GDB Cheatsheet

gdb_cheatsheet.txt

* Run the program

gdb$ r arg1 arg2 ...                                    # Run program until it hits a breakpoint

* Environment variable

gdb$ set environment VAR=VALUE
gdb$ unset environment VAR
gdb$ show environmet                 # Show all environment variable
gdb$ show environment VAR         # Show environment variable VAR

* Setting breakpoint

gdb$ b 3                                   # Set breakpoint in line 3 of the executable's source code
gdb$ b main                              # Set breakpoint at function main
gdb$ b *0x800415                     # Set breakpoint at address 0x800415 
gdb$ b foo.c:3                           # Set breakpoint at line 3 in file foo.c
gdb$ c                                      # Continue execution after a breakpoint is hit
gdb$ advance POINT                   # Continue execution until temporary breakpoint POINT is hit

* Source code

gdb$ list                                   # To examine source
gdb$ list N                                # Display source from line N
gdb$ list func_name                   # Display source from func_name function

* Examine Variable

gdb$ p ADD/VAR/REG                           # Print content of address/variable/register in a human readable format    
gdb$ disp VAR/ADD/REG                       # Display VAR/ADD/REG each time code is run

* Changing value of a variable

gdb$ set var x = 10                             # Set value of x to 10

* Various info about the binary

gdb$ info target                           # exec section information
gdb$ maint info sections                   # Extra information about sections
gdb$ maint info sections .text .data       # Print sections selectively
gdb$ maint info sections CODE              # Print sections selectively
gdb$ info functions                        # Print function informations
gdb$ info variables                        # Print all global and static variable informations
gdb$ info registers                        # Print values of all the registers

* Stepping through code

gdb$ n                                     # Execute next line but don't step into function
gdb$ s                                     # Execute next line if its a function step into in and execute first line
gdb$ ni                                    # Execute next instruction. If its a call instruction, step over.
gdb$ si                                    # Execute next instruction. If its a call instruction, step into it.
gdb$ finish                               # Finish current function execution and go back to its caller

* Disassemble

gdb$ set disassembly-flavor intel          # Change disassembled code to intel flavored assembly code
gdb$ disassemble FUNCTION_NAME             # Disassemble a function named FUNCTION_NAME
gdb$ disassemble /s FUNCTION_NAME          # Disassemble with source code attached
gdb$ disassemble /rs FUNCTION_NAME         # With raw instructions like objdump -d 
gdb$ disassemble /rs FILE::FUNCTION_NAME   # Disassemble function in a specific file

* Examine Memory

gdb$ x/Nb ADDRESS/SYMBOL_NAME              # Print N raw bytes from ADDRESS or symbol SYMBOL_NAME
gdb$ x/i $eip                                             # Print current instructionj

* Shard library

gdb$ set exec-wrapper env 'LD_PRELOAD=./sharedlib.so' # Debug with LD_PRELOAD
gdb$ file /usr/bin/ls

gdb$ set stop-on-solib-events                            # Stop program on shared lib acitivity

* TUI Mode

gdb$ tui [enable | disable]
gdb$ layout [asm | src | regs | split]
gdb$ focus [asm | src | regs | cmd]
gdb$ info win
gdb$ winheight NAME_OF_WINDOW [+ | -]count # change window hight by count

gdb$ set trace-commands on
gdb$ set logging on

Resources:
https://web.archive.org/web/20200414104650/https://cs.brown.edu/courses/cs033/docs/guides/gdb.pdf
https://web.archive.org/web/20200304210826/http://www.unknownroad.com/rtfm/gdbtut/gdbtoc.html
https://www.youtube.com/watch?v=PorfLSr3DDI
https://web.archive.org/save/http://www.brendangregg.com/blog/2016-08-09/gdb-example-ncurses.html  # tui mode
https://www.techbeamers.com/how-to-use-gdb-top-debugging-tips/
http://www.brendangregg.com/blog/2016-08-09/gdb-example-ncurses.html
http://truthbk.github.io/gdb-ld_preload-and-libc/

Code Browsing:
Cscope: https://courses.cs.washington.edu/courses/cse451/14wi/tutorials/tutorial_cscope.html

Resources:

• How do I show what fields a struct has in GDB?