arch/arm/include/asm/futex.h

   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 */