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