x86 Instruction Set Reference

PUSHF/PUSHFD: Push EFLAGS Register onto the Stack (x86 Instruction Set Reference)

The PUSHF (push flags) and PUSHFD (push flags double) mnemonics reference the same opcode. The PUSHF instruction is intended for use when the operand-size attribute is 16 and the PUSHFD instruction for when the operand-size attribute is 32. 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.

When in virtual-8086 mode and the I/O privilege level (IOPL) is less than 3, the PUSHF/PUSHFD instruction causes a general protection exception (#GP).

In the real-address mode, if the ESP or SP register is 1, 3, or 5 when the PUSHA/PUSHAD instruction is executed, the processor shuts down due to a lack of stack space. No exception is generated to indicate this condition.

if(PE == 0 || (PE == 1 && (VM == 0 || (VM == 1 && IOPL == 3)))) {
	if(OperandSize == 32) Push(EFLAGS & 0xFCFFFF); //VM and RF EFLAG bits are cleared in image stored on the stack
	else Push(EFLAGS[0..15]);
}
//In Virtual-8086 Mode with IOPL less than 3
else Exception(GP(0)); //Trap to virtual-8086 monitor

None.