unified (weak) sys_pipe implementation

This replaces the duplicated arch-specific versions of "sys_pipe()" with
one unified implementation.  This removes almost 250 lines of duplicated
code.

It's marked __weak, so that *if* an architecture wants to override the
default implementation it can do so by simply having its own replacement
version, since many architectures use alternate calling conventions for
the 'pipe()' system call for legacy reasons (ie traditional UNIX
implementations often return the two file descriptors in registers)

I still haven't changed the cris version even though Linus says the BKL
isn't needed.  The arch maintainer can easily do it if there are really
no obstacles.

Signed-off-by: Ulrich Drepper <drepper@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/pipe.c

@@ -1075,6 +1075,23 @@ int do_pipe(int *fd)
 	return error;
 }
 
+/*
+ * sys_pipe() is the normal C calling standard for creating
+ * a pipe. It's not the way Unix traditionally does this, though.
+ */
+asmlinkage long __weak sys_pipe(int __user *fildes)
+{
+	int fd[2];
+	int error;
+
+	error = do_pipe(fd);
+	if (!error) {
+		if (copy_to_user(fildes, fd, sizeof(fd)))
+			error = -EFAULT;
+	}
+	return error;
+}
+
 /*
  * pipefs should _never_ be mounted by userland - too much of security hassle,
  * no real gain from having the whole whorehouse mounted. So we don't need