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Subject[PATCH 3/5] select: add poll_select_set_timeout() and poll_select_copy_remaining() helpers

From: Thomas Gleixner <tglx@linutronix.de>
Date: Sun, 31 Aug 2008 08:16:57 -0700
Subject: [PATCH] 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: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
---
fs/compat.c | 51 ++++++++++++++++++++++++++++++++++
fs/select.c | 75
++++++++++++++++++++++++++++++++++++++++++++++++++ include/linux/poll.h
| 2 + 3 files changed, 128 insertions(+), 0 deletions(-)
diff --git a/fs/compat.c b/fs/compat.c
index 075d050..424767c 100644
--- a/fs/compat.c
+++ b/fs/compat.c
@@ -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.
diff --git a/fs/select.c b/fs/select.c
index da0e882..1180a62 100644
--- a/fs/select.c
+++ b/fs/select.c
@@ -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)
diff --git a/include/linux/poll.h b/include/linux/poll.h
index ef45382..f65de51 100644
--- a/include/linux/poll.h
+++ b/include/linux/poll.h
@@ -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 */
--
1.5.5.1


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