Below is the code for openO system call in the user program. open: push dword mo

Question

Below is the code for openO system call in the user program. open: push dword mode push dword flags push dword path mov push eax int eax, 5 80h 1. What is the purpose of the first threeinstructions (push)? 2. What is the significance of number 5? 3. What is the use of 80h? 4. Where will register eax be used? 5. How will register eax be used? 6. How does instruction int affect the mode? 7. What is the problem caused by the instruction int for VMM? 8. Why is the TLB entries not useful when the OS memory is virtualized?

Explanation / Answer

1.
dword is basically dealing with the operand size.
Mode is mode of addressing.
Flags are the register bits that are affected. For example, the carry flag, the sign bit.
Path is the address where the file that needs to be opened is stored.

2. Move 5 bytes into the eax register which is of 32 bits.

3. int 80h is calling the Kernel.

4. EAX is used to call the accumulator since it is used by a number of arithmetic operations.

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