform a throw, Java style. Throw will unwind through this call,
  96    so there better not be any handlers or exception thrown here. */
  97
  98 extern "C" void
  99 _Jv_Throw (jthrowable value)
 100 {
 101   java_exception_header *xh
 102     = static_cast<java_exception_header *>(_Jv_AllocRawObj (sizeof (*xh)));
 103
 104   if (value == NULL)
 105     value = new java::lang::NullPointerException ();
 106   xh->value = value;
 107
 108   memcpy (&xh->unwindHeader.exception_class, &__gcj_exception_class,
 109           sizeof xh->unwindHeader.exception_class);
 110   xh->unwindHeader.exception_cleanup = NULL;
 111
 112   /* We're happy with setjmp/longjmp exceptions or region-based
 113      exception handlers: entry points are provided here for both.  */
 114   _Unwind_Reason_Code code;
 115 #ifdef SJLJ_EXCEPTIONS
 116   code = _Unwind_SjLj_RaiseException (&xh->unwindHeader);
 117 #else
 118   code = _Unwind_RaiseException (&xh->unwindHeader);
 119 #endif
 120
 121   /* If code == _URC_END_OF_STACK, then we reached top of stack without
 122      finding a handler for the exception.  Since each thread is run in
 123      a try/catch, this oughtn't happen.  If code is something else, we
 124      encountered some sort of heinous lossage from which we could not
 125      recover.  As is the way of such things, almost certainly we will have
 126      crashed before now, rather than actually being able to diagnose the
 127      problem.  */
 128   abort();
 129 }
 130
 131 \f
 132 #include "unwind-pe.h"
 133 \f
 134 struct lsda_header_info
 135 {
 136   _Unwind_Ptr Start;
 137   _Unwind_Ptr LPStart;
 138   const unsigned char *TType;
 139   const unsigned char *action_table;
 140   unsigned char ttype_encoding;
 141   unsigned char call_site_encoding;
 142 };
 143
 144 static const unsigned char *
 145 parse_lsda_header (_Unwind_Context *context, const unsigned char *p,
 146                    lsda_header_info *info)
 147 {
 148   _uleb128_t tmp;
 149   unsigned char lpstart_encoding;
 150
 151   info->Start = (context ? _Unwind_GetRegionStart (context) : 0);
 152
 153   // Find @LPStart, the base to which landing pad offsets are relative.
 154   lpstart_encoding = *p++;
 155   if (lpstart_encoding != DW_EH_PE_omit)
 156     p = read_encoded_value (context, lpstart_encoding, p, &info->LPStart);
 157   else
 158     info->LPStart = info->Start;
 159
 160   // Find @TType, the base of the handler and exception spec type data.
 161   info->ttype_encoding = *p++;
 162   if (info->ttype_encoding != DW_EH_PE_omit)
 163     {
 164       p = read_uleb128 (p, &tmp);
 165       info->TType = p + tmp;
 166     }
 167   else
 168     info->TType = 0;
 169
 170   // The encoding and length of the call-site table; the action table
 171   // immediately follows.
 172   info->call_site_encoding = *p++;
 173   p = read_uleb128 (p, &tmp);
 174   info->action_table = p + tmp;
 175
 176   return p;
 177 }
 178
 179 #ifdef __ARM_EABI_UNWINDER__
 180
 181 static void **
 182 get_ttype_entry(_Unwind_Context *, lsda_header_info* info, _uleb128_t i)
 183 {
 184   _Unwind_Ptr ptr;
 185
 186   ptr = (_Unwind_Ptr) (info->TType - (i * 4));
 187   ptr = _Unwind_decode_target2(ptr);
 188
 189   return reinterpret_cast<void **>(ptr);
 190 }
 191
 192 #else
 193
 194 static void **
 195 get_ttype_entry (_Unwind_Context *context, lsda_header_info *info, long i)
 196 {
 197   _Unwind_Ptr ptr;
 198
 199   i *= size_of_encoded_value (info->ttype_encoding);
 200   read_encoded_value (context, info->ttype_encoding, info->TType - i, &ptr);
 201
 202   return reinterpret_cast<void **>(ptr);
 203 }
 204
 205 #endif
 206
 207 // Using a different personality function name causes link failures
 208 // when trying to mix code using different exception handling models.
 209 #ifdef SJLJ_EXCEPTIONS
 210 #define PERSONALITY_FUNCTION    __gcj_personality_sj0
 211 #define __builtin_eh_return_data_regno(x) x
 212 #else
 213 #define PERSONALITY_FUNCTION    __gcj_personality_v0
 214 #endif
 215
 216 #ifdef __ARM_EABI_UNWINDER__
 217
 218 #define CONTINUE_UNWINDING \
 219   do                                                            \
 220     {                                                           \
 221       if (__gnu_unwind_frame(ue_header, context) != _URC_OK)    \
 222         return _URC_FAILURE;                                    \
 223       return _URC_CONTINUE_UNWIND;                              \
 224     }                                                           \
 225   while (0)
 226
 227 extern "C" _Unwind_Reason_Code
 228 PERSONALITY_FUNCTION (_Unwind_State state,
 229                       struct _Unwind_Exception* ue_header,
 230                       struct _Unwind_Context* context)
 231 #else
 232
 233 #define CONTINUE_UNWINDING return _URC_CONTINUE_UNWIND
 234
 235 extern "C" _Unwind_Reason_Code
 236 PERSONALITY_FUNCTION (int version,
 237                       _Unwind_Action actions,
 238                       _Unwind_Exception_Class exception_class,
 239                       struct _Unwind_Exception *ue_header,
 240                       struct _Unwind_Context *context)
 241
 242 #endif
 243 {
 244   java_exception_header *xh = get_exception_header_from_ue (ue_header);
 245
 246   lsda_header_info info;
 247   const unsigned char *language_specific_data;
 248   const unsigned char *action_record;
 249   const unsigned char *p;
 250   _Unwind_Ptr landing_pad, ip;
 251   int handler_switch_value;
 252   bool saw_cleanup;
 253   bool saw_handler;
 254   bool foreign_exception;
 255   int ip_before_insn = 0;
 256
 257 #ifdef __ARM_EABI_UNWINDER__
 258   _Unwind_Action actions;
 259
 260   switch (state & _US_ACTION_MASK)
 261     {
 262     case _US_VIRTUAL_UNWIND_FRAME:
 263       actions = _UA_SEARCH_PHASE;
 264       break;
 265
 266     case _US_UNWIND_FRAME_STARTING:
 267       actions = _UA_CLEANUP_PHASE;
 268       if (!(state & _US_FORCE_UNWIND)
 269           && ue_header->barrier_cache.sp == _Unwind_GetGR(context, 13))
 270         actions |= _UA_HANDLER_FRAME;
 271       break;
 272
 273     case _US_UNWIND_FRAME_RESUME:
 274       CONTINUE_UNWINDING;
 275       break;
 276
 277     default:
 278       std::abort();
 279     }
 280   actions |= state & _US_FORCE_UNWIND;
 281
 282   // We don't know which runtime we're working with, so can't check this.
 283   // However the ABI routines hide this from us, and we don't actually need
 284   // to know.
 285   foreign_exception = false;
 286
 287   // The dwarf unwinder assumes the context structure holds things like the
 288   // function and LSDA pointers.  The ARM implementation caches these in
 289   // the exception header (UCB).  To avoid rewriting everything we make the
 290   // virtual IP register point at the UCB.
 291   ip = (_Unwind_Ptr) ue_header;
 292   _Unwind_SetGR(context, 12, ip);
 293
 294 #else
 295   // Interface version check.
 296   if (version != 1)
 297     return _URC_FATAL_PHASE1_ERROR;
 298   foreign_exception = exception_class != __gcj_exception_class;
 299 #endif
 300
 301   // Shortcut for phase 2 found handler for domestic exception.
 302   if (actions == (_UA_CLEANUP_PHASE | _UA_HANDLER_FRAME)
 303       && !foreign_exception)
 304     {
 305       handler_switch_value = xh->handlerSwitchValue;
 306       landing_pad = xh->landingPad;
 307       goto install_context;
 308     }
 309
 310   // FIXME: In Phase 1, record _Unwind_GetIPInfo in xh->obj as a part of
 311   // the stack trace for this exception.  This will only collect Java
 312   // frames, but perhaps that is acceptable.
 313   // FIXME2: _Unwind_GetIPInfo is nonsensical for SJLJ, being a call-site
 314   // index instead of a PC value.  We could perhaps arrange for
 315   // _Unwind_GetRegionStart to return context->fc->jbuf[1], which
 316   // is the address of the handler label for __builtin_longjmp, but
 317   // there is no solution for DONT_USE_BUILTIN_SETJMP.
 318
 319   language_specific_data = (const unsigned char *)
 320     _Unwind_GetLanguageSpecificData (context);
 321
 322   // If no LSDA, then there are no handlers or cleanups.
 323   if (! language_specific_data)
 324     CONTINUE_UNWINDING;
 325
 326   // Parse the LSDA header.
 327   p = parse_lsda_header (context, language_specific_data, &info);
 328 #ifdef HAVE_GETIPINFO
 329   ip = _Unwind_GetIPInfo (context, &ip_before_insn);
 330 #else
 331   ip = _Unwind_GetIP (context);
 332 #endif
 333   if (! ip_before_insn)
 334     --ip;
 335   landing_pad = 0;
 336   action_record = 0;
 337   handler_switch_value = 0;
 338
 339 #ifdef SJLJ_EXCEPTIONS
 340   // The given "IP" is an index into the call-site table, with two
 341   // exceptions -- -1 means no-action, and 0 means terminate.  But
 342   // since we're using uleb128 values, we've not got random access
 343   // to the array.
 344   if ((int) ip <= 0)
 345     return _URC_CONTINUE_UNWIND;
 346   else
 347     {
 348       _uleb128_t cs_lp, cs_action;
 349       do
 350         {
 351           p = read_uleb128 (p, &cs_lp);
 352           p = read_uleb128 (p, &cs_action);
 353         }
 354       while (--ip);
 355
 356       // Can never have null landing pad for sjlj -- that would have
 357       // been indicated by a -1 call site index.
 358       landing_pad = cs_lp + 1;
 359       if (cs_action)
 360         action_record = info.action_table + cs_action - 1;
 361       goto found_something;
 362     }
 363 #else
 364   // Search the call-site table for the action associated with this IP.
 365   while (p < info.action_table)
 366     {
 367       _Unwind_Ptr cs_start, cs_len, cs_lp;
 368       _uleb128_t cs_action;
 369
 370       // Note that all call-site encodings are "absolute" displacements.
 371       p = read_encoded_value (0, info.call_site_encoding, p, &cs_start);
 372       p = read_encoded_value (0, info.call_site_encoding, p, &cs_len);
 373       p = read_encoded_value (0, info.call_site_encoding, p, &cs_lp);
 374       p = read_uleb128 (p, &cs_action);
 375
 376       // The table is sorted, so if we've passed the ip, stop.
 377       if (ip < info.Start + cs_start)
 378         p = info.action_table;
 379       else if (ip < info.Start + cs_start + cs_len)
 380         {
 381           if (cs_lp)
 382             landing_pad = info.LPStart + cs_lp;
 383           if (cs_action)
 384             action_record = info.action_table + cs_action - 1;
 385           goto found_something;
 386         }
 387     }
 388 #endif // SJLJ_EXCEPTIONS
 389
 390   // If ip is not present in the table, C++ would call terminate.
 391   // ??? It is perhaps better to tweek the LSDA so that no-action
 392   // is mapped to no-entry for Java.
 393   CONTINUE_UNWINDING;
 394
 395  found_something:
 396   saw_cleanup = false;
 397   saw_handler = false;
 398
 399   if (landing_pad == 0)
 400     {
 401       // If ip is present, and has a null landing pad, there are
 402       // no cleanups or handlers to be run.
 403     }
 404   else if (action_record == 0)
 405     {
 406       // If ip is present, has a non-null landing pad, and a null
 407       // action table offset, then there are only cleanups present.
 408       // Cleanups use a zero switch value, as set above.
 409       saw_cleanup = true;
 410     }
 411   else
 412     {
 413       // Otherwise we have a catch handler.
 414       _sleb128_t ar_filter, ar_disp;
 415
 416       while (1)
 417         {
 418           p = action_record;
 419           p = read_sleb128 (p, &ar_filter);
 420           read_sleb128 (p, &ar_disp);
 421
 422           if (ar_filter == 0)
 423             {
 424               // Zero filter values are cleanups.
 425               saw_cleanup = true;
 426             }
 427
 428           // During forced unwinding, we only run cleanups.  With a
 429           // foreign exception class, we have no class info to match.
 430           else if ((actions & _UA_FORCE_UNWIND)
 431                    || foreign_exception)
 432             ;
 433
 434           else if (ar_filter > 0)
 435             {
 436               // Positive filter values are handlers.
 437
 438               void **catch_word = get_ttype_entry (context, &info, ar_filter);
 439               jclass catch_type = (jclass)*catch_word;
 440
 441               // FIXME: This line is a kludge to work around exception
 442               // handlers written in C++, which don't yet use indirect
 443               // dispatch.
 444               if (catch_type == *(void **)&java::lang::Class::class$)
 445                 catch_type = (jclass)catch_word;
 446
 447               if (_Jv_IsInstanceOf (xh->value, catch_type))
 448                 {
 449                   handler_switch_value = ar_filter;
 450                   saw_handler = true;
 451                   break;
 452                 }
 453             }
 454           else
 455             {
 456               // Negative filter values are exception specifications,
 457               // which Java does not use.
 458               // ??? Perhaps better to make them an index into a table
 459               // of null-terminated strings instead of playing games
 460               // with Utf8Const+1 as above.
 461               abort ();
 462             }
 463
 464           if (ar_disp == 0)
 465             break;
 466           action_record = p + ar_disp;
 467         }
 468     }
 469
 470   if (! saw_handler && ! saw_cleanup)
 471         CONTINUE_UNWINDING;
 472
 473   if (actions & _UA_SEARCH_PHASE)
 474     {
 475       if (! saw_handler)
 476         CONTINUE_UNWINDING;
 477
 478       // For domestic exceptions, we cache data from phase 1 for phase 2.
 479       if (! foreign_exception)
 480         {
 481           xh->handlerSwitchValue = handler_switch_value;
 482           xh->landingPad = landing_pad;
 483         }
 484       return _URC_HANDLER_FOUND;
 485     }
 486
 487  install_context:
 488   _Unwind_SetGR (context, __builtin_eh_return_data_regno (0),
 489                  (_Unwind_Ptr) &xh->unwindHeader);
 490   _Unwind_SetGR (context, __builtin_eh_return_data_regno (1),
 491                  handler_switch_value);
 492   _Unwind_SetIP (context, landing_pad);
 493 #ifdef __ARM_EABI_UNWINDER__
 494   if (saw_cleanup)
 495     __cxa_begin_cleanup(ue_header);
 496 #endif
 497   return _URC_INSTALL_CONTEXT;
 498 }