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Re:Tracking down a segfault that suddenly started happening by robertnn on Monday January 18, 2021 @08:26AM (#25821536)
I really enjoy stories like this. Thanks for sharing. Must have been really satisfying to get it working!
Re:Tracking down a segfault that suddenly started happening by jagrsw on Monday January 18, 2021 @08:36AM (#25821610)
Another one then :)

A few months ago I tried to run CSGO under Wayland. I recompiled libSDL.so b/c the one delivered with CSGO doesn't support Wayland, and ran with it LD_PRELOAD'ed. The game crashed upon start. After another debugging session with gdb/strace, I figured out that the CSGO binary is calling

  strstr()
with one of its arguments passed as a negative value from some other function, and it happens under Wayland only for some reason. Now, when preloading two libraries, and setting one environment flag I was able to play CSGO under Wayland.

  cat apps/strstr.c 
  #define _GNU_SOURCE
  #include <string.h>
  #include <dlfcn.h>
  #include <stdint.h>
  #include <inttypes.h>
  
  char *strstr(const char *haystack, const char *needle) {
   if ((uintptr_t)haystack > (uintptr_t)0xFFFFFFFF00000000) {
    return NULL;
   }
  
   char* (*p)(const char *haystack, const char *needle) = dlsym(RTLD_NEXT, "strstr");
   return p(haystack, needle);
  }
  
  $ SDL_VIDEODRIVER=wayland LD_PRELOAD=/home/<user>/apps/strstr.so:/home/<user>/Downloads/SDL-master/build/.libs/libSDL2-2.0.so.0.12.1 steam
But after playing with all those strace's/gdb's/LD_PRELOAD's my trust factor in CSGO (the score which says how likely I am to cheat in the near future), went down from Green (good player) to Red (Significantly Bad - will start cheating any moment:) within a week. And that's for 2012 account, with Prime enabled since 2016, and a couple of hundred matchmaking games played, and many more casual/FFA games. So YMMV :)

I wrote to [email protected] asking if they could verify if my account really deserves this rating, because every second CSGO match is again blatant cheaters now, but since nothing changed since a week (when I wrote it), this probably means that LD_PRELOAD'ing your steam is not a good idea :).

Re:Tracking down a segfault that suddenly started happening by finnthehuman on Monday January 18, 2021 @11:23AM (#25823293)
>but since nothing changed since a week (when I wrote it), this probably means that LD_PRELOAD'ing your steam is not a good idea :).

Welcome to the "knows too much to be trustworthy" category of perceived-troublemaker.

Re:Tracking down a segfault that suddenly started happening by feb on Monday January 18, 2021 @10:23AM (#25822605)
And this story gives an extra argument in favor of dynamic libraries as they make it easier to fix some bugs in compiled applications (except for games which check if someone messed with LD_PRELOAD).