1 //===------------------------- cxa_exception.cpp --------------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is dual licensed under the MIT and the University of Illinois Open
6 // Source Licenses. See LICENSE.TXT for details.
9 // This file implements the "Exception Handling APIs"
10 // http://mentorembedded.github.io/cxx-abi/abi-eh.html
11 // http://www.intel.com/design/itanium/downloads/245358.htm
13 //===----------------------------------------------------------------------===//
16 #include "cxa_exception.hpp"
17 #include "cxa_handlers.hpp"
18 #include "private_typeinfo.h"
24 Exception Header Layout:
26 +---------------------------+-----------------------------+---------------+
27 | __cxa_exception | _Unwind_Exception CLNGC++\0 | thrown object |
28 +---------------------------+-----------------------------+---------------+
31 +-------------------------------------------------------+
33 +---------------------------+-----------------------------+
34 | __cxa_dependent_exception | _Unwind_Exception CLNGC++\1 |
35 +---------------------------+-----------------------------+
37 Exception Handling Table Layout:
39 +-----------------+--------+
40 | lpStartEncoding | (char) |
41 +---------+-------+--------+---------------+-----------------------+
42 | lpStart | (encoded with lpStartEncoding) | defaults to funcStart |
43 +---------+-----+--------+-----------------+---------------+-------+
44 | ttypeEncoding | (char) | Encoding of the type_info table |
45 +---------------+-+------+----+----------------------------+----------------+
46 | classInfoOffset | (ULEB128) | Offset to type_info table, defaults to null |
47 +-----------------++--------+-+----------------------------+----------------+
48 | callSiteEncoding | (char) | Encoding for Call Site Table |
49 +------------------+--+-----+-----+------------------------+--------------------------+
50 | callSiteTableLength | (ULEB128) | Call Site Table length, used to find Action table |
51 +---------------------+-----------+---------------------------------------------------+
53 +---------------------+-----------+------------------------------------------------+
54 | Beginning of Call Site Table The current ip lies within the |
55 | ... (start, length) range of one of these |
56 | call sites. There may be action needed. |
57 | +-------------+---------------------------------+------------------------------+ |
58 | | start | (encoded with callSiteEncoding) | offset relative to funcStart | |
59 | | length | (encoded with callSiteEncoding) | length of code fragment | |
60 | | landingPad | (encoded with callSiteEncoding) | offset relative to lpStart | |
61 | | actionEntry | (ULEB128) | Action Table Index 1-based | |
62 | | | | actionEntry == 0 -> cleanup | |
63 | +-------------+---------------------------------+------------------------------+ |
65 +----------------------------------------------------------------------------------+
67 +---------------------+-----------+------------------------------------------------+
68 | Beginning of Call Site Table The current ip is a 1-based index into |
69 | ... this table. Or it is -1 meaning no |
70 | action is needed. Or it is 0 meaning |
72 | +-------------+---------------------------------+------------------------------+ |
73 | | landingPad | (ULEB128) | offset relative to lpStart | |
74 | | actionEntry | (ULEB128) | Action Table Index 1-based | |
75 | | | | actionEntry == 0 -> cleanup | |
76 | +-------------+---------------------------------+------------------------------+ |
78 +----------------------------------------------------------------------------------+
80 +---------------------------------------------------------------------+
81 | Beginning of Action Table ttypeIndex == 0 : cleanup |
82 | ... ttypeIndex > 0 : catch |
83 | ttypeIndex < 0 : exception spec |
84 | +--------------+-----------+--------------------------------------+ |
85 | | ttypeIndex | (SLEB128) | Index into type_info Table (1-based) | |
86 | | actionOffset | (SLEB128) | Offset into next Action Table entry | |
87 | +--------------+-----------+--------------------------------------+ |
89 +---------------------------------------------------------------------+-----------------+
90 | type_info Table, but classInfoOffset does *not* point here! |
91 | +----------------+------------------------------------------------+-----------------+ |
92 | | Nth type_info* | Encoded with ttypeEncoding, 0 means catch(...) | ttypeIndex == N | |
93 | +----------------+------------------------------------------------+-----------------+ |
95 | +----------------+------------------------------------------------+-----------------+ |
96 | | 1st type_info* | Encoded with ttypeEncoding, 0 means catch(...) | ttypeIndex == 1 | |
97 | +----------------+------------------------------------------------+-----------------+ |
98 | +---------------------------------------+-----------+------------------------------+ |
99 | | 1st ttypeIndex for 1st exception spec | (ULEB128) | classInfoOffset points here! | |
100 | | ... | (ULEB128) | | |
101 | | Mth ttypeIndex for 1st exception spec | (ULEB128) | | |
102 | | 0 | (ULEB128) | | |
103 | +---------------------------------------+------------------------------------------+ |
105 | +---------------------------------------+------------------------------------------+ |
106 | | 0 | (ULEB128) | throw() | |
107 | +---------------------------------------+------------------------------------------+ |
109 | +---------------------------------------+------------------------------------------+ |
110 | | 1st ttypeIndex for Nth exception spec | (ULEB128) | | |
111 | | ... | (ULEB128) | | |
112 | | Mth ttypeIndex for Nth exception spec | (ULEB128) | | |
113 | | 0 | (ULEB128) | | |
114 | +---------------------------------------+------------------------------------------+ |
115 +---------------------------------------------------------------------------------------+
119 * ttypeIndex in the Action Table, and in the exception spec table, is an index,
120 not a byte count, if positive. It is a negative index offset of
121 classInfoOffset and the sizeof entry depends on ttypeEncoding.
122 But if ttypeIndex is negative, it is a positive 1-based byte offset into the
124 And if ttypeIndex is zero, it refers to a catch (...).
126 * landingPad can be 0, this implies there is nothing to be done.
128 * landingPad != 0 and actionEntry == 0 implies a cleanup needs to be done
131 * A cleanup can also be found under landingPad != 0 and actionEntry != 0 in
132 the Action Table with ttypeIndex == 0.
143 // Heavily borrowed from llvm/examples/ExceptionDemo/ExceptionDemo.cpp
148 DW_EH_PE_absptr = 0x00,
149 DW_EH_PE_uleb128 = 0x01,
150 DW_EH_PE_udata2 = 0x02,
151 DW_EH_PE_udata4 = 0x03,
152 DW_EH_PE_udata8 = 0x04,
153 DW_EH_PE_sleb128 = 0x09,
154 DW_EH_PE_sdata2 = 0x0A,
155 DW_EH_PE_sdata4 = 0x0B,
156 DW_EH_PE_sdata8 = 0x0C,
157 DW_EH_PE_pcrel = 0x10,
158 DW_EH_PE_textrel = 0x20,
159 DW_EH_PE_datarel = 0x30,
160 DW_EH_PE_funcrel = 0x40,
161 DW_EH_PE_aligned = 0x50,
162 DW_EH_PE_indirect = 0x80,
166 /// Read a uleb128 encoded value and advance pointer
167 /// See Variable Length Data Appendix C in:
168 /// @link http://dwarfstd.org/Dwarf4.pdf @unlink
169 /// @param data reference variable holding memory pointer to decode from
170 /// @returns decoded value
173 readULEB128(const uint8_t** data)
175 uintptr_t result = 0;
178 const uint8_t *p = *data;
182 result |= static_cast<uintptr_t>(byte & 0x7F) << shift;
184 } while (byte & 0x80);
189 /// Read a sleb128 encoded value and advance pointer
190 /// See Variable Length Data Appendix C in:
191 /// @link http://dwarfstd.org/Dwarf4.pdf @unlink
192 /// @param data reference variable holding memory pointer to decode from
193 /// @returns decoded value
196 readSLEB128(const uint8_t** data)
198 uintptr_t result = 0;
201 const uint8_t *p = *data;
205 result |= static_cast<uintptr_t>(byte & 0x7F) << shift;
207 } while (byte & 0x80);
209 if ((byte & 0x40) && (shift < (sizeof(result) << 3)))
210 result |= static_cast<uintptr_t>(~0) << shift;
211 return static_cast<intptr_t>(result);
214 /// Read a pointer encoded value and advance pointer
215 /// See Variable Length Data in:
216 /// @link http://dwarfstd.org/Dwarf3.pdf @unlink
217 /// @param data reference variable holding memory pointer to decode from
218 /// @param encoding dwarf encoding type
219 /// @returns decoded value
222 readEncodedPointer(const uint8_t** data, uint8_t encoding)
224 uintptr_t result = 0;
225 if (encoding == DW_EH_PE_omit)
227 const uint8_t* p = *data;
229 switch (encoding & 0x0F)
231 case DW_EH_PE_absptr:
232 result = *((uintptr_t*)p);
233 p += sizeof(uintptr_t);
235 case DW_EH_PE_uleb128:
236 result = readULEB128(&p);
238 case DW_EH_PE_sleb128:
239 result = static_cast<uintptr_t>(readSLEB128(&p));
241 case DW_EH_PE_udata2:
242 result = *((uint16_t*)p);
243 p += sizeof(uint16_t);
245 case DW_EH_PE_udata4:
246 result = *((uint32_t*)p);
247 p += sizeof(uint32_t);
249 case DW_EH_PE_udata8:
250 result = static_cast<uintptr_t>(*((uint64_t*)p));
251 p += sizeof(uint64_t);
253 case DW_EH_PE_sdata2:
254 result = static_cast<uintptr_t>(*((int16_t*)p));
255 p += sizeof(int16_t);
257 case DW_EH_PE_sdata4:
258 result = static_cast<uintptr_t>(*((int32_t*)p));
259 p += sizeof(int32_t);
261 case DW_EH_PE_sdata8:
262 result = static_cast<uintptr_t>(*((int64_t*)p));
263 p += sizeof(int64_t);
270 // then add relative offset
271 switch (encoding & 0x70)
273 case DW_EH_PE_absptr:
278 result += (uintptr_t)(*data);
280 case DW_EH_PE_textrel:
281 case DW_EH_PE_datarel:
282 case DW_EH_PE_funcrel:
283 case DW_EH_PE_aligned:
289 // then apply indirection
290 if (result && (encoding & DW_EH_PE_indirect))
291 result = *((uintptr_t*)result);
298 call_terminate(bool native_exception, _Unwind_Exception* unwind_exception)
300 __cxa_begin_catch(unwind_exception);
301 if (native_exception)
303 // Use the stored terminate_handler if possible
304 __cxa_exception* exception_header = (__cxa_exception*)(unwind_exception+1) - 1;
305 std::__terminate(exception_header->terminateHandler);
311 const __shim_type_info*
312 get_shim_type_info(uint64_t ttypeIndex, const uint8_t* classInfo,
313 uint8_t ttypeEncoding, bool native_exception,
314 _Unwind_Exception* unwind_exception)
318 // this should not happen. Indicates corrupted eh_table.
319 call_terminate(native_exception, unwind_exception);
321 switch (ttypeEncoding & 0x0F)
323 case DW_EH_PE_absptr:
324 ttypeIndex *= sizeof(void*);
326 case DW_EH_PE_udata2:
327 case DW_EH_PE_sdata2:
330 case DW_EH_PE_udata4:
331 case DW_EH_PE_sdata4:
334 case DW_EH_PE_udata8:
335 case DW_EH_PE_sdata8:
339 // this should not happen. Indicates corrupted eh_table.
340 call_terminate(native_exception, unwind_exception);
342 classInfo -= ttypeIndex;
343 return (const __shim_type_info*)readEncodedPointer(&classInfo, ttypeEncoding);
347 This is checking a thrown exception type, excpType, against a possibly empty
348 list of catchType's which make up an exception spec.
350 An exception spec acts like a catch handler, but in reverse. This "catch
351 handler" will catch an excpType if and only if none of the catchType's in
352 the list will catch a excpType. If any catchType in the list can catch an
353 excpType, then this exception spec does not catch the excpType.
357 exception_spec_can_catch(int64_t specIndex, const uint8_t* classInfo,
358 uint8_t ttypeEncoding, const __shim_type_info* excpType,
359 void* adjustedPtr, _Unwind_Exception* unwind_exception)
363 // this should not happen. Indicates corrupted eh_table.
364 call_terminate(false, unwind_exception);
366 // specIndex is negative of 1-based byte offset into classInfo;
367 specIndex = -specIndex;
369 const uint8_t* temp = classInfo + specIndex;
370 // If any type in the spec list can catch excpType, return false, else return true
371 // adjustments to adjustedPtr are ignored.
374 uint64_t ttypeIndex = readULEB128(&temp);
377 const __shim_type_info* catchType = get_shim_type_info(ttypeIndex,
382 void* tempPtr = adjustedPtr;
383 if (catchType->can_catch(excpType, tempPtr))
391 get_thrown_object_ptr(_Unwind_Exception* unwind_exception)
393 // Even for foreign exceptions, the exception object is *probably* at unwind_exception + 1
394 // Regardless, this library is prohibited from touching a foreign exception
395 void* adjustedPtr = unwind_exception + 1;
396 if (unwind_exception->exception_class == kOurDependentExceptionClass)
397 adjustedPtr = ((__cxa_dependent_exception*)adjustedPtr - 1)->primaryException;
406 int64_t ttypeIndex; // > 0 catch handler, < 0 exception spec handler, == 0 a cleanup
407 const uint8_t* actionRecord; // Currently unused. Retained to ease future maintenance.
408 const uint8_t* languageSpecificData; // Needed only for __cxa_call_unexpected
409 uintptr_t landingPad; // null -> nothing found, else something found
410 void* adjustedPtr; // Used in cxa_exception.cpp
411 _Unwind_Reason_Code reason; // One of _URC_FATAL_PHASE1_ERROR,
412 // _URC_FATAL_PHASE2_ERROR,
413 // _URC_CONTINUE_UNWIND,
414 // _URC_HANDLER_FOUND
417 } // unnamed namespace
421 set_registers(_Unwind_Exception* unwind_exception, _Unwind_Context* context,
422 const scan_results& results)
425 _Unwind_SetGR(context, 0, reinterpret_cast<uintptr_t>(unwind_exception));
426 _Unwind_SetGR(context, 1, static_cast<uintptr_t>(results.ttypeIndex));
428 _Unwind_SetGR(context, __builtin_eh_return_data_regno(0),
429 reinterpret_cast<uintptr_t>(unwind_exception));
430 _Unwind_SetGR(context, __builtin_eh_return_data_regno(1),
431 static_cast<uintptr_t>(results.ttypeIndex));
433 _Unwind_SetIP(context, results.landingPad);
437 There are 3 types of scans needed:
439 1. Scan for handler with native or foreign exception. If handler found,
440 save state and return _URC_HANDLER_FOUND, else return _URC_CONTINUE_UNWIND.
441 May also report an error on invalid input.
442 May terminate for invalid exception table.
445 2. Scan for handler with foreign exception. Must return _URC_HANDLER_FOUND,
447 _UA_CLEANUP_PHASE && _UA_HANDLER_FRAME && !native_exception
449 3. Scan for cleanups. If a handler is found and this isn't forced unwind,
450 then terminate, otherwise ignore the handler and keep looking for cleanup.
451 If a cleanup is found, return _URC_HANDLER_FOUND, else return _URC_CONTINUE_UNWIND.
452 May also report an error on invalid input.
453 May terminate for invalid exception table.
454 _UA_CLEANUP_PHASE && !_UA_HANDLER_FRAME
459 scan_eh_tab(scan_results& results, _Unwind_Action actions, bool native_exception,
460 _Unwind_Exception* unwind_exception, _Unwind_Context* context)
462 // Initialize results to found nothing but an error
463 results.ttypeIndex = 0;
464 results.actionRecord = 0;
465 results.languageSpecificData = 0;
466 results.landingPad = 0;
467 results.adjustedPtr = 0;
468 results.reason = _URC_FATAL_PHASE1_ERROR;
469 // Check for consistent actions
470 if (actions & _UA_SEARCH_PHASE)
473 if (actions & (_UA_CLEANUP_PHASE | _UA_HANDLER_FRAME | _UA_FORCE_UNWIND))
475 // None of these flags should be set during Phase 1
477 results.reason = _URC_FATAL_PHASE1_ERROR;
481 else if (actions & _UA_CLEANUP_PHASE)
483 if ((actions & _UA_HANDLER_FRAME) && (actions & _UA_FORCE_UNWIND))
485 // _UA_HANDLER_FRAME should only be set if phase 1 found a handler.
486 // If _UA_FORCE_UNWIND is set, phase 1 shouldn't have happened.
488 results.reason = _URC_FATAL_PHASE2_ERROR;
492 else // Neither _UA_SEARCH_PHASE nor _UA_CLEANUP_PHASE is set
494 // One of these should be set.
496 results.reason = _URC_FATAL_PHASE1_ERROR;
499 // Start scan by getting exception table address
500 const uint8_t* lsda = (const uint8_t*)_Unwind_GetLanguageSpecificData(context);
503 // There is no exception table
504 results.reason = _URC_CONTINUE_UNWIND;
507 results.languageSpecificData = lsda;
508 // Get the current instruction pointer and offset it before next
509 // instruction in the current frame which threw the exception.
510 uintptr_t ip = _Unwind_GetIP(context) - 1;
511 // Get beginning current frame's code (as defined by the
512 // emitted dwarf code)
513 uintptr_t funcStart = _Unwind_GetRegionStart(context);
515 if (ip == uintptr_t(-1))
518 results.reason = _URC_CONTINUE_UNWIND;
522 call_terminate(native_exception, unwind_exception);
523 // ip is 1-based index into call site table
525 uintptr_t ipOffset = ip - funcStart;
527 const uint8_t* classInfo = NULL;
528 // Note: See JITDwarfEmitter::EmitExceptionTable(...) for corresponding
530 // Parse LSDA header.
531 uint8_t lpStartEncoding = *lsda++;
532 const uint8_t* lpStart = (const uint8_t*)readEncodedPointer(&lsda, lpStartEncoding);
534 lpStart = (const uint8_t*)funcStart;
535 uint8_t ttypeEncoding = *lsda++;
536 if (ttypeEncoding != DW_EH_PE_omit)
538 // Calculate type info locations in emitted dwarf code which
539 // were flagged by type info arguments to llvm.eh.selector
541 uintptr_t classInfoOffset = readULEB128(&lsda);
542 classInfo = lsda + classInfoOffset;
544 // Walk call-site table looking for range that
545 // includes current PC.
546 uint8_t callSiteEncoding = *lsda++;
548 (void)callSiteEncoding; // On arm callSiteEncoding is never used
550 uint32_t callSiteTableLength = static_cast<uint32_t>(readULEB128(&lsda));
551 const uint8_t* callSiteTableStart = lsda;
552 const uint8_t* callSiteTableEnd = callSiteTableStart + callSiteTableLength;
553 const uint8_t* actionTableStart = callSiteTableEnd;
554 const uint8_t* callSitePtr = callSiteTableStart;
555 while (callSitePtr < callSiteTableEnd)
557 // There is one entry per call site.
559 // The call sites are non-overlapping in [start, start+length)
560 // The call sites are ordered in increasing value of start
561 uintptr_t start = readEncodedPointer(&callSitePtr, callSiteEncoding);
562 uintptr_t length = readEncodedPointer(&callSitePtr, callSiteEncoding);
563 uintptr_t landingPad = readEncodedPointer(&callSitePtr, callSiteEncoding);
564 uintptr_t actionEntry = readULEB128(&callSitePtr);
565 if ((start <= ipOffset) && (ipOffset < (start + length)))
567 // ip is 1-based index into this table
568 uintptr_t landingPad = readULEB128(&callSitePtr);
569 uintptr_t actionEntry = readULEB128(&callSitePtr);
573 // Found the call site containing ip.
578 results.reason = _URC_CONTINUE_UNWIND;
581 landingPad = (uintptr_t)lpStart + landingPad;
585 if (actionEntry == 0)
588 // If this is a type 1 or type 2 search, there are no handlers
589 // If this is a type 3 search, you want to install the cleanup.
590 if ((actions & _UA_CLEANUP_PHASE) && !(actions & _UA_HANDLER_FRAME))
592 results.ttypeIndex = 0; // Redundant but clarifying
593 results.landingPad = landingPad;
594 results.reason = _URC_HANDLER_FOUND;
598 results.reason = _URC_CONTINUE_UNWIND;
601 // Convert 1-based byte offset into
602 const uint8_t* action = actionTableStart + (actionEntry - 1);
603 // Scan action entries until you find a matching handler, cleanup, or the end of action list
606 const uint8_t* actionRecord = action;
607 int64_t ttypeIndex = readSLEB128(&action);
610 // Found a catch, does it actually catch?
611 // First check for catch (...)
612 const __shim_type_info* catchType =
613 get_shim_type_info(static_cast<uint64_t>(ttypeIndex),
614 classInfo, ttypeEncoding,
615 native_exception, unwind_exception);
618 // Found catch (...) catches everything, including foreign exceptions
619 // If this is a type 1 search save state and return _URC_HANDLER_FOUND
620 // If this is a type 2 search save state and return _URC_HANDLER_FOUND
621 // If this is a type 3 search !_UA_FORCE_UNWIND, we should have found this in phase 1!
622 // If this is a type 3 search _UA_FORCE_UNWIND, ignore handler and continue scan
623 if ((actions & _UA_SEARCH_PHASE) || (actions & _UA_HANDLER_FRAME))
625 // Save state and return _URC_HANDLER_FOUND
626 results.ttypeIndex = ttypeIndex;
627 results.actionRecord = actionRecord;
628 results.landingPad = landingPad;
629 results.adjustedPtr = get_thrown_object_ptr(unwind_exception);
630 results.reason = _URC_HANDLER_FOUND;
633 else if (!(actions & _UA_FORCE_UNWIND))
635 // It looks like the exception table has changed
636 // on us. Likely stack corruption!
637 call_terminate(native_exception, unwind_exception);
640 // Else this is a catch (T) clause and will never
641 // catch a foreign exception
642 else if (native_exception)
644 __cxa_exception* exception_header = (__cxa_exception*)(unwind_exception+1) - 1;
645 void* adjustedPtr = get_thrown_object_ptr(unwind_exception);
646 const __shim_type_info* excpType =
647 static_cast<const __shim_type_info*>(exception_header->exceptionType);
648 if (adjustedPtr == 0 || excpType == 0)
650 // Something very bad happened
651 call_terminate(native_exception, unwind_exception);
653 if (catchType->can_catch(excpType, adjustedPtr))
655 // Found a matching handler
656 // If this is a type 1 search save state and return _URC_HANDLER_FOUND
657 // If this is a type 3 search and !_UA_FORCE_UNWIND, we should have found this in phase 1!
658 // If this is a type 3 search and _UA_FORCE_UNWIND, ignore handler and continue scan
659 if (actions & _UA_SEARCH_PHASE)
661 // Save state and return _URC_HANDLER_FOUND
662 results.ttypeIndex = ttypeIndex;
663 results.actionRecord = actionRecord;
664 results.landingPad = landingPad;
665 results.adjustedPtr = adjustedPtr;
666 results.reason = _URC_HANDLER_FOUND;
669 else if (!(actions & _UA_FORCE_UNWIND))
671 // It looks like the exception table has changed
672 // on us. Likely stack corruption!
673 call_terminate(native_exception, unwind_exception);
677 // Scan next action ...
679 else if (ttypeIndex < 0)
681 // Found an exception spec. If this is a foreign exception,
682 // it is always caught.
683 if (native_exception)
685 // Does the exception spec catch this native exception?
686 __cxa_exception* exception_header = (__cxa_exception*)(unwind_exception+1) - 1;
687 void* adjustedPtr = get_thrown_object_ptr(unwind_exception);
688 const __shim_type_info* excpType =
689 static_cast<const __shim_type_info*>(exception_header->exceptionType);
690 if (adjustedPtr == 0 || excpType == 0)
692 // Something very bad happened
693 call_terminate(native_exception, unwind_exception);
695 if (exception_spec_can_catch(ttypeIndex, classInfo,
696 ttypeEncoding, excpType,
697 adjustedPtr, unwind_exception))
699 // native exception caught by exception spec
700 // If this is a type 1 search, save state and return _URC_HANDLER_FOUND
701 // If this is a type 3 search !_UA_FORCE_UNWIND, we should have found this in phase 1!
702 // If this is a type 3 search _UA_FORCE_UNWIND, ignore handler and continue scan
703 if (actions & _UA_SEARCH_PHASE)
705 // Save state and return _URC_HANDLER_FOUND
706 results.ttypeIndex = ttypeIndex;
707 results.actionRecord = actionRecord;
708 results.landingPad = landingPad;
709 results.adjustedPtr = adjustedPtr;
710 results.reason = _URC_HANDLER_FOUND;
713 else if (!(actions & _UA_FORCE_UNWIND))
715 // It looks like the exception table has changed
716 // on us. Likely stack corruption!
717 call_terminate(native_exception, unwind_exception);
723 // foreign exception caught by exception spec
724 // If this is a type 1 search, save state and return _URC_HANDLER_FOUND
725 // If this is a type 2 search, save state and return _URC_HANDLER_FOUND
726 // If this is a type 3 search !_UA_FORCE_UNWIND, we should have found this in phase 1!
727 // If this is a type 3 search _UA_FORCE_UNWIND, ignore handler and continue scan
728 if ((actions & _UA_SEARCH_PHASE) || (actions & _UA_HANDLER_FRAME))
730 // Save state and return _URC_HANDLER_FOUND
731 results.ttypeIndex = ttypeIndex;
732 results.actionRecord = actionRecord;
733 results.landingPad = landingPad;
734 results.adjustedPtr = get_thrown_object_ptr(unwind_exception);
735 results.reason = _URC_HANDLER_FOUND;
738 else if (!(actions & _UA_FORCE_UNWIND))
740 // It looks like the exception table has changed
741 // on us. Likely stack corruption!
742 call_terminate(native_exception, unwind_exception);
745 // Scan next action ...
747 else // ttypeIndex == 0
750 // If this is a type 1 search, ignore it and continue scan
751 // If this is a type 2 search, ignore it and continue scan
752 // If this is a type 3 search, save state and return _URC_HANDLER_FOUND
753 if ((actions & _UA_CLEANUP_PHASE) && !(actions & _UA_HANDLER_FRAME))
755 // Save state and return _URC_HANDLER_FOUND
756 results.ttypeIndex = ttypeIndex;
757 results.actionRecord = actionRecord;
758 results.landingPad = landingPad;
759 results.adjustedPtr = get_thrown_object_ptr(unwind_exception);
760 results.reason = _URC_HANDLER_FOUND;
764 const uint8_t* temp = action;
765 int64_t actionOffset = readSLEB128(&temp);
766 if (actionOffset == 0)
768 // End of action list, no matching handler or cleanup found
769 results.reason = _URC_CONTINUE_UNWIND;
773 action += actionOffset;
774 } // there is no break out of this loop, only return
777 else if (ipOffset < start)
779 // There is no call site for this ip
780 // Something bad has happened. We should never get here.
781 // Possible stack corruption.
782 call_terminate(native_exception, unwind_exception);
785 } // there might be some tricky cases which break out of this loop
787 // It is possible that no eh table entry specify how to handle
788 // this exception. By spec, terminate it immediately.
789 call_terminate(native_exception, unwind_exception);
795 The personality function branches on actions like so:
799 If _UA_CLEANUP_PHASE or _UA_HANDLER_FRAME or _UA_FORCE_UNWIND there's
800 an error from above, return _URC_FATAL_PHASE1_ERROR.
802 Scan for anything that could stop unwinding:
804 1. A catch clause that will catch this exception
805 (will never catch foreign).
806 2. A catch (...) (will always catch foreign).
807 3. An exception spec that will catch this exception
808 (will always catch foreign).
809 If a handler is found
812 return _URC_HANDLER_FOUND
813 Else a handler not found
814 return _URC_CONTINUE_UNWIND
820 How did this happen? return _URC_FATAL_PHASE2_ERROR
822 Do _UA_SEARCH_PHASE to recover state
824 Recover state from header
825 Transfer control to landing pad. return _URC_INSTALL_CONTEXT
829 This branch handles both normal C++ non-catching handlers (cleanups)
830 and forced unwinding.
831 Scan for anything that can not stop unwinding:
835 If a cleanup is found
836 transfer control to it. return _URC_INSTALL_CONTEXT
837 Else a cleanup is not found: return _URC_CONTINUE_UNWIND
842 __gxx_personality_sj0
846 (int version, _Unwind_Action actions, uint64_t exceptionClass,
847 _Unwind_Exception* unwind_exception, _Unwind_Context* context)
849 if (version != 1 || unwind_exception == 0 || context == 0)
850 return _URC_FATAL_PHASE1_ERROR;
851 bool native_exception = (exceptionClass & get_vendor_and_language) ==
852 (kOurExceptionClass & get_vendor_and_language);
853 scan_results results;
854 if (actions & _UA_SEARCH_PHASE)
856 // Phase 1 search: All we're looking for in phase 1 is a handler that
858 scan_eh_tab(results, actions, native_exception, unwind_exception, context);
859 if (results.reason == _URC_HANDLER_FOUND)
861 // Found one. Can we cache the results somewhere to optimize phase 2?
862 if (native_exception)
864 __cxa_exception* exception_header = (__cxa_exception*)(unwind_exception+1) - 1;
865 exception_header->handlerSwitchValue = static_cast<int>(results.ttypeIndex);
866 exception_header->actionRecord = results.actionRecord;
867 exception_header->languageSpecificData = results.languageSpecificData;
868 exception_header->catchTemp = reinterpret_cast<void*>(results.landingPad);
869 exception_header->adjustedPtr = results.adjustedPtr;
871 return _URC_HANDLER_FOUND;
873 // Did not find a catching-handler. Return the results of the scan
874 // (normally _URC_CONTINUE_UNWIND, but could have been _URC_FATAL_PHASE1_ERROR
875 // if we were called improperly).
876 return results.reason;
878 if (actions & _UA_CLEANUP_PHASE)
881 // Did we find a catching handler in phase 1?
882 if (actions & _UA_HANDLER_FRAME)
884 // Yes, phase 1 said we have a catching handler here.
885 // Did we cache the results of the scan?
886 if (native_exception)
888 // Yes, reload the results from the cache.
889 __cxa_exception* exception_header = (__cxa_exception*)(unwind_exception+1) - 1;
890 results.ttypeIndex = exception_header->handlerSwitchValue;
891 results.actionRecord = exception_header->actionRecord;
892 results.languageSpecificData = exception_header->languageSpecificData;
893 results.landingPad = reinterpret_cast<uintptr_t>(exception_header->catchTemp);
894 results.adjustedPtr = exception_header->adjustedPtr;
898 // No, do the scan again to reload the results.
899 scan_eh_tab(results, actions, native_exception, unwind_exception, context);
900 // Phase 1 told us we would find a handler. Now in Phase 2 we
901 // didn't find a handler. The eh table should not be changing!
902 if (results.reason != _URC_HANDLER_FOUND)
903 call_terminate(native_exception, unwind_exception);
905 // Jump to the handler
906 set_registers(unwind_exception, context, results);
907 return _URC_INSTALL_CONTEXT;
909 // Either we didn't do a phase 1 search (due to forced unwinding), or
910 // phase 1 reported no catching-handlers.
911 // Search for a (non-catching) cleanup
912 scan_eh_tab(results, actions, native_exception, unwind_exception, context);
913 if (results.reason == _URC_HANDLER_FOUND)
915 // Found a non-catching handler. Jump to it:
916 set_registers(unwind_exception, context, results);
917 return _URC_INSTALL_CONTEXT;
919 // Did not find a cleanup. Return the results of the scan
920 // (normally _URC_CONTINUE_UNWIND, but could have been _URC_FATAL_PHASE2_ERROR
921 // if we were called improperly).
922 return results.reason;
924 // We were called improperly: neither a phase 1 or phase 2 search
925 return _URC_FATAL_PHASE1_ERROR;
928 __attribute__((noreturn))
930 __cxa_call_unexpected(void* arg)
932 _Unwind_Exception* unwind_exception = static_cast<_Unwind_Exception*>(arg);
933 if (unwind_exception == 0)
934 call_terminate(false, unwind_exception);
935 __cxa_begin_catch(unwind_exception);
936 bool native_old_exception =
937 (unwind_exception->exception_class & get_vendor_and_language) ==
938 (kOurExceptionClass & get_vendor_and_language);
939 std::unexpected_handler u_handler;
940 std::terminate_handler t_handler;
941 __cxa_exception* old_exception_header = 0;
944 if (native_old_exception)
946 old_exception_header = (__cxa_exception*)(unwind_exception+1) - 1;
947 t_handler = old_exception_header->terminateHandler;
948 u_handler = old_exception_header->unexpectedHandler;
949 // If std::__unexpected(u_handler) rethrows the same exception,
950 // these values get overwritten by the rethrow. So save them now:
951 ttypeIndex = old_exception_header->handlerSwitchValue;
952 lsda = old_exception_header->languageSpecificData;
956 t_handler = std::get_terminate();
957 u_handler = std::get_unexpected();
961 std::__unexpected(u_handler);
965 // If the old exception is foreign, then all we can do is terminate.
966 // We have no way to recover the needed old exception spec. There's
967 // no way to pass that information here. And the personality routine
968 // can't call us directly and do anything but terminate() if we throw
970 if (native_old_exception)
973 // old_exception_header->languageSpecificData
974 // old_exception_header->actionRecord
976 // const uint8_t* classInfo
977 // uint8_t ttypeEncoding
978 uint8_t lpStartEncoding = *lsda++;
979 const uint8_t* lpStart = (const uint8_t*)readEncodedPointer(&lsda, lpStartEncoding);
980 (void)lpStart; // purposefully unused. Just needed to increment lsda.
981 uint8_t ttypeEncoding = *lsda++;
982 if (ttypeEncoding == DW_EH_PE_omit)
983 std::__terminate(t_handler);
984 uintptr_t classInfoOffset = readULEB128(&lsda);
985 const uint8_t* classInfo = lsda + classInfoOffset;
986 // Is this new exception catchable by the exception spec at ttypeIndex?
987 // The answer is obviously yes if the new and old exceptions are the same exception
990 __cxa_eh_globals* globals = __cxa_get_globals_fast();
991 __cxa_exception* new_exception_header = globals->caughtExceptions;
992 if (new_exception_header == 0)
993 // This shouldn't be able to happen!
994 std::__terminate(t_handler);
995 bool native_new_exception =
996 (new_exception_header->unwindHeader.exception_class & get_vendor_and_language) ==
997 (kOurExceptionClass & get_vendor_and_language);
999 if (native_new_exception && (new_exception_header != old_exception_header))
1001 const __shim_type_info* excpType =
1002 static_cast<const __shim_type_info*>(new_exception_header->exceptionType);
1004 new_exception_header->unwindHeader.exception_class == kOurDependentExceptionClass ?
1005 ((__cxa_dependent_exception*)new_exception_header)->primaryException :
1006 new_exception_header + 1;
1007 if (!exception_spec_can_catch(ttypeIndex, classInfo, ttypeEncoding,
1008 excpType, adjustedPtr, unwind_exception))
1010 // We need to __cxa_end_catch, but for the old exception,
1011 // not the new one. This is a little tricky ...
1012 // Disguise new_exception_header as a rethrown exception, but
1013 // don't actually rethrow it. This means you can temporarily
1014 // end the catch clause enclosing new_exception_header without
1015 // __cxa_end_catch destroying new_exception_header.
1016 new_exception_header->handlerCount = -new_exception_header->handlerCount;
1017 globals->uncaughtExceptions += 1;
1018 // Call __cxa_end_catch for new_exception_header
1020 // Call __cxa_end_catch for old_exception_header
1022 // Renter this catch clause with new_exception_header
1023 __cxa_begin_catch(&new_exception_header->unwindHeader);
1024 // Rethrow new_exception_header
1028 // Will a std::bad_exception be catchable by the exception spec at
1031 // throw std::bad_exception();
1032 const __shim_type_info* excpType =
1033 static_cast<const __shim_type_info*>(&typeid(std::bad_exception));
1034 std::bad_exception be;
1036 if (!exception_spec_can_catch(ttypeIndex, classInfo, ttypeEncoding,
1037 excpType, adjustedPtr, unwind_exception))
1039 // We need to __cxa_end_catch for both the old exception and the
1040 // new exception. Technically we should do it in that order.
1041 // But it is expedient to do it in the opposite order:
1042 // Call __cxa_end_catch for new_exception_header
1044 // Throw std::bad_exception will __cxa_end_catch for
1045 // old_exception_header
1050 std::__terminate(t_handler);