gdb.md

GDB Basics

If you have the source, compile with -g to enable debug information, gdb then has access to the source code.

Show register content

i r
(info registers)

Start execution

r
r < input_file
r -x -y -z blabla

Set a breakpoint

b main          (needs symbols)
b *0x08041234

Continue execution

c

Single Step

ni/nexti            (treats a 'call' as one instruction)
si/stepi            (also steps into the callee)

next                (needs -g, next source line)
step                (needs -g, next source line)

Display memory

x/32wx $esp
x/16gx 0x08049876
x/f $eax            (float)
x/20i main          (disassemble)

Sizes

b   byte
h   16bit word
w   32bit word
g   64bit word

Show call stack

bt
(backtrace)

Show process memory layout

info proc mappings

Execute shell commands

!ls

Show source code of function (needs -g)

list main

Display current instruction on each break/step

display/i $eip