arm64: futex: Bound number of LDXR/STXR loops in FUTEX_WAKE_OP
[sfrench/cifs-2.6.git] / arch / arm64 / include / asm / futex.h
1 /*
2  * Copyright (C) 2012 ARM Ltd.
3  *
4  * This program is free software; you can redistribute it and/or modify
5  * it under the terms of the GNU General Public License version 2 as
6  * published by the Free Software Foundation.
7  *
8  * This program is distributed in the hope that it will be useful,
9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
11  * GNU General Public License for more details.
12  *
13  * You should have received a copy of the GNU General Public License
14  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
15  */
16 #ifndef __ASM_FUTEX_H
17 #define __ASM_FUTEX_H
18
19 #ifdef __KERNEL__
20
21 #include <linux/futex.h>
22 #include <linux/uaccess.h>
23
24 #include <asm/errno.h>
25
26 #define FUTEX_MAX_LOOPS 128 /* What's the largest number you can think of? */
27
28 #define __futex_atomic_op(insn, ret, oldval, uaddr, tmp, oparg)         \
29 do {                                                                    \
30         unsigned int loops = FUTEX_MAX_LOOPS;                           \
31                                                                         \
32         uaccess_enable();                                               \
33         asm volatile(                                                   \
34 "       prfm    pstl1strm, %2\n"                                        \
35 "1:     ldxr    %w1, %2\n"                                              \
36         insn "\n"                                                       \
37 "2:     stlxr   %w0, %w3, %2\n"                                         \
38 "       cbz     %w0, 3f\n"                                              \
39 "       sub     %w4, %w4, %w0\n"                                        \
40 "       cbnz    %w4, 1b\n"                                              \
41 "       mov     %w0, %w7\n"                                             \
42 "3:\n"                                                                  \
43 "       dmb     ish\n"                                                  \
44 "       .pushsection .fixup,\"ax\"\n"                                   \
45 "       .align  2\n"                                                    \
46 "4:     mov     %w0, %w6\n"                                             \
47 "       b       3b\n"                                                   \
48 "       .popsection\n"                                                  \
49         _ASM_EXTABLE(1b, 4b)                                            \
50         _ASM_EXTABLE(2b, 4b)                                            \
51         : "=&r" (ret), "=&r" (oldval), "+Q" (*uaddr), "=&r" (tmp),      \
52           "+r" (loops)                                                  \
53         : "r" (oparg), "Ir" (-EFAULT), "Ir" (-EAGAIN)                   \
54         : "memory");                                                    \
55         uaccess_disable();                                              \
56 } while (0)
57
58 static inline int
59 arch_futex_atomic_op_inuser(int op, int oparg, int *oval, u32 __user *_uaddr)
60 {
61         int oldval, ret, tmp;
62         u32 __user *uaddr = __uaccess_mask_ptr(_uaddr);
63
64         pagefault_disable();
65
66         switch (op) {
67         case FUTEX_OP_SET:
68                 __futex_atomic_op("mov  %w3, %w5",
69                                   ret, oldval, uaddr, tmp, oparg);
70                 break;
71         case FUTEX_OP_ADD:
72                 __futex_atomic_op("add  %w3, %w1, %w5",
73                                   ret, oldval, uaddr, tmp, oparg);
74                 break;
75         case FUTEX_OP_OR:
76                 __futex_atomic_op("orr  %w3, %w1, %w5",
77                                   ret, oldval, uaddr, tmp, oparg);
78                 break;
79         case FUTEX_OP_ANDN:
80                 __futex_atomic_op("and  %w3, %w1, %w5",
81                                   ret, oldval, uaddr, tmp, ~oparg);
82                 break;
83         case FUTEX_OP_XOR:
84                 __futex_atomic_op("eor  %w3, %w1, %w5",
85                                   ret, oldval, uaddr, tmp, oparg);
86                 break;
87         default:
88                 ret = -ENOSYS;
89         }
90
91         pagefault_enable();
92
93         if (!ret)
94                 *oval = oldval;
95
96         return ret;
97 }
98
99 static inline int
100 futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *_uaddr,
101                               u32 oldval, u32 newval)
102 {
103         int ret = 0;
104         unsigned int loops = FUTEX_MAX_LOOPS;
105         u32 val, tmp;
106         u32 __user *uaddr;
107
108         if (!access_ok(_uaddr, sizeof(u32)))
109                 return -EFAULT;
110
111         uaddr = __uaccess_mask_ptr(_uaddr);
112         uaccess_enable();
113         asm volatile("// futex_atomic_cmpxchg_inatomic\n"
114 "       prfm    pstl1strm, %2\n"
115 "1:     ldxr    %w1, %2\n"
116 "       sub     %w3, %w1, %w5\n"
117 "       cbnz    %w3, 4f\n"
118 "2:     stlxr   %w3, %w6, %2\n"
119 "       cbz     %w3, 3f\n"
120 "       sub     %w4, %w4, %w3\n"
121 "       cbnz    %w4, 1b\n"
122 "       mov     %w0, %w8\n"
123 "3:\n"
124 "       dmb     ish\n"
125 "4:\n"
126 "       .pushsection .fixup,\"ax\"\n"
127 "5:     mov     %w0, %w7\n"
128 "       b       4b\n"
129 "       .popsection\n"
130         _ASM_EXTABLE(1b, 5b)
131         _ASM_EXTABLE(2b, 5b)
132         : "+r" (ret), "=&r" (val), "+Q" (*uaddr), "=&r" (tmp), "+r" (loops)
133         : "r" (oldval), "r" (newval), "Ir" (-EFAULT), "Ir" (-EAGAIN)
134         : "memory");
135         uaccess_disable();
136
137         *uval = val;
138         return ret;
139 }
140
141 #endif /* __KERNEL__ */
142 #endif /* __ASM_FUTEX_H */