1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _ASM_ARM_FUTEX_H
3 #define _ASM_ARM_FUTEX_H
4
5 #ifdef __KERNEL__
6
7 #include <linux/futex.h>
8 #include <linux/uaccess.h>
9 #include <asm/errno.h>
10
11 #define __futex_atomic_ex_table(err_reg) \
12 "3:\n" \
13 " .pushsection __ex_table,\"a\"\n" \
14 " .align 3\n" \
15 " .long 1b, 4f, 2b, 4f\n" \
16 " .popsection\n" \
17 " .pushsection .text.fixup,\"ax\"\n" \
18 " .align 2\n" \
19 "4: mov %0, " err_reg "\n" \
20 " b 3b\n" \
21 " .popsection"
22
23 #ifdef CONFIG_SMP
24
25 #define __futex_atomic_op(insn, ret, oldval, tmp, uaddr, oparg) \
26 ({ \
27 unsigned int __ua_flags; \
28 smp_mb(); \
29 prefetchw(uaddr); \
30 __ua_flags = uaccess_save_and_enable(); \
31 __asm__ __volatile__( \
32 "1: ldrex %1, [%3]\n" \
33 " " insn "\n" \
34 "2: strex %2, %0, [%3]\n" \
35 " teq %2, #0\n" \
36 " bne 1b\n" \
37 " mov %0, #0\n" \
38 __futex_atomic_ex_table("%5") \
39 : "=&r" (ret), "=&r" (oldval), "=&r" (tmp) \
40 : "r" (uaddr), "r" (oparg), "Ir" (-EFAULT) \
41 : "cc", "memory"); \
42 uaccess_restore(__ua_flags); \
43 })
44
45 static inline int
46 futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
47 u32 oldval, u32 newval)
48 {
49 unsigned int __ua_flags;
50 int ret;
51 u32 val;
52
53 if (!access_ok(uaddr, sizeof(u32)))
54 return -EFAULT;
55
56 smp_mb();
57 /* Prefetching cannot fault */
58 prefetchw(uaddr);
59 __ua_flags = uaccess_save_and_enable();
60 __asm__ __volatile__("@futex_atomic_cmpxchg_inatomic\n"
61 "1: ldrex %1, [%4]\n"
62 " teq %1, %2\n"
63 " ite eq @ explicit IT needed for the 2b label\n"
64 "2: strexeq %0, %3, [%4]\n"
65 " movne %0, #0\n"
66 " teq %0, #0\n"
67 " bne 1b\n"
68 __futex_atomic_ex_table("%5")
69 : "=&r" (ret), "=&r" (val)
70 : "r" (oldval), "r" (newval), "r" (uaddr), "Ir" (-EFAULT)
71 : "cc", "memory");
72 uaccess_restore(__ua_flags);
73 smp_mb();
74
75 *uval = val;
76 return ret;
77 }
78
79 #else /* !SMP, we can work around lack of atomic ops by disabling preemption */
80
81 #include <linux/preempt.h>
82 #include <asm/domain.h>
83
84 #define __futex_atomic_op(insn, ret, oldval, tmp, uaddr, oparg) \
85 ({ \
86 unsigned int __ua_flags = uaccess_save_and_enable(); \
87 __asm__ __volatile__( \
88 "1: " TUSER(ldr) " %1, [%3]\n" \
89 " " insn "\n" \
90 "2: " TUSER(str) " %0, [%3]\n" \
91 " mov %0, #0\n" \
92 __futex_atomic_ex_table("%5") \
93 : "=&r" (ret), "=&r" (oldval), "=&r" (tmp) \
94 : "r" (uaddr), "r" (oparg), "Ir" (-EFAULT) \
95 : "cc", "memory"); \
96 uaccess_restore(__ua_flags); \
97 })
98
99 static inline int
100 futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
101 u32 oldval, u32 newval)
102 {
103 unsigned int __ua_flags;
104 int ret = 0;
105 u32 val;
106
107 if (!access_ok(uaddr, sizeof(u32)))
108 return -EFAULT;
109
110 preempt_disable();
111 __ua_flags = uaccess_save_and_enable();
112 __asm__ __volatile__("@futex_atomic_cmpxchg_inatomic\n"
113 " .syntax unified\n"
114 "1: " TUSER(ldr) " %1, [%4]\n"
115 " teq %1, %2\n"
116 " it eq @ explicit IT needed for the 2b label\n"
117 "2: " TUSERCOND(str, eq) " %3, [%4]\n"
118 __futex_atomic_ex_table("%5")
119 : "+r" (ret), "=&r" (val)
120 : "r" (oldval), "r" (newval), "r" (uaddr), "Ir" (-EFAULT)
121 : "cc", "memory");
122 uaccess_restore(__ua_flags);
123
124 *uval = val;
125 preempt_enable();
126
127 return ret;
128 }
129
130 #endif /* !SMP */
131
132 static inline int
133 arch_futex_atomic_op_inuser(int op, int oparg, int *oval, u32 __user *uaddr)
134 {
135 int oldval = 0, ret, tmp;
136
137 if (!access_ok(uaddr, sizeof(u32)))
138 return -EFAULT;
139
140 #ifndef CONFIG_SMP
141 preempt_disable();
142 #endif
143
144 switch (op) {
145 case FUTEX_OP_SET:
146 __futex_atomic_op("mov %0, %4", ret, oldval, tmp, uaddr, oparg);
147 break;
148 case FUTEX_OP_ADD:
149 __futex_atomic_op("add %0, %1, %4", ret, oldval, tmp, uaddr, oparg);
150 break;
151 case FUTEX_OP_OR:
152 __futex_atomic_op("orr %0, %1, %4", ret, oldval, tmp, uaddr, oparg);
153 break;
154 case FUTEX_OP_ANDN:
155 __futex_atomic_op("and %0, %1, %4", ret, oldval, tmp, uaddr, ~oparg);
156 break;
157 case FUTEX_OP_XOR:
158 __futex_atomic_op("eor %0, %1, %4", ret, oldval, tmp, uaddr, oparg);
159 break;
160 default:
161 ret = -ENOSYS;
162 }
163
164 #ifndef CONFIG_SMP
165 preempt_enable();
166 #endif
167
168 /*
169 * Store unconditionally. If ret != 0 the extra store is the least
170 * of the worries but GCC cannot figure out that __futex_atomic_op()
171 * is either setting ret to -EFAULT or storing the old value in
172 * oldval which results in a uninitialized warning at the call site.
173 */
174 *oval = oldval;
175
176 return ret;
177 }
178
179 #endif /* __KERNEL__ */
180 #endif /* _ASM_ARM_FUTEX_H */
181
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