--- gdb notes ---

 I suggest getting the program to start running
 before trying to examine it. Here's a way
 to set a breakpointat the beginning and then
 get it loaded up and running ... but only to the
 first line.

 $ gdb bomblab_warmup
 (gdb) break main
 (gdb) start

 Then you can examine various things like

 (gdb) info reg         show registers 
 (gdb) info functions   (long list; objdump is probably better)
 (gdb) disas main       (or look in objdump)
 (gdb) disas thing1
 (gdb) disas thing2
 (gdb) disas f

 As well as look at memory with the many "x" (examine)
 commands, which show it in many different formats.

   x/<repeat><format><size> address

   repeat = how many, e.g. 16 or 32

   format = x hex
            d decimal
            i instruction
            c character
            f float

   size   = b byte ( 8 bits = 2 hex)
            w word (32 bits = 8 hex = 4 bytes)

   address = 0x8048420
             or main
	     or main+3

 examples

 # Show 16 char bytes
 x/16cb 0x8048520

 # Examine string at this location.
 x/s 0x8048520

 # Show 16 hex bytes
 x/16xb 0x8048520

 # Show 16 hex words
 x/16xw 0x8048520

 # Show 16 address words
 x/16aw 0x8048520

 # Show 16 decimal words
 x/16dw 0x8048520

 # Show 16 instructions (whether they are or not)
  x/16iw 0x8048520
 
 # Show as floating point
 x/16fw 0x8048520

stepping through the code

 (gdb) si       stepi   "step instruction"
 (gdb) finish   continue until this function finishes
 (gdb) ni       next    "next instruction" ... if function call, procede until it exits

 (gdb) display/3i $pc   # set automatic display of next 3 instructions 

Print output from a function (and execute it!) :
(If you can figure out its return and args.)

 (gdb) print (int) f(10)

Print data at an address (using mostly C notation)
(Here the "int*" says to trat this as 
 a pointer to an int, and the first * 
 follow that pointer ... thus printing
 it as an int.)

 (gdb) print *(int*)(0x08048403)

Print value of a register.
 (gdb) print $esp
 
Or follow the pointer and print what's there.
 (gdb) print *$esp

Set data at memory locations (mostly C notation)

 (gdb) set *(int*)0x08048403 = 0x1  # change 4 bytes
 (gdb) set *(char*)0x08048403 = 'a' # change 1 byte
 (gdb) set *$esp = 1234             # change 4 bytes on stack

--- gdbtui -------

You can also run gdb in a split terminal window with the asssembly
always displayed ... google for "gdbtui" documation.

 $ gdbtui warmup
 (gdb) break main
 (gdb) start
 (gdb) layout asm   # assembly
 (gdb) layout reg   # split assembly to show registers too
 (gdb) stepi        # si for short; or "nexti" or "finish"