Lines 19 and 26 are calls to open and write, respectively.
The open call expects two parameters: filename and flags.
Moving up from line 19, we see two push instructions (lines
16 and 18) that push arguments onto the stack. In line 16 we
push the value 0x440 – the O CREAT | O APPEND flags. In
line 18 we push %eax – this register will point to the location
where the filename .csh can be found.
Debugging the assembly further reveals that %eax holds
an address on the stack that contains the filename string.
Looking earlier in the code, we can see the that %eax is assigned
the effective address of 0xffffffd8(%ebp) in line 17. In
lines 11-14 the value of 0xffffffd8(%ebp) is set using %eax.
Looking more closely at line 11, we see that%eax is assigned
the value .csh located at address 0x80484d8. (A similar assignment
happens with %al: null is loaded from the memory
and stored just after .csh.)
To summarize, lines 11-14 load the string .csh into the
stack starting at 0xffffffd8(%ebp). 0xffffffd8(%ebp) is later
used as a parameter to the open syscall in lines 17-19.
Following the flow of the write call is much simpler. Line
24 pushes the address $0x8049600, which contains the script