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#include <linux/syscalls.h>
  15
  16#include <asm/uaccess.h>
  17
  18
  19/*
  20 * Fetch a robust-list pointer. Bit 0 signals PI futexes:
  21 */
  22static inline int
  23fetch_robust_entry(compat_uptr_t *uentry, struct robust_list __user **entry,
  24                   compat_uptr_t __user *head, unsigned int *pi)
  25{
  26        if (get_user(*uentry, head))
  27                return -EFAULT;
  28
  29        *entry = compat_ptr((*uentry) & ~1);
  30        *pi = (unsigned int)(*uentry) & 1;
  31
  32        return 0;
  33}
  34
  35static void __user *futex_uaddr(struct robust_list __user *entry,
  36                                compat_long_t futex_offset)
  37{
  38        compat_uptr_t base = ptr_to_compat(entry);
  39        void __user *uaddr = compat_ptr(base + futex_offset);
  40
  41        return uaddr;
  42}
  43
  44/*
  45 * Walk curr->robust_list (very carefully, it's a userspace list!)
  46 * and mark any locks found there dead, and notify any waiters.
  47 *
  48 * We silently return on any sign of list-walking problem.
  49 */
  50void compat_exit_robust_list(struct task_struct *curr)
  51{
  52        struct compat_robust_list_head __user *head = curr->compat_robust_list;
  53        struct robust_list __user *entry, *next_entry, *pending;
  54        unsigned int limit = ROBUST_LIST_LIMIT, pi, pip;
  55        unsigned int uninitialized_var(next_pi);
  56        compat_uptr_t uentry, next_uentry, upending;
  57        compat_long_t futex_offset;
  58        int rc;
  59
  60        if (!futex_cmpxchg_enabled)
  61                return;
  62
  63        /*
  64         * Fetch the list head (which was registered earlier, via
  65         * sys_set_robust_list()):
  66         */
  67        if (fetch_robust_entry(&uentry, &entry, &head->list.next, &pi))
  68                return;
  69        /*
  70         * Fetch the relative futex offset:
  71         */
  72        if (get_user(futex_offset, &head->futex_offset))
  73                return;
  74        /*
  75         * Fetch any possibly pending lock-add first, and handle it
  76         * if it exists:
  77         */
  78        if (fetch_robust_entry(&upending, &pending,
  79                               &head->list_op_pending, &pip))
  80                return;
  81
  82        next_entry = NULL;      /* avoid warning with gcc */
  83        while (entry != (struct robust_list __user *) &head->list) {
  84                /*
  85                 * Fetch the next entry in the list before calling
  86                 * handle_futex_death:
  87                 */
  88                rc = fetch_robust_entry(&next_uentry, &next_entry,
  89                        (compat_uptr_t __user *)&entry->next, &next_pi);
  90                /*
  91                 * A pending lock might already be on the list, so
  92                 * dont process it twice:
  93                 */
  94                if (entry != pending) {
  95                        void __user *uaddr = futex_uaddr(entry, futex_offset);
  96
  97                        if (handle_futex_death(uaddr, curr, pi))
  98                                return;
  99                }
 100                if (rc)
 101                        return;
 102                uentry = next_uentry;
 103                entry = next_entry;
 104                pi = next_pi;
 105                /*
 106                 * Avoid excessively long or circular lists:
 107                 */
 108                if (!--limit)
 109                        break;
 110
 111                cond_resched();
 112        }
 113        if (pending) {
 114                void __user *uaddr = futex_uaddr(pending, futex_offset);
 115
 116                handle_futex_death(uaddr, curr, pip);
 117        }
 118}
 119
 120COMPAT_SYSCALL_DEFINE2(set_robust_list,
 121                struct compat_robust_list_head __user *, head,
 122                compat_size_t, len)
 123{
 124        if (!futex_cmpxchg_enabled)
 125                return -ENOSYS;
 126
 127        if (unlikely(len != sizeof(*head)))
 128                return -EINVAL;
 129
 130        current->compat_robust_list = head;
 131
 132        return 0;
 133}
 134
 135COMPAT_SYSCALL_DEFINE3(get_robust_list, int, pid,
 136                        compat_uptr_t __user *, head_ptr,
 137                        compat_size_t __user *, len_ptr)
 138{
 139        struct compat_robust_list_head __user *head;
 140        unsigned long ret;
 141        struct task_struct *p;
 142
 143        if (!futex_cmpxchg_enabled)
 144                return -ENOSYS;
 145
 146        rcu_read_lock();
 147
 148        ret = -ESRCH;
 149        if (!pid)
 150                p = current;
 151        else {
 152                p = find_task_by_vpid(pid);
 153                if (!p)
 154                        goto err_unlock;
 155        }
 156
 157        ret = -EPERM;
 158        if (!ptrace_may_access(p, PTRACE_MODE_READ))
 159                goto err_unlock;
 160
 161        head = p->compat_robust_list;
 162        rcu_read_unlock();
 163
 164        if (put_user(sizeof(*head), len_ptr))
 165                return -EFAULT;
 166        return put_user(ptr_to_compat(head), head_ptr);
 167
 168err_unlock:
 169        rcu_read_unlock();
 170
 171        return ret;
 172}
 173
 174COMPAT_SYSCALL_DEFINE6(futex, u32 __user *, uaddr, int, op, u32, val,
 175                struct compat_timespec __user *, utime, u32 __user *, uaddr2,
 176                u32, val3)
 177{
 178        struct timespec ts;
 179        ktime_t t, *tp = NULL;
 180        int val2 = 0;
 181        int cmd = op & FUTEX_CMD_MASK;
 182
 183        if (utime && (cmd == FUTEX_WAIT || cmd == FUTEX_LOCK_PI ||
 184                      cmd == FUTEX_WAIT_BITSET ||
 185                      cmd == FUTEX_WAIT_REQUEUE_PI)) {
 186                if (get_compat_timespec(&ts, utime))
 187                        return -EFAULT;
 188                if (!timespec_valid(&ts))
 189                        return -EINVAL;
 190
 191                t = timespec_to_ktime(ts);
 192                if (cmd == FUTEX_WAIT)
 193                        t = ktime_add_safe(ktime_get(), t);
 194                tp = &t;
 195        }
 196        if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE ||
 197            cmd == FUTEX_CMP_REQUEUE_PI || cmd == FUTEX_WAKE_OP)
 198                val2 = (int) (unsigned long) utime;
 199
 200        return do_futex(uaddr, op, val, tp, uaddr2, val2, val3);
 201}
 202
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