futex.h

/* SPDX-License-Identifier: GPL-2.0-only */
/*
 * Copyright (C) 2012 ARM Ltd.
 */
#ifndef __ASM_FUTEX_H
#define __ASM_FUTEX_H

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

#include <asm/errno.h>

#define FUTEX_MAX_LOOPS	128 /* What's the largest number you can think of? */

#define __futex_atomic_op(insn, ret, oldval, uaddr, tmp, oparg)		\
do {									\
	unsigned int loops = FUTEX_MAX_LOOPS;				\
									\
	uaccess_enable_privileged();					\
	asm volatile(							\
"	prfm	pstl1strm, %2\n"					\
"1:	ldxr	%w1, %2\n"						\
	insn "\n"							\
"2:	stlxr	%w0, %w3, %2\n"						\
"	cbz	%w0, 3f\n"						\
"	sub	%w4, %w4, %w0\n"					\
"	cbnz	%w4, 1b\n"						\
"	mov	%w0, %w6\n"						\
"3:\n"									\
"	dmb	ish\n"							\
	_ASM_EXTABLE_UACCESS_ERR(1b, 3b, %w0)				\
	_ASM_EXTABLE_UACCESS_ERR(2b, 3b, %w0)				\
	: "=&r" (ret), "=&r" (oldval), "+Q" (*uaddr), "=&r" (tmp),	\
	  "+r" (loops)							\
	: "r" (oparg), "Ir" (-EAGAIN)					\
	: "memory");							\
	uaccess_disable_privileged();					\
} while (0)

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

	if (!access_ok(_uaddr, sizeof(u32)))
		return -EFAULT;

	switch (op) {
	case FUTEX_OP_SET:
		__futex_atomic_op("mov	%w3, %w5",
				  ret, oldval, uaddr, tmp, oparg);
		break;
	case FUTEX_OP_ADD:
		__futex_atomic_op("add	%w3, %w1, %w5",
				  ret, oldval, uaddr, tmp, oparg);
		break;
	case FUTEX_OP_OR:
		__futex_atomic_op("orr	%w3, %w1, %w5",
				  ret, oldval, uaddr, tmp, oparg);
		break;
	case FUTEX_OP_ANDN:
		__futex_atomic_op("and	%w3, %w1, %w5",
				  ret, oldval, uaddr, tmp, ~oparg);
		break;
	case FUTEX_OP_XOR:
		__futex_atomic_op("eor	%w3, %w1, %w5",
				  ret, oldval, uaddr, tmp, oparg);
		break;
	default:
		ret = -ENOSYS;
	}

	if (!ret)
		*oval = oldval;

	return ret;
}

static inline int
futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *_uaddr,
			      u32 oldval, u32 newval)
{
	int ret = 0;
	unsigned int loops = FUTEX_MAX_LOOPS;
	u32 val, tmp;
	u32 __user *uaddr;

	if (!access_ok(_uaddr, sizeof(u32)))
		return -EFAULT;

	uaddr = __uaccess_mask_ptr(_uaddr);
	uaccess_enable_privileged();
	asm volatile("// futex_atomic_cmpxchg_inatomic\n"
"	prfm	pstl1strm, %2\n"
"1:	ldxr	%w1, %2\n"
"	sub	%w3, %w1, %w5\n"
"	cbnz	%w3, 4f\n"
"2:	stlxr	%w3, %w6, %2\n"
"	cbz	%w3, 3f\n"
"	sub	%w4, %w4, %w3\n"
"	cbnz	%w4, 1b\n"
"	mov	%w0, %w7\n"
"3:\n"
"	dmb	ish\n"
"4:\n"
	_ASM_EXTABLE_UACCESS_ERR(1b, 4b, %w0)
	_ASM_EXTABLE_UACCESS_ERR(2b, 4b, %w0)
	: "+r" (ret), "=&r" (val), "+Q" (*uaddr), "=&r" (tmp), "+r" (loops)
	: "r" (oldval), "r" (newval), "Ir" (-EAGAIN)
	: "memory");
	uaccess_disable_privileged();

	if (!ret)
		*uval = val;

	return ret;
}

#endif /* __ASM_FUTEX_H */