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/alternative.h>
  25 #include <asm/cpufeature.h>
  26 #include <asm/errno.h>
  27 #include <asm/sysreg.h>
  28
  29 #define FUTEX_MAX_LOOPS 128 /* What's the largest number you can think of? */
  30
  31 #define __futex_atomic_op(insn, ret, oldval, uaddr, tmp, oparg)         \
  32 do {                                                                    \
  33         unsigned int loops = FUTEX_MAX_LOOPS;                           \
  34                                                                         \
  35         asm volatile(                                                   \
  36         ALTERNATIVE("nop", SET_PSTATE_PAN(0), ARM64_HAS_PAN,            \
  37                     CONFIG_ARM64_PAN)                                   \
  38 "       prfm    pstl1strm, %2\n"                                        \
  39 "1:     ldxr    %w1, %2\n"                                              \
  40         insn "\n"                                                       \
  41 "2:     stlxr   %w0, %w3, %2\n"                                         \
  42 "       cbz     %w0, 3f\n"                                              \
  43 "       sub     %w4, %w4, %w0\n"                                        \
  44 "       cbnz    %w4, 1b\n"                                              \
  45 "       mov     %w0, %w7\n"                                             \
  46 "3:\n"                                                                  \
  47 "       dmb     ish\n"                                                  \
  48 "       .pushsection .fixup,\"ax\"\n"                                   \
  49 "       .align  2\n"                                                    \
  50 "4:     mov     %w0, %w6\n"                                             \
  51 "       b       3b\n"                                                   \
  52 "       .popsection\n"                                                  \
  53         _ASM_EXTABLE(1b, 4b)                                            \
  54         _ASM_EXTABLE(2b, 4b)                                            \
  55         ALTERNATIVE("nop", SET_PSTATE_PAN(1), ARM64_HAS_PAN,            \
  56                     CONFIG_ARM64_PAN)                                   \
  57         : "=&r" (ret), "=&r" (oldval), "+Q" (*uaddr), "=&r" (tmp),      \
  58           "+r" (loops)                                                  \
  59         : "r" (oparg), "Ir" (-EFAULT), "Ir" (-EAGAIN)                   \
  60         : "memory");                                                    \
  61 } while (0)
  62
  63 static inline int
  64 arch_futex_atomic_op_inuser(int op, int oparg, int *oval, u32 __user *uaddr)
  65 {
  66         int oldval = 0, ret, tmp;
  67
  68         pagefault_disable();
  69
  70         switch (op) {
  71         case FUTEX_OP_SET:
  72                 __futex_atomic_op("mov  %w3, %w5",
  73                                   ret, oldval, uaddr, tmp, oparg);
  74                 break;
  75         case FUTEX_OP_ADD:
  76                 __futex_atomic_op("add  %w3, %w1, %w5",
  77                                   ret, oldval, uaddr, tmp, oparg);
  78                 break;
  79         case FUTEX_OP_OR:
  80                 __futex_atomic_op("orr  %w3, %w1, %w5",
  81                                   ret, oldval, uaddr, tmp, oparg);
  82                 break;
  83         case FUTEX_OP_ANDN:
  84                 __futex_atomic_op("and  %w3, %w1, %w5",
  85                                   ret, oldval, uaddr, tmp, ~oparg);
  86                 break;
  87         case FUTEX_OP_XOR:
  88                 __futex_atomic_op("eor  %w3, %w1, %w5",
  89                                   ret, oldval, uaddr, tmp, oparg);
  90                 break;
  91         default:
  92                 ret = -ENOSYS;
  93         }
  94
  95         pagefault_enable();
  96
  97         if (!ret)
  98                 *oval = oldval;
  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         unsigned int loops = FUTEX_MAX_LOOPS;
 109         u32 val, tmp;
 110         u32 __user *uaddr;
 111
 112         if (!access_ok(VERIFY_WRITE, _uaddr, sizeof(u32)))
 113                 return -EFAULT;
 114
 115         uaddr = __uaccess_mask_ptr(_uaddr);
 116         asm volatile("// futex_atomic_cmpxchg_inatomic\n"
 117 ALTERNATIVE("nop", SET_PSTATE_PAN(0), ARM64_HAS_PAN, CONFIG_ARM64_PAN)
 118 "       prfm    pstl1strm, %2\n"
 119 "1:     ldxr    %w1, %2\n"
 120 "       sub     %w3, %w1, %w5\n"
 121 "       cbnz    %w3, 4f\n"
 122 "2:     stlxr   %w3, %w6, %2\n"
 123 "       cbz     %w3, 3f\n"
 124 "       sub     %w4, %w4, %w3\n"
 125 "       cbnz    %w4, 1b\n"
 126 "       mov     %w0, %w8\n"
 127 "3:\n"
 128 "       dmb     ish\n"
 129 "4:\n"
 130 "       .pushsection .fixup,\"ax\"\n"
 131 "5:     mov     %w0, %w7\n"
 132 "       b       4b\n"
 133 "       .popsection\n"
 134         _ASM_EXTABLE(1b, 5b)
 135         _ASM_EXTABLE(2b, 5b)
 136 ALTERNATIVE("nop", SET_PSTATE_PAN(1), ARM64_HAS_PAN, CONFIG_ARM64_PAN)
 137         : "+r" (ret), "=&r" (val), "+Q" (*uaddr), "=&r" (tmp), "+r" (loops)
 138         : "r" (oldval), "r" (newval), "Ir" (-EFAULT), "Ir" (-EAGAIN)
 139         : "memory");
 140
 141         *uval = val;
 142         return ret;
 143 }
 144
 145 #endif /* __KERNEL__ */
 146 #endif /* __ASM_FUTEX_H */