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What does qword mean in assembly?
qword indicates this operand describes an address of quad-word size, in Intel’s x86 family of processors this means 8 bytes (a word is 2 bytes long).
What does qword do?
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 the purpose of MOV instruction?
The mov instruction copies the data item referred to by its second operand (i.e. register contents, memory contents, or a constant value) into the location referred to by its first operand (i.e. a register or memory).
What does MOV QWORD,’/ / bin / sh’mean?
When you type ‘//bin/sh’you’re expressing an 8-char array. By prefixing with qword you’re instructing the assembler to treat the right hand operand as an inline 64-bit integer. By default it will probably treat it as a pointer to that string, or some other behaviour. And after the instruction shr, my strings should be looks like ‘%00//bin/s’ no?
What does MOV QWORD RBX mean in Linux?
In this case the mov instruction byte (BB) also contains a 7-bit field which describes the register we’re moving into (rbx) and the type of right-hand operand (literal). But note carefully: the literal is notin the same order as the ASCII representation we saw above.
What does MOV QWORD PTR DS, R8 mean?
Except for specific-meaning special segment registers (such as fs in 32bit windows, and gs in Linux and 64-bit windows), this can be widely ignored if not operating in 16bit modes. The brackets are coupled with the previously discussed ptr keyword and are used to highlight the address is being dereferenced before the operation is performed.
Which is the opcode of the MOV instruction?
Lets go over the instruction piece by piece: This is the opcode part of the instruction. It describes the base operation the CPU is required to perform. mov is an opcode instructing a CPU to copy data from the second operand to the first operand. The first operand on the mov instruction is a target operand, and the second is the source.