GDB - Opty-Forks/SSof GitHub Wiki

GDB Basics

Below is a simple list of basic GDB commands. They should get you going for most of our exercises

To analyse a program with gdb type gdb <file_to_analyse>
To disassemble a function use: disassemble <fn_name> or disassemble <memory_address>
- e.g. disassemble main or disassemble 0x0804843b.
- in gdp-peda you can use pdisass <fn_name/address> to do it with colours.
b <memory_address> inserts a breakpoint at address memory_address
- eg b *0x0804846a or b *main+47
r runs the current program
c continues execution until the next breakpoint
n executes the next instrution
s steps into function fn when the instruction is a call fn
p prints the value of an expression
- p variable_name prints the content of the variable (if the symbol variable_name is defined)
- p &variable_name prints the address where the variable is in memory
- p *memory_address prints the content in this address
bt prints a backtrace of the entire stack, that is, shows how you got to the current frame
info f prints the information about the current frame. This is usefull whenever you need to know where the return address of the function is stored and/or the value contained there.
stack n shows the n registers of the stack after esp.
x/nx $rsp --- shows the n registers after the register $rsp
x/nx address --- shows the n registers after the address address