LXR linux/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
  45static inline int
  46futex_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
  99static inline int
 100futex_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
 132static inline int
 133arch_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 */
 181