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 #include <asm/errno.h>
  24
  25 #define __futex_atomic_op(insn, ret, oldval, uaddr, tmp, oparg)         \
  26         asm volatile(                                                   \
  27 "1:     ldxr    %w1, %2\n"                                              \
  28         insn "\n"                                                       \
  29 "2:     stlxr   %w3, %w0, %2\n"                                         \
  30 "       cbnz    %w3, 1b\n"                                              \
  31 "       dmb     ish\n"                                                  \
  32 "3:\n"                                                                  \
  33 "       .pushsection .fixup,\"ax\"\n"                                   \
  34 "       .align  2\n"                                                    \
  35 "4:     mov     %w0, %w5\n"                                             \
  36 "       b       3b\n"                                                   \
  37 "       .popsection\n"                                                  \
  38 "       .pushsection __ex_table,\"a\"\n"                                \
  39 "       .align  3\n"                                                    \
  40 "       .quad   1b, 4b, 2b, 4b\n"                                       \
  41 "       .popsection\n"                                                  \
  42         : "=&r" (ret), "=&r" (oldval), "+Q" (*uaddr), "=&r" (tmp)       \
  43         : "r" (oparg), "Ir" (-EFAULT)                                   \
  44         : "memory")
  45
  46 static inline int
  47 futex_atomic_op_inuser (int encoded_op, u32 __user *uaddr)
  48 {
  49         int op = (encoded_op >> 28) & 7;
  50         int cmp = (encoded_op >> 24) & 15;
  51         int oparg = (encoded_op << 8) >> 20;
  52         int cmparg = (encoded_op << 20) >> 20;
  53         int oldval = 0, ret, tmp;
  54
  55         if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28))
  56                 oparg = 1 << oparg;
  57
  58         if (!access_ok(VERIFY_WRITE, uaddr, sizeof(u32)))
  59                 return -EFAULT;
  60
  61         pagefault_disable();    /* implies preempt_disable() */
  62
  63         switch (op) {
  64         case FUTEX_OP_SET:
  65                 __futex_atomic_op("mov  %w0, %w4",
  66                                   ret, oldval, uaddr, tmp, oparg);
  67                 break;
  68         case FUTEX_OP_ADD:
  69                 __futex_atomic_op("add  %w0, %w1, %w4",
  70                                   ret, oldval, uaddr, tmp, oparg);
  71                 break;
  72         case FUTEX_OP_OR:
  73                 __futex_atomic_op("orr  %w0, %w1, %w4",
  74                                   ret, oldval, uaddr, tmp, oparg);
  75                 break;
  76         case FUTEX_OP_ANDN:
  77                 __futex_atomic_op("and  %w0, %w1, %w4",
  78                                   ret, oldval, uaddr, tmp, ~oparg);
  79                 break;
  80         case FUTEX_OP_XOR:
  81                 __futex_atomic_op("eor  %w0, %w1, %w4",
  82                                   ret, oldval, uaddr, tmp, oparg);
  83                 break;
  84         default:
  85                 ret = -ENOSYS;
  86         }
  87
  88         pagefault_enable();     /* subsumes preempt_enable() */
  89
  90         if (!ret) {
  91                 switch (cmp) {
  92                 case FUTEX_OP_CMP_EQ: ret = (oldval == cmparg); break;
  93                 case FUTEX_OP_CMP_NE: ret = (oldval != cmparg); break;
  94                 case FUTEX_OP_CMP_LT: ret = (oldval < cmparg); break;
  95                 case FUTEX_OP_CMP_GE: ret = (oldval >= cmparg); break;
  96                 case FUTEX_OP_CMP_LE: ret = (oldval <= cmparg); break;
  97                 case FUTEX_OP_CMP_GT: ret = (oldval > cmparg); break;
  98                 default: ret = -ENOSYS;
  99                 }
 100         }
 101         return ret;
 102 }
 103
 104 static inline int
 105 futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
 106                               u32 oldval, u32 newval)
 107 {
 108         int ret = 0;
 109         u32 val, tmp;
 110
 111         if (!access_ok(VERIFY_WRITE, uaddr, sizeof(u32)))
 112                 return -EFAULT;
 113
 114         asm volatile("// futex_atomic_cmpxchg_inatomic\n"
 115 "1:     ldxr    %w1, %2\n"
 116 "       sub     %w3, %w1, %w4\n"
 117 "       cbnz    %w3, 3f\n"
 118 "2:     stlxr   %w3, %w5, %2\n"
 119 "       cbnz    %w3, 1b\n"
 120 "       dmb     ish\n"
 121 "3:\n"
 122 "       .pushsection .fixup,\"ax\"\n"
 123 "4:     mov     %w0, %w6\n"
 124 "       b       3b\n"
 125 "       .popsection\n"
 126 "       .pushsection __ex_table,\"a\"\n"
 127 "       .align  3\n"
 128 "       .quad   1b, 4b, 2b, 4b\n"
 129 "       .popsection\n"
 130         : "+r" (ret), "=&r" (val), "+Q" (*uaddr), "=&r" (tmp)
 131         : "r" (oldval), "r" (newval), "Ir" (-EFAULT)
 132         : "memory");
 133
 134         *uval = val;
 135         return ret;
 136 }
 137
 138 #endif /* __KERNEL__ */
 139 #endif /* __ASM_FUTEX_H */