GDB cheatsheet

• gdb ./[program] : debug program with GDB
• gdb --args ./[program] [args] : debug program with GDB

must compile the program using flags -O0 -g.

Basic

• r: run program
• bt : show call stack / backtrace
• up : move up call stack
• down : move down call stack
• frame : show stack frame
• n : next
• s : step into
• c : continue
• finish : step out of function
• ni : next instruction
• si : step into instruction
• q : quit

Breakpoints

• b [line] : add breakpoint at line X of current file
• b [function] : add breakpoint at function X
• b *[address] : add breakpoint at address/pointer X
• info break : list breakpoints
• clear : delete all breakpoints
• watch [X] : add watchpoint on variable X

Info

• p [X] : print variable X
• p/x [X] : print variable X in hexadecimal
• p [c expression] : print C expression
• display [X] : print variable X each step
• what [X] : print type of variable X
• i frame : show stack frame
• i locals : show local variables
• i args : show function args
• i registers ax rip rbp cs ss ds : show registers
• display/i $pc : show PC when changed
• x/100xg $sp : print stack memory
  • 100 : number of entries
  • x : hexadecimal
  • g : 8 bytes per entry
• set var [X] : change variable value

Code

• l : shows the next set of code
• l - : show the prev set of code
• l [line] : show code on line X
• l [start line, end line] : show code at line S to E
• l [function] : show code of function X
• disassemble : show ASM code
• file [code file] : load code file
• file [bin] : load ELF bin and symbols

Split view (TUI)

• tui enable/disable : enable tui for split view
• layout split : layout code/asm
• layout asm : layout asm
• layout reg : layout regisers

Reverse debugging

• target record-full : enable reverse debugging
• rn : reverse next
• rs : reverse step
• rc : reverse continue

might not always work properly!

Remote

• tar rem [ip]:[port] : connect to remote target (localhost -> :1234)
• symbol-file [bin] : load symbols
• gdb -x=[script.gdb] : load GDB script (text file with a list of GDB commands)

Valgrind

• valgrind ./[program] : run program under valgrind
  • --leak-check=full : detect memory leaks, read after free

must compile the program using flags -O0 -g.