GDB-gef

GNU Debugger (GNU), with the gef wrapper to provide us with extended features.

GDB Command Reference - Index pageSysprogs

Top (Debugging with GDB)sourceware.org

GDB/GEF Cheatsheet - TrebledJ's PagesTrebledJ's Pages

Commands

Cheatsheet link

1. Run the program

• run, r

gdb <binary>
gef> run

2. Breakpoints

2.1 Set breakpoint on the main function

gef> break main
gef> b main

2.2 Navigate through the program

a. nexti: go instruction by instruction through the program, without stepping into function calls

b. next: go through each line of code, without stepping into function calls

c. stepi: go instruction by instruction, while stepping into function calls

d. step: go through each line of code, while stepping into function calls

Summary table

Command	Navigate through?	Step into function calls (eg. puts())?
nexti	Instructions	NO
next	Line of code (may consist of multiple instructions)	NO
stepi	Instructions	YES
step	Line of code (may consist of multiple instructions)	YES

2.3 Example on a specific instruction

• Eg. hello world function

gef> disassemble main # "disass" works too
Dump of assembler code for function main:
   xxx
   0x0804840f <+20>:	push   0x80484b0
   0x08048414 <+25>:	call   0x80482d0 <puts@plt>
   xxx
End of assembler dump.

• Set breakpoint on the call to puts

gef> break *main+25
gef> break *0x08048414
gef> break *puts

2.4 Other commands

gef> info breakpoints
gef> delete <Num> # "del" or "d" works too

3. Memory

gef> x/nfu <addresss>

• To print memory (refer to cheat sheet link above)

  • n: How many units to print (default 1)

  • f: Format character

  • u: Unit

gef> x/a <address> # print pointer address
gef> x/10c <address> # print 10 chars
gef> x/s <address> # print as C string