What does Pushq mean?

● pushq. – Subtract 8 from stack pointer. – Store value at new stack top location (%rsp) ● popq. – Retrieve value at current stack top (%rsp)

What is x86-64 assembly?

x86-64 (also known as just x64 and/or AMD64) is the 64-bit version of the x86/IA32 instruction set. Below is our overview of its features that are relevant to CS107. There is more extensive coverage on these topics in Chapter 3 of the B&O textbook. See also our x86-64 sheet for a compact reference.

What does Pushq do in assembly?

The first instruction executed on function entry is pushq %rbp . This saves the caller’s value for %rbp into the callee’s stack. (Since %rbp is callee-saved, the callee must save it.) The second instruction is movq %rsp, %rbp .

What is register RBX?

rbx – register b extended. rcx – register c extended. rdx – register d extended. rbp – register base pointer (start of stack) rsp – register stack pointer (current location in stack, growing downwards)

What do Pushq and POPQ do?

pushq %rdx ;Decrements the stack pointer and then stores the source operand on the top of the stack. popq %rdx ;Loads the value from the top of the stack to the location specified with the destination operand (or explicit opcode) and then increments the stack pointer.

What is x86 vs x64?

x86 refers to a 32-bit CPU and operating system while x64 refers to a 64-bit CPU and operating system. Does having more amount of bits in each operating system have any benefits? Your 64-bit system can also run 32-bit programs as they are backwards compatible.

What is MOV instruction in assembly language?

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 is MOV x86?

What is EAX in assembly?

eax is the 32-bit, “int” size register. It was added in 1985 during the transition to 32-bit processors with the 80386 CPU. It was added in 1979 with the 8086 CPU, but is used in DOS or BIOS code to this day. al and ah are the 8-bit, “char” size registers.

What is the operand size of PUSHFD in 64 bit?

In 64-bit mode, the instruction’s default operation is to decrement the stack pointer (RSP) by 8 and pushes RFLAGS on the stack. 16-bit operation is supported using the operand size override prefix 66H. 32-bit operand size cannot be encoded in this mode.

What does push do on an Intel 8086?

For the Intel ® 8086 processor, the PUSH SP instruction pushes the new value of the SP register (that is the value after it has been decremented by 2).

When to use PUSHF / PUSHFD in virtual 8086?

When operating in virtual-8086 mode (EFLAGS.VM = 1) without the virtual-8086 mode extensions (CR4.VME = 0), the PUSHF/PUSHFD instructions can be used only if IOPL = 3; otherwise, a general-protection exception (#GP) occurs.

What’s the operand size of PUSHF in assembler?

Some assemblers may force the operand size to 16 when PUSHF is used and to 32 when PUSHFD is used. Others may treat these mnemonics as synonyms (PUSHF/PUSHFD) and use the current setting of the operand-size attribute to determine the size of values to be pushed from the stack, regardless of the mnemonic used.