include/asm-x86_64/futex.h

#ifndef _ASM_FUTEX_H
#define _ASM_FUTEX_H

#ifdef __KERNEL__

#include <linux/futex.h>
#include <asm/errno.h>
#include <asm/system.h>
#include <asm/uaccess.h>

#define __futex_atomic_op1(insn, ret, oldval, uaddr, oparg) \
  __asm__ __volatile (						\
"1:	" insn "\n"						\
"2:	.section .fixup,\"ax\"\n\
3:	mov	%3, %1\n\
	jmp	2b\n\
	.previous\n\
	.section __ex_table,\"a\"\n\
	.align	8\n\
	.quad	1b,3b\n\
	.previous"						\
	: "=r" (oldval), "=r" (ret), "=m" (*uaddr)		\
	: "i" (-EFAULT), "m" (*uaddr), "0" (oparg), "1" (0))

#define __futex_atomic_op2(insn, ret, oldval, uaddr, oparg) \
  __asm__ __volatile (						\
"1:	movl	%2, %0\n\
	movl	%0, %3\n"					\
	insn "\n"						\
"2:	" LOCK_PREFIX "cmpxchgl %3, %2\n\
	jnz	1b\n\
3:	.section .fixup,\"ax\"\n\
4:	mov	%5, %1\n\
	jmp	3b\n\
	.previous\n\
	.section __ex_table,\"a\"\n\
	.align	8\n\
	.quad	1b,4b,2b,4b\n\
	.previous"						\
	: "=&a" (oldval), "=&r" (ret), "=m" (*uaddr),		\
	  "=&r" (tem)						\
	: "r" (oparg), "i" (-EFAULT), "m" (*uaddr), "1" (0))

static inline int
futex_atomic_op_inuser (int encoded_op, int __user *uaddr)
{
	int op = (encoded_op >> 28) & 7;
	int cmp = (encoded_op >> 24) & 15;
	int oparg = (encoded_op << 8) >> 20;
	int cmparg = (encoded_op << 20) >> 20;
	int oldval = 0, ret, tem;
	if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28))
		oparg = 1 << oparg;

	if (! access_ok (VERIFY_WRITE, uaddr, sizeof(int)))
		return -EFAULT;

	inc_preempt_count();

	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;
	}

	dec_preempt_count();

	if (!ret) {
		switch (cmp) {
		case FUTEX_OP_CMP_EQ: ret = (oldval == cmparg); break;
		case FUTEX_OP_CMP_NE: ret = (oldval != cmparg); break;
		case FUTEX_OP_CMP_LT: ret = (oldval < cmparg); break;
		case FUTEX_OP_CMP_GE: ret = (oldval >= cmparg); break;
		case FUTEX_OP_CMP_LE: ret = (oldval <= cmparg); break;
		case FUTEX_OP_CMP_GT: ret = (oldval > cmparg); break;
		default: ret = -ENOSYS;
		}
	}
	return ret;
}

#endif
#endif