mirror of
https://github.com/Noratrieb/uwuwind.git
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61 lines
2.7 KiB
C++
61 lines
2.7 KiB
C++
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bool findUnwindSections(int_t targetAddr, UnwindInfoSections &info)
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{
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// Use DLFO_STRUCT_HAS_EH_DBASE to determine the existence of
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// `_dl_find_object`. Use _LIBUNWIND_SUPPORT_DWARF_INDEX, because libunwind
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// support for _dl_find_object on other unwind formats is not implemented,
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// yet.
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#if defined(DLFO_STRUCT_HAS_EH_DBASE) & defined(_LIBUNWIND_SUPPORT_DWARF_INDEX)
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// We expect `_dl_find_object` to return PT_GNU_EH_FRAME.
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#if DLFO_EH_SEGMENT_TYPE != PT_GNU_EH_FRAME
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#error _dl_find_object retrieves an unexpected section type
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#endif
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// We look-up `dl_find_object` dynamically at runtime to ensure backwards
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// compatibility with earlier version of glibc not yet providing it. On older
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// systems, we gracefully fallback to `dl_iterate_phdr`. Cache the pointer
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// so we only look it up once. Do manual lock to avoid _cxa_guard_acquire.
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static decltype(_dl_find_object) *dlFindObject;
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static bool dlFindObjectChecked = false;
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if (!dlFindObjectChecked)
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{
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dlFindObject = reinterpret_cast<decltype(_dl_find_object) *>(
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dlsym(RTLD_DEFAULT, "_dl_find_object"));
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dlFindObjectChecked = true;
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}
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// Try to find the unwind info using `dl_find_object`
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dl_find_object findResult;
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if (dlFindObject && dlFindObject((void *)targetAddr, &findResult) == 0)
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{
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if (findResult.dlfo_eh_frame == nullptr)
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{
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// Found an entry for `targetAddr`, but there is no unwind info.
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return false;
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}
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info.dso_base = reinterpret_cast<uintptr_t>(findResult.dlfo_map_start);
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info.text_segment_length = static_cast<size_t>(
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(char *)findResult.dlfo_map_end - (char *)findResult.dlfo_map_start);
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// Record the start of PT_GNU_EH_FRAME.
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info.dwarf_index_section =
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reinterpret_cast<uintptr_t>(findResult.dlfo_eh_frame);
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// `_dl_find_object` does not give us the size of PT_GNU_EH_FRAME.
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// Setting length to `SIZE_MAX` effectively disables all range checks.
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info.dwarf_index_section_length = SIZE_MAX;
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EHHeaderParser<LocalAddressSpace>::EHHeaderInfo hdrInfo;
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if (!EHHeaderParser<LocalAddressSpace>::decodeEHHdr(
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*this, info.dwarf_index_section, info.dwarf_index_section_length,
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hdrInfo))
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{
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return false;
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}
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// Record the start of the FDE and use SIZE_MAX to indicate that we do
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// not know the end address.
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info.dwarf_section = hdrInfo.eh_frame_ptr;
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info.dwarf_section_length = SIZE_MAX;
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return true;
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}
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#endif
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dl_iterate_cb_data cb_data = {this, &info, targetAddr};
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int found = dl_iterate_phdr(findUnwindSectionsByPhdr, &cb_data);
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return static_cast<bool>(found);
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}
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