Question

x86, 32bit system language question

1. Your stack looks like

0x1050 55

0x1054 57 <- ESP

0x1058 58

You execute push 0x1050 instruction. Stack grows down. How does you stack look like after this instruction?

2. Your stack looks like

0x1050 55

0x1054 57 <- ESP

0x1058 58

You execute pop eax instruction. Stack grows down. What is inside eax and how does you stack look like after this instruction?

Answer 1

Question 1.

Initial State of Stack

0x1050 55

0x1054 57 <- ESP

0x1058 58

Execution of instruction

push 0x1050

step 1. (Increment Stack Pointer) ESP = ESP - 4 = 0x1054 - 0x4 = 0x1050

step 2. Store memory value of 0x1050 in new ESP location

step 3. So 0x1050 memory location is updated by it's value itself

Final State of Stack

0x1050 55 <- ESP

0x1054 57

0x1058 58

Question 2

Initial State of Stack

0x1050 55

0x1054 57 <- ESP

0x1058 58

Executing the instruction

pop eax

step 1. Store value of memory location pointed by ESP to register eax = 57

step 2. (Decrement Stack Pointer) ESP = ESP + 4 = 0x1054 + 0x4 = 0x1058

Final State of Stack

0x1050 55

0x1054 57

0x1058 58 <- ESP

eax = 57

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