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comparison libcxxabi/src/cxa_personality.cpp @ 150:1d019706d866

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LLVM10
author anatofuz
date Thu, 13 Feb 2020 15:10:13 +0900
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147:c2174574ed3a 150:1d019706d866
1 //===------------------------- cxa_exception.cpp --------------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //
8 // This file implements the "Exception Handling APIs"
9 // https://itanium-cxx-abi.github.io/cxx-abi/abi-eh.html
10 // http://www.intel.com/design/itanium/downloads/245358.htm
11 //
12 //===----------------------------------------------------------------------===//
13
14 #include <assert.h>
15 #include <stdlib.h>
16 #include <string.h>
17 #include <typeinfo>
18
19 #include "__cxxabi_config.h"
20 #include "cxa_exception.h"
21 #include "cxa_handlers.h"
22 #include "private_typeinfo.h"
23 #include "unwind.h"
24
25 #if defined(__SEH__) && !defined(__USING_SJLJ_EXCEPTIONS__)
26 #include <windows.h>
27 #include <winnt.h>
28
29 extern "C" EXCEPTION_DISPOSITION _GCC_specific_handler(PEXCEPTION_RECORD,
30 void *, PCONTEXT,
31 PDISPATCHER_CONTEXT,
32 _Unwind_Personality_Fn);
33 #endif
34
35 /*
36 Exception Header Layout:
37
38 +---------------------------+-----------------------------+---------------+
39 | __cxa_exception | _Unwind_Exception CLNGC++\0 | thrown object |
40 +---------------------------+-----------------------------+---------------+
41 ^
42 |
43 +-------------------------------------------------------+
44 |
45 +---------------------------+-----------------------------+
46 | __cxa_dependent_exception | _Unwind_Exception CLNGC++\1 |
47 +---------------------------+-----------------------------+
48
49 Exception Handling Table Layout:
50
51 +-----------------+--------+
52 | lpStartEncoding | (char) |
53 +---------+-------+--------+---------------+-----------------------+
54 | lpStart | (encoded with lpStartEncoding) | defaults to funcStart |
55 +---------+-----+--------+-----------------+---------------+-------+
56 | ttypeEncoding | (char) | Encoding of the type_info table |
57 +---------------+-+------+----+----------------------------+----------------+
58 | classInfoOffset | (ULEB128) | Offset to type_info table, defaults to null |
59 +-----------------++--------+-+----------------------------+----------------+
60 | callSiteEncoding | (char) | Encoding for Call Site Table |
61 +------------------+--+-----+-----+------------------------+--------------------------+
62 | callSiteTableLength | (ULEB128) | Call Site Table length, used to find Action table |
63 +---------------------+-----------+---------------------------------------------------+
64 #ifndef __USING_SJLJ_EXCEPTIONS__
65 +---------------------+-----------+------------------------------------------------+
66 | Beginning of Call Site Table The current ip lies within the |
67 | ... (start, length) range of one of these |
68 | call sites. There may be action needed. |
69 | +-------------+---------------------------------+------------------------------+ |
70 | | start | (encoded with callSiteEncoding) | offset relative to funcStart | |
71 | | length | (encoded with callSiteEncoding) | length of code fragment | |
72 | | landingPad | (encoded with callSiteEncoding) | offset relative to lpStart | |
73 | | actionEntry | (ULEB128) | Action Table Index 1-based | |
74 | | | | actionEntry == 0 -> cleanup | |
75 | +-------------+---------------------------------+------------------------------+ |
76 | ... |
77 +----------------------------------------------------------------------------------+
78 #else // __USING_SJLJ_EXCEPTIONS__
79 +---------------------+-----------+------------------------------------------------+
80 | Beginning of Call Site Table The current ip is a 1-based index into |
81 | ... this table. Or it is -1 meaning no |
82 | action is needed. Or it is 0 meaning |
83 | terminate. |
84 | +-------------+---------------------------------+------------------------------+ |
85 | | landingPad | (ULEB128) | offset relative to lpStart | |
86 | | actionEntry | (ULEB128) | Action Table Index 1-based | |
87 | | | | actionEntry == 0 -> cleanup | |
88 | +-------------+---------------------------------+------------------------------+ |
89 | ... |
90 +----------------------------------------------------------------------------------+
91 #endif // __USING_SJLJ_EXCEPTIONS__
92 +---------------------------------------------------------------------+
93 | Beginning of Action Table ttypeIndex == 0 : cleanup |
94 | ... ttypeIndex > 0 : catch |
95 | ttypeIndex < 0 : exception spec |
96 | +--------------+-----------+--------------------------------------+ |
97 | | ttypeIndex | (SLEB128) | Index into type_info Table (1-based) | |
98 | | actionOffset | (SLEB128) | Offset into next Action Table entry | |
99 | +--------------+-----------+--------------------------------------+ |
100 | ... |
101 +---------------------------------------------------------------------+-----------------+
102 | type_info Table, but classInfoOffset does *not* point here! |
103 | +----------------+------------------------------------------------+-----------------+ |
104 | | Nth type_info* | Encoded with ttypeEncoding, 0 means catch(...) | ttypeIndex == N | |
105 | +----------------+------------------------------------------------+-----------------+ |
106 | ... |
107 | +----------------+------------------------------------------------+-----------------+ |
108 | | 1st type_info* | Encoded with ttypeEncoding, 0 means catch(...) | ttypeIndex == 1 | |
109 | +----------------+------------------------------------------------+-----------------+ |
110 | +---------------------------------------+-----------+------------------------------+ |
111 | | 1st ttypeIndex for 1st exception spec | (ULEB128) | classInfoOffset points here! | |
112 | | ... | (ULEB128) | | |
113 | | Mth ttypeIndex for 1st exception spec | (ULEB128) | | |
114 | | 0 | (ULEB128) | | |
115 | +---------------------------------------+------------------------------------------+ |
116 | ... |
117 | +---------------------------------------+------------------------------------------+ |
118 | | 0 | (ULEB128) | throw() | |
119 | +---------------------------------------+------------------------------------------+ |
120 | ... |
121 | +---------------------------------------+------------------------------------------+ |
122 | | 1st ttypeIndex for Nth exception spec | (ULEB128) | | |
123 | | ... | (ULEB128) | | |
124 | | Mth ttypeIndex for Nth exception spec | (ULEB128) | | |
125 | | 0 | (ULEB128) | | |
126 | +---------------------------------------+------------------------------------------+ |
127 +---------------------------------------------------------------------------------------+
128
129 Notes:
130
131 * ttypeIndex in the Action Table, and in the exception spec table, is an index,
132 not a byte count, if positive. It is a negative index offset of
133 classInfoOffset and the sizeof entry depends on ttypeEncoding.
134 But if ttypeIndex is negative, it is a positive 1-based byte offset into the
135 type_info Table.
136 And if ttypeIndex is zero, it refers to a catch (...).
137
138 * landingPad can be 0, this implies there is nothing to be done.
139
140 * landingPad != 0 and actionEntry == 0 implies a cleanup needs to be done
141 @landingPad.
142
143 * A cleanup can also be found under landingPad != 0 and actionEntry != 0 in
144 the Action Table with ttypeIndex == 0.
145 */
146
147 namespace __cxxabiv1
148 {
149
150 namespace
151 {
152
153 template <class AsType>
154 uintptr_t readPointerHelper(const uint8_t*& p) {
155 AsType value;
156 memcpy(&value, p, sizeof(AsType));
157 p += sizeof(AsType);
158 return static_cast<uintptr_t>(value);
159 }
160
161 } // end namespace
162
163 extern "C"
164 {
165
166 // private API
167
168 // Heavily borrowed from llvm/examples/ExceptionDemo/ExceptionDemo.cpp
169
170 // DWARF Constants
171 enum
172 {
173 DW_EH_PE_absptr = 0x00,
174 DW_EH_PE_uleb128 = 0x01,
175 DW_EH_PE_udata2 = 0x02,
176 DW_EH_PE_udata4 = 0x03,
177 DW_EH_PE_udata8 = 0x04,
178 DW_EH_PE_sleb128 = 0x09,
179 DW_EH_PE_sdata2 = 0x0A,
180 DW_EH_PE_sdata4 = 0x0B,
181 DW_EH_PE_sdata8 = 0x0C,
182 DW_EH_PE_pcrel = 0x10,
183 DW_EH_PE_textrel = 0x20,
184 DW_EH_PE_datarel = 0x30,
185 DW_EH_PE_funcrel = 0x40,
186 DW_EH_PE_aligned = 0x50,
187 DW_EH_PE_indirect = 0x80,
188 DW_EH_PE_omit = 0xFF
189 };
190
191 /// Read a uleb128 encoded value and advance pointer
192 /// See Variable Length Data Appendix C in:
193 /// @link http://dwarfstd.org/Dwarf4.pdf @unlink
194 /// @param data reference variable holding memory pointer to decode from
195 /// @returns decoded value
196 static
197 uintptr_t
198 readULEB128(const uint8_t** data)
199 {
200 uintptr_t result = 0;
201 uintptr_t shift = 0;
202 unsigned char byte;
203 const uint8_t *p = *data;
204 do
205 {
206 byte = *p++;
207 result |= static_cast<uintptr_t>(byte & 0x7F) << shift;
208 shift += 7;
209 } while (byte & 0x80);
210 *data = p;
211 return result;
212 }
213
214 /// Read a sleb128 encoded value and advance pointer
215 /// See Variable Length Data Appendix C in:
216 /// @link http://dwarfstd.org/Dwarf4.pdf @unlink
217 /// @param data reference variable holding memory pointer to decode from
218 /// @returns decoded value
219 static
220 intptr_t
221 readSLEB128(const uint8_t** data)
222 {
223 uintptr_t result = 0;
224 uintptr_t shift = 0;
225 unsigned char byte;
226 const uint8_t *p = *data;
227 do
228 {
229 byte = *p++;
230 result |= static_cast<uintptr_t>(byte & 0x7F) << shift;
231 shift += 7;
232 } while (byte & 0x80);
233 *data = p;
234 if ((byte & 0x40) && (shift < (sizeof(result) << 3)))
235 result |= static_cast<uintptr_t>(~0) << shift;
236 return static_cast<intptr_t>(result);
237 }
238
239 /// Read a pointer encoded value and advance pointer
240 /// See Variable Length Data in:
241 /// @link http://dwarfstd.org/Dwarf3.pdf @unlink
242 /// @param data reference variable holding memory pointer to decode from
243 /// @param encoding dwarf encoding type
244 /// @returns decoded value
245 static
246 uintptr_t
247 readEncodedPointer(const uint8_t** data, uint8_t encoding)
248 {
249 uintptr_t result = 0;
250 if (encoding == DW_EH_PE_omit)
251 return result;
252 const uint8_t* p = *data;
253 // first get value
254 switch (encoding & 0x0F)
255 {
256 case DW_EH_PE_absptr:
257 result = readPointerHelper<uintptr_t>(p);
258 break;
259 case DW_EH_PE_uleb128:
260 result = readULEB128(&p);
261 break;
262 case DW_EH_PE_sleb128:
263 result = static_cast<uintptr_t>(readSLEB128(&p));
264 break;
265 case DW_EH_PE_udata2:
266 result = readPointerHelper<uint16_t>(p);
267 break;
268 case DW_EH_PE_udata4:
269 result = readPointerHelper<uint32_t>(p);
270 break;
271 case DW_EH_PE_udata8:
272 result = readPointerHelper<uint64_t>(p);
273 break;
274 case DW_EH_PE_sdata2:
275 result = readPointerHelper<int16_t>(p);
276 break;
277 case DW_EH_PE_sdata4:
278 result = readPointerHelper<int32_t>(p);
279 break;
280 case DW_EH_PE_sdata8:
281 result = readPointerHelper<int64_t>(p);
282 break;
283 default:
284 // not supported
285 abort();
286 break;
287 }
288 // then add relative offset
289 switch (encoding & 0x70)
290 {
291 case DW_EH_PE_absptr:
292 // do nothing
293 break;
294 case DW_EH_PE_pcrel:
295 if (result)
296 result += (uintptr_t)(*data);
297 break;
298 case DW_EH_PE_textrel:
299 case DW_EH_PE_datarel:
300 case DW_EH_PE_funcrel:
301 case DW_EH_PE_aligned:
302 default:
303 // not supported
304 abort();
305 break;
306 }
307 // then apply indirection
308 if (result && (encoding & DW_EH_PE_indirect))
309 result = *((uintptr_t*)result);
310 *data = p;
311 return result;
312 }
313
314 static
315 void
316 call_terminate(bool native_exception, _Unwind_Exception* unwind_exception)
317 {
318 __cxa_begin_catch(unwind_exception);
319 if (native_exception)
320 {
321 // Use the stored terminate_handler if possible
322 __cxa_exception* exception_header = (__cxa_exception*)(unwind_exception+1) - 1;
323 std::__terminate(exception_header->terminateHandler);
324 }
325 std::terminate();
326 }
327
328 #if defined(_LIBCXXABI_ARM_EHABI)
329 static const void* read_target2_value(const void* ptr)
330 {
331 uintptr_t offset = *reinterpret_cast<const uintptr_t*>(ptr);
332 if (!offset)
333 return 0;
334 // "ARM EABI provides a TARGET2 relocation to describe these typeinfo
335 // pointers. The reason being it allows their precise semantics to be
336 // deferred to the linker. For bare-metal they turn into absolute
337 // relocations. For linux they turn into GOT-REL relocations."
338 // https://gcc.gnu.org/ml/gcc-patches/2009-08/msg00264.html
339 #if defined(LIBCXXABI_BAREMETAL)
340 return reinterpret_cast<const void*>(reinterpret_cast<uintptr_t>(ptr) +
341 offset);
342 #else
343 return *reinterpret_cast<const void **>(reinterpret_cast<uintptr_t>(ptr) +
344 offset);
345 #endif
346 }
347
348 static const __shim_type_info*
349 get_shim_type_info(uint64_t ttypeIndex, const uint8_t* classInfo,
350 uint8_t ttypeEncoding, bool native_exception,
351 _Unwind_Exception* unwind_exception)
352 {
353 if (classInfo == 0)
354 {
355 // this should not happen. Indicates corrupted eh_table.
356 call_terminate(native_exception, unwind_exception);
357 }
358
359 assert(((ttypeEncoding == DW_EH_PE_absptr) || // LLVM or GCC 4.6
360 (ttypeEncoding == DW_EH_PE_pcrel) || // GCC 4.7 baremetal
361 (ttypeEncoding == (DW_EH_PE_pcrel | DW_EH_PE_indirect))) && // GCC 4.7 linux
362 "Unexpected TTypeEncoding");
363 (void)ttypeEncoding;
364
365 const uint8_t* ttypePtr = classInfo - ttypeIndex * sizeof(uintptr_t);
366 return reinterpret_cast<const __shim_type_info *>(
367 read_target2_value(ttypePtr));
368 }
369 #else // !defined(_LIBCXXABI_ARM_EHABI)
370 static
371 const __shim_type_info*
372 get_shim_type_info(uint64_t ttypeIndex, const uint8_t* classInfo,
373 uint8_t ttypeEncoding, bool native_exception,
374 _Unwind_Exception* unwind_exception)
375 {
376 if (classInfo == 0)
377 {
378 // this should not happen. Indicates corrupted eh_table.
379 call_terminate(native_exception, unwind_exception);
380 }
381 switch (ttypeEncoding & 0x0F)
382 {
383 case DW_EH_PE_absptr:
384 ttypeIndex *= sizeof(void*);
385 break;
386 case DW_EH_PE_udata2:
387 case DW_EH_PE_sdata2:
388 ttypeIndex *= 2;
389 break;
390 case DW_EH_PE_udata4:
391 case DW_EH_PE_sdata4:
392 ttypeIndex *= 4;
393 break;
394 case DW_EH_PE_udata8:
395 case DW_EH_PE_sdata8:
396 ttypeIndex *= 8;
397 break;
398 default:
399 // this should not happen. Indicates corrupted eh_table.
400 call_terminate(native_exception, unwind_exception);
401 }
402 classInfo -= ttypeIndex;
403 return (const __shim_type_info*)readEncodedPointer(&classInfo, ttypeEncoding);
404 }
405 #endif // !defined(_LIBCXXABI_ARM_EHABI)
406
407 /*
408 This is checking a thrown exception type, excpType, against a possibly empty
409 list of catchType's which make up an exception spec.
410
411 An exception spec acts like a catch handler, but in reverse. This "catch
412 handler" will catch an excpType if and only if none of the catchType's in
413 the list will catch a excpType. If any catchType in the list can catch an
414 excpType, then this exception spec does not catch the excpType.
415 */
416 #if defined(_LIBCXXABI_ARM_EHABI)
417 static
418 bool
419 exception_spec_can_catch(int64_t specIndex, const uint8_t* classInfo,
420 uint8_t ttypeEncoding, const __shim_type_info* excpType,
421 void* adjustedPtr, _Unwind_Exception* unwind_exception)
422 {
423 if (classInfo == 0)
424 {
425 // this should not happen. Indicates corrupted eh_table.
426 call_terminate(false, unwind_exception);
427 }
428
429 assert(((ttypeEncoding == DW_EH_PE_absptr) || // LLVM or GCC 4.6
430 (ttypeEncoding == DW_EH_PE_pcrel) || // GCC 4.7 baremetal
431 (ttypeEncoding == (DW_EH_PE_pcrel | DW_EH_PE_indirect))) && // GCC 4.7 linux
432 "Unexpected TTypeEncoding");
433 (void)ttypeEncoding;
434
435 // specIndex is negative of 1-based byte offset into classInfo;
436 specIndex = -specIndex;
437 --specIndex;
438 const void** temp = reinterpret_cast<const void**>(
439 reinterpret_cast<uintptr_t>(classInfo) +
440 static_cast<uintptr_t>(specIndex) * sizeof(uintptr_t));
441 // If any type in the spec list can catch excpType, return false, else return true
442 // adjustments to adjustedPtr are ignored.
443 while (true)
444 {
445 // ARM EHABI exception specification table (filter table) consists of
446 // several pointers which will directly point to the type info object
447 // (instead of ttypeIndex). The table will be terminated with 0.
448 const void** ttypePtr = temp++;
449 if (*ttypePtr == 0)
450 break;
451 // We can get the __shim_type_info simply by performing a
452 // R_ARM_TARGET2 relocation, and cast the result to __shim_type_info.
453 const __shim_type_info* catchType =
454 static_cast<const __shim_type_info*>(read_target2_value(ttypePtr));
455 void* tempPtr = adjustedPtr;
456 if (catchType->can_catch(excpType, tempPtr))
457 return false;
458 }
459 return true;
460 }
461 #else
462 static
463 bool
464 exception_spec_can_catch(int64_t specIndex, const uint8_t* classInfo,
465 uint8_t ttypeEncoding, const __shim_type_info* excpType,
466 void* adjustedPtr, _Unwind_Exception* unwind_exception)
467 {
468 if (classInfo == 0)
469 {
470 // this should not happen. Indicates corrupted eh_table.
471 call_terminate(false, unwind_exception);
472 }
473 // specIndex is negative of 1-based byte offset into classInfo;
474 specIndex = -specIndex;
475 --specIndex;
476 const uint8_t* temp = classInfo + specIndex;
477 // If any type in the spec list can catch excpType, return false, else return true
478 // adjustments to adjustedPtr are ignored.
479 while (true)
480 {
481 uint64_t ttypeIndex = readULEB128(&temp);
482 if (ttypeIndex == 0)
483 break;
484 const __shim_type_info* catchType = get_shim_type_info(ttypeIndex,
485 classInfo,
486 ttypeEncoding,
487 true,
488 unwind_exception);
489 void* tempPtr = adjustedPtr;
490 if (catchType->can_catch(excpType, tempPtr))
491 return false;
492 }
493 return true;
494 }
495 #endif
496
497 static
498 void*
499 get_thrown_object_ptr(_Unwind_Exception* unwind_exception)
500 {
501 // Even for foreign exceptions, the exception object is *probably* at unwind_exception + 1
502 // Regardless, this library is prohibited from touching a foreign exception
503 void* adjustedPtr = unwind_exception + 1;
504 if (__getExceptionClass(unwind_exception) == kOurDependentExceptionClass)
505 adjustedPtr = ((__cxa_dependent_exception*)adjustedPtr - 1)->primaryException;
506 return adjustedPtr;
507 }
508
509 namespace
510 {
511
512 struct scan_results
513 {
514 int64_t ttypeIndex; // > 0 catch handler, < 0 exception spec handler, == 0 a cleanup
515 const uint8_t* actionRecord; // Currently unused. Retained to ease future maintenance.
516 const uint8_t* languageSpecificData; // Needed only for __cxa_call_unexpected
517 uintptr_t landingPad; // null -> nothing found, else something found
518 void* adjustedPtr; // Used in cxa_exception.cpp
519 _Unwind_Reason_Code reason; // One of _URC_FATAL_PHASE1_ERROR,
520 // _URC_FATAL_PHASE2_ERROR,
521 // _URC_CONTINUE_UNWIND,
522 // _URC_HANDLER_FOUND
523 };
524
525 } // unnamed namespace
526
527 static
528 void
529 set_registers(_Unwind_Exception* unwind_exception, _Unwind_Context* context,
530 const scan_results& results)
531 {
532 #if defined(__USING_SJLJ_EXCEPTIONS__)
533 #define __builtin_eh_return_data_regno(regno) regno
534 #endif
535 _Unwind_SetGR(context, __builtin_eh_return_data_regno(0),
536 reinterpret_cast<uintptr_t>(unwind_exception));
537 _Unwind_SetGR(context, __builtin_eh_return_data_regno(1),
538 static_cast<uintptr_t>(results.ttypeIndex));
539 _Unwind_SetIP(context, results.landingPad);
540 }
541
542 /*
543 There are 3 types of scans needed:
544
545 1. Scan for handler with native or foreign exception. If handler found,
546 save state and return _URC_HANDLER_FOUND, else return _URC_CONTINUE_UNWIND.
547 May also report an error on invalid input.
548 May terminate for invalid exception table.
549 _UA_SEARCH_PHASE
550
551 2. Scan for handler with foreign exception. Must return _URC_HANDLER_FOUND,
552 or call terminate.
553 _UA_CLEANUP_PHASE && _UA_HANDLER_FRAME && !native_exception
554
555 3. Scan for cleanups. If a handler is found and this isn't forced unwind,
556 then terminate, otherwise ignore the handler and keep looking for cleanup.
557 If a cleanup is found, return _URC_HANDLER_FOUND, else return _URC_CONTINUE_UNWIND.
558 May also report an error on invalid input.
559 May terminate for invalid exception table.
560 _UA_CLEANUP_PHASE && !_UA_HANDLER_FRAME
561 */
562
563 static void scan_eh_tab(scan_results &results, _Unwind_Action actions,
564 bool native_exception,
565 _Unwind_Exception *unwind_exception,
566 _Unwind_Context *context) {
567 // Initialize results to found nothing but an error
568 results.ttypeIndex = 0;
569 results.actionRecord = 0;
570 results.languageSpecificData = 0;
571 results.landingPad = 0;
572 results.adjustedPtr = 0;
573 results.reason = _URC_FATAL_PHASE1_ERROR;
574 // Check for consistent actions
575 if (actions & _UA_SEARCH_PHASE)
576 {
577 // Do Phase 1
578 if (actions & (_UA_CLEANUP_PHASE | _UA_HANDLER_FRAME | _UA_FORCE_UNWIND))
579 {
580 // None of these flags should be set during Phase 1
581 // Client error
582 results.reason = _URC_FATAL_PHASE1_ERROR;
583 return;
584 }
585 }
586 else if (actions & _UA_CLEANUP_PHASE)
587 {
588 if ((actions & _UA_HANDLER_FRAME) && (actions & _UA_FORCE_UNWIND))
589 {
590 // _UA_HANDLER_FRAME should only be set if phase 1 found a handler.
591 // If _UA_FORCE_UNWIND is set, phase 1 shouldn't have happened.
592 // Client error
593 results.reason = _URC_FATAL_PHASE2_ERROR;
594 return;
595 }
596 }
597 else // Neither _UA_SEARCH_PHASE nor _UA_CLEANUP_PHASE is set
598 {
599 // One of these should be set.
600 // Client error
601 results.reason = _URC_FATAL_PHASE1_ERROR;
602 return;
603 }
604 // Start scan by getting exception table address
605 const uint8_t *lsda = (const uint8_t *)_Unwind_GetLanguageSpecificData(context);
606 if (lsda == 0)
607 {
608 // There is no exception table
609 results.reason = _URC_CONTINUE_UNWIND;
610 return;
611 }
612 results.languageSpecificData = lsda;
613 // Get the current instruction pointer and offset it before next
614 // instruction in the current frame which threw the exception.
615 uintptr_t ip = _Unwind_GetIP(context) - 1;
616 // Get beginning current frame's code (as defined by the
617 // emitted dwarf code)
618 uintptr_t funcStart = _Unwind_GetRegionStart(context);
619 #ifdef __USING_SJLJ_EXCEPTIONS__
620 if (ip == uintptr_t(-1))
621 {
622 // no action
623 results.reason = _URC_CONTINUE_UNWIND;
624 return;
625 }
626 else if (ip == 0)
627 call_terminate(native_exception, unwind_exception);
628 // ip is 1-based index into call site table
629 #else // !__USING_SJLJ_EXCEPTIONS__
630 uintptr_t ipOffset = ip - funcStart;
631 #endif // !defined(_USING_SLJL_EXCEPTIONS__)
632 const uint8_t* classInfo = NULL;
633 // Note: See JITDwarfEmitter::EmitExceptionTable(...) for corresponding
634 // dwarf emission
635 // Parse LSDA header.
636 uint8_t lpStartEncoding = *lsda++;
637 const uint8_t* lpStart = (const uint8_t*)readEncodedPointer(&lsda, lpStartEncoding);
638 if (lpStart == 0)
639 lpStart = (const uint8_t*)funcStart;
640 uint8_t ttypeEncoding = *lsda++;
641 if (ttypeEncoding != DW_EH_PE_omit)
642 {
643 // Calculate type info locations in emitted dwarf code which
644 // were flagged by type info arguments to llvm.eh.selector
645 // intrinsic
646 uintptr_t classInfoOffset = readULEB128(&lsda);
647 classInfo = lsda + classInfoOffset;
648 }
649 // Walk call-site table looking for range that
650 // includes current PC.
651 uint8_t callSiteEncoding = *lsda++;
652 #ifdef __USING_SJLJ_EXCEPTIONS__
653 (void)callSiteEncoding; // When using SjLj exceptions, callSiteEncoding is never used
654 #endif
655 uint32_t callSiteTableLength = static_cast<uint32_t>(readULEB128(&lsda));
656 const uint8_t* callSiteTableStart = lsda;
657 const uint8_t* callSiteTableEnd = callSiteTableStart + callSiteTableLength;
658 const uint8_t* actionTableStart = callSiteTableEnd;
659 const uint8_t* callSitePtr = callSiteTableStart;
660 while (callSitePtr < callSiteTableEnd)
661 {
662 // There is one entry per call site.
663 #ifndef __USING_SJLJ_EXCEPTIONS__
664 // The call sites are non-overlapping in [start, start+length)
665 // The call sites are ordered in increasing value of start
666 uintptr_t start = readEncodedPointer(&callSitePtr, callSiteEncoding);
667 uintptr_t length = readEncodedPointer(&callSitePtr, callSiteEncoding);
668 uintptr_t landingPad = readEncodedPointer(&callSitePtr, callSiteEncoding);
669 uintptr_t actionEntry = readULEB128(&callSitePtr);
670 if ((start <= ipOffset) && (ipOffset < (start + length)))
671 #else // __USING_SJLJ_EXCEPTIONS__
672 // ip is 1-based index into this table
673 uintptr_t landingPad = readULEB128(&callSitePtr);
674 uintptr_t actionEntry = readULEB128(&callSitePtr);
675 if (--ip == 0)
676 #endif // __USING_SJLJ_EXCEPTIONS__
677 {
678 // Found the call site containing ip.
679 #ifndef __USING_SJLJ_EXCEPTIONS__
680 if (landingPad == 0)
681 {
682 // No handler here
683 results.reason = _URC_CONTINUE_UNWIND;
684 return;
685 }
686 landingPad = (uintptr_t)lpStart + landingPad;
687 #else // __USING_SJLJ_EXCEPTIONS__
688 ++landingPad;
689 #endif // __USING_SJLJ_EXCEPTIONS__
690 if (actionEntry == 0)
691 {
692 // Found a cleanup
693 // If this is a type 1 or type 2 search, there are no handlers
694 // If this is a type 3 search, you want to install the cleanup.
695 if ((actions & _UA_CLEANUP_PHASE) && !(actions & _UA_HANDLER_FRAME))
696 {
697 results.ttypeIndex = 0; // Redundant but clarifying
698 results.landingPad = landingPad;
699 results.reason = _URC_HANDLER_FOUND;
700 return;
701 }
702 // No handler here
703 results.reason = _URC_CONTINUE_UNWIND;
704 return;
705 }
706 // Convert 1-based byte offset into
707 const uint8_t* action = actionTableStart + (actionEntry - 1);
708 // Scan action entries until you find a matching handler, cleanup, or the end of action list
709 while (true)
710 {
711 const uint8_t* actionRecord = action;
712 int64_t ttypeIndex = readSLEB128(&action);
713 if (ttypeIndex > 0)
714 {
715 // Found a catch, does it actually catch?
716 // First check for catch (...)
717 const __shim_type_info* catchType =
718 get_shim_type_info(static_cast<uint64_t>(ttypeIndex),
719 classInfo, ttypeEncoding,
720 native_exception, unwind_exception);
721 if (catchType == 0)
722 {
723 // Found catch (...) catches everything, including foreign exceptions
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))
729 {
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;
736 return;
737 }
738 else if (!(actions & _UA_FORCE_UNWIND))
739 {
740 // It looks like the exception table has changed
741 // on us. Likely stack corruption!
742 call_terminate(native_exception, unwind_exception);
743 }
744 }
745 // Else this is a catch (T) clause and will never
746 // catch a foreign exception
747 else if (native_exception)
748 {
749 __cxa_exception* exception_header = (__cxa_exception*)(unwind_exception+1) - 1;
750 void* adjustedPtr = get_thrown_object_ptr(unwind_exception);
751 const __shim_type_info* excpType =
752 static_cast<const __shim_type_info*>(exception_header->exceptionType);
753 if (adjustedPtr == 0 || excpType == 0)
754 {
755 // Something very bad happened
756 call_terminate(native_exception, unwind_exception);
757 }
758 if (catchType->can_catch(excpType, adjustedPtr))
759 {
760 // Found a matching handler
761 // If this is a type 1 search save state and return _URC_HANDLER_FOUND
762 // If this is a type 3 search and !_UA_FORCE_UNWIND, we should have found this in phase 1!
763 // If this is a type 3 search and _UA_FORCE_UNWIND, ignore handler and continue scan
764 if (actions & _UA_SEARCH_PHASE)
765 {
766 // Save state and return _URC_HANDLER_FOUND
767 results.ttypeIndex = ttypeIndex;
768 results.actionRecord = actionRecord;
769 results.landingPad = landingPad;
770 results.adjustedPtr = adjustedPtr;
771 results.reason = _URC_HANDLER_FOUND;
772 return;
773 }
774 else if (!(actions & _UA_FORCE_UNWIND))
775 {
776 // It looks like the exception table has changed
777 // on us. Likely stack corruption!
778 call_terminate(native_exception, unwind_exception);
779 }
780 }
781 }
782 // Scan next action ...
783 }
784 else if (ttypeIndex < 0)
785 {
786 // Found an exception spec. If this is a foreign exception,
787 // it is always caught.
788 if (native_exception)
789 {
790 // Does the exception spec catch this native exception?
791 __cxa_exception* exception_header = (__cxa_exception*)(unwind_exception+1) - 1;
792 void* adjustedPtr = get_thrown_object_ptr(unwind_exception);
793 const __shim_type_info* excpType =
794 static_cast<const __shim_type_info*>(exception_header->exceptionType);
795 if (adjustedPtr == 0 || excpType == 0)
796 {
797 // Something very bad happened
798 call_terminate(native_exception, unwind_exception);
799 }
800 if (exception_spec_can_catch(ttypeIndex, classInfo,
801 ttypeEncoding, excpType,
802 adjustedPtr, unwind_exception))
803 {
804 // native exception caught by exception spec
805 // If this is a type 1 search, save state and return _URC_HANDLER_FOUND
806 // If this is a type 3 search !_UA_FORCE_UNWIND, we should have found this in phase 1!
807 // If this is a type 3 search _UA_FORCE_UNWIND, ignore handler and continue scan
808 if (actions & _UA_SEARCH_PHASE)
809 {
810 // Save state and return _URC_HANDLER_FOUND
811 results.ttypeIndex = ttypeIndex;
812 results.actionRecord = actionRecord;
813 results.landingPad = landingPad;
814 results.adjustedPtr = adjustedPtr;
815 results.reason = _URC_HANDLER_FOUND;
816 return;
817 }
818 else if (!(actions & _UA_FORCE_UNWIND))
819 {
820 // It looks like the exception table has changed
821 // on us. Likely stack corruption!
822 call_terminate(native_exception, unwind_exception);
823 }
824 }
825 }
826 else
827 {
828 // foreign exception caught by exception spec
829 // If this is a type 1 search, save state and return _URC_HANDLER_FOUND
830 // If this is a type 2 search, save state and return _URC_HANDLER_FOUND
831 // If this is a type 3 search !_UA_FORCE_UNWIND, we should have found this in phase 1!
832 // If this is a type 3 search _UA_FORCE_UNWIND, ignore handler and continue scan
833 if ((actions & _UA_SEARCH_PHASE) || (actions & _UA_HANDLER_FRAME))
834 {
835 // Save state and return _URC_HANDLER_FOUND
836 results.ttypeIndex = ttypeIndex;
837 results.actionRecord = actionRecord;
838 results.landingPad = landingPad;
839 results.adjustedPtr = get_thrown_object_ptr(unwind_exception);
840 results.reason = _URC_HANDLER_FOUND;
841 return;
842 }
843 else if (!(actions & _UA_FORCE_UNWIND))
844 {
845 // It looks like the exception table has changed
846 // on us. Likely stack corruption!
847 call_terminate(native_exception, unwind_exception);
848 }
849 }
850 // Scan next action ...
851 }
852 else // ttypeIndex == 0
853 {
854 // Found a cleanup
855 // If this is a type 1 search, ignore it and continue scan
856 // If this is a type 2 search, ignore it and continue scan
857 // If this is a type 3 search, save state and return _URC_HANDLER_FOUND
858 if ((actions & _UA_CLEANUP_PHASE) && !(actions & _UA_HANDLER_FRAME))
859 {
860 // Save state and return _URC_HANDLER_FOUND
861 results.ttypeIndex = ttypeIndex;
862 results.actionRecord = actionRecord;
863 results.landingPad = landingPad;
864 results.adjustedPtr = get_thrown_object_ptr(unwind_exception);
865 results.reason = _URC_HANDLER_FOUND;
866 return;
867 }
868 }
869 const uint8_t* temp = action;
870 int64_t actionOffset = readSLEB128(&temp);
871 if (actionOffset == 0)
872 {
873 // End of action list, no matching handler or cleanup found
874 results.reason = _URC_CONTINUE_UNWIND;
875 return;
876 }
877 // Go to next action
878 action += actionOffset;
879 } // there is no break out of this loop, only return
880 }
881 #ifndef __USING_SJLJ_EXCEPTIONS__
882 else if (ipOffset < start)
883 {
884 // There is no call site for this ip
885 // Something bad has happened. We should never get here.
886 // Possible stack corruption.
887 call_terminate(native_exception, unwind_exception);
888 }
889 #endif // !__USING_SJLJ_EXCEPTIONS__
890 } // there might be some tricky cases which break out of this loop
891
892 // It is possible that no eh table entry specify how to handle
893 // this exception. By spec, terminate it immediately.
894 call_terminate(native_exception, unwind_exception);
895 }
896
897 // public API
898
899 /*
900 The personality function branches on actions like so:
901
902 _UA_SEARCH_PHASE
903
904 If _UA_CLEANUP_PHASE or _UA_HANDLER_FRAME or _UA_FORCE_UNWIND there's
905 an error from above, return _URC_FATAL_PHASE1_ERROR.
906
907 Scan for anything that could stop unwinding:
908
909 1. A catch clause that will catch this exception
910 (will never catch foreign).
911 2. A catch (...) (will always catch foreign).
912 3. An exception spec that will catch this exception
913 (will always catch foreign).
914 If a handler is found
915 If not foreign
916 Save state in header
917 return _URC_HANDLER_FOUND
918 Else a handler not found
919 return _URC_CONTINUE_UNWIND
920
921 _UA_CLEANUP_PHASE
922
923 If _UA_HANDLER_FRAME
924 If _UA_FORCE_UNWIND
925 How did this happen? return _URC_FATAL_PHASE2_ERROR
926 If foreign
927 Do _UA_SEARCH_PHASE to recover state
928 else
929 Recover state from header
930 Transfer control to landing pad. return _URC_INSTALL_CONTEXT
931
932 Else
933
934 This branch handles both normal C++ non-catching handlers (cleanups)
935 and forced unwinding.
936 Scan for anything that can not stop unwinding:
937
938 1. A cleanup.
939
940 If a cleanup is found
941 transfer control to it. return _URC_INSTALL_CONTEXT
942 Else a cleanup is not found: return _URC_CONTINUE_UNWIND
943 */
944
945 #if !defined(_LIBCXXABI_ARM_EHABI)
946 #if defined(__SEH__) && !defined(__USING_SJLJ_EXCEPTIONS__)
947 static _Unwind_Reason_Code __gxx_personality_imp
948 #else
949 _LIBCXXABI_FUNC_VIS _Unwind_Reason_Code
950 #ifdef __USING_SJLJ_EXCEPTIONS__
951 __gxx_personality_sj0
952 #else
953 __gxx_personality_v0
954 #endif
955 #endif
956 (int version, _Unwind_Action actions, uint64_t exceptionClass,
957 _Unwind_Exception* unwind_exception, _Unwind_Context* context)
958 {
959 if (version != 1 || unwind_exception == 0 || context == 0)
960 return _URC_FATAL_PHASE1_ERROR;
961
962 bool native_exception = (exceptionClass & get_vendor_and_language) ==
963 (kOurExceptionClass & get_vendor_and_language);
964 scan_results results;
965 if (actions & _UA_SEARCH_PHASE)
966 {
967 // Phase 1 search: All we're looking for in phase 1 is a handler that
968 // halts unwinding
969 scan_eh_tab(results, actions, native_exception, unwind_exception, context);
970 if (results.reason == _URC_HANDLER_FOUND)
971 {
972 // Found one. Can we cache the results somewhere to optimize phase 2?
973 if (native_exception)
974 {
975 __cxa_exception* exception_header = (__cxa_exception*)(unwind_exception+1) - 1;
976 exception_header->handlerSwitchValue = static_cast<int>(results.ttypeIndex);
977 exception_header->actionRecord = results.actionRecord;
978 exception_header->languageSpecificData = results.languageSpecificData;
979 exception_header->catchTemp = reinterpret_cast<void*>(results.landingPad);
980 exception_header->adjustedPtr = results.adjustedPtr;
981 }
982 return _URC_HANDLER_FOUND;
983 }
984 // Did not find a catching-handler. Return the results of the scan
985 // (normally _URC_CONTINUE_UNWIND, but could have been _URC_FATAL_PHASE1_ERROR
986 // if we were called improperly).
987 return results.reason;
988 }
989 if (actions & _UA_CLEANUP_PHASE)
990 {
991 // Phase 2 search:
992 // Did we find a catching handler in phase 1?
993 if (actions & _UA_HANDLER_FRAME)
994 {
995 // Yes, phase 1 said we have a catching handler here.
996 // Did we cache the results of the scan?
997 if (native_exception)
998 {
999 // Yes, reload the results from the cache.
1000 __cxa_exception* exception_header = (__cxa_exception*)(unwind_exception+1) - 1;
1001 results.ttypeIndex = exception_header->handlerSwitchValue;
1002 results.actionRecord = exception_header->actionRecord;
1003 results.languageSpecificData = exception_header->languageSpecificData;
1004 results.landingPad = reinterpret_cast<uintptr_t>(exception_header->catchTemp);
1005 results.adjustedPtr = exception_header->adjustedPtr;
1006 }
1007 else
1008 {
1009 // No, do the scan again to reload the results.
1010 scan_eh_tab(results, actions, native_exception, unwind_exception, context);
1011 // Phase 1 told us we would find a handler. Now in Phase 2 we
1012 // didn't find a handler. The eh table should not be changing!
1013 if (results.reason != _URC_HANDLER_FOUND)
1014 call_terminate(native_exception, unwind_exception);
1015 }
1016 // Jump to the handler
1017 set_registers(unwind_exception, context, results);
1018 return _URC_INSTALL_CONTEXT;
1019 }
1020 // Either we didn't do a phase 1 search (due to forced unwinding), or
1021 // phase 1 reported no catching-handlers.
1022 // Search for a (non-catching) cleanup
1023 scan_eh_tab(results, actions, native_exception, unwind_exception, context);
1024 if (results.reason == _URC_HANDLER_FOUND)
1025 {
1026 // Found a non-catching handler. Jump to it:
1027 set_registers(unwind_exception, context, results);
1028 return _URC_INSTALL_CONTEXT;
1029 }
1030 // Did not find a cleanup. Return the results of the scan
1031 // (normally _URC_CONTINUE_UNWIND, but could have been _URC_FATAL_PHASE2_ERROR
1032 // if we were called improperly).
1033 return results.reason;
1034 }
1035 // We were called improperly: neither a phase 1 or phase 2 search
1036 return _URC_FATAL_PHASE1_ERROR;
1037 }
1038
1039 #if defined(__SEH__) && !defined(__USING_SJLJ_EXCEPTIONS__)
1040 extern "C" _LIBCXXABI_FUNC_VIS EXCEPTION_DISPOSITION
1041 __gxx_personality_seh0(PEXCEPTION_RECORD ms_exc, void *this_frame,
1042 PCONTEXT ms_orig_context, PDISPATCHER_CONTEXT ms_disp)
1043 {
1044 return _GCC_specific_handler(ms_exc, this_frame, ms_orig_context, ms_disp,
1045 __gxx_personality_imp);
1046 }
1047 #endif
1048
1049 #else
1050
1051 extern "C" _Unwind_Reason_Code __gnu_unwind_frame(_Unwind_Exception*,
1052 _Unwind_Context*);
1053
1054 // Helper function to unwind one frame.
1055 // ARM EHABI 7.3 and 7.4: If the personality function returns _URC_CONTINUE_UNWIND, the
1056 // personality routine should update the virtual register set (VRS) according to the
1057 // corresponding frame unwinding instructions (ARM EHABI 9.3.)
1058 static _Unwind_Reason_Code continue_unwind(_Unwind_Exception* unwind_exception,
1059 _Unwind_Context* context)
1060 {
1061 if (__gnu_unwind_frame(unwind_exception, context) != _URC_OK)
1062 return _URC_FAILURE;
1063 return _URC_CONTINUE_UNWIND;
1064 }
1065
1066 // ARM register names
1067 #if !defined(LIBCXXABI_USE_LLVM_UNWINDER)
1068 static const uint32_t REG_UCB = 12; // Register to save _Unwind_Control_Block
1069 #endif
1070 static const uint32_t REG_SP = 13;
1071
1072 static void save_results_to_barrier_cache(_Unwind_Exception* unwind_exception,
1073 const scan_results& results)
1074 {
1075 unwind_exception->barrier_cache.bitpattern[0] = (uint32_t)results.adjustedPtr;
1076 unwind_exception->barrier_cache.bitpattern[1] = (uint32_t)results.actionRecord;
1077 unwind_exception->barrier_cache.bitpattern[2] = (uint32_t)results.languageSpecificData;
1078 unwind_exception->barrier_cache.bitpattern[3] = (uint32_t)results.landingPad;
1079 unwind_exception->barrier_cache.bitpattern[4] = (uint32_t)results.ttypeIndex;
1080 }
1081
1082 static void load_results_from_barrier_cache(scan_results& results,
1083 const _Unwind_Exception* unwind_exception)
1084 {
1085 results.adjustedPtr = (void*)unwind_exception->barrier_cache.bitpattern[0];
1086 results.actionRecord = (const uint8_t*)unwind_exception->barrier_cache.bitpattern[1];
1087 results.languageSpecificData = (const uint8_t*)unwind_exception->barrier_cache.bitpattern[2];
1088 results.landingPad = (uintptr_t)unwind_exception->barrier_cache.bitpattern[3];
1089 results.ttypeIndex = (int64_t)(int32_t)unwind_exception->barrier_cache.bitpattern[4];
1090 }
1091
1092 extern "C" _LIBCXXABI_FUNC_VIS _Unwind_Reason_Code
1093 __gxx_personality_v0(_Unwind_State state,
1094 _Unwind_Exception* unwind_exception,
1095 _Unwind_Context* context)
1096 {
1097 if (unwind_exception == 0 || context == 0)
1098 return _URC_FATAL_PHASE1_ERROR;
1099
1100 bool native_exception = __isOurExceptionClass(unwind_exception);
1101
1102 #if !defined(LIBCXXABI_USE_LLVM_UNWINDER)
1103 // Copy the address of _Unwind_Control_Block to r12 so that
1104 // _Unwind_GetLanguageSpecificData() and _Unwind_GetRegionStart() can
1105 // return correct address.
1106 _Unwind_SetGR(context, REG_UCB, reinterpret_cast<uint32_t>(unwind_exception));
1107 #endif
1108
1109 // Check the undocumented force unwinding behavior
1110 bool is_force_unwinding = state & _US_FORCE_UNWIND;
1111 state &= ~_US_FORCE_UNWIND;
1112
1113 scan_results results;
1114 switch (state) {
1115 case _US_VIRTUAL_UNWIND_FRAME:
1116 if (is_force_unwinding)
1117 return continue_unwind(unwind_exception, context);
1118
1119 // Phase 1 search: All we're looking for in phase 1 is a handler that halts unwinding
1120 scan_eh_tab(results, _UA_SEARCH_PHASE, native_exception, unwind_exception, context);
1121 if (results.reason == _URC_HANDLER_FOUND)
1122 {
1123 unwind_exception->barrier_cache.sp = _Unwind_GetGR(context, REG_SP);
1124 if (native_exception)
1125 save_results_to_barrier_cache(unwind_exception, results);
1126 return _URC_HANDLER_FOUND;
1127 }
1128 // Did not find the catch handler
1129 if (results.reason == _URC_CONTINUE_UNWIND)
1130 return continue_unwind(unwind_exception, context);
1131 return results.reason;
1132
1133 case _US_UNWIND_FRAME_STARTING:
1134 // TODO: Support force unwinding in the phase 2 search.
1135 // NOTE: In order to call the cleanup functions, _Unwind_ForcedUnwind()
1136 // will call this personality function with (_US_FORCE_UNWIND |
1137 // _US_UNWIND_FRAME_STARTING).
1138
1139 // Phase 2 search
1140 if (unwind_exception->barrier_cache.sp == _Unwind_GetGR(context, REG_SP))
1141 {
1142 // Found a catching handler in phase 1
1143 if (native_exception)
1144 {
1145 // Load the result from the native exception barrier cache.
1146 load_results_from_barrier_cache(results, unwind_exception);
1147 results.reason = _URC_HANDLER_FOUND;
1148 }
1149 else
1150 {
1151 // Search for the catching handler again for the foreign exception.
1152 scan_eh_tab(results, static_cast<_Unwind_Action>(_UA_CLEANUP_PHASE | _UA_HANDLER_FRAME),
1153 native_exception, unwind_exception, context);
1154 if (results.reason != _URC_HANDLER_FOUND) // phase1 search should guarantee to find one
1155 call_terminate(native_exception, unwind_exception);
1156 }
1157
1158 // Install the context for the catching handler
1159 set_registers(unwind_exception, context, results);
1160 return _URC_INSTALL_CONTEXT;
1161 }
1162
1163 // Either we didn't do a phase 1 search (due to forced unwinding), or
1164 // phase 1 reported no catching-handlers.
1165 // Search for a (non-catching) cleanup
1166 scan_eh_tab(results, _UA_CLEANUP_PHASE, native_exception, unwind_exception, context);
1167 if (results.reason == _URC_HANDLER_FOUND)
1168 {
1169 // Found a non-catching handler
1170
1171 // ARM EHABI 8.4.2: Before we can jump to the cleanup handler, we have to setup some
1172 // internal data structures, so that __cxa_end_cleanup() can get unwind_exception from
1173 // __cxa_get_globals().
1174 __cxa_begin_cleanup(unwind_exception);
1175
1176 // Install the context for the cleanup handler
1177 set_registers(unwind_exception, context, results);
1178 return _URC_INSTALL_CONTEXT;
1179 }
1180
1181 // Did not find any handler
1182 if (results.reason == _URC_CONTINUE_UNWIND)
1183 return continue_unwind(unwind_exception, context);
1184 return results.reason;
1185
1186 case _US_UNWIND_FRAME_RESUME:
1187 return continue_unwind(unwind_exception, context);
1188 }
1189
1190 // We were called improperly: neither a phase 1 or phase 2 search
1191 return _URC_FATAL_PHASE1_ERROR;
1192 }
1193 #endif
1194
1195
1196 __attribute__((noreturn))
1197 _LIBCXXABI_FUNC_VIS void
1198 __cxa_call_unexpected(void* arg)
1199 {
1200 _Unwind_Exception* unwind_exception = static_cast<_Unwind_Exception*>(arg);
1201 if (unwind_exception == 0)
1202 call_terminate(false, unwind_exception);
1203 __cxa_begin_catch(unwind_exception);
1204 bool native_old_exception = __isOurExceptionClass(unwind_exception);
1205 std::unexpected_handler u_handler;
1206 std::terminate_handler t_handler;
1207 __cxa_exception* old_exception_header = 0;
1208 int64_t ttypeIndex;
1209 const uint8_t* lsda;
1210 if (native_old_exception)
1211 {
1212 old_exception_header = (__cxa_exception*)(unwind_exception+1) - 1;
1213 t_handler = old_exception_header->terminateHandler;
1214 u_handler = old_exception_header->unexpectedHandler;
1215 // If std::__unexpected(u_handler) rethrows the same exception,
1216 // these values get overwritten by the rethrow. So save them now:
1217 #if defined(_LIBCXXABI_ARM_EHABI)
1218 ttypeIndex = (int64_t)(int32_t)unwind_exception->barrier_cache.bitpattern[4];
1219 lsda = (const uint8_t*)unwind_exception->barrier_cache.bitpattern[2];
1220 #else
1221 ttypeIndex = old_exception_header->handlerSwitchValue;
1222 lsda = old_exception_header->languageSpecificData;
1223 #endif
1224 }
1225 else
1226 {
1227 t_handler = std::get_terminate();
1228 u_handler = std::get_unexpected();
1229 }
1230 try
1231 {
1232 std::__unexpected(u_handler);
1233 }
1234 catch (...)
1235 {
1236 // If the old exception is foreign, then all we can do is terminate.
1237 // We have no way to recover the needed old exception spec. There's
1238 // no way to pass that information here. And the personality routine
1239 // can't call us directly and do anything but terminate() if we throw
1240 // from here.
1241 if (native_old_exception)
1242 {
1243 // Have:
1244 // old_exception_header->languageSpecificData
1245 // old_exception_header->actionRecord
1246 // Need
1247 // const uint8_t* classInfo
1248 // uint8_t ttypeEncoding
1249 uint8_t lpStartEncoding = *lsda++;
1250 const uint8_t* lpStart = (const uint8_t*)readEncodedPointer(&lsda, lpStartEncoding);
1251 (void)lpStart; // purposefully unused. Just needed to increment lsda.
1252 uint8_t ttypeEncoding = *lsda++;
1253 if (ttypeEncoding == DW_EH_PE_omit)
1254 std::__terminate(t_handler);
1255 uintptr_t classInfoOffset = readULEB128(&lsda);
1256 const uint8_t* classInfo = lsda + classInfoOffset;
1257 // Is this new exception catchable by the exception spec at ttypeIndex?
1258 // The answer is obviously yes if the new and old exceptions are the same exception
1259 // If no
1260 // throw;
1261 __cxa_eh_globals* globals = __cxa_get_globals_fast();
1262 __cxa_exception* new_exception_header = globals->caughtExceptions;
1263 if (new_exception_header == 0)
1264 // This shouldn't be able to happen!
1265 std::__terminate(t_handler);
1266 bool native_new_exception = __isOurExceptionClass(&new_exception_header->unwindHeader);
1267 void* adjustedPtr;
1268 if (native_new_exception && (new_exception_header != old_exception_header))
1269 {
1270 const __shim_type_info* excpType =
1271 static_cast<const __shim_type_info*>(new_exception_header->exceptionType);
1272 adjustedPtr =
1273 __getExceptionClass(&new_exception_header->unwindHeader) == kOurDependentExceptionClass ?
1274 ((__cxa_dependent_exception*)new_exception_header)->primaryException :
1275 new_exception_header + 1;
1276 if (!exception_spec_can_catch(ttypeIndex, classInfo, ttypeEncoding,
1277 excpType, adjustedPtr, unwind_exception))
1278 {
1279 // We need to __cxa_end_catch, but for the old exception,
1280 // not the new one. This is a little tricky ...
1281 // Disguise new_exception_header as a rethrown exception, but
1282 // don't actually rethrow it. This means you can temporarily
1283 // end the catch clause enclosing new_exception_header without
1284 // __cxa_end_catch destroying new_exception_header.
1285 new_exception_header->handlerCount = -new_exception_header->handlerCount;
1286 globals->uncaughtExceptions += 1;
1287 // Call __cxa_end_catch for new_exception_header
1288 __cxa_end_catch();
1289 // Call __cxa_end_catch for old_exception_header
1290 __cxa_end_catch();
1291 // Renter this catch clause with new_exception_header
1292 __cxa_begin_catch(&new_exception_header->unwindHeader);
1293 // Rethrow new_exception_header
1294 throw;
1295 }
1296 }
1297 // Will a std::bad_exception be catchable by the exception spec at
1298 // ttypeIndex?
1299 // If no
1300 // throw std::bad_exception();
1301 const __shim_type_info* excpType =
1302 static_cast<const __shim_type_info*>(&typeid(std::bad_exception));
1303 std::bad_exception be;
1304 adjustedPtr = &be;
1305 if (!exception_spec_can_catch(ttypeIndex, classInfo, ttypeEncoding,
1306 excpType, adjustedPtr, unwind_exception))
1307 {
1308 // We need to __cxa_end_catch for both the old exception and the
1309 // new exception. Technically we should do it in that order.
1310 // But it is expedient to do it in the opposite order:
1311 // Call __cxa_end_catch for new_exception_header
1312 __cxa_end_catch();
1313 // Throw std::bad_exception will __cxa_end_catch for
1314 // old_exception_header
1315 throw be;
1316 }
1317 }
1318 }
1319 std::__terminate(t_handler);
1320 }
1321
1322 } // extern "C"
1323
1324 } // __cxxabiv1