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>
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 @@
#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.