futex.h

  1/* SPDX-License-Identifier: GPL-2.0-only */
  2/*
  3 * Copyright (C) 2012 ARM Ltd.
  4 */
  5#ifndef __ASM_FUTEX_H
  6#define __ASM_FUTEX_H
  7
  8#include <linux/futex.h>
  9#include <linux/uaccess.h>
 10
 11#include <asm/errno.h>
 12
 13#define FUTEX_MAX_LOOPS	128 /* What's the largest number you can think of? */
 14
 15#define __futex_atomic_op(insn, ret, oldval, uaddr, tmp, oparg)		\
 16do {									\
 17	unsigned int loops = FUTEX_MAX_LOOPS;				\
 18									\
 19	uaccess_enable_privileged();					\
 20	asm volatile(							\
 21"	prfm	pstl1strm, %2\n"					\
 22"1:	ldxr	%w1, %2\n"						\
 23	insn "\n"							\
 24"2:	stlxr	%w0, %w3, %2\n"						\
 25"	cbz	%w0, 3f\n"						\
 26"	sub	%w4, %w4, %w0\n"					\
 27"	cbnz	%w4, 1b\n"						\
 28"	mov	%w0, %w6\n"						\
 29"3:\n"									\
 30"	dmb	ish\n"							\
 31	_ASM_EXTABLE_UACCESS_ERR(1b, 3b, %w0)				\
 32	_ASM_EXTABLE_UACCESS_ERR(2b, 3b, %w0)				\
 33	: "=&r" (ret), "=&r" (oldval), "+Q" (*uaddr), "=&r" (tmp),	\
 34	  "+r" (loops)							\
 35	: "r" (oparg), "Ir" (-EAGAIN)					\
 36	: "memory");							\
 37	uaccess_disable_privileged();					\
 38} while (0)
 39
 40static inline int
 41arch_futex_atomic_op_inuser(int op, int oparg, int *oval, u32 __user *_uaddr)
 42{
 43	int oldval = 0, ret, tmp;
 44	u32 __user *uaddr = __uaccess_mask_ptr(_uaddr);
 45
 46	if (!access_ok(_uaddr, sizeof(u32)))
 47		return -EFAULT;
 48
 49	switch (op) {
 50	case FUTEX_OP_SET:
 51		__futex_atomic_op("mov	%w3, %w5",
 52				  ret, oldval, uaddr, tmp, oparg);
 53		break;
 54	case FUTEX_OP_ADD:
 55		__futex_atomic_op("add	%w3, %w1, %w5",
 56				  ret, oldval, uaddr, tmp, oparg);
 57		break;
 58	case FUTEX_OP_OR:
 59		__futex_atomic_op("orr	%w3, %w1, %w5",
 60				  ret, oldval, uaddr, tmp, oparg);
 61		break;
 62	case FUTEX_OP_ANDN:
 63		__futex_atomic_op("and	%w3, %w1, %w5",
 64				  ret, oldval, uaddr, tmp, ~oparg);
 65		break;
 66	case FUTEX_OP_XOR:
 67		__futex_atomic_op("eor	%w3, %w1, %w5",
 68				  ret, oldval, uaddr, tmp, oparg);
 69		break;
 70	default:
 71		ret = -ENOSYS;
 72	}
 73
 74	if (!ret)
 75		*oval = oldval;
 76
 77	return ret;
 78}
 79
 80static inline int
 81futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *_uaddr,
 82			      u32 oldval, u32 newval)
 83{
 84	int ret = 0;
 85	unsigned int loops = FUTEX_MAX_LOOPS;
 86	u32 val, tmp;
 87	u32 __user *uaddr;
 88
 89	if (!access_ok(_uaddr, sizeof(u32)))
 90		return -EFAULT;
 91
 92	uaddr = __uaccess_mask_ptr(_uaddr);
 93	uaccess_enable_privileged();
 94	asm volatile("// futex_atomic_cmpxchg_inatomic\n"
 95"	prfm	pstl1strm, %2\n"
 96"1:	ldxr	%w1, %2\n"
 97"	sub	%w3, %w1, %w5\n"
 98"	cbnz	%w3, 4f\n"
 99"2:	stlxr	%w3, %w6, %2\n"
100"	cbz	%w3, 3f\n"
101"	sub	%w4, %w4, %w3\n"
102"	cbnz	%w4, 1b\n"
103"	mov	%w0, %w7\n"
104"3:\n"
105"	dmb	ish\n"
106"4:\n"
107	_ASM_EXTABLE_UACCESS_ERR(1b, 4b, %w0)
108	_ASM_EXTABLE_UACCESS_ERR(2b, 4b, %w0)
109	: "+r" (ret), "=&r" (val), "+Q" (*uaddr), "=&r" (tmp), "+r" (loops)
110	: "r" (oldval), "r" (newval), "Ir" (-EAGAIN)
111	: "memory");
112	uaccess_disable_privileged();
113
114	if (!ret)
115		*uval = val;
116
117	return ret;
118}
119
120#endif /* __ASM_FUTEX_H */