gdb.py is a command line debugger similar to gdb but with only few features: no symbol support, no C language support, no thread support, etc. gdb.py is based on python-ptrace.

Some commands

• cont: continue execution
• stepi: execute one instruction
• step: execute one instruction, but don't enter into calls
• help: display help

Features

• print command displays value as decimal and hexadecimal, but also the related memory mapping (if any)

  (gdb) print $eip
  Decimal: 3086383120
  Hexadecimal: 0xb7f67810
  Address is part of mapping: 0xb7f67000-0xb7f81000 => /lib/ld-2.6.1.so (r-xp)
  

• Nice output of signal: see python-ptrace signal handling
• Syscall tracer with command "sys": see python-ptrace system call tracer. Short example:

  (gdb) sys
  long access(char* filename='/etc/ld.so.nohwcap' at 0xb7f7f35b, int mode=F_OK) = -2 (No such file or directory)
  

• Supports multiple processes

  (gdb) proclist
  <PtraceProcess #24187> (active)
  <PtraceProcess #24188>
  (gdb) proc
  Process ID: 24187 (parent: 24182)
  Process state: T (traced)
  Process command line: ['tests/fork_execve']
  (...)
  (gdb) switch; proc
  Switch to <PtraceProcess #24188>
  Process ID: 24188 (parent: 24187)
  Process state: T (traced)
  Process command line: ['/bin/ls']
  (...)
  

• Allow multiple commands on the same line using ";" separator

  (gdb) print $eax; set $ax=0xdead; print $eax
  Decimal: 0
  Hexadecimal: 0x00000000
  Set $ax to 57005
  Decimal: 57005
  Hexadecimal: 0x0000dead
  

• Only written in pure Python code, so it's easy to extend
• Expression parser supports all arithmetic operator (a+b, a/b, a<<b, a&b, ...), parenthesis, use of registers, etc. and pointer dereference (eg. "print *($ebx+0xc)")

Screnshot

$ ./gdb.py ls
execve(/bin/ls, ['/bin/ls'], [/* 40 vars */]) = 16182
(gdb) where
ASM 0xb7f47810: MOV EAX, ESP <==
ASM 0xb7f47812: CALL 0xb7f47a60
ASM 0xb7f47817: MOV EDI, EAX
ASM 0xb7f47819: CALL 0xb7f47800
(gdb) regs
     EBX = 0xb7f4781e
     ECX = 0x0001d2f4
     EDX = 0xb7f61ff4
     ESI = 0x00000000
     (...)
(gdb) proc
Process ID: 16182
Process command line: ['/bin/ls']
Process environment: ['TERM=xterm', 'SHELL=/bin/bash', (...)]
Process working directory: /home/haypo/prog/fusil/ptrace/trunk
(gdb) stack
STACK: 0xbfc58000..0xbfc6e000
STACK -8: 0x00000000
STACK -4: 0xb7f4781e
STACK +0: 0x00000001
STACK +4: 0xbfc6c6bb
STACK +8: 0x00000000
(gdb) maps
MAPS: 08048000-0805b000 r-xp 00000000 08:03 2588939    /bin/ls
MAPS: 0805b000-0805c000 rw-p 00012000 08:03 2588939    /bin/ls
(...)
MAPS: b7f61000-b7f63000 rw-p 00019000 08:03 1540553    /lib/ld-2.6.1.so
MAPS: bfc58000-bfc6e000 rw-p bfc58000 00:00 0          [stack]
MAPS: ffffe000-fffff000 r-xp 00000000 00:00 0          [vdso]
(gdb) quit
Quit.
Terminate <PtraceProcess pid=16182>
Quit gdb.