- Find binary file info (if debug symbols exist)
info functions
info variables # for global variables
info registers # inspect CPU registers
info scope <scope_name> # for local variables
info brakpoints # review all breakpoints
- Ripping symbols off a binary file
objcopy --only-keep-debug <file_with_debug_symbols> <output_file>
- Stripping symbols off a binary file
strip --strip-debug --strip-unneeded <file_with_debug_symbols>
- Adding debug symbols to a binary itself
objcopy --add-gnu-debuglink=<debug_file> <binary_file>
- Load symbol file within GDB
symbol-file <symbole_file>
- List symbols from object file
man nm # see a full list of symbol types
nm <object_file>
nm -A <object_file> | grep <function_name>
nm -n <object_file> # display in address sorted order
nm -g <object_file> # list external symbols
nm -S <object_file> # display size
| Symbol Type | Meaning |
|-------------|-----------------------------------------|
| A | Absolute Symbol |
| B | In the Uninitialized Data Section (BSS) |
| D | In the Initialized Data Section |
| N | Debugging Symbol |
| T | In the Text Section |
| U | Symbol Undefined right now |
Strace helps to understand how program interact with OS by tracing all System Calls made by the program. It also tells us about arguments passed and has great filtering capabilities.
| Flag | Meaning |
|-----------------|-----------------------------|
| -o <file_name> | Redirect outout to a file |
| -t | Add Absolute Timestamp |
| -r | Add Relative Timestamp |
| -e <syscall> | Trace by specific Syscall |
| -p <process_id> | Attach to a running process |
| -c | Print Statistics |
break *<address>
break <function_name>
break <line_num>
enable <breakpoint_num> # breakpoint_num can be found from info breakpoints command
disable <breakpoint_num>
delete <breakpoint_num>
help x # additional info
x/FMT address # FMT is <repeat_count><format_letter><size_letter>
- Disassemble a specific function
disassemble <func_name>
continue
stepi <> # per instruction
step <N> # per line
help <command>
set {<data_type>} <mem_addr> = <value> # modify value in mem
set $i = 10
set argv[1] = $i # change argument value
set $dyn = (char *)malloc(10) # assign a part of mem
x/10xb $dyn # examine allocated mem
call strcpy($dyn, argv[0]); # use any functions which is linked to binary (find them by info functions)
- Use strings utility to display all strings which is inside binary
strings main
set disassembly-flavor intel
condition <bp_num> <condition> # for e.g. condition 1 counter == 5
| Register | Functionality |
|----------|------------------------------------|
| r0 - r3 | function arguments & return values |
| r4 - r11 | local variables |
| r13 | stack pointer |
| r14 | link registe |
| r15 | program counter |
