select: add poll_select_set_timeout() and poll_select_copy_remaining() helpers

[mirror_ubuntu-artful-kernel.git] / fs / compat.c

diff --git a/fs/compat.c b/fs/compat.c
index 075d0509970de479c78e796cb4ce11d94945fbb5..424767c954a0fbe33c93ab03dd7de327b643007a 100644 (file)
--- 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.