linux/arch/x86/include/asm/futex.h

#ifndef _ASM_X86_FUTEX_H
#define _ASM_X86_FUTEX_H

#ifdef __KERNEL__

#include <linux/futex.h>
#include <linux/uaccess.h>

#include <asm/asm.h>
#include <asm/errno.h>
#include <asm/processor.h>
#include <asm/smap.h>

#define __futex_atomic_op1(insn, ret, oldval, uaddr, oparg)	\
	asm volatile("\t" ASM_STAC "\n"				\
		     "1:\t" insn "\n"				\
		     "2:\t" ASM_CLAC "\n"			\
		     "\t.section .fixup,\"ax\"\n"		\
		     "3:\tmov\t%3, %1\n"			\
		     "\tjmp\t2b\n"				\
		     "\t.previous\n"				\
		     _ASM_EXTABLE(1b, 3b)			\
		     : "=r" (oldval), "=r" (ret), "+m" (*uaddr)	\
		     : "i" (-EFAULT), "0" (oparg), "1" (0))

#define __futex_atomic_op2(insn, ret, oldval, uaddr, oparg)	\
	asm volatile("\t" ASM_STAC "\n"				\
		     "1:\tmovl	%2, %0\n"			\
		     "\tmovl\t%0, %3\n"				\
		     "\t" insn "\n"				\
		     "2:\t" LOCK_PREFIX "cmpxchgl %3, %2\n"	\
		     "\tjnz\t1b\n"				\
		     "3:\t" ASM_CLAC "\n"			\
		     "\t.section .fixup,\"ax\"\n"		\
		     "4:\tmov\t%5, %1\n"			\
		     "\tjmp\t3b\n"				\
		     "\t.previous\n"				\
		     _ASM_EXTABLE(1b, 4b)			\
		     _ASM_EXTABLE(2b, 4b)			\
		     : "=&a" (oldval), "=&r" (ret),		\
		       "+m" (*uaddr), "=&r" (tem)		\
		     : "r" (oparg), "i" (-EFAULT), "1" (0))

static inline int arch_futex_atomic_op_inuser(int op, int oparg, int *oval,
		u32 __user *uaddr)
{
	int oldval = 0, ret, tem;

	pagefault_disable();

	switch (op) {
	case FUTEX_OP_SET:
		__futex_atomic_op1("xchgl %0, %2", ret, oldval, uaddr, oparg);
		break;
	case FUTEX_OP_ADD:
		__futex_atomic_op1(LOCK_PREFIX "xaddl %0, %2", ret, oldval,
				   uaddr, oparg);
		break;
	case FUTEX_OP_OR:
		__futex_atomic_op2("orl %4, %3", ret, oldval, uaddr, oparg);
		break;
	case FUTEX_OP_ANDN:
		__futex_atomic_op2("andl %4, %3", ret, oldval, uaddr, ~oparg);
		break;
	case FUTEX_OP_XOR:
		__futex_atomic_op2("xorl %4, %3", ret, oldval, uaddr, oparg);
		break;
	default:
		ret = -ENOSYS;
	}

	pagefault_enable();

	if (!ret)
		*oval = oldval;

	return ret;
}

static inline int futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
						u32 oldval, u32 newval)
{
	return user_atomic_cmpxchg_inatomic(uval, uaddr, oldval, newval);
}

#endif
#endif /* _ASM_X86_FUTEX_H */