(gdb) disas phase_f Dump of assembler code for function phase_f: 0x080487d0 <pha

Question

(gdb) disas phase_f

Dump of assembler code for function phase_f:

0x080487d0

<phase_f+0>:

push

%ebp

0x080487d1

<phase_f+1>:

mov

%esp,%ebp

0x080487d3

<phase_f+3>:

sub

$0x28,%esp

0x080487d6

<phase_f+6>:

lea

-0x8(%ebp),%eax

0x080487d9

<phase_f+9>:

mov

%eax,0xc(%esp)

0x080487dd

<phase_f+13>:

lea

-0x4(%ebp),%eax

0x080487e0

<phase_f+16>:

mov

%eax,0x8(%esp)

0x080487e4

<phase_f+20>:

movl

$0x80490cf,0x4(%esp)

0x080487ec

<phase_f+28>:

mov

0x8(%ebp),%eax

0x080487ef

<phase_f+31>:

mov

%eax,(%esp)

0x080487f2

<phase_f+34>:

call

0x8048574 <sscanf@plt>

0x080487f7

<phase_f+39>:

mov

-0x4(%ebp),%edx

0x080487fa

<phase_f+42>:

mov

-0x8(%ebp),%eax

0x080487fd

<phase_f+45>:

cmp

%eax,%edx

0x080487ff

<phase_f+47>:

je

0x8048806 <phase_f+54>

0x08048801

<phase_f+49>:

call

0x8048f97 <explode_bomb>

0x08048806

<phase_f+54>:

leave

0x08048807

<phase_f+55>:

ret

End of assembler dump.

0x080487d0

<phase_f+0>:

push

%ebp

0x080487d1

<phase_f+1>:

mov

%esp,%ebp

0x080487d3

<phase_f+3>:

sub

$0x28,%esp

0x080487d6

<phase_f+6>:

lea

-0x8(%ebp),%eax

0x080487d9

<phase_f+9>:

mov

%eax,0xc(%esp)

0x080487dd

<phase_f+13>:

lea

-0x4(%ebp),%eax

0x080487e0

<phase_f+16>:

mov

%eax,0x8(%esp)

0x080487e4

<phase_f+20>:

movl

$0x80490cf,0x4(%esp)

0x080487ec

<phase_f+28>:

mov

0x8(%ebp),%eax

0x080487ef

<phase_f+31>:

mov

%eax,(%esp)

0x080487f2

<phase_f+34>:

call

0x8048574 <sscanf@plt>

0x080487f7

<phase_f+39>:

mov

-0x4(%ebp),%edx

0x080487fa

<phase_f+42>:

mov

-0x8(%ebp),%eax

0x080487fd

<phase_f+45>:

cmp

%eax,%edx

0x080487ff

<phase_f+47>:

je

0x8048806 <phase_f+54>

0x08048801

<phase_f+49>:

call

0x8048f97 <explode_bomb>

0x08048806

<phase_f+54>:

leave

0x08048807

<phase_f+55>:

ret

Explanation / Answer

You want to look at the format string passed to sscanf. Write the gdb command(s) to display this string.

Answer: x/s $esp+4

2.What are -8(%ebp) and -4(%ebp) used for? They are local variables, but be more speci?c than that.

The ebp are used to overwrite.They are the local variables. something accessible in C code that has a guaranteed fixed location relative to the current base pointer

3.(10 points) Let

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