linux/kernel/futex_compat.c
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   1/*
   2 * linux/kernel/futex_compat.c
   3 *
   4 * Futex compatibililty routines.
   5 *
   6 * Copyright 2006, Red Hat, Inc., Ingo Molnar
   7 */
   8
   9#include <linux/linkage.h>
  10#include <linux/compat.h>
  11#include <linux/nsproxy.h>
  12#include <linux/futex.h>
  13#include <linux/ptrace.h>
  14
  15#include <asm/uaccess.h>
  16
  17
  18/*
  19 * Fetch a robust-list pointer. Bit 0 signals PI futexes:
  20 */
  21static inline int
  22fetch_robust_entry(compat_uptr_t *uentry, struct robust_list __user **entry,
  23                   compat_uptr_t __user *head, unsigned int *pi)
  24{
  25        if (get_user(*uentry, head))
  26                return -EFAULT;
  27
  28        *entry = compat_ptr((*uentry) & ~1);
  29        *pi = (unsigned int)(*uentry) & 1;
  30
  31        return 0;
  32}
  33
  34static void __user *futex_uaddr(struct robust_list __user *entry,
  35                                compat_long_t futex_offset)
  36{
  37        compat_uptr_t base = ptr_to_compat(entry);
  38        void __user *uaddr = compat_ptr(base + futex_offset);
  39
  40        return uaddr;
  41}
  42
  43/*
  44 * Walk curr->robust_list (very carefully, it's a userspace list!)
  45 * and mark any locks found there dead, and notify any waiters.
  46 *
  47 * We silently return on any sign of list-walking problem.
  48 */
  49void compat_exit_robust_list(struct task_struct *curr)
  50{
  51        struct compat_robust_list_head __user *head = curr->compat_robust_list;
  52        struct robust_list __user *entry, *next_entry, *pending;
  53        unsigned int limit = ROBUST_LIST_LIMIT, pi, pip;
  54        unsigned int uninitialized_var(next_pi);
  55        compat_uptr_t uentry, next_uentry, upending;
  56        compat_long_t futex_offset;
  57        int rc;
  58
  59        if (!futex_cmpxchg_enabled)
  60                return;
  61
  62        /*
  63         * Fetch the list head (which was registered earlier, via
  64         * sys_set_robust_list()):
  65         */
  66        if (fetch_robust_entry(&uentry, &entry, &head->list.next, &pi))
  67                return;
  68        /*
  69         * Fetch the relative futex offset:
  70         */
  71        if (get_user(futex_offset, &head->futex_offset))
  72                return;
  73        /*
  74         * Fetch any possibly pending lock-add first, and handle it
  75         * if it exists:
  76         */
  77        if (fetch_robust_entry(&upending, &pending,
  78                               &head->list_op_pending, &pip))
  79                return;
  80
  81        next_entry = NULL;      /* avoid warning with gcc */
  82        while (entry != (struct robust_list __user *) &head->list) {
  83                /*
  84                 * Fetch the next entry in the list before calling
  85                 * handle_futex_death:
  86                 */
  87                rc = fetch_robust_entry(&next_uentry, &next_entry,
  88                        (compat_uptr_t __user *)&entry->next, &next_pi);
  89                /*
  90                 * A pending lock might already be on the list, so
  91                 * dont process it twice:
  92                 */
  93                if (entry != pending) {
  94                        void __user *uaddr = futex_uaddr(entry, futex_offset);
  95
  96                        if (handle_futex_death(uaddr, curr, pi))
  97                                return;
  98                }
  99                if (rc)
 100                        return;
 101                uentry = next_uentry;
 102                entry = next_entry;
 103                pi = next_pi;
 104                /*
 105                 * Avoid excessively long or circular lists:
 106                 */
 107                if (!--limit)
 108                        break;
 109
 110                cond_resched();
 111        }
 112        if (pending) {
 113                void __user *uaddr = futex_uaddr(pending, futex_offset);
 114
 115                handle_futex_death(uaddr, curr, pip);
 116        }
 117}
 118
 119asmlinkage long
 120compat_sys_set_robust_list(struct compat_robust_list_head __user *head,
 121                           compat_size_t len)
 122{
 123        if (!futex_cmpxchg_enabled)
 124                return -ENOSYS;
 125
 126        if (unlikely(len != sizeof(*head)))
 127                return -EINVAL;
 128
 129        current->compat_robust_list = head;
 130
 131        return 0;
 132}
 133
 134asmlinkage long
 135compat_sys_get_robust_list(int pid, compat_uptr_t __user *head_ptr,
 136                           compat_size_t __user *len_ptr)
 137{
 138        struct compat_robust_list_head __user *head;
 139        unsigned long ret;
 140        struct task_struct *p;
 141
 142        if (!futex_cmpxchg_enabled)
 143                return -ENOSYS;
 144
 145        WARN_ONCE(1, "deprecated: get_robust_list will be deleted in 2013.\n");
 146
 147        rcu_read_lock();
 148
 149        ret = -ESRCH;
 150        if (!pid)
 151                p = current;
 152        else {
 153                p = find_task_by_vpid(pid);
 154                if (!p)
 155                        goto err_unlock;
 156        }
 157
 158        ret = -EPERM;
 159        if (!ptrace_may_access(p, PTRACE_MODE_READ))
 160                goto err_unlock;
 161
 162        head = p->compat_robust_list;
 163        rcu_read_unlock();
 164
 165        if (put_user(sizeof(*head), len_ptr))
 166                return -EFAULT;
 167        return put_user(ptr_to_compat(head), head_ptr);
 168
 169err_unlock:
 170        rcu_read_unlock();
 171
 172        return ret;
 173}
 174
 175asmlinkage long compat_sys_futex(u32 __user *uaddr, int op, u32 val,
 176                struct compat_timespec __user *utime, u32 __user *uaddr2,
 177                u32 val3)
 178{
 179        struct timespec ts;
 180        ktime_t t, *tp = NULL;
 181        int val2 = 0;
 182        int cmd = op & FUTEX_CMD_MASK;
 183
 184        if (utime && (cmd == FUTEX_WAIT || cmd == FUTEX_LOCK_PI ||
 185                      cmd == FUTEX_WAIT_BITSET ||
 186                      cmd == FUTEX_WAIT_REQUEUE_PI)) {
 187                if (get_compat_timespec(&ts, utime))
 188                        return -EFAULT;
 189                if (!timespec_valid(&ts))
 190                        return -EINVAL;
 191
 192                t = timespec_to_ktime(ts);
 193                if (cmd == FUTEX_WAIT)
 194                        t = ktime_add_safe(ktime_get(), t);
 195                tp = &t;
 196        }
 197        if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE ||
 198            cmd == FUTEX_CMP_REQUEUE_PI || cmd == FUTEX_WAKE_OP)
 199                val2 = (int) (unsigned long) utime;
 200
 201        return do_futex(uaddr, op, val, tp, uaddr2, val2, val3);
 202}
 203
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