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SHOW WORK AND EXPLAIN! 0x401050 <what>: push %ebp 0x401051 <what+1>: mov %esp,%e

ID: 3540548 • Letter: S

Question


SHOW WORK AND EXPLAIN!

0x401050    <what>:         push   %ebp
0x401051    <what+1>:       mov    %esp,%ebp
0x401053    <what+3>:       sub    $0xc,%esp
0x401056    <what+6>:       mov    0x8(%ebp),%eax
0x401059    <what+9>:       add    $0x4,%eax
0x40105c    <what+12>:      mov    %eax,0xfffffffc(%ebp)
0x40105f    <what+15>:      mov    0x8(%ebp),%eax
0x401062    <what+18>:      imul   0xc(%ebp),%eax
0x401066    <what+22>:      mov    %eax,0xfffffff8(%ebp)
0x401069    <what+25>:      mov    0xc(%ebp),%edx
0x40106c    <what+28>:      mov    0x8(%ebp),%eax
0x40106f    <what+31>:      sub    %edx,%eax
0x401071    <what+33>:      mov    %eax,0xfffffff4(%ebp)
0x401074    <what+36>:      mov    0xfffffff8(%ebp),%eax
0x401077    <what+39>:      add    0xfffffffc(%ebp),%eax
0x40107a    <what+42>:      add    0xfffffff4(%ebp),%eax
0x40107d    <what+45>:      leave
0x40107e    <what+46>:      ret
0x401089    <main>:         push   %ebp
0x40108a    <main+1>:       mov    %esp,%ebp
0x40108c    <main+3>:       sub    $0x18,%esp
0x40108f    <main+6>:       and    $0xfffffff0,%esp
0x401092    <main+9>:       mov    $0x0,%eax
0x401097    <main+14>:      mov    %eax,0xfffffff0(%ebp)
0x40109a    <main+17>:      mov    0xfffffff0(%ebp),%eax
0x40109d    <main+20>:      call   0x401420 <_alloca>
0x4010a2    <main+25>:      call   0x4014b0 <__main>
0x4010a7    <main+30>:      mov    0xc(%ebp),%eax
0x4010aa    <main+33>:      add    $0x4,%eax
0x4010ad    <main+36>:      mov    (%eax),%eax
0x4010af    <main+38>:      mov    %eax,(%esp)
0x4010b2    <main+41>:      call   0x4014d0 <atoi>
0x4010b7    <main+46>:      mov    %eax,0xfffffffc(%ebp)
0x4010ba    <main+49>:      mov    0xc(%ebp),%eax
0x4010bd    <main+52>:      add    $0x8,%eax
0x4010c0    <main+55>:      mov    (%eax),%eax
0x4010c2    <main+57>:      mov    %eax,(%esp)
0x4010c5    <main+60>:      call   0x4014d0 <atoi>
0x4010ca    <main+65>:      mov    %eax,0xfffffff8(%ebp)
0x4010cd    <main+68>:      mov    0xfffffff8(%ebp),%eax
0x4010d0    <main+71>:      inc    %eax
0x4010d1    <main+72>:      mov    %eax,0x4(%esp)
0x4010d5    <main+76>:      mov    0xfffffffc(%ebp),%eax
0x4010d8    <main+79>:      add    $0x2,%eax
0x4010db    <main+82>:      mov    %eax,(%esp)
0x4010de    <main+85>:      call   0x401050 <what>
0x4010e3    <main+90>:      mov    %eax,0xfffffff4(%ebp)
0x4010e6    <main+93>:      mov    0xfffffff4(%ebp),%eax
0x4010e9    <main+96>:      mov    %eax,0x4(%esp)
0x4010ed    <main+100>:     movl   $0x40107f,(%esp)
0x4010f4    <main+107>:     call   0x4014c0 <printf>
0x4010f9    <main+112>:     mov    $0x0,%eax
0x4010fe    <main+117>:     leave
0x4010ff    <main+118>:     ret

This program is invoked from the command line as shown:

./program 5 7

The procedure named what is called from main, and returns to main with the value:

Question 12 options:

1)

11

2)

24

3)

42

4)

66

  

          

1)

         

11

          

          

2)

         

24

          

          

3)

         

42

          

          

4)

         

66

       

Explanation / Answer

" What " returns the value 42. option 3 is correct.

Explanation:

After moving two values onto stack, what performs the addition by calling "add    $0x4,%eax" . Then it is multiplied in the next instruction and then 3 values are subtracted and two values are added by two add instruction...this amounts to 42.