Commit b773ad40 authored by Thomas Gleixner's avatar Thomas Gleixner Committed by Arjan van de Ven
Browse files

select: add poll_select_set_timeout() and poll_select_copy_remaining() helpers 



This patch adds 2 helpers that will be used for the hrtimer based select/poll:

poll_select_set_timeout() is a helper that takes a timeout (as a second, nanosecond
pair) and turns that into a "struct timespec" that represents the absolute end time.
This is a common operation in the many select() and poll() variants and needs various,
common, sanity checks.

poll_select_copy_remaining() is a helper that takes care of copying the remaining
time to userspace, as select(), pselect() and ppoll() do. This function comes in
both a natural and a compat implementation (due to datastructure differences).

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarArjan van de Ven <arjan@linux.intel.com>
parent df0cc053

fs/compat.c

+51 −0
Original line number Diff line number Diff line
@@ -1436,6 +1436,57 @@ out_ret: 


#define __COMPAT_NFDBITS       (8 * sizeof(compat_ulong_t))



static int poll_select_copy_remaining(struct timespec *end_time, void __user *p,

				      int timeval, int ret)

{

	struct timespec ts;



	if (!p)

		return ret;



	if (current->personality & STICKY_TIMEOUTS)

		goto sticky;



	/* No update for zero timeout */

	if (!end_time->tv_sec && !end_time->tv_nsec)

		return ret;



	ktime_get_ts(&ts);

	ts = timespec_sub(*end_time, ts);

	if (ts.tv_sec < 0)

		ts.tv_sec = ts.tv_nsec = 0;



	if (timeval) {

		struct compat_timeval rtv;



		rtv.tv_sec = ts.tv_sec;

		rtv.tv_usec = ts.tv_nsec / NSEC_PER_USEC;



		if (!copy_to_user(p, &rtv, sizeof(rtv)))

			return ret;

	} else {

		struct compat_timespec rts;



		rts.tv_sec = ts.tv_sec;

		rts.tv_nsec = ts.tv_nsec;



		if (!copy_to_user(p, &rts, sizeof(rts)))

			return ret;

	}

	/*

	 * If an application puts its timeval in read-only memory, we

	 * don't want the Linux-specific update to the timeval to

	 * cause a fault after the select has completed

	 * successfully. However, because we're not updating the

	 * timeval, we can't restart the system call.

	 */



sticky:

	if (ret == -ERESTARTNOHAND)

		ret = -EINTR;

	return ret;

}



/*

 * Ooo, nasty.  We need here to frob 32-bit unsigned longs to

 * 64-bit unsigned longs.

fs/select.c

+75 −0
Original line number Diff line number Diff line
@@ -130,6 +130,81 @@ static void __pollwait(struct file *filp, wait_queue_head_t *wait_address, 
	add_wait_queue(wait_address, &entry->wait);

}



/**

 * poll_select_set_timeout - helper function to setup the timeout value

 * @to:		pointer to timespec variable for the final timeout

 * @sec:	seconds (from user space)

 * @nsec:	nanoseconds (from user space)

 *

 * Note, we do not use a timespec for the user space value here, That

 * way we can use the function for timeval and compat interfaces as well.

 *

 * Returns -EINVAL if sec/nsec are not normalized. Otherwise 0.

 */

int poll_select_set_timeout(struct timespec *to, long sec, long nsec)

{

	struct timespec ts = {.tv_sec = sec, .tv_nsec = nsec};



	if (!timespec_valid(&ts))

		return -EINVAL;



	/* Optimize for the zero timeout value here */

	if (!sec && !nsec) {

		to->tv_sec = to->tv_nsec = 0;

	} else {

		ktime_get_ts(to);

		*to = timespec_add_safe(*to, ts);

	}

	return 0;

}



static int poll_select_copy_remaining(struct timespec *end_time, void __user *p,

				      int timeval, int ret)

{

	struct timespec rts;

	struct timeval rtv;



	if (!p)

		return ret;



	if (current->personality & STICKY_TIMEOUTS)

		goto sticky;



	/* No update for zero timeout */

	if (!end_time->tv_sec && !end_time->tv_nsec)

		return ret;



	ktime_get_ts(&rts);

	rts = timespec_sub(*end_time, rts);

	if (rts.tv_sec < 0)

		rts.tv_sec = rts.tv_nsec = 0;



	if (timeval) {

		rtv.tv_sec = rts.tv_sec;

		rtv.tv_usec = rts.tv_nsec / NSEC_PER_USEC;



		if (!copy_to_user(p, &rtv, sizeof(rtv)))

			return ret;



	} else if (!copy_to_user(p, &rts, sizeof(rts)))

		return ret;



	/*

	 * If an application puts its timeval in read-only memory, we

	 * don't want the Linux-specific update to the timeval to

	 * cause a fault after the select has completed

	 * successfully. However, because we're not updating the

	 * timeval, we can't restart the system call.

	 */



sticky:

	if (ret == -ERESTARTNOHAND)

		ret = -EINTR;

	return ret;

}







#define FDS_IN(fds, n)		(fds->in + n)

#define FDS_OUT(fds, n)		(fds->out + n)

#define FDS_EX(fds, n)		(fds->ex + n)

include/linux/poll.h

+2 −0
Original line number Diff line number Diff line
@@ -120,6 +120,8 @@ extern int do_sys_poll(struct pollfd __user * ufds, unsigned int nfds, 
extern int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp,

			   fd_set __user *exp, s64 *timeout);



extern int poll_select_set_timeout(struct timespec *to, long sec, long nsec);



#endif /* KERNEL */



#endif /* _LINUX_POLL_H */

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