I am new to GDB, so I have some questions:
How can I look at content of the stack?
Example: to see content of register, I type info registers. For the stack, what should it be?
How can I see the content of $0x4(%esp)? When I type print /d $0x4(%esp), GDB gives an error.
Platform: Linux and GDB
info frame to show the stack frame info
To read the memory at given addresses you should take a look at x
x/x $esp for hex x/d $esp for signed x/u $esp for unsigned etc. x uses the format syntax, you could also take a look at the current instruction via x/i $eip etc.
You need to use gdb's memory-display commands. The basic one is x, for examine. There's an example on the linked-to page that uses
gdb> x/4xw $sp
to print "four words (w ) of memory above the stack pointer (here, $sp) in hexadecimal (x)". The quotation is slightly paraphrased.
Use:
bt - backtrace: show stack functions and argsinfo frame - show stack start/end/args/locals pointers x/100x $sp - show stack memory(gdb) bt
#0 zzz () at zzz.c:96
#1 0xf7d39cba in yyy (arg=arg@entry=0x0) at yyy.c:542
#2 0xf7d3a4f6 in yyyinit () at yyy.c:590
#3 0x0804ac0c in gnninit () at gnn.c:374
#4 main (argc=1, argv=0xffffd5e4) at gnn.c:389
(gdb) info frame
Stack level 0, frame at 0xffeac770:
eip = 0x8049047 in main (goo.c:291); saved eip 0xf7f1fea1
source language c.
Arglist at 0xffeac768, args: argc=1, argv=0xffffd5e4
Locals at 0xffeac768, Previous frame's sp is 0xffeac770
Saved registers:
ebx at 0xffeac75c, ebp at 0xffeac768, esi at 0xffeac760, edi at 0xffeac764, eip at 0xffeac76c
(gdb) x/10x $sp
0xffeac63c: 0xf7d39cba 0xf7d3c0d8 0xf7d3c21b 0x00000001
0xffeac64c: 0xf78d133f 0xffeac6f4 0xf7a14450 0xffeac678
0xffeac65c: 0x00000000 0xf7d3790e
Source: Stackoverflow.com