gmsv_segfault

Warning

HERE BE DRAGONS

VERY EXPERIMENTAL (and old) Garry's Mod server binary module for crash signal handling and debugging. Used on Metastruct and partner servers for past ~10 years for the (very frequent) crash reason debugging.

Catches fatal signals (SIGSEGV, SIGABRT, SIGBUS, SIGILL, SIGQUIT, SIGHUP, SIGUSR1, SIGUSR2) and dumps:

• Signal info and fault address
• CPU register state
• C++ backtrace via libunwind (with demangled symbols)
• Lua stack trace and stack contents
• Thread crash detection

Example crash dump: example_crash.log

Also includes:

• physics crash mitigation (requires additional cursed stuff)

Custom signals to send to SRCDS

• SIGUSR1: Lua watchdog to break infinite loops
• SIGUSR2: to dump manually.

Crash log is written to $PWD/logs/<timestamp>.log with a symlink at logs/latest.log.

Build

1. Install premake
2. Install dependencies

   apt-get install libunwind-dev binutils-dev liblzma-dev build-essential

3. Copy this repo inside the gbins alongside all the other binary modules (or really just rewrite build, please)

Install

1. Put gmsv_segfault_linux.dll into garrysmod/lua/bin/ (there is a precompiled version in Releases).
2. install autorun lua to server.

Notes

• Debug builds (#define CRASH_DEBUG) register:

  Lua function	C function	Description
  docrash	lua_dosegfault	Triggers a SIGSEGV
  docrash_stack	lua_dostack	Triggers a stack overflow
  docrash_nullptr	lua_docrash_nullptr	Calls through a null pointer
  docrash_thread	lua_docrash_thread	Crashes in a separate thread

• Originally extracted from gitlab.com/metastruct/internal/gbins (internal)

• Depends on gmsv_physframe_linux.dll for stopping physics in a way that (sometimes) prevents further crashing to allow the occasional countdown while players can save their dupes.

Thanks

Garry, Metastruct, FreezeBug, BlueShank, MetaMan, SpiralP, CapsAdmin, etc, etc etc