1//===----------------------------------------------------------------------===//
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// Abstracts accessing local vs remote address spaces.
9//
10//===----------------------------------------------------------------------===//
11
12#ifndef __ADDRESSSPACE_HPP__
13#define __ADDRESSSPACE_HPP__
14
15#include <stdint.h>
16#include <stdio.h>
17#include <stdlib.h>
18#include <string.h>
19
20#include "libunwind.h"
21#include "config.h"
22#include "dwarf2.h"
23#include "EHHeaderParser.hpp"
24#include "Registers.hpp"
25
26#ifndef _LIBUNWIND_USE_DLADDR
27  #if !(defined(_LIBUNWIND_IS_BAREMETAL) || defined(_WIN32) || defined(_AIX))
28    #define _LIBUNWIND_USE_DLADDR 1
29  #else
30    #define _LIBUNWIND_USE_DLADDR 0
31  #endif
32#endif
33
34#if _LIBUNWIND_USE_DLADDR
35#include <dlfcn.h>
36#if defined(__ELF__) && defined(_LIBUNWIND_LINK_DL_LIB)
37#pragma comment(lib, "dl")
38#endif
39#endif
40
41#if defined(_LIBUNWIND_ARM_EHABI)
42struct EHABIIndexEntry {
43  uint32_t functionOffset;
44  uint32_t data;
45};
46#endif
47
48#if defined(_AIX)
49namespace libunwind {
50char *getFuncNameFromTBTable(uintptr_t pc, uint16_t &NameLen,
51                             unw_word_t *offset);
52}
53#endif
54
55#ifdef __APPLE__
56
57  struct dyld_unwind_sections
58  {
59    const struct mach_header*   mh;
60    const void*                 dwarf_section;
61    uintptr_t                   dwarf_section_length;
62    const void*                 compact_unwind_section;
63    uintptr_t                   compact_unwind_section_length;
64  };
65
66  // In 10.7.0 or later, libSystem.dylib implements this function.
67  extern "C" bool _dyld_find_unwind_sections(void *, dyld_unwind_sections *);
68
69namespace libunwind {
70  bool findDynamicUnwindSections(void *, unw_dynamic_unwind_sections *);
71}
72
73#elif defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND) && defined(_LIBUNWIND_IS_BAREMETAL)
74
75// When statically linked on bare-metal, the symbols for the EH table are looked
76// up without going through the dynamic loader.
77
78// The following linker script may be used to produce the necessary sections and symbols.
79// Unless the --eh-frame-hdr linker option is provided, the section is not generated
80// and does not take space in the output file.
81//
82//   .eh_frame :
83//   {
84//       __eh_frame_start = .;
85//       KEEP(*(.eh_frame))
86//       __eh_frame_end = .;
87//   }
88//
89//   .eh_frame_hdr :
90//   {
91//       KEEP(*(.eh_frame_hdr))
92//   }
93//
94//   __eh_frame_hdr_start = SIZEOF(.eh_frame_hdr) > 0 ? ADDR(.eh_frame_hdr) : 0;
95//   __eh_frame_hdr_end = SIZEOF(.eh_frame_hdr) > 0 ? . : 0;
96
97extern char __eh_frame_start;
98extern char __eh_frame_end;
99
100#if defined(_LIBUNWIND_SUPPORT_DWARF_INDEX)
101extern char __eh_frame_hdr_start;
102extern char __eh_frame_hdr_end;
103#endif
104
105#elif defined(_LIBUNWIND_ARM_EHABI) && defined(_LIBUNWIND_IS_BAREMETAL)
106
107// When statically linked on bare-metal, the symbols for the EH table are looked
108// up without going through the dynamic loader.
109extern char __exidx_start;
110extern char __exidx_end;
111
112#elif defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND) && defined(_WIN32)
113
114#include <windows.h>
115#include <psapi.h>
116
117#elif defined(_LIBUNWIND_USE_DL_ITERATE_PHDR) ||                               \
118      defined(_LIBUNWIND_USE_DL_UNWIND_FIND_EXIDX)
119
120#include <link.h>
121
122#endif
123
124namespace libunwind {
125
126/// Used by findUnwindSections() to return info about needed sections.
127struct UnwindInfoSections {
128#if defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND) ||                                \
129    defined(_LIBUNWIND_SUPPORT_COMPACT_UNWIND) ||                              \
130    defined(_LIBUNWIND_USE_DL_ITERATE_PHDR)
131  // No dso_base for SEH.
132  uintptr_t       dso_base;
133#endif
134#if defined(_LIBUNWIND_USE_DL_ITERATE_PHDR)
135  size_t          text_segment_length;
136#endif
137#if defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
138  uintptr_t       dwarf_section;
139  size_t          dwarf_section_length;
140#endif
141#if defined(_LIBUNWIND_SUPPORT_DWARF_INDEX)
142  uintptr_t       dwarf_index_section;
143  size_t          dwarf_index_section_length;
144#endif
145#if defined(_LIBUNWIND_SUPPORT_COMPACT_UNWIND)
146  uintptr_t       compact_unwind_section;
147  size_t          compact_unwind_section_length;
148#endif
149#if defined(_LIBUNWIND_ARM_EHABI)
150  uintptr_t       arm_section;
151  size_t          arm_section_length;
152#endif
153};
154
155
156/// LocalAddressSpace is used as a template parameter to UnwindCursor when
157/// unwinding a thread in the same process.  The wrappers compile away,
158/// making local unwinds fast.
159class _LIBUNWIND_HIDDEN LocalAddressSpace {
160public:
161  typedef uintptr_t pint_t;
162  typedef intptr_t  sint_t;
163  uint8_t         get8(pint_t addr) {
164    uint8_t val;
165    memcpy(&val, (void *)addr, sizeof(val));
166    return val;
167  }
168  uint16_t         get16(pint_t addr) {
169    uint16_t val;
170    memcpy(&val, (void *)addr, sizeof(val));
171    return val;
172  }
173  uint32_t         get32(pint_t addr) {
174    uint32_t val;
175    memcpy(&val, (void *)addr, sizeof(val));
176    return val;
177  }
178  uint64_t         get64(pint_t addr) {
179    uint64_t val;
180    memcpy(&val, (void *)addr, sizeof(val));
181    return val;
182  }
183  double           getDouble(pint_t addr) {
184    double val;
185    memcpy(&val, (void *)addr, sizeof(val));
186    return val;
187  }
188  v128             getVector(pint_t addr) {
189    v128 val;
190    memcpy(&val, (void *)addr, sizeof(val));
191    return val;
192  }
193  uintptr_t       getP(pint_t addr);
194  uint64_t        getRegister(pint_t addr);
195  static uint64_t getULEB128(pint_t &addr, pint_t end);
196  static int64_t  getSLEB128(pint_t &addr, pint_t end);
197
198  pint_t getEncodedP(pint_t &addr, pint_t end, uint8_t encoding,
199                     pint_t datarelBase = 0);
200  bool findFunctionName(pint_t addr, char *buf, size_t bufLen,
201                        unw_word_t *offset);
202  bool findUnwindSections(pint_t targetAddr, UnwindInfoSections &info);
203  bool findOtherFDE(pint_t targetAddr, pint_t &fde);
204
205  static LocalAddressSpace sThisAddressSpace;
206};
207
208inline uintptr_t LocalAddressSpace::getP(pint_t addr) {
209#if __SIZEOF_POINTER__ == 8
210  return get64(addr);
211#else
212  return get32(addr);
213#endif
214}
215
216inline uint64_t LocalAddressSpace::getRegister(pint_t addr) {
217#if __SIZEOF_POINTER__ == 8 || defined(__mips64)
218  return get64(addr);
219#else
220  return get32(addr);
221#endif
222}
223
224/// Read a ULEB128 into a 64-bit word.
225inline uint64_t LocalAddressSpace::getULEB128(pint_t &addr, pint_t end) {
226  const uint8_t *p = (uint8_t *)addr;
227  const uint8_t *pend = (uint8_t *)end;
228  uint64_t result = 0;
229  int bit = 0;
230  do {
231    uint64_t b;
232
233    if (p == pend)
234      _LIBUNWIND_ABORT("truncated uleb128 expression");
235
236    b = *p & 0x7f;
237
238    if (bit >= 64 || b << bit >> bit != b) {
239      _LIBUNWIND_ABORT("malformed uleb128 expression");
240    } else {
241      result |= b << bit;
242      bit += 7;
243    }
244  } while (*p++ >= 0x80);
245  addr = (pint_t) p;
246  return result;
247}
248
249/// Read a SLEB128 into a 64-bit word.
250inline int64_t LocalAddressSpace::getSLEB128(pint_t &addr, pint_t end) {
251  const uint8_t *p = (uint8_t *)addr;
252  const uint8_t *pend = (uint8_t *)end;
253  uint64_t result = 0;
254  int bit = 0;
255  uint8_t byte;
256  do {
257    if (p == pend)
258      _LIBUNWIND_ABORT("truncated sleb128 expression");
259    byte = *p++;
260    result |= (uint64_t)(byte & 0x7f) << bit;
261    bit += 7;
262  } while (byte & 0x80);
263  // sign extend negative numbers
264  if ((byte & 0x40) != 0 && bit < 64)
265    result |= (-1ULL) << bit;
266  addr = (pint_t) p;
267  return (int64_t)result;
268}
269
270inline LocalAddressSpace::pint_t
271LocalAddressSpace::getEncodedP(pint_t &addr, pint_t end, uint8_t encoding,
272                               pint_t datarelBase) {
273  pint_t startAddr = addr;
274  const uint8_t *p = (uint8_t *)addr;
275  pint_t result;
276
277  // first get value
278  switch (encoding & 0x0F) {
279  case DW_EH_PE_ptr:
280    result = getP(addr);
281    p += sizeof(pint_t);
282    addr = (pint_t) p;
283    break;
284  case DW_EH_PE_uleb128:
285    result = (pint_t)getULEB128(addr, end);
286    break;
287  case DW_EH_PE_udata2:
288    result = get16(addr);
289    p += 2;
290    addr = (pint_t) p;
291    break;
292  case DW_EH_PE_udata4:
293    result = get32(addr);
294    p += 4;
295    addr = (pint_t) p;
296    break;
297  case DW_EH_PE_udata8:
298    result = (pint_t)get64(addr);
299    p += 8;
300    addr = (pint_t) p;
301    break;
302  case DW_EH_PE_sleb128:
303    result = (pint_t)getSLEB128(addr, end);
304    break;
305  case DW_EH_PE_sdata2:
306    // Sign extend from signed 16-bit value.
307    result = (pint_t)(int16_t)get16(addr);
308    p += 2;
309    addr = (pint_t) p;
310    break;
311  case DW_EH_PE_sdata4:
312    // Sign extend from signed 32-bit value.
313    result = (pint_t)(int32_t)get32(addr);
314    p += 4;
315    addr = (pint_t) p;
316    break;
317  case DW_EH_PE_sdata8:
318    result = (pint_t)get64(addr);
319    p += 8;
320    addr = (pint_t) p;
321    break;
322  default:
323    _LIBUNWIND_ABORT("unknown pointer encoding");
324  }
325
326  // then add relative offset
327  switch (encoding & 0x70) {
328  case DW_EH_PE_absptr:
329    // do nothing
330    break;
331  case DW_EH_PE_pcrel:
332    result += startAddr;
333    break;
334  case DW_EH_PE_textrel:
335    _LIBUNWIND_ABORT("DW_EH_PE_textrel pointer encoding not supported");
336    break;
337  case DW_EH_PE_datarel:
338    // DW_EH_PE_datarel is only valid in a few places, so the parameter has a
339    // default value of 0, and we abort in the event that someone calls this
340    // function with a datarelBase of 0 and DW_EH_PE_datarel encoding.
341    if (datarelBase == 0)
342      _LIBUNWIND_ABORT("DW_EH_PE_datarel is invalid with a datarelBase of 0");
343    result += datarelBase;
344    break;
345  case DW_EH_PE_funcrel:
346    _LIBUNWIND_ABORT("DW_EH_PE_funcrel pointer encoding not supported");
347    break;
348  case DW_EH_PE_aligned:
349    _LIBUNWIND_ABORT("DW_EH_PE_aligned pointer encoding not supported");
350    break;
351  default:
352    _LIBUNWIND_ABORT("unknown pointer encoding");
353    break;
354  }
355
356  if (encoding & DW_EH_PE_indirect)
357    result = getP(result);
358
359  return result;
360}
361
362#if defined(_LIBUNWIND_USE_DL_ITERATE_PHDR)
363
364// The ElfW() macro for pointer-size independent ELF header traversal is not
365// provided by <link.h> on some systems (e.g., FreeBSD). On these systems the
366// data structures are just called Elf_XXX. Define ElfW() locally.
367#if !defined(ElfW)
368  #define ElfW(type) Elf_##type
369#endif
370#if !defined(Elf_Half)
371  typedef ElfW(Half) Elf_Half;
372#endif
373#if !defined(Elf_Phdr)
374  typedef ElfW(Phdr) Elf_Phdr;
375#endif
376#if !defined(Elf_Addr)
377  typedef ElfW(Addr) Elf_Addr;
378#endif
379
380struct _LIBUNWIND_HIDDEN dl_iterate_cb_data {
381  LocalAddressSpace *addressSpace;
382  UnwindInfoSections *sects;
383  uintptr_t targetAddr;
384};
385
386#if defined(_LIBUNWIND_USE_FRAME_HEADER_CACHE)
387#include "FrameHeaderCache.hpp"
388
389// Typically there is one cache per process, but when libunwind is built as a
390// hermetic static library, then each shared object may have its own cache.
391static FrameHeaderCache TheFrameHeaderCache;
392#endif
393
394static bool checkAddrInSegment(const Elf_Phdr *phdr, size_t image_base,
395                               dl_iterate_cb_data *cbdata) {
396  if (phdr->p_type == PT_LOAD) {
397    uintptr_t begin = image_base + phdr->p_vaddr;
398    uintptr_t end = begin + phdr->p_memsz;
399    if (cbdata->targetAddr >= begin && cbdata->targetAddr < end) {
400      cbdata->sects->dso_base = begin;
401      cbdata->sects->text_segment_length = phdr->p_memsz;
402      return true;
403    }
404  }
405  return false;
406}
407
408static bool checkForUnwindInfoSegment(const Elf_Phdr *phdr, size_t image_base,
409                                      dl_iterate_cb_data *cbdata) {
410#if defined(_LIBUNWIND_SUPPORT_DWARF_INDEX)
411  if (phdr->p_type == PT_GNU_EH_FRAME) {
412    EHHeaderParser<LocalAddressSpace>::EHHeaderInfo hdrInfo;
413    uintptr_t eh_frame_hdr_start = image_base + phdr->p_vaddr;
414    cbdata->sects->dwarf_index_section = eh_frame_hdr_start;
415    cbdata->sects->dwarf_index_section_length = phdr->p_memsz;
416    if (EHHeaderParser<LocalAddressSpace>::decodeEHHdr(
417            *cbdata->addressSpace, eh_frame_hdr_start,
418            eh_frame_hdr_start + phdr->p_memsz, hdrInfo)) {
419      // .eh_frame_hdr records the start of .eh_frame, but not its size.
420      // Rely on a zero terminator to find the end of the section.
421      cbdata->sects->dwarf_section = hdrInfo.eh_frame_ptr;
422      cbdata->sects->dwarf_section_length = SIZE_MAX;
423      return true;
424    }
425  }
426  return false;
427#elif defined(_LIBUNWIND_ARM_EHABI)
428  if (phdr->p_type == PT_ARM_EXIDX) {
429    uintptr_t exidx_start = image_base + phdr->p_vaddr;
430    cbdata->sects->arm_section = exidx_start;
431    cbdata->sects->arm_section_length = phdr->p_memsz;
432    return true;
433  }
434  return false;
435#else
436#error Need one of _LIBUNWIND_SUPPORT_DWARF_INDEX or _LIBUNWIND_ARM_EHABI
437#endif
438}
439
440static int findUnwindSectionsByPhdr(struct dl_phdr_info *pinfo,
441                                    size_t pinfo_size, void *data) {
442  auto cbdata = static_cast<dl_iterate_cb_data *>(data);
443  if (pinfo->dlpi_phnum == 0 || cbdata->targetAddr < pinfo->dlpi_addr)
444    return 0;
445#if defined(_LIBUNWIND_USE_FRAME_HEADER_CACHE)
446  if (TheFrameHeaderCache.find(pinfo, pinfo_size, data))
447    return 1;
448#else
449  // Avoid warning about unused variable.
450  (void)pinfo_size;
451#endif
452
453  Elf_Addr image_base = pinfo->dlpi_addr;
454
455  // Most shared objects seen in this callback function likely don't contain the
456  // target address, so optimize for that. Scan for a matching PT_LOAD segment
457  // first and bail when it isn't found.
458  bool found_text = false;
459  for (Elf_Half i = 0; i < pinfo->dlpi_phnum; ++i) {
460    if (checkAddrInSegment(&pinfo->dlpi_phdr[i], image_base, cbdata)) {
461      found_text = true;
462      break;
463    }
464  }
465  if (!found_text)
466    return 0;
467
468  // PT_GNU_EH_FRAME and PT_ARM_EXIDX are usually near the end. Iterate
469  // backward.
470  bool found_unwind = false;
471  for (Elf_Half i = pinfo->dlpi_phnum; i > 0; i--) {
472    const Elf_Phdr *phdr = &pinfo->dlpi_phdr[i - 1];
473    if (checkForUnwindInfoSegment(phdr, image_base, cbdata)) {
474      found_unwind = true;
475      break;
476    }
477  }
478  if (!found_unwind)
479    return 0;
480
481#if defined(_LIBUNWIND_USE_FRAME_HEADER_CACHE)
482  TheFrameHeaderCache.add(cbdata->sects);
483#endif
484  return 1;
485}
486
487#endif  // defined(_LIBUNWIND_USE_DL_ITERATE_PHDR)
488
489
490inline bool LocalAddressSpace::findUnwindSections(pint_t targetAddr,
491                                                  UnwindInfoSections &info) {
492#ifdef __APPLE__
493  dyld_unwind_sections dyldInfo;
494  if (_dyld_find_unwind_sections((void *)targetAddr, &dyldInfo)) {
495    info.dso_base                      = (uintptr_t)dyldInfo.mh;
496 #if defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
497    info.dwarf_section                 = (uintptr_t)dyldInfo.dwarf_section;
498    info.dwarf_section_length          = (size_t)dyldInfo.dwarf_section_length;
499 #endif
500    info.compact_unwind_section        = (uintptr_t)dyldInfo.compact_unwind_section;
501    info.compact_unwind_section_length = (size_t)dyldInfo.compact_unwind_section_length;
502    return true;
503  }
504
505  unw_dynamic_unwind_sections dynamicUnwindSectionInfo;
506  if (findDynamicUnwindSections((void *)targetAddr,
507                                &dynamicUnwindSectionInfo)) {
508    info.dso_base = dynamicUnwindSectionInfo.dso_base;
509#if defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
510    info.dwarf_section = (uintptr_t)dynamicUnwindSectionInfo.dwarf_section;
511    info.dwarf_section_length = dynamicUnwindSectionInfo.dwarf_section_length;
512#endif
513    info.compact_unwind_section =
514        (uintptr_t)dynamicUnwindSectionInfo.compact_unwind_section;
515    info.compact_unwind_section_length =
516        dynamicUnwindSectionInfo.compact_unwind_section_length;
517    return true;
518  }
519
520#elif defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND) && defined(_LIBUNWIND_IS_BAREMETAL)
521  info.dso_base = 0;
522  // Bare metal is statically linked, so no need to ask the dynamic loader
523  info.dwarf_section_length = (size_t)(&__eh_frame_end - &__eh_frame_start);
524  info.dwarf_section =        (uintptr_t)(&__eh_frame_start);
525  _LIBUNWIND_TRACE_UNWINDING("findUnwindSections: section %p length %p",
526                             (void *)info.dwarf_section, (void *)info.dwarf_section_length);
527#if defined(_LIBUNWIND_SUPPORT_DWARF_INDEX)
528  info.dwarf_index_section =        (uintptr_t)(&__eh_frame_hdr_start);
529  info.dwarf_index_section_length = (size_t)(&__eh_frame_hdr_end - &__eh_frame_hdr_start);
530  _LIBUNWIND_TRACE_UNWINDING("findUnwindSections: index section %p length %p",
531                             (void *)info.dwarf_index_section, (void *)info.dwarf_index_section_length);
532#endif
533  if (info.dwarf_section_length)
534    return true;
535#elif defined(_LIBUNWIND_ARM_EHABI) && defined(_LIBUNWIND_IS_BAREMETAL)
536  // Bare metal is statically linked, so no need to ask the dynamic loader
537  info.arm_section =        (uintptr_t)(&__exidx_start);
538  info.arm_section_length = (size_t)(&__exidx_end - &__exidx_start);
539  _LIBUNWIND_TRACE_UNWINDING("findUnwindSections: section %p length %p",
540                             (void *)info.arm_section, (void *)info.arm_section_length);
541  if (info.arm_section && info.arm_section_length)
542    return true;
543#elif defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND) && defined(_WIN32)
544  HMODULE mods[1024];
545  HANDLE process = GetCurrentProcess();
546  DWORD needed;
547
548  if (!EnumProcessModules(process, mods, sizeof(mods), &needed)) {
549    DWORD err = GetLastError();
550    _LIBUNWIND_TRACE_UNWINDING("findUnwindSections: EnumProcessModules failed, "
551                               "returned error %d", (int)err);
552    (void)err;
553    return false;
554  }
555
556  for (unsigned i = 0; i < (needed / sizeof(HMODULE)); i++) {
557    PIMAGE_DOS_HEADER pidh = (PIMAGE_DOS_HEADER)mods[i];
558    PIMAGE_NT_HEADERS pinh = (PIMAGE_NT_HEADERS)((BYTE *)pidh + pidh->e_lfanew);
559    PIMAGE_FILE_HEADER pifh = (PIMAGE_FILE_HEADER)&pinh->FileHeader;
560    PIMAGE_SECTION_HEADER pish = IMAGE_FIRST_SECTION(pinh);
561    bool found_obj = false;
562    bool found_hdr = false;
563
564    info.dso_base = (uintptr_t)mods[i];
565    for (unsigned j = 0; j < pifh->NumberOfSections; j++, pish++) {
566      uintptr_t begin = pish->VirtualAddress + (uintptr_t)mods[i];
567      uintptr_t end = begin + pish->Misc.VirtualSize;
568      if (!strncmp((const char *)pish->Name, ".text",
569                   IMAGE_SIZEOF_SHORT_NAME)) {
570        if (targetAddr >= begin && targetAddr < end)
571          found_obj = true;
572      } else if (!strncmp((const char *)pish->Name, ".eh_frame",
573                          IMAGE_SIZEOF_SHORT_NAME)) {
574        info.dwarf_section = begin;
575        info.dwarf_section_length = pish->Misc.VirtualSize;
576        found_hdr = true;
577      }
578      if (found_obj && found_hdr)
579        return true;
580    }
581  }
582  return false;
583#elif defined(_LIBUNWIND_SUPPORT_SEH_UNWIND) && defined(_WIN32)
584  // Don't even bother, since Windows has functions that do all this stuff
585  // for us.
586  (void)targetAddr;
587  (void)info;
588  return true;
589#elif defined(_LIBUNWIND_SUPPORT_TBTAB_UNWIND)
590  // The traceback table is used for unwinding.
591  (void)targetAddr;
592  (void)info;
593  return true;
594#elif defined(_LIBUNWIND_USE_DL_UNWIND_FIND_EXIDX)
595  int length = 0;
596  info.arm_section =
597      (uintptr_t)dl_unwind_find_exidx((_Unwind_Ptr)targetAddr, &length);
598  info.arm_section_length = (size_t)length * sizeof(EHABIIndexEntry);
599  if (info.arm_section && info.arm_section_length)
600    return true;
601#elif defined(_LIBUNWIND_USE_DL_ITERATE_PHDR)
602  // Use DLFO_STRUCT_HAS_EH_DBASE to determine the existence of
603  // `_dl_find_object`. Use _LIBUNWIND_SUPPORT_DWARF_INDEX, because libunwind
604  // support for _dl_find_object on other unwind formats is not implemented,
605  // yet.
606#if defined(DLFO_STRUCT_HAS_EH_DBASE) & defined(_LIBUNWIND_SUPPORT_DWARF_INDEX)
607  // We expect `_dl_find_object` to return PT_GNU_EH_FRAME.
608#if DLFO_EH_SEGMENT_TYPE != PT_GNU_EH_FRAME
609#error _dl_find_object retrieves an unexpected section type
610#endif
611  // We look-up `dl_find_object` dynamically at runtime to ensure backwards
612  // compatibility with earlier version of glibc not yet providing it. On older
613  // systems, we gracefully fallback to `dl_iterate_phdr`. Cache the pointer
614  // so we only look it up once. Do manual lock to avoid _cxa_guard_acquire.
615  static decltype(_dl_find_object) *dlFindObject;
616  static bool dlFindObjectChecked = false;
617  if (!dlFindObjectChecked) {
618    dlFindObject = reinterpret_cast<decltype(_dl_find_object) *>(
619        dlsym(RTLD_DEFAULT, "_dl_find_object"));
620    dlFindObjectChecked = true;
621  }
622  // Try to find the unwind info using `dl_find_object`
623  dl_find_object findResult;
624  if (dlFindObject && dlFindObject((void *)targetAddr, &findResult) == 0) {
625    if (findResult.dlfo_eh_frame == nullptr) {
626      // Found an entry for `targetAddr`, but there is no unwind info.
627      return false;
628    }
629    info.dso_base = reinterpret_cast<uintptr_t>(findResult.dlfo_map_start);
630    info.text_segment_length = static_cast<size_t>(
631        (char *)findResult.dlfo_map_end - (char *)findResult.dlfo_map_start);
632
633    // Record the start of PT_GNU_EH_FRAME.
634    info.dwarf_index_section =
635        reinterpret_cast<uintptr_t>(findResult.dlfo_eh_frame);
636    // `_dl_find_object` does not give us the size of PT_GNU_EH_FRAME.
637    // Setting length to `SIZE_MAX` effectively disables all range checks.
638    info.dwarf_index_section_length = SIZE_MAX;
639    EHHeaderParser<LocalAddressSpace>::EHHeaderInfo hdrInfo;
640    if (!EHHeaderParser<LocalAddressSpace>::decodeEHHdr(
641            *this, info.dwarf_index_section,
642            info.dwarf_index_section + info.dwarf_index_section_length,
643            hdrInfo)) {
644      return false;
645    }
646    // Record the start of the FDE and use SIZE_MAX to indicate that we do
647    // not know the end address.
648    info.dwarf_section = hdrInfo.eh_frame_ptr;
649    info.dwarf_section_length = SIZE_MAX;
650    return true;
651  }
652#endif
653  dl_iterate_cb_data cb_data = {this, &info, targetAddr};
654  int found = dl_iterate_phdr(findUnwindSectionsByPhdr, &cb_data);
655  return static_cast<bool>(found);
656#endif
657
658  return false;
659}
660
661inline bool LocalAddressSpace::findOtherFDE(pint_t targetAddr, pint_t &fde) {
662  // TO DO: if OS has way to dynamically register FDEs, check that.
663  (void)targetAddr;
664  (void)fde;
665  return false;
666}
667
668inline bool LocalAddressSpace::findFunctionName(pint_t addr, char *buf,
669                                                size_t bufLen,
670                                                unw_word_t *offset) {
671#if _LIBUNWIND_USE_DLADDR
672  Dl_info dyldInfo;
673  if (dladdr((void *)addr, &dyldInfo)) {
674    if (dyldInfo.dli_sname != NULL) {
675      snprintf(buf, bufLen, "%s", dyldInfo.dli_sname);
676      *offset = (addr - (pint_t) dyldInfo.dli_saddr);
677      return true;
678    }
679  }
680#elif defined(_AIX)
681  uint16_t nameLen;
682  char *funcName = getFuncNameFromTBTable(addr, nameLen, offset);
683  if (funcName != NULL) {
684    snprintf(buf, bufLen, "%.*s", nameLen, funcName);
685    return true;
686  }
687#else
688  (void)addr;
689  (void)buf;
690  (void)bufLen;
691  (void)offset;
692#endif
693  return false;
694}
695
696} // namespace libunwind
697
698#endif // __ADDRESSSPACE_HPP__
699