root/kernel/futex_compat.c

DEFINITIONS

1. fetch_robust_entry
2. futex_uaddr
3. compat_exit_robust_list
4. compat_sys_set_robust_list
5. compat_sys_get_robust_list
6. compat_sys_futex

/*
 * linux/kernel/futex_compat.c
 *
 * Futex compatibililty routines.
 *
 * Copyright 2006, Red Hat, Inc., Ingo Molnar
 */

#include <linux/linkage.h>
#include <linux/compat.h>
#include <linux/nsproxy.h>
#include <linux/futex.h>

#include <asm/uaccess.h>


/*
 * Fetch a robust-list pointer. Bit 0 signals PI futexes:
 */
static inline int
fetch_robust_entry(compat_uptr_t *uentry, struct robust_list __user **entry,
                   compat_uptr_t __user *head, int *pi)
{
        if (get_user(*uentry, head))
                return -EFAULT;

        *entry = compat_ptr((*uentry) & ~1);
        *pi = (unsigned int)(*uentry) & 1;

        return 0;
}

static void __user *futex_uaddr(struct robust_list __user *entry,
                                compat_long_t futex_offset)
{
        compat_uptr_t base = ptr_to_compat(entry);
        void __user *uaddr = compat_ptr(base + futex_offset);

        return uaddr;
}

/*
 * Walk curr->robust_list (very carefully, it's a userspace list!)
 * and mark any locks found there dead, and notify any waiters.
 *
 * We silently return on any sign of list-walking problem.
 */
void compat_exit_robust_list(struct task_struct *curr)
{
        struct compat_robust_list_head __user *head = curr->compat_robust_list;
        struct robust_list __user *entry, *next_entry, *pending;
        unsigned int limit = ROBUST_LIST_LIMIT, pi, next_pi, pip;
        compat_uptr_t uentry, next_uentry, upending;
        compat_long_t futex_offset;
        int rc;

        if (!futex_cmpxchg_enabled)
                return;

        /*
         * Fetch the list head (which was registered earlier, via
         * sys_set_robust_list()):
         */
        if (fetch_robust_entry(&uentry, &entry, &head->list.next, &pi))
                return;
        /*
         * Fetch the relative futex offset:
         */
        if (get_user(futex_offset, &head->futex_offset))
                return;
        /*
         * Fetch any possibly pending lock-add first, and handle it
         * if it exists:
         */
        if (fetch_robust_entry(&upending, &pending,
                               &head->list_op_pending, &pip))
                return;

        next_entry = NULL;      /* avoid warning with gcc */
        while (entry != (struct robust_list __user *) &head->list) {
                /*
                 * Fetch the next entry in the list before calling
                 * handle_futex_death:
                 */
                rc = fetch_robust_entry(&next_uentry, &next_entry,
                        (compat_uptr_t __user *)&entry->next, &next_pi);
                /*
                 * A pending lock might already be on the list, so
                 * dont process it twice:
                 */
                if (entry != pending) {
                        void __user *uaddr = futex_uaddr(entry, futex_offset);

                        if (handle_futex_death(uaddr, curr, pi))
                                return;
                }
                if (rc)
                        return;
                uentry = next_uentry;
                entry = next_entry;
                pi = next_pi;
                /*
                 * Avoid excessively long or circular lists:
                 */
                if (!--limit)
                        break;

                cond_resched();
        }
        if (pending) {
                void __user *uaddr = futex_uaddr(pending, futex_offset);

                handle_futex_death(uaddr, curr, pip);
        }
}

asmlinkage long
compat_sys_set_robust_list(struct compat_robust_list_head __user *head,
                           compat_size_t len)
{
        if (!futex_cmpxchg_enabled)
                return -ENOSYS;

        if (unlikely(len != sizeof(*head)))
                return -EINVAL;

        current->compat_robust_list = head;

        return 0;
}

asmlinkage long
compat_sys_get_robust_list(int pid, compat_uptr_t __user *head_ptr,
                           compat_size_t __user *len_ptr)
{
        struct compat_robust_list_head __user *head;
        unsigned long ret;

        if (!futex_cmpxchg_enabled)
                return -ENOSYS;

        if (!pid)
                head = current->compat_robust_list;
        else {
                struct task_struct *p;

                ret = -ESRCH;
                read_lock(&tasklist_lock);
                p = find_task_by_vpid(pid);
                if (!p)
                        goto err_unlock;
                ret = -EPERM;
                if ((current->euid != p->euid) && (current->euid != p->uid) &&
                                !capable(CAP_SYS_PTRACE))
                        goto err_unlock;
                head = p->compat_robust_list;
                read_unlock(&tasklist_lock);
        }

        if (put_user(sizeof(*head), len_ptr))
                return -EFAULT;
        return put_user(ptr_to_compat(head), head_ptr);

err_unlock:
        read_unlock(&tasklist_lock);

        return ret;
}

asmlinkage long compat_sys_futex(u32 __user *uaddr, int op, u32 val,
                struct compat_timespec __user *utime, u32 __user *uaddr2,
                u32 val3)
{
        struct timespec ts;
        ktime_t t, *tp = NULL;
        int val2 = 0;
        int cmd = op & FUTEX_CMD_MASK;

        if (utime && (cmd == FUTEX_WAIT || cmd == FUTEX_LOCK_PI ||
                      cmd == FUTEX_WAIT_BITSET)) {
                if (get_compat_timespec(&ts, utime))
                        return -EFAULT;
                if (!timespec_valid(&ts))
                        return -EINVAL;

                t = timespec_to_ktime(ts);
                if (cmd == FUTEX_WAIT)
                        t = ktime_add_safe(ktime_get(), t);
                tp = &t;
        }
        if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE)
                val2 = (int) (unsigned long) utime;

        return do_futex(uaddr, op, val, tp, uaddr2, val2, val3);
}