kmsg: use do_div() to divide 64bit integer

On Tue, May 8, 2012 at 10:02 AM, Stephen Rothwell <sfr@canb.auug.org.au> wrote:
> kernel/built-in.o: In function `devkmsg_read':
> printk.c:(.text+0x27e8): undefined reference to `__udivdi3'
> Most probably the "msg->ts_nsec / 1000" since
> ts_nsec is a u64 and this is a 32 bit build ...

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Kay Sievers <kay@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

kernel/printk.c

@@ -407,6 +407,7 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf,
 {
 	struct devkmsg_user *user = file->private_data;
 	struct log *msg;
+	u64 ts_usec;
 	size_t i;
 	size_t len;
 	ssize_t ret;
@@ -441,8 +442,10 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf,
 	}
 
 	msg = log_from_idx(user->idx);
+	ts_usec = msg->ts_nsec;
+	do_div(ts_usec, 1000);
 	len = sprintf(user->buf, "%u,%llu,%llu;",
-		      msg->level, user->seq, msg->ts_nsec / 1000);
+		      msg->level, user->seq, ts_usec);
 
 	/* escape non-printable characters */
 	for (i = 0; i < msg->text_len; i++) {