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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.

New alterative fresh out of the oven thanks to BlueShank: https://github.com/blueshank-gh/plugin_crashcapture

Old related plugin for SRCDS watchdog: serverplugin_guarddog

image

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