Contents
What does qword PTR mean?
qword ptr is a hint for the assembler to create a move op-code (machine code) using a 64bit constant address. The value that is provided is a 32bit value (8 hex-digits => 8 times a hex-digit/letter => 8 * 4bits => 32bit).
What is PTR in assembly language?
The dword ptr means “write a doubleword”. Yes, it stands for pointer, because you put a memory address as destination.
What does mov eax do?
4 Answers. The instruction mov eax, eax may be a no-operation code but that is not what you have here. You’re loading from memory, as indicated by the [] “contents-of” characters. It loads eax with the contents of memory (a 32-bit dword in this case) that is currently pointed to by eax .
What is RSP used for?
The rsp and the rbp are used to keep track of the stack frame. With rbp referring to the base pointer (the previous top of the stack) and rsp pointing (ideally) always to the current top of the stack. mov rbp rsp // This puts the base pointer at the current head of the stack pointing at the, just pushed, old rbp.
What happens when you push RBP?
“push” stores a constant or 64-bit register out onto the stack. The 64-bit registers are the ones like “rax” or “r8”, not the 32-bit registers like “eax” or “r8d”. “pop” retrieves the last value pushed from the stack.
What does (% RBP mean?
Basically, the question is, does -8(%rbp) mean that it’s taking a value from a register (maybe the last 8 bytes of rbp) or is it taking a value from memory (floating point value at an offset of -8 from the address contained in rbp).
What does MOV QWORD PTR DS [ Rax + 18 ] mean?
In our case, this means rax + 18. This means rax probably points to a structure, a class, an array or some other complex memory object, and we’re accessing the member at offset 18 of that memory structure. As there isn’t any prefix or postfix indicating the number’s base, I’ll assume it’s in hex.
What are the directives for byte ptr and dword PTR?
To get around this instance, we must use a pointer directive, such as mov BYTE PTR [ESI], 5 ; Store 8-bit value mov WORD PTR [ESI], 5 ; Store 16-bit value mov DWORD PTR [ESI], 5 ; Store 32-bit value These instructions require operands to be the same size.
What do commas mean in mov QWORD PTR DS?
Commas are simply operand separators, indicating the first operand has ended and the second is about to begin. r8. Compared to the first operand, the second one is a piece of cake. This simply means the value currently in register r8 is the source value, and what will be assigned to the address rax+18.
What does QWORD PTR [ hexvalue ] mean in Assembly?
In your code, mov rax, qword ptr [ff4053c0h] means “take 8 bytes from data segment offset FF4053C0h and put them in RAX”. As you are pointing correctly, the presence of a base register like rsp clearly indicates stack segment.