1 //===------------------------- cxa_exception.cpp --------------------------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is dual licensed under the MIT and the University of Illinois Open
6 // Source Licenses. See LICENSE.TXT for details.
7 //
8 //
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
12 //
13 //===----------------------------------------------------------------------===//
14
15 #include <assert.h>
16 #include <stdlib.h>
17 #include <string.h>
18 #include <typeinfo>
19
20 #include "config.h"
21 #include "cxa_exception.hpp"
22 #include "cxa_handlers.hpp"
23 #include "private_typeinfo.h"
24 #include "unwind.h"
25
26 /*
27 Exception Header Layout:
28
29 +---------------------------+-----------------------------+---------------+
30 | __cxa_exception | _Unwind_Exception CLNGC++\0 | thrown object |
31 +---------------------------+-----------------------------+---------------+
32 ^
33 |
34 +-------------------------------------------------------+
35 |
36 +---------------------------+-----------------------------+
37 | __cxa_dependent_exception | _Unwind_Exception CLNGC++\1 |
38 +---------------------------+-----------------------------+
39
40 Exception Handling Table Layout:
41
42 +-----------------+--------+
43 | lpStartEncoding | (char) |
44 +---------+-------+--------+---------------+-----------------------+
45 | lpStart | (encoded with lpStartEncoding) | defaults to funcStart |
46 +---------+-----+--------+-----------------+---------------+-------+
47 | ttypeEncoding | (char) | Encoding of the type_info table |
48 +---------------+-+------+----+----------------------------+----------------+
49 | classInfoOffset | (ULEB128) | Offset to type_info table, defaults to null |
50 +-----------------++--------+-+----------------------------+----------------+
51 | callSiteEncoding | (char) | Encoding for Call Site Table |
52 +------------------+--+-----+-----+------------------------+--------------------------+
53 | callSiteTableLength | (ULEB128) | Call Site Table length, used to find Action table |
54 +---------------------+-----------+---------------------------------------------------+
55 #ifndef __USING_SJLJ_EXCEPTIONS__
56 +---------------------+-----------+------------------------------------------------+
57 | Beginning of Call Site Table The current ip lies within the |
58 | ... (start, length) range of one of these |
59 | call sites. There may be action needed. |
60 | +-------------+---------------------------------+------------------------------+ |
61 | | start | (encoded with callSiteEncoding) | offset relative to funcStart | |
62 | | length | (encoded with callSiteEncoding) | length of code fragment | |
63 | | landingPad | (encoded with callSiteEncoding) | offset relative to lpStart | |
64 | | actionEntry | (ULEB128) | Action Table Index 1-based | |
65 | | | | actionEntry == 0 -> cleanup | |
66 | +-------------+---------------------------------+------------------------------+ |
67 | ... |
68 +----------------------------------------------------------------------------------+
69 #else // __USING_SJLJ_EXCEPTIONS__
70 +---------------------+-----------+------------------------------------------------+
71 | Beginning of Call Site Table The current ip is a 1-based index into |
72 | ... this table. Or it is -1 meaning no |
73 | action is needed. Or it is 0 meaning |
74 | terminate. |
75 | +-------------+---------------------------------+------------------------------+ |
76 | | landingPad | (ULEB128) | offset relative to lpStart | |
77 | | actionEntry | (ULEB128) | Action Table Index 1-based | |
78 | | | | actionEntry == 0 -> cleanup | |
79 | +-------------+---------------------------------+------------------------------+ |
80 | ... |
81 +----------------------------------------------------------------------------------+
82 #endif // __USING_SJLJ_EXCEPTIONS__
83 +---------------------------------------------------------------------+
84 | Beginning of Action Table ttypeIndex == 0 : cleanup |
85 | ... ttypeIndex > 0 : catch |
86 | ttypeIndex < 0 : exception spec |
87 | +--------------+-----------+--------------------------------------+ |
88 | | ttypeIndex | (SLEB128) | Index into type_info Table (1-based) | |
89 | | actionOffset | (SLEB128) | Offset into next Action Table entry | |
90 | +--------------+-----------+--------------------------------------+ |
91 | ... |
92 +---------------------------------------------------------------------+-----------------+
93 | type_info Table, but classInfoOffset does *not* point here! |
94 | +----------------+------------------------------------------------+-----------------+ |
95 | | Nth type_info* | Encoded with ttypeEncoding, 0 means catch(...) | ttypeIndex == N | |
96 | +----------------+------------------------------------------------+-----------------+ |
97 | ... |
98 | +----------------+------------------------------------------------+-----------------+ |
99 | | 1st type_info* | Encoded with ttypeEncoding, 0 means catch(...) | ttypeIndex == 1 | |
100 | +----------------+------------------------------------------------+-----------------+ |
101 | +---------------------------------------+-----------+------------------------------+ |
102 | | 1st ttypeIndex for 1st exception spec | (ULEB128) | classInfoOffset points here! | |
103 | | ... | (ULEB128) | | |
104 | | Mth ttypeIndex for 1st exception spec | (ULEB128) | | |
105 | | 0 | (ULEB128) | | |
106 | +---------------------------------------+------------------------------------------+ |
107 | ... |
108 | +---------------------------------------+------------------------------------------+ |
109 | | 0 | (ULEB128) | throw() | |
110 | +---------------------------------------+------------------------------------------+ |
111 | ... |
112 | +---------------------------------------+------------------------------------------+ |
113 | | 1st ttypeIndex for Nth exception spec | (ULEB128) | | |
114 | | ... | (ULEB128) | | |
115 | | Mth ttypeIndex for Nth exception spec | (ULEB128) | | |
116 | | 0 | (ULEB128) | | |
117 | +---------------------------------------+------------------------------------------+ |
118 +---------------------------------------------------------------------------------------+
119
120 Notes:
121
122 * ttypeIndex in the Action Table, and in the exception spec table, is an index,
123 not a byte count, if positive. It is a negative index offset of
124 classInfoOffset and the sizeof entry depends on ttypeEncoding.
125 But if ttypeIndex is negative, it is a positive 1-based byte offset into the
126 type_info Table.
127 And if ttypeIndex is zero, it refers to a catch (...).
128
129 * landingPad can be 0, this implies there is nothing to be done.
130
131 * landingPad != 0 and actionEntry == 0 implies a cleanup needs to be done
132 @landingPad.
133
134 * A cleanup can also be found under landingPad != 0 and actionEntry != 0 in
135 the Action Table with ttypeIndex == 0.
136 */
137
138 namespace __cxxabiv1
139 {
140
141 namespace
142 {
143
144 template <class AsType>
readPointerHelper(const uint8_t * & p)145 uintptr_t readPointerHelper(const uint8_t*& p) {
146 AsType value;
147 memcpy(&value, p, sizeof(AsType));
148 p += sizeof(AsType);
149 return static_cast<uintptr_t>(value);
150 }
151
152 } // end namespace
153
154 extern "C"
155 {
156
157 // private API
158
159 // Heavily borrowed from llvm/examples/ExceptionDemo/ExceptionDemo.cpp
160
161 // DWARF Constants
162 enum
163 {
164 DW_EH_PE_absptr = 0x00,
165 DW_EH_PE_uleb128 = 0x01,
166 DW_EH_PE_udata2 = 0x02,
167 DW_EH_PE_udata4 = 0x03,
168 DW_EH_PE_udata8 = 0x04,
169 DW_EH_PE_sleb128 = 0x09,
170 DW_EH_PE_sdata2 = 0x0A,
171 DW_EH_PE_sdata4 = 0x0B,
172 DW_EH_PE_sdata8 = 0x0C,
173 DW_EH_PE_pcrel = 0x10,
174 DW_EH_PE_textrel = 0x20,
175 DW_EH_PE_datarel = 0x30,
176 DW_EH_PE_funcrel = 0x40,
177 DW_EH_PE_aligned = 0x50,
178 DW_EH_PE_indirect = 0x80,
179 DW_EH_PE_omit = 0xFF
180 };
181
182 /// Read a uleb128 encoded value and advance pointer
183 /// See Variable Length Data Appendix C in:
184 /// @link http://dwarfstd.org/Dwarf4.pdf @unlink
185 /// @param data reference variable holding memory pointer to decode from
186 /// @returns decoded value
187 static
188 uintptr_t
readULEB128(const uint8_t ** data)189 readULEB128(const uint8_t** data)
190 {
191 uintptr_t result = 0;
192 uintptr_t shift = 0;
193 unsigned char byte;
194 const uint8_t *p = *data;
195 do
196 {
197 byte = *p++;
198 result |= static_cast<uintptr_t>(byte & 0x7F) << shift;
199 shift += 7;
200 } while (byte & 0x80);
201 *data = p;
202 return result;
203 }
204
205 /// Read a sleb128 encoded value and advance pointer
206 /// See Variable Length Data Appendix C in:
207 /// @link http://dwarfstd.org/Dwarf4.pdf @unlink
208 /// @param data reference variable holding memory pointer to decode from
209 /// @returns decoded value
210 static
211 intptr_t
readSLEB128(const uint8_t ** data)212 readSLEB128(const uint8_t** data)
213 {
214 uintptr_t result = 0;
215 uintptr_t shift = 0;
216 unsigned char byte;
217 const uint8_t *p = *data;
218 do
219 {
220 byte = *p++;
221 result |= static_cast<uintptr_t>(byte & 0x7F) << shift;
222 shift += 7;
223 } while (byte & 0x80);
224 *data = p;
225 if ((byte & 0x40) && (shift < (sizeof(result) << 3)))
226 result |= static_cast<uintptr_t>(~0) << shift;
227 return static_cast<intptr_t>(result);
228 }
229
230 /// Read a pointer encoded value and advance pointer
231 /// See Variable Length Data in:
232 /// @link http://dwarfstd.org/Dwarf3.pdf @unlink
233 /// @param data reference variable holding memory pointer to decode from
234 /// @param encoding dwarf encoding type
235 /// @returns decoded value
236 static
237 uintptr_t
readEncodedPointer(const uint8_t ** data,uint8_t encoding)238 readEncodedPointer(const uint8_t** data, uint8_t encoding)
239 {
240 uintptr_t result = 0;
241 if (encoding == DW_EH_PE_omit)
242 return result;
243 const uint8_t* p = *data;
244 // first get value
245 switch (encoding & 0x0F)
246 {
247 case DW_EH_PE_absptr:
248 result = readPointerHelper<uintptr_t>(p);
249 break;
250 case DW_EH_PE_uleb128:
251 result = readULEB128(&p);
252 break;
253 case DW_EH_PE_sleb128:
254 result = static_cast<uintptr_t>(readSLEB128(&p));
255 break;
256 case DW_EH_PE_udata2:
257 result = readPointerHelper<uint16_t>(p);
258 break;
259 case DW_EH_PE_udata4:
260 result = readPointerHelper<uint32_t>(p);
261 break;
262 case DW_EH_PE_udata8:
263 result = readPointerHelper<uint64_t>(p);
264 break;
265 case DW_EH_PE_sdata2:
266 result = readPointerHelper<int16_t>(p);
267 break;
268 case DW_EH_PE_sdata4:
269 result = readPointerHelper<int32_t>(p);
270 break;
271 case DW_EH_PE_sdata8:
272 result = readPointerHelper<int64_t>(p);
273 break;
274 default:
275 // not supported
276 abort();
277 break;
278 }
279 // then add relative offset
280 switch (encoding & 0x70)
281 {
282 case DW_EH_PE_absptr:
283 // do nothing
284 break;
285 case DW_EH_PE_pcrel:
286 if (result)
287 result += (uintptr_t)(*data);
288 break;
289 case DW_EH_PE_textrel:
290 case DW_EH_PE_datarel:
291 case DW_EH_PE_funcrel:
292 case DW_EH_PE_aligned:
293 default:
294 // not supported
295 abort();
296 break;
297 }
298 // then apply indirection
299 if (result && (encoding & DW_EH_PE_indirect))
300 result = *((uintptr_t*)result);
301 *data = p;
302 return result;
303 }
304
305 static
306 void
call_terminate(bool native_exception,_Unwind_Exception * unwind_exception)307 call_terminate(bool native_exception, _Unwind_Exception* unwind_exception)
308 {
309 __cxa_begin_catch(unwind_exception);
310 if (native_exception)
311 {
312 // Use the stored terminate_handler if possible
313 __cxa_exception* exception_header = (__cxa_exception*)(unwind_exception+1) - 1;
314 std::__terminate(exception_header->terminateHandler);
315 }
316 std::terminate();
317 }
318
319 #if LIBCXXABI_ARM_EHABI
read_target2_value(const void * ptr)320 static const void* read_target2_value(const void* ptr)
321 {
322 uintptr_t offset = *reinterpret_cast<const uintptr_t*>(ptr);
323 if (!offset)
324 return 0;
325 // "ARM EABI provides a TARGET2 relocation to describe these typeinfo
326 // pointers. The reason being it allows their precise semantics to be
327 // deferred to the linker. For bare-metal they turn into absolute
328 // relocations. For linux they turn into GOT-REL relocations."
329 // https://gcc.gnu.org/ml/gcc-patches/2009-08/msg00264.html
330 #if LIBCXXABI_BAREMETAL
331 return reinterpret_cast<const void*>(reinterpret_cast<uintptr_t>(ptr) +
332 offset);
333 #else
334 return *reinterpret_cast<const void **>(reinterpret_cast<uintptr_t>(ptr) +
335 offset);
336 #endif
337 }
338
339 static const __shim_type_info*
get_shim_type_info(uint64_t ttypeIndex,const uint8_t * classInfo,uint8_t ttypeEncoding,bool native_exception,_Unwind_Exception * unwind_exception)340 get_shim_type_info(uint64_t ttypeIndex, const uint8_t* classInfo,
341 uint8_t ttypeEncoding, bool native_exception,
342 _Unwind_Exception* unwind_exception)
343 {
344 if (classInfo == 0)
345 {
346 // this should not happen. Indicates corrupted eh_table.
347 call_terminate(native_exception, unwind_exception);
348 }
349
350 assert(ttypeEncoding == DW_EH_PE_absptr && "Unexpected TTypeEncoding");
351 (void)ttypeEncoding;
352
353 const uint8_t* ttypePtr = classInfo - ttypeIndex * sizeof(uintptr_t);
354 return reinterpret_cast<const __shim_type_info *>(
355 read_target2_value(ttypePtr));
356 }
357 #else // !LIBCXXABI_ARM_EHABI
358 static
359 const __shim_type_info*
get_shim_type_info(uint64_t ttypeIndex,const uint8_t * classInfo,uint8_t ttypeEncoding,bool native_exception,_Unwind_Exception * unwind_exception)360 get_shim_type_info(uint64_t ttypeIndex, const uint8_t* classInfo,
361 uint8_t ttypeEncoding, bool native_exception,
362 _Unwind_Exception* unwind_exception)
363 {
364 if (classInfo == 0)
365 {
366 // this should not happen. Indicates corrupted eh_table.
367 call_terminate(native_exception, unwind_exception);
368 }
369 switch (ttypeEncoding & 0x0F)
370 {
371 case DW_EH_PE_absptr:
372 ttypeIndex *= sizeof(void*);
373 break;
374 case DW_EH_PE_udata2:
375 case DW_EH_PE_sdata2:
376 ttypeIndex *= 2;
377 break;
378 case DW_EH_PE_udata4:
379 case DW_EH_PE_sdata4:
380 ttypeIndex *= 4;
381 break;
382 case DW_EH_PE_udata8:
383 case DW_EH_PE_sdata8:
384 ttypeIndex *= 8;
385 break;
386 default:
387 // this should not happen. Indicates corrupted eh_table.
388 call_terminate(native_exception, unwind_exception);
389 }
390 classInfo -= ttypeIndex;
391 return (const __shim_type_info*)readEncodedPointer(&classInfo, ttypeEncoding);
392 }
393 #endif // !LIBCXXABI_ARM_EHABI
394
395 /*
396 This is checking a thrown exception type, excpType, against a possibly empty
397 list of catchType's which make up an exception spec.
398
399 An exception spec acts like a catch handler, but in reverse. This "catch
400 handler" will catch an excpType if and only if none of the catchType's in
401 the list will catch a excpType. If any catchType in the list can catch an
402 excpType, then this exception spec does not catch the excpType.
403 */
404 #if LIBCXXABI_ARM_EHABI
405 static
406 bool
exception_spec_can_catch(int64_t specIndex,const uint8_t * classInfo,uint8_t ttypeEncoding,const __shim_type_info * excpType,void * adjustedPtr,_Unwind_Exception * unwind_exception)407 exception_spec_can_catch(int64_t specIndex, const uint8_t* classInfo,
408 uint8_t ttypeEncoding, const __shim_type_info* excpType,
409 void* adjustedPtr, _Unwind_Exception* unwind_exception)
410 {
411 if (classInfo == 0)
412 {
413 // this should not happen. Indicates corrupted eh_table.
414 call_terminate(false, unwind_exception);
415 }
416
417 assert(ttypeEncoding == DW_EH_PE_absptr && "Unexpected TTypeEncoding");
418 (void)ttypeEncoding;
419
420 // specIndex is negative of 1-based byte offset into classInfo;
421 specIndex = -specIndex;
422 --specIndex;
423 const void** temp = reinterpret_cast<const void**>(
424 reinterpret_cast<uintptr_t>(classInfo) +
425 static_cast<uintptr_t>(specIndex) * sizeof(uintptr_t));
426 // If any type in the spec list can catch excpType, return false, else return true
427 // adjustments to adjustedPtr are ignored.
428 while (true)
429 {
430 // ARM EHABI exception specification table (filter table) consists of
431 // several pointers which will directly point to the type info object
432 // (instead of ttypeIndex). The table will be terminated with 0.
433 const void** ttypePtr = temp++;
434 if (*ttypePtr == 0)
435 break;
436 // We can get the __shim_type_info simply by performing a
437 // R_ARM_TARGET2 relocation, and cast the result to __shim_type_info.
438 const __shim_type_info* catchType =
439 static_cast<const __shim_type_info*>(read_target2_value(ttypePtr));
440 void* tempPtr = adjustedPtr;
441 if (catchType->can_catch(excpType, tempPtr))
442 return false;
443 }
444 return true;
445 }
446 #else
447 static
448 bool
exception_spec_can_catch(int64_t specIndex,const uint8_t * classInfo,uint8_t ttypeEncoding,const __shim_type_info * excpType,void * adjustedPtr,_Unwind_Exception * unwind_exception)449 exception_spec_can_catch(int64_t specIndex, const uint8_t* classInfo,
450 uint8_t ttypeEncoding, const __shim_type_info* excpType,
451 void* adjustedPtr, _Unwind_Exception* unwind_exception)
452 {
453 if (classInfo == 0)
454 {
455 // this should not happen. Indicates corrupted eh_table.
456 call_terminate(false, unwind_exception);
457 }
458 // specIndex is negative of 1-based byte offset into classInfo;
459 specIndex = -specIndex;
460 --specIndex;
461 const uint8_t* temp = classInfo + specIndex;
462 // If any type in the spec list can catch excpType, return false, else return true
463 // adjustments to adjustedPtr are ignored.
464 while (true)
465 {
466 uint64_t ttypeIndex = readULEB128(&temp);
467 if (ttypeIndex == 0)
468 break;
469 const __shim_type_info* catchType = get_shim_type_info(ttypeIndex,
470 classInfo,
471 ttypeEncoding,
472 true,
473 unwind_exception);
474 void* tempPtr = adjustedPtr;
475 if (catchType->can_catch(excpType, tempPtr))
476 return false;
477 }
478 return true;
479 }
480 #endif
481
482 static
483 void*
get_thrown_object_ptr(_Unwind_Exception * unwind_exception)484 get_thrown_object_ptr(_Unwind_Exception* unwind_exception)
485 {
486 // Even for foreign exceptions, the exception object is *probably* at unwind_exception + 1
487 // Regardless, this library is prohibited from touching a foreign exception
488 void* adjustedPtr = unwind_exception + 1;
489 if (unwind_exception->exception_class == kOurDependentExceptionClass)
490 adjustedPtr = ((__cxa_dependent_exception*)adjustedPtr - 1)->primaryException;
491 return adjustedPtr;
492 }
493
494 namespace
495 {
496
497 struct scan_results
498 {
499 int64_t ttypeIndex; // > 0 catch handler, < 0 exception spec handler, == 0 a cleanup
500 const uint8_t* actionRecord; // Currently unused. Retained to ease future maintenance.
501 const uint8_t* languageSpecificData; // Needed only for __cxa_call_unexpected
502 uintptr_t landingPad; // null -> nothing found, else something found
503 void* adjustedPtr; // Used in cxa_exception.cpp
504 _Unwind_Reason_Code reason; // One of _URC_FATAL_PHASE1_ERROR,
505 // _URC_FATAL_PHASE2_ERROR,
506 // _URC_CONTINUE_UNWIND,
507 // _URC_HANDLER_FOUND
508 };
509
510 } // unnamed namespace
511
512 static
513 void
set_registers(_Unwind_Exception * unwind_exception,_Unwind_Context * context,const scan_results & results)514 set_registers(_Unwind_Exception* unwind_exception, _Unwind_Context* context,
515 const scan_results& results)
516 {
517 _Unwind_SetGR(context, __builtin_eh_return_data_regno(0),
518 reinterpret_cast<uintptr_t>(unwind_exception));
519 _Unwind_SetGR(context, __builtin_eh_return_data_regno(1),
520 static_cast<uintptr_t>(results.ttypeIndex));
521 _Unwind_SetIP(context, results.landingPad);
522 }
523
524 /*
525 There are 3 types of scans needed:
526
527 1. Scan for handler with native or foreign exception. If handler found,
528 save state and return _URC_HANDLER_FOUND, else return _URC_CONTINUE_UNWIND.
529 May also report an error on invalid input.
530 May terminate for invalid exception table.
531 _UA_SEARCH_PHASE
532
533 2. Scan for handler with foreign exception. Must return _URC_HANDLER_FOUND,
534 or call terminate.
535 _UA_CLEANUP_PHASE && _UA_HANDLER_FRAME && !native_exception
536
537 3. Scan for cleanups. If a handler is found and this isn't forced unwind,
538 then terminate, otherwise ignore the handler and keep looking for cleanup.
539 If a cleanup is found, return _URC_HANDLER_FOUND, else return _URC_CONTINUE_UNWIND.
540 May also report an error on invalid input.
541 May terminate for invalid exception table.
542 _UA_CLEANUP_PHASE && !_UA_HANDLER_FRAME
543 */
544
scan_eh_tab(scan_results & results,_Unwind_Action actions,bool native_exception,_Unwind_Exception * unwind_exception,_Unwind_Context * context)545 static void scan_eh_tab(scan_results &results, _Unwind_Action actions,
546 bool native_exception,
547 _Unwind_Exception *unwind_exception,
548 _Unwind_Context *context) {
549 // Initialize results to found nothing but an error
550 results.ttypeIndex = 0;
551 results.actionRecord = 0;
552 results.languageSpecificData = 0;
553 results.landingPad = 0;
554 results.adjustedPtr = 0;
555 results.reason = _URC_FATAL_PHASE1_ERROR;
556 // Check for consistent actions
557 if (actions & _UA_SEARCH_PHASE)
558 {
559 // Do Phase 1
560 if (actions & (_UA_CLEANUP_PHASE | _UA_HANDLER_FRAME | _UA_FORCE_UNWIND))
561 {
562 // None of these flags should be set during Phase 1
563 // Client error
564 results.reason = _URC_FATAL_PHASE1_ERROR;
565 return;
566 }
567 }
568 else if (actions & _UA_CLEANUP_PHASE)
569 {
570 if ((actions & _UA_HANDLER_FRAME) && (actions & _UA_FORCE_UNWIND))
571 {
572 // _UA_HANDLER_FRAME should only be set if phase 1 found a handler.
573 // If _UA_FORCE_UNWIND is set, phase 1 shouldn't have happened.
574 // Client error
575 results.reason = _URC_FATAL_PHASE2_ERROR;
576 return;
577 }
578 }
579 else // Neither _UA_SEARCH_PHASE nor _UA_CLEANUP_PHASE is set
580 {
581 // One of these should be set.
582 // Client error
583 results.reason = _URC_FATAL_PHASE1_ERROR;
584 return;
585 }
586 // Start scan by getting exception table address
587 const uint8_t *lsda = (const uint8_t *)_Unwind_GetLanguageSpecificData(context);
588 if (lsda == 0)
589 {
590 // There is no exception table
591 results.reason = _URC_CONTINUE_UNWIND;
592 return;
593 }
594 results.languageSpecificData = lsda;
595 // Get the current instruction pointer and offset it before next
596 // instruction in the current frame which threw the exception.
597 uintptr_t ip = _Unwind_GetIP(context) - 1;
598 // Get beginning current frame's code (as defined by the
599 // emitted dwarf code)
600 uintptr_t funcStart = _Unwind_GetRegionStart(context);
601 #ifdef __USING_SJLJ_EXCEPTIONS__
602 if (ip == uintptr_t(-1))
603 {
604 // no action
605 results.reason = _URC_CONTINUE_UNWIND;
606 return;
607 }
608 else if (ip == 0)
609 call_terminate(native_exception, unwind_exception);
610 // ip is 1-based index into call site table
611 #else // !__USING_SJLJ_EXCEPTIONS__
612 uintptr_t ipOffset = ip - funcStart;
613 #endif // !defined(_USING_SLJL_EXCEPTIONS__)
614 const uint8_t* classInfo = NULL;
615 // Note: See JITDwarfEmitter::EmitExceptionTable(...) for corresponding
616 // dwarf emission
617 // Parse LSDA header.
618 uint8_t lpStartEncoding = *lsda++;
619 const uint8_t* lpStart = (const uint8_t*)readEncodedPointer(&lsda, lpStartEncoding);
620 if (lpStart == 0)
621 lpStart = (const uint8_t*)funcStart;
622 uint8_t ttypeEncoding = *lsda++;
623 if (ttypeEncoding != DW_EH_PE_omit)
624 {
625 // Calculate type info locations in emitted dwarf code which
626 // were flagged by type info arguments to llvm.eh.selector
627 // intrinsic
628 uintptr_t classInfoOffset = readULEB128(&lsda);
629 classInfo = lsda + classInfoOffset;
630 }
631 // Walk call-site table looking for range that
632 // includes current PC.
633 uint8_t callSiteEncoding = *lsda++;
634 #ifdef __USING_SJLJ_EXCEPTIONS__
635 (void)callSiteEncoding; // When using SjLj exceptions, callSiteEncoding is never used
636 #endif
637 uint32_t callSiteTableLength = static_cast<uint32_t>(readULEB128(&lsda));
638 const uint8_t* callSiteTableStart = lsda;
639 const uint8_t* callSiteTableEnd = callSiteTableStart + callSiteTableLength;
640 const uint8_t* actionTableStart = callSiteTableEnd;
641 const uint8_t* callSitePtr = callSiteTableStart;
642 while (callSitePtr < callSiteTableEnd)
643 {
644 // There is one entry per call site.
645 #ifndef __USING_SJLJ_EXCEPTIONS__
646 // The call sites are non-overlapping in [start, start+length)
647 // The call sites are ordered in increasing value of start
648 uintptr_t start = readEncodedPointer(&callSitePtr, callSiteEncoding);
649 uintptr_t length = readEncodedPointer(&callSitePtr, callSiteEncoding);
650 uintptr_t landingPad = readEncodedPointer(&callSitePtr, callSiteEncoding);
651 uintptr_t actionEntry = readULEB128(&callSitePtr);
652 if ((start <= ipOffset) && (ipOffset < (start + length)))
653 #else // __USING_SJLJ_EXCEPTIONS__
654 // ip is 1-based index into this table
655 uintptr_t landingPad = readULEB128(&callSitePtr);
656 uintptr_t actionEntry = readULEB128(&callSitePtr);
657 if (--ip == 0)
658 #endif // __USING_SJLJ_EXCEPTIONS__
659 {
660 // Found the call site containing ip.
661 #ifndef __USING_SJLJ_EXCEPTIONS__
662 if (landingPad == 0)
663 {
664 // No handler here
665 results.reason = _URC_CONTINUE_UNWIND;
666 return;
667 }
668 landingPad = (uintptr_t)lpStart + landingPad;
669 #else // __USING_SJLJ_EXCEPTIONS__
670 ++landingPad;
671 #endif // __USING_SJLJ_EXCEPTIONS__
672 if (actionEntry == 0)
673 {
674 // Found a cleanup
675 // If this is a type 1 or type 2 search, there are no handlers
676 // If this is a type 3 search, you want to install the cleanup.
677 if ((actions & _UA_CLEANUP_PHASE) && !(actions & _UA_HANDLER_FRAME))
678 {
679 results.ttypeIndex = 0; // Redundant but clarifying
680 results.landingPad = landingPad;
681 results.reason = _URC_HANDLER_FOUND;
682 return;
683 }
684 // No handler here
685 results.reason = _URC_CONTINUE_UNWIND;
686 return;
687 }
688 // Convert 1-based byte offset into
689 const uint8_t* action = actionTableStart + (actionEntry - 1);
690 // Scan action entries until you find a matching handler, cleanup, or the end of action list
691 while (true)
692 {
693 const uint8_t* actionRecord = action;
694 int64_t ttypeIndex = readSLEB128(&action);
695 if (ttypeIndex > 0)
696 {
697 // Found a catch, does it actually catch?
698 // First check for catch (...)
699 const __shim_type_info* catchType =
700 get_shim_type_info(static_cast<uint64_t>(ttypeIndex),
701 classInfo, ttypeEncoding,
702 native_exception, unwind_exception);
703 if (catchType == 0)
704 {
705 // Found catch (...) catches everything, including foreign exceptions
706 // If this is a type 1 search save state and return _URC_HANDLER_FOUND
707 // If this is a type 2 search save state and return _URC_HANDLER_FOUND
708 // If this is a type 3 search !_UA_FORCE_UNWIND, we should have found this in phase 1!
709 // If this is a type 3 search _UA_FORCE_UNWIND, ignore handler and continue scan
710 if ((actions & _UA_SEARCH_PHASE) || (actions & _UA_HANDLER_FRAME))
711 {
712 // Save state and return _URC_HANDLER_FOUND
713 results.ttypeIndex = ttypeIndex;
714 results.actionRecord = actionRecord;
715 results.landingPad = landingPad;
716 results.adjustedPtr = get_thrown_object_ptr(unwind_exception);
717 results.reason = _URC_HANDLER_FOUND;
718 return;
719 }
720 else if (!(actions & _UA_FORCE_UNWIND))
721 {
722 // It looks like the exception table has changed
723 // on us. Likely stack corruption!
724 call_terminate(native_exception, unwind_exception);
725 }
726 }
727 // Else this is a catch (T) clause and will never
728 // catch a foreign exception
729 else if (native_exception)
730 {
731 __cxa_exception* exception_header = (__cxa_exception*)(unwind_exception+1) - 1;
732 void* adjustedPtr = get_thrown_object_ptr(unwind_exception);
733 const __shim_type_info* excpType =
734 static_cast<const __shim_type_info*>(exception_header->exceptionType);
735 if (adjustedPtr == 0 || excpType == 0)
736 {
737 // Something very bad happened
738 call_terminate(native_exception, unwind_exception);
739 }
740 if (catchType->can_catch(excpType, adjustedPtr))
741 {
742 // Found a matching handler
743 // If this is a type 1 search save state and return _URC_HANDLER_FOUND
744 // If this is a type 3 search and !_UA_FORCE_UNWIND, we should have found this in phase 1!
745 // If this is a type 3 search and _UA_FORCE_UNWIND, ignore handler and continue scan
746 if (actions & _UA_SEARCH_PHASE)
747 {
748 // Save state and return _URC_HANDLER_FOUND
749 results.ttypeIndex = ttypeIndex;
750 results.actionRecord = actionRecord;
751 results.landingPad = landingPad;
752 results.adjustedPtr = adjustedPtr;
753 results.reason = _URC_HANDLER_FOUND;
754 return;
755 }
756 else if (!(actions & _UA_FORCE_UNWIND))
757 {
758 // It looks like the exception table has changed
759 // on us. Likely stack corruption!
760 call_terminate(native_exception, unwind_exception);
761 }
762 }
763 }
764 // Scan next action ...
765 }
766 else if (ttypeIndex < 0)
767 {
768 // Found an exception spec. If this is a foreign exception,
769 // it is always caught.
770 if (native_exception)
771 {
772 // Does the exception spec catch this native exception?
773 __cxa_exception* exception_header = (__cxa_exception*)(unwind_exception+1) - 1;
774 void* adjustedPtr = get_thrown_object_ptr(unwind_exception);
775 const __shim_type_info* excpType =
776 static_cast<const __shim_type_info*>(exception_header->exceptionType);
777 if (adjustedPtr == 0 || excpType == 0)
778 {
779 // Something very bad happened
780 call_terminate(native_exception, unwind_exception);
781 }
782 if (exception_spec_can_catch(ttypeIndex, classInfo,
783 ttypeEncoding, excpType,
784 adjustedPtr, unwind_exception))
785 {
786 // native exception caught by exception spec
787 // If this is a type 1 search, save state and return _URC_HANDLER_FOUND
788 // If this is a type 3 search !_UA_FORCE_UNWIND, we should have found this in phase 1!
789 // If this is a type 3 search _UA_FORCE_UNWIND, ignore handler and continue scan
790 if (actions & _UA_SEARCH_PHASE)
791 {
792 // Save state and return _URC_HANDLER_FOUND
793 results.ttypeIndex = ttypeIndex;
794 results.actionRecord = actionRecord;
795 results.landingPad = landingPad;
796 results.adjustedPtr = adjustedPtr;
797 results.reason = _URC_HANDLER_FOUND;
798 return;
799 }
800 else if (!(actions & _UA_FORCE_UNWIND))
801 {
802 // It looks like the exception table has changed
803 // on us. Likely stack corruption!
804 call_terminate(native_exception, unwind_exception);
805 }
806 }
807 }
808 else
809 {
810 // foreign exception caught by exception spec
811 // If this is a type 1 search, save state and return _URC_HANDLER_FOUND
812 // If this is a type 2 search, save state and return _URC_HANDLER_FOUND
813 // If this is a type 3 search !_UA_FORCE_UNWIND, we should have found this in phase 1!
814 // If this is a type 3 search _UA_FORCE_UNWIND, ignore handler and continue scan
815 if ((actions & _UA_SEARCH_PHASE) || (actions & _UA_HANDLER_FRAME))
816 {
817 // Save state and return _URC_HANDLER_FOUND
818 results.ttypeIndex = ttypeIndex;
819 results.actionRecord = actionRecord;
820 results.landingPad = landingPad;
821 results.adjustedPtr = get_thrown_object_ptr(unwind_exception);
822 results.reason = _URC_HANDLER_FOUND;
823 return;
824 }
825 else if (!(actions & _UA_FORCE_UNWIND))
826 {
827 // It looks like the exception table has changed
828 // on us. Likely stack corruption!
829 call_terminate(native_exception, unwind_exception);
830 }
831 }
832 // Scan next action ...
833 }
834 else // ttypeIndex == 0
835 {
836 // Found a cleanup
837 // If this is a type 1 search, ignore it and continue scan
838 // If this is a type 2 search, ignore it and continue scan
839 // If this is a type 3 search, save state and return _URC_HANDLER_FOUND
840 if ((actions & _UA_CLEANUP_PHASE) && !(actions & _UA_HANDLER_FRAME))
841 {
842 // Save state and return _URC_HANDLER_FOUND
843 results.ttypeIndex = ttypeIndex;
844 results.actionRecord = actionRecord;
845 results.landingPad = landingPad;
846 results.adjustedPtr = get_thrown_object_ptr(unwind_exception);
847 results.reason = _URC_HANDLER_FOUND;
848 return;
849 }
850 }
851 const uint8_t* temp = action;
852 int64_t actionOffset = readSLEB128(&temp);
853 if (actionOffset == 0)
854 {
855 // End of action list, no matching handler or cleanup found
856 results.reason = _URC_CONTINUE_UNWIND;
857 return;
858 }
859 // Go to next action
860 action += actionOffset;
861 } // there is no break out of this loop, only return
862 }
863 #ifndef __USING_SJLJ_EXCEPTIONS__
864 else if (ipOffset < start)
865 {
866 // There is no call site for this ip
867 // Something bad has happened. We should never get here.
868 // Possible stack corruption.
869 call_terminate(native_exception, unwind_exception);
870 }
871 #endif // !__USING_SJLJ_EXCEPTIONS__
872 } // there might be some tricky cases which break out of this loop
873
874 // It is possible that no eh table entry specify how to handle
875 // this exception. By spec, terminate it immediately.
876 call_terminate(native_exception, unwind_exception);
877 }
878
879 // public API
880
881 /*
882 The personality function branches on actions like so:
883
884 _UA_SEARCH_PHASE
885
886 If _UA_CLEANUP_PHASE or _UA_HANDLER_FRAME or _UA_FORCE_UNWIND there's
887 an error from above, return _URC_FATAL_PHASE1_ERROR.
888
889 Scan for anything that could stop unwinding:
890
891 1. A catch clause that will catch this exception
892 (will never catch foreign).
893 2. A catch (...) (will always catch foreign).
894 3. An exception spec that will catch this exception
895 (will always catch foreign).
896 If a handler is found
897 If not foreign
898 Save state in header
899 return _URC_HANDLER_FOUND
900 Else a handler not found
901 return _URC_CONTINUE_UNWIND
902
903 _UA_CLEANUP_PHASE
904
905 If _UA_HANDLER_FRAME
906 If _UA_FORCE_UNWIND
907 How did this happen? return _URC_FATAL_PHASE2_ERROR
908 If foreign
909 Do _UA_SEARCH_PHASE to recover state
910 else
911 Recover state from header
912 Transfer control to landing pad. return _URC_INSTALL_CONTEXT
913
914 Else
915
916 This branch handles both normal C++ non-catching handlers (cleanups)
917 and forced unwinding.
918 Scan for anything that can not stop unwinding:
919
920 1. A cleanup.
921
922 If a cleanup is found
923 transfer control to it. return _URC_INSTALL_CONTEXT
924 Else a cleanup is not found: return _URC_CONTINUE_UNWIND
925 */
926
927 #if !LIBCXXABI_ARM_EHABI
928 _Unwind_Reason_Code
929 #ifdef __USING_SJLJ_EXCEPTIONS__
__gxx_personality_sj0(int version,_Unwind_Action actions,uint64_t exceptionClass,_Unwind_Exception * unwind_exception,_Unwind_Context * context)930 __gxx_personality_sj0
931 #else
932 __gxx_personality_v0
933 #endif
934 (int version, _Unwind_Action actions, uint64_t exceptionClass,
935 _Unwind_Exception* unwind_exception, _Unwind_Context* context)
936 {
937 if (version != 1 || unwind_exception == 0 || context == 0)
938 return _URC_FATAL_PHASE1_ERROR;
939
940 bool native_exception = (exceptionClass & get_vendor_and_language) ==
941 (kOurExceptionClass & get_vendor_and_language);
942 scan_results results;
943 if (actions & _UA_SEARCH_PHASE)
944 {
945 // Phase 1 search: All we're looking for in phase 1 is a handler that
946 // halts unwinding
947 scan_eh_tab(results, actions, native_exception, unwind_exception, context);
948 if (results.reason == _URC_HANDLER_FOUND)
949 {
950 // Found one. Can we cache the results somewhere to optimize phase 2?
951 if (native_exception)
952 {
953 __cxa_exception* exception_header = (__cxa_exception*)(unwind_exception+1) - 1;
954 exception_header->handlerSwitchValue = static_cast<int>(results.ttypeIndex);
955 exception_header->actionRecord = results.actionRecord;
956 exception_header->languageSpecificData = results.languageSpecificData;
957 exception_header->catchTemp = reinterpret_cast<void*>(results.landingPad);
958 exception_header->adjustedPtr = results.adjustedPtr;
959 }
960 return _URC_HANDLER_FOUND;
961 }
962 // Did not find a catching-handler. Return the results of the scan
963 // (normally _URC_CONTINUE_UNWIND, but could have been _URC_FATAL_PHASE1_ERROR
964 // if we were called improperly).
965 return results.reason;
966 }
967 if (actions & _UA_CLEANUP_PHASE)
968 {
969 // Phase 2 search:
970 // Did we find a catching handler in phase 1?
971 if (actions & _UA_HANDLER_FRAME)
972 {
973 // Yes, phase 1 said we have a catching handler here.
974 // Did we cache the results of the scan?
975 if (native_exception)
976 {
977 // Yes, reload the results from the cache.
978 __cxa_exception* exception_header = (__cxa_exception*)(unwind_exception+1) - 1;
979 results.ttypeIndex = exception_header->handlerSwitchValue;
980 results.actionRecord = exception_header->actionRecord;
981 results.languageSpecificData = exception_header->languageSpecificData;
982 results.landingPad = reinterpret_cast<uintptr_t>(exception_header->catchTemp);
983 results.adjustedPtr = exception_header->adjustedPtr;
984 }
985 else
986 {
987 // No, do the scan again to reload the results.
988 scan_eh_tab(results, actions, native_exception, unwind_exception, context);
989 // Phase 1 told us we would find a handler. Now in Phase 2 we
990 // didn't find a handler. The eh table should not be changing!
991 if (results.reason != _URC_HANDLER_FOUND)
992 call_terminate(native_exception, unwind_exception);
993 }
994 // Jump to the handler
995 set_registers(unwind_exception, context, results);
996 return _URC_INSTALL_CONTEXT;
997 }
998 // Either we didn't do a phase 1 search (due to forced unwinding), or
999 // phase 1 reported no catching-handlers.
1000 // Search for a (non-catching) cleanup
1001 scan_eh_tab(results, actions, native_exception, unwind_exception, context);
1002 if (results.reason == _URC_HANDLER_FOUND)
1003 {
1004 // Found a non-catching handler. Jump to it:
1005 set_registers(unwind_exception, context, results);
1006 return _URC_INSTALL_CONTEXT;
1007 }
1008 // Did not find a cleanup. Return the results of the scan
1009 // (normally _URC_CONTINUE_UNWIND, but could have been _URC_FATAL_PHASE2_ERROR
1010 // if we were called improperly).
1011 return results.reason;
1012 }
1013 // We were called improperly: neither a phase 1 or phase 2 search
1014 return _URC_FATAL_PHASE1_ERROR;
1015 }
1016 #else
1017
1018 extern "C" _Unwind_Reason_Code __gnu_unwind_frame(_Unwind_Exception*,
1019 _Unwind_Context*);
1020
1021 // Helper function to unwind one frame.
1022 // ARM EHABI 7.3 and 7.4: If the personality function returns _URC_CONTINUE_UNWIND, the
1023 // personality routine should update the virtual register set (VRS) according to the
1024 // corresponding frame unwinding instructions (ARM EHABI 9.3.)
continue_unwind(_Unwind_Exception * unwind_exception,_Unwind_Context * context)1025 static _Unwind_Reason_Code continue_unwind(_Unwind_Exception* unwind_exception,
1026 _Unwind_Context* context)
1027 {
1028 if (__gnu_unwind_frame(unwind_exception, context) != _URC_OK)
1029 return _URC_FAILURE;
1030 return _URC_CONTINUE_UNWIND;
1031 }
1032
1033 // ARM register names
1034 #if !LIBCXXABI_USE_LLVM_UNWINDER
1035 static const uint32_t REG_UCB = 12; // Register to save _Unwind_Control_Block
1036 #endif
1037 static const uint32_t REG_SP = 13;
1038
save_results_to_barrier_cache(_Unwind_Exception * unwind_exception,const scan_results & results)1039 static void save_results_to_barrier_cache(_Unwind_Exception* unwind_exception,
1040 const scan_results& results)
1041 {
1042 unwind_exception->barrier_cache.bitpattern[0] = (uint32_t)results.adjustedPtr;
1043 unwind_exception->barrier_cache.bitpattern[1] = (uint32_t)results.actionRecord;
1044 unwind_exception->barrier_cache.bitpattern[2] = (uint32_t)results.languageSpecificData;
1045 unwind_exception->barrier_cache.bitpattern[3] = (uint32_t)results.landingPad;
1046 unwind_exception->barrier_cache.bitpattern[4] = (uint32_t)results.ttypeIndex;
1047 }
1048
load_results_from_barrier_cache(scan_results & results,const _Unwind_Exception * unwind_exception)1049 static void load_results_from_barrier_cache(scan_results& results,
1050 const _Unwind_Exception* unwind_exception)
1051 {
1052 results.adjustedPtr = (void*)unwind_exception->barrier_cache.bitpattern[0];
1053 results.actionRecord = (const uint8_t*)unwind_exception->barrier_cache.bitpattern[1];
1054 results.languageSpecificData = (const uint8_t*)unwind_exception->barrier_cache.bitpattern[2];
1055 results.landingPad = (uintptr_t)unwind_exception->barrier_cache.bitpattern[3];
1056 results.ttypeIndex = (int64_t)(int32_t)unwind_exception->barrier_cache.bitpattern[4];
1057 }
1058
1059 extern "C" _Unwind_Reason_Code
__gxx_personality_v0(_Unwind_State state,_Unwind_Exception * unwind_exception,_Unwind_Context * context)1060 __gxx_personality_v0(_Unwind_State state,
1061 _Unwind_Exception* unwind_exception,
1062 _Unwind_Context* context)
1063 {
1064 if (unwind_exception == 0 || context == 0)
1065 return _URC_FATAL_PHASE1_ERROR;
1066
1067 bool native_exception = (unwind_exception->exception_class & get_vendor_and_language) ==
1068 (kOurExceptionClass & get_vendor_and_language);
1069
1070 #if !LIBCXXABI_USE_LLVM_UNWINDER
1071 // Copy the address of _Unwind_Control_Block to r12 so that
1072 // _Unwind_GetLanguageSpecificData() and _Unwind_GetRegionStart() can
1073 // return correct address.
1074 _Unwind_SetGR(context, REG_UCB, reinterpret_cast<uint32_t>(unwind_exception));
1075 #endif
1076
1077 // Check the undocumented force unwinding behavior
1078 bool is_force_unwinding = state & _US_FORCE_UNWIND;
1079 state &= ~_US_FORCE_UNWIND;
1080
1081 scan_results results;
1082 switch (state) {
1083 case _US_VIRTUAL_UNWIND_FRAME:
1084 if (is_force_unwinding)
1085 return continue_unwind(unwind_exception, context);
1086
1087 // Phase 1 search: All we're looking for in phase 1 is a handler that halts unwinding
1088 scan_eh_tab(results, _UA_SEARCH_PHASE, native_exception, unwind_exception, context);
1089 if (results.reason == _URC_HANDLER_FOUND)
1090 {
1091 unwind_exception->barrier_cache.sp = _Unwind_GetGR(context, REG_SP);
1092 if (native_exception)
1093 save_results_to_barrier_cache(unwind_exception, results);
1094 return _URC_HANDLER_FOUND;
1095 }
1096 // Did not find the catch handler
1097 if (results.reason == _URC_CONTINUE_UNWIND)
1098 return continue_unwind(unwind_exception, context);
1099 return results.reason;
1100
1101 case _US_UNWIND_FRAME_STARTING:
1102 // TODO: Support force unwinding in the phase 2 search.
1103 // NOTE: In order to call the cleanup functions, _Unwind_ForcedUnwind()
1104 // will call this personality function with (_US_FORCE_UNWIND |
1105 // _US_UNWIND_FRAME_STARTING).
1106
1107 // Phase 2 search
1108 if (unwind_exception->barrier_cache.sp == _Unwind_GetGR(context, REG_SP))
1109 {
1110 // Found a catching handler in phase 1
1111 if (native_exception)
1112 {
1113 // Load the result from the native exception barrier cache.
1114 load_results_from_barrier_cache(results, unwind_exception);
1115 results.reason = _URC_HANDLER_FOUND;
1116 }
1117 else
1118 {
1119 // Search for the catching handler again for the foreign exception.
1120 scan_eh_tab(results, static_cast<_Unwind_Action>(_UA_CLEANUP_PHASE | _UA_HANDLER_FRAME),
1121 native_exception, unwind_exception, context);
1122 if (results.reason != _URC_HANDLER_FOUND) // phase1 search should guarantee to find one
1123 call_terminate(native_exception, unwind_exception);
1124 }
1125
1126 // Install the context for the catching handler
1127 set_registers(unwind_exception, context, results);
1128 return _URC_INSTALL_CONTEXT;
1129 }
1130
1131 // Either we didn't do a phase 1 search (due to forced unwinding), or
1132 // phase 1 reported no catching-handlers.
1133 // Search for a (non-catching) cleanup
1134 scan_eh_tab(results, _UA_CLEANUP_PHASE, native_exception, unwind_exception, context);
1135 if (results.reason == _URC_HANDLER_FOUND)
1136 {
1137 // Found a non-catching handler
1138
1139 // ARM EHABI 8.4.2: Before we can jump to the cleanup handler, we have to setup some
1140 // internal data structures, so that __cxa_end_cleanup() can get unwind_exception from
1141 // __cxa_get_globals().
1142 __cxa_begin_cleanup(unwind_exception);
1143
1144 // Install the context for the cleanup handler
1145 set_registers(unwind_exception, context, results);
1146 return _URC_INSTALL_CONTEXT;
1147 }
1148
1149 // Did not find any handler
1150 if (results.reason == _URC_CONTINUE_UNWIND)
1151 return continue_unwind(unwind_exception, context);
1152 return results.reason;
1153
1154 case _US_UNWIND_FRAME_RESUME:
1155 return continue_unwind(unwind_exception, context);
1156 }
1157
1158 // We were called improperly: neither a phase 1 or phase 2 search
1159 return _URC_FATAL_PHASE1_ERROR;
1160 }
1161 #endif
1162
1163
1164 __attribute__((noreturn))
1165 void
__cxa_call_unexpected(void * arg)1166 __cxa_call_unexpected(void* arg)
1167 {
1168 _Unwind_Exception* unwind_exception = static_cast<_Unwind_Exception*>(arg);
1169 if (unwind_exception == 0)
1170 call_terminate(false, unwind_exception);
1171 __cxa_begin_catch(unwind_exception);
1172 bool native_old_exception =
1173 (unwind_exception->exception_class & get_vendor_and_language) ==
1174 (kOurExceptionClass & get_vendor_and_language);
1175 std::unexpected_handler u_handler;
1176 std::terminate_handler t_handler;
1177 __cxa_exception* old_exception_header = 0;
1178 int64_t ttypeIndex;
1179 const uint8_t* lsda;
1180 if (native_old_exception)
1181 {
1182 old_exception_header = (__cxa_exception*)(unwind_exception+1) - 1;
1183 t_handler = old_exception_header->terminateHandler;
1184 u_handler = old_exception_header->unexpectedHandler;
1185 // If std::__unexpected(u_handler) rethrows the same exception,
1186 // these values get overwritten by the rethrow. So save them now:
1187 #if LIBCXXABI_ARM_EHABI
1188 ttypeIndex = (int64_t)(int32_t)unwind_exception->barrier_cache.bitpattern[4];
1189 lsda = (const uint8_t*)unwind_exception->barrier_cache.bitpattern[2];
1190 #else
1191 ttypeIndex = old_exception_header->handlerSwitchValue;
1192 lsda = old_exception_header->languageSpecificData;
1193 #endif
1194 }
1195 else
1196 {
1197 t_handler = std::get_terminate();
1198 u_handler = std::get_unexpected();
1199 }
1200 try
1201 {
1202 std::__unexpected(u_handler);
1203 }
1204 catch (...)
1205 {
1206 // If the old exception is foreign, then all we can do is terminate.
1207 // We have no way to recover the needed old exception spec. There's
1208 // no way to pass that information here. And the personality routine
1209 // can't call us directly and do anything but terminate() if we throw
1210 // from here.
1211 if (native_old_exception)
1212 {
1213 // Have:
1214 // old_exception_header->languageSpecificData
1215 // old_exception_header->actionRecord
1216 // Need
1217 // const uint8_t* classInfo
1218 // uint8_t ttypeEncoding
1219 uint8_t lpStartEncoding = *lsda++;
1220 const uint8_t* lpStart = (const uint8_t*)readEncodedPointer(&lsda, lpStartEncoding);
1221 (void)lpStart; // purposefully unused. Just needed to increment lsda.
1222 uint8_t ttypeEncoding = *lsda++;
1223 if (ttypeEncoding == DW_EH_PE_omit)
1224 std::__terminate(t_handler);
1225 uintptr_t classInfoOffset = readULEB128(&lsda);
1226 const uint8_t* classInfo = lsda + classInfoOffset;
1227 // Is this new exception catchable by the exception spec at ttypeIndex?
1228 // The answer is obviously yes if the new and old exceptions are the same exception
1229 // If no
1230 // throw;
1231 __cxa_eh_globals* globals = __cxa_get_globals_fast();
1232 __cxa_exception* new_exception_header = globals->caughtExceptions;
1233 if (new_exception_header == 0)
1234 // This shouldn't be able to happen!
1235 std::__terminate(t_handler);
1236 bool native_new_exception =
1237 (new_exception_header->unwindHeader.exception_class & get_vendor_and_language) ==
1238 (kOurExceptionClass & get_vendor_and_language);
1239 void* adjustedPtr;
1240 if (native_new_exception && (new_exception_header != old_exception_header))
1241 {
1242 const __shim_type_info* excpType =
1243 static_cast<const __shim_type_info*>(new_exception_header->exceptionType);
1244 adjustedPtr =
1245 new_exception_header->unwindHeader.exception_class == kOurDependentExceptionClass ?
1246 ((__cxa_dependent_exception*)new_exception_header)->primaryException :
1247 new_exception_header + 1;
1248 if (!exception_spec_can_catch(ttypeIndex, classInfo, ttypeEncoding,
1249 excpType, adjustedPtr, unwind_exception))
1250 {
1251 // We need to __cxa_end_catch, but for the old exception,
1252 // not the new one. This is a little tricky ...
1253 // Disguise new_exception_header as a rethrown exception, but
1254 // don't actually rethrow it. This means you can temporarily
1255 // end the catch clause enclosing new_exception_header without
1256 // __cxa_end_catch destroying new_exception_header.
1257 new_exception_header->handlerCount = -new_exception_header->handlerCount;
1258 globals->uncaughtExceptions += 1;
1259 // Call __cxa_end_catch for new_exception_header
1260 __cxa_end_catch();
1261 // Call __cxa_end_catch for old_exception_header
1262 __cxa_end_catch();
1263 // Renter this catch clause with new_exception_header
1264 __cxa_begin_catch(&new_exception_header->unwindHeader);
1265 // Rethrow new_exception_header
1266 throw;
1267 }
1268 }
1269 // Will a std::bad_exception be catchable by the exception spec at
1270 // ttypeIndex?
1271 // If no
1272 // throw std::bad_exception();
1273 const __shim_type_info* excpType =
1274 static_cast<const __shim_type_info*>(&typeid(std::bad_exception));
1275 std::bad_exception be;
1276 adjustedPtr = &be;
1277 if (!exception_spec_can_catch(ttypeIndex, classInfo, ttypeEncoding,
1278 excpType, adjustedPtr, unwind_exception))
1279 {
1280 // We need to __cxa_end_catch for both the old exception and the
1281 // new exception. Technically we should do it in that order.
1282 // But it is expedient to do it in the opposite order:
1283 // Call __cxa_end_catch for new_exception_header
1284 __cxa_end_catch();
1285 // Throw std::bad_exception will __cxa_end_catch for
1286 // old_exception_header
1287 throw be;
1288 }
1289 }
1290 }
1291 std::__terminate(t_handler);
1292 }
1293
1294 } // extern "C"
1295
1296 } // __cxxabiv1
1297