gdb: How To Use In Reverse engineering CTFs

 gdb (GNU Debugger) is a powerful tool for debugging programs in C and other languages. It allows you to inspect the program's state, set breakpoints, step through code, and examine variables.

Start gdb:

Open a terminal and run gdb with the executable as an argument:

gdb ./your_program

Replace your_program with the name of your executable.

Run the Program:

Once inside gdb, you can run your program by typing:

run [program arguments]

It points out exactly where the segmentation fault occurred.

Review Assembly Code:

If you want to inspect the assembly code, use disassemble:

disassemble main

Set a Breakpoint:

Use breakpoints to stop the program’s execution at a specific line.

break main

Set a breakpoint at a specific line number:

break <line_number>

Continue Execution:

Continue the program’s execution until the next breakpoint or until it completes:

continue

Step through Code:

Use step to execute the next line of code and enter into functions:

step

Use next to execute the next line of code, but it won't enter functions:

next

Print Variables:

To print the value of a variable, use the print command:

print variable_name

Backtrace (Call Stack):

To see the call stack (backtrace), use:

bt

Inspect Memory:

View the content of memory at a specific address:

x/size_format address

For example, to print the contents of 4 bytes at the address stored in the rsp register:

x/4x $rsp

Info Registers:

Display the values of all registers:

info registers

View Source Code:

Use list to show the source code around the current line:

list

Quit gdb:

To exit gdb, type:

quit