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tag: v2.6.35-rc4
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/*
* 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;
const struct cred *cred = current_cred(), *pcred;

if (!futex_cmpxchg_enabled)
return -ENOSYS;

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

ret = -ESRCH;
rcu_read_lock();
p = find_task_by_vpid(pid);
if (!p)
goto err_unlock;
ret = -EPERM;
pcred = __task_cred(p);
if (cred->euid != pcred->euid &&
cred->euid != pcred->uid &&
!capable(CAP_SYS_PTRACE))
goto err_unlock;
head = p->compat_robust_list;
rcu_read_unlock();
}

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

err_unlock:
rcu_read_unlock();

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 ||
cmd == FUTEX_WAIT_REQUEUE_PI)) {
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 ||
cmd == FUTEX_CMP_REQUEUE_PI || cmd == FUTEX_WAKE_OP)
val2 = (int) (unsigned long) utime;

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