Android Tombstone .NET Symbolication

Workflow

Step 1: Parse the Tombstone Backtrace

Each backtrace frame has this format:

#NN pc OFFSET  /path/to/library.so (optional_symbol+0xNN) (BuildId: HEXSTRING)

Extract: frame number, PC offset (hex, already library-relative), library name, and BuildId (32–40 hex chars).

Symbolicate all threads by default (background threads like GC/finalizer often have useful .NET frames). The crashing thread's backtrace is listed first; additional threads appear after --- --- --- markers.

Format notes:

• The script auto-detects #NN pc frame lines with or without a backtrace: header, and strips logcat timestamp/tag prefixes automatically.
• Logcat-captured tombstones often omit BuildIds. Recover via adb shell readelf -n, CI build artifacts, or the .NET runtime NuGet package.
• GitHub issue pastes may mangle #1 pc into issue links — replace org/repo#N pc with #N pc before saving to a file.
• If the script fails to parse a format, fall back to manual extraction of #NN pc OFFSET library.so (BuildId: HEX) tuples.

Step 2: Identify .NET Runtime Libraries

Filter frames to .NET runtime libraries:

| Library | Runtime | |---------|---------| | libmonosgen-2.0.so | Mono (MAUI, Xamarin, interpreter) | | libcoreclr.so | CoreCLR (JIT mode) | | libSystem.*.so | .NET BCL native components (Native, Globalization.Native, IO.Compression.Native, Security.Cryptography.Native.OpenSsl, Net.Security.Native) |

NativeAOT: No libcoreclr.so or libmonosgen-2.0.so — the runtime is statically linked into the app binary (e.g., libMyApp.so). The libSystem.*.so BCL libraries remain separate and can be symbolicated via the symbol server. For the app binary itself, you need the app's own debug symbols.

Skip libc.so, libart.so, and other Android system libraries unless the user specifically asks.

Step 3: Download Debug Symbols

For each unique .NET BuildId, download debug symbols:

https://msdl.microsoft.com/download/symbols/_.debug/elf-buildid-sym-<BUILDID>/_.debug

curl -sL "https://msdl.microsoft.com/download/symbols/_.debug/elf-buildid-sym-1eb39fc72918c7c6c0c610b79eb3d3d47b2f81be/_.debug" \
  -o libmonosgen-2.0.so.debug

Verify with file libmonosgen-2.0.so.debug — should show ELF 64-bit ... with debug_info, not stripped. If the download returns 404 or HTML, symbols are not published for that build. Do not add or subtract library base addresses — offsets in tombstones are already library-relative.

Step 4: Symbolicate Each Frame

llvm-symbolizer --obj=libmonosgen-2.0.so.debug -f -C 0x222098

Output:

ves_icall_System_Environment_FailFast
/__w/1/s/src/runtime/src/mono/mono/metadata/icall.c:6244

The /__w/1/s/ prefix is the CI workspace root — the meaningful path starts at src/runtime/, mapping to dotnet/dotnet VMR.

Step 5: Present the Symbolicated Backtrace

Combine original frame numbers with resolved function names and source locations:

#00  libc.so              abort+164
#01  libmonosgen-2.0.so   ves_icall_System_Environment_FailFast        (mono/metadata/icall.c:6244)
#02  libmonosgen-2.0.so   do_icall                                     (mono/mini/interp.c:2457)
#03  libmonosgen-2.0.so   mono_interp_exec_method                      (mono/mini/interp.c)

For unresolved frames (??), keep the original line with BuildId and PC offset.

Automation Script

scripts/Symbolicate-Tombstone.ps1 automates the full workflow:

pwsh scripts/Symbolicate-Tombstone.ps1 -TombstoneFile tombstone_01.txt -LlvmSymbolizer llvm-symbolizer

Flags: -CrashingThreadOnly (limit to crashing thread), -OutputFile path (write to file), -ParseOnly (report libraries/BuildIds/URLs without downloading), -SkipVersionLookup (skip runtime version identification).

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