I notice now that the code from systat is mapped to very low memory addresses unlike my own programs. I think that's why I am getting errors. Curious how this is happening.
>From: Anindya Mukherjee >Sent: February 4, 2021 3:59 PM >To: misc@openbsd.org <misc@openbsd.org> >Subject: gdb issue > >Hi, > >I'm trying to debug the systat utility for learning purposes. I enabled >-g -O0 in the Makefile, and built it in /usr/src/usr.bin/systat. It >builds and runs fine. However, gdb cannot insert any breakspoints. I'm >on a very recent snapshot and everything is fully patched. > >I set kern.global_ptrace=1 and gdb can attach. Trying to insert a >breakpoint causes the following error: > >$ gdb >GNU gdb 6.3 >Copyright 2004 Free Software Foundation, Inc. >GDB is free software, covered by the GNU General Public License, and you are >welcome to change it and/or distribute copies of it under certain conditions. >Type "show copying" to see the conditions. >There is absolutely no warranty for GDB. Type "show warranty" for details. >This GDB was configured as "amd64-unknown-openbsd6.8" > >(gdb) file systat >Reading symbols from /usr/src/usr.bin/systat/systat...done. >(gdb) attach 51616 >Attaching to program: /usr/src/usr.bin/systat/systat, process 51616 >[Switching to thread 588561] >0x00000b5f3d6c5c8a in ?? () >(gdb) b engine.c:1156 >Breakpoint 1 at 0x13aca: file engine.c, line 1156. >(gdb) info b >Num Type Disp Enb Address What >1 breakpoint keep y 0x0000000000013aca in message_set at engine.c:1156 >(gdb) c >Continuing. >Warning: >Cannot insert breakpoint 1. >Error accessing memory address 0x13aca: Input/output error. > >If I build a simple C program debugging works fine. I can even debug >tmux built from git fine with either gdb or egdb. Any ideas? How >would one proceed if one was investigating a bug? > >Thanks, >Anindya
