fix(native): resolve symbols from split-debug files on Linux#1836
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tustanivsky wants to merge 6 commits into
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fix(native): resolve symbols from split-debug files on Linux#1836tustanivsky wants to merge 6 commits into
tustanivsky wants to merge 6 commits into
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The crash daemon resolved frame symbols by picking the nearest preceding entry from the module's .dynsym without bounding the match by st_size. For binaries stripped of their .symtab (the norm for release builds that ship a split-debug companion), most addresses fall into gaps between exported symbols and got attributed to unrelated neighboring functions, producing plausible-looking but wrong stacktraces. - Require the target address to lie within [st_value, st_value + st_size) instead of accepting the nearest preceding symbol; an unresolved frame beats a wrong name. - Prefer .symtab over .dynsym (it is a superset when present). - When the module has no .symtab, follow the .gnu_debuglink section per the GDB split-debug conventions (<dir>/<name>, <dir>/.debug/<name>, /usr/lib/debug/<dir>/<name>), validating candidates by GNU build-id equality, and read the full symbol table from the companion file. - Cache the resolved symbol-table source per module and scan the table in fixed-size chunks, reading only the winning name from the string table, so large debug companions are never loaded into memory wholesale.
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The symbol-source cache was a bounded 64-slot table keyed by module name; once full, further modules got no symbolication. Direct-map it by module index instead, sized to the module cap. Being BSS, only touched slots are committed, and the name key (now redundant) is dropped.
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This PR fixes invalid stacktraces produced by the crash daemon on Linux for binaries that were stripped of their
.symtab- the standard layout for release builds that ship a separate debug file (e.g. Unreal Engine, which runsobjcopy --strip-allpost-link and stores symbols in a.gnu_debuglinkcompanion).Since #1764, the daemon resolved frame names by picking the nearest preceding entry from the module's
.dynsymwithout bounding the match byst_size. For stripped binaries the dynamic table covers only exported symbols (small fraction of all functions in a UE title), so most addresses fall into gaps between exported symbols and get attributed to unrelated neighboring functions.Key Changes
st_size: a symbol only matches when the target address lies within [st_value, st_value + st_size). An unresolved frame (bare instruction_addr) beats a wrong name..symtabover.dynsym: the full table is a superset when present; the previous preference order was backwards for executables..gnu_debuglink: when the module has no.symtab, search for the split-debug companion per the GDB conventions (<dir>/<name>,<dir>/.debug/<name>,/usr/lib/debug/<dir>/<name>) and read its full symbol table. Candidates are validated by GNU build-id equality; when either file lacks a build-id, the candidate is accepted without CRC verification.No changes to unwinding: the frame addresses were already correct (pre-captured DWARF backtrace), only their naming was wrong. #1747's remote unwinding for non-crashed threads is untouched (libunwind already bounds its lookups internally).
Testing
Checked manually against UE 5.7.4 sample project build on Ubuntu 26.04 LTS:
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