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 = 0, 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(VERIFY_WRITE, _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         if (!ret)
 138                 *uval = val;
 139
 140         return ret;
 141 }
 142
 143 #endif /* __KERNEL__ */
 144 #endif /* __ASM_FUTEX_H */