C Index

Debugging

Check if the system have restrictions to attach to other processes or other hardening measures, check sysctl settings such as; kernel.yama.ptrace_scope;

kernel.yama.ptrace_scope=0
All processes can be debugged, they must have same uid.
kernel.yama.ptrace_scope=1
Only a parent process can be debugged.
kernel.yama.ptrace_scope=2
Require user privileges to use ptrace CAP_SYS_PTRACE capability.
kernel.yama.ptrace_scope=3
No processes may be traced with ptrace.

Before debug;

        # echo 0 | sudo tee /proc/sys/kernel/yama/ptrace_scope
        # sysctl -w kernel.yama.ptrace_scope=0

        

After debug;

        # echo 1 | sudo tee /proc/sys/kernel/yama/ptrace_scope
        # sysctl -w kernel.yama.ptrace_scope=1
        

GDB

If the program needs arguments you can set it;

        (gdb)set args -parameter1 -parameter2
        

To start gdb in TUI mode press;

Ctrl-x A
Enter or leave TUI.
Ctrl-x 0
TUI with only one window.
Ctrl-x 2
TUI with more than two windows.
Ctrl-x o
Change active window.
Ctrl-x s
TUI single key mode.
Ctrl-L s
Refresh screen.
Up
Scroll
Down
Scroll
Left
Scroll
Right
Scroll
        (gdb) info win
        (gdb) fs next
        (gdb) fs SRC
        
        b - backtrace
        info locals
        display
        print
        x
        catch syscall open
        

When new thread is created you receive a notification. To get information about threads;

        info threads
        

To select thread;

        thread 1
        
        break linespec thread threadno
        

Strace

        $ strace -c ./program -o ~/program.strace
        
        $ strace -p 1337 -o ~/program.strace
        

C program with autotools GDB Quick Start, Learning C with GDB and Memory Layout and the Stack are great sources of introductory information. Stopping and Starting multi-thread programs

C Index

This is part of the Hive System Documentation. Copyright (C) 2019 Hive Team. See the file Gnu Free Documentation License for copying conditions.