fs: add ksys_chroot() helper; remove-in kernel calls to sys_chroot()

Using this helper allows us to avoid the in-kernel calls to the
sys_chroot() syscall. The ksys_ prefix denotes that this function is
meant as a drop-in replacement for the syscall. In particular, it uses the
same calling convention as sys_chroot().

In the near future, the fs-external callers of ksys_chroot() should be
converted to use kern_path()/set_fs_root() directly. Then ksys_chroot()
can be moved within sys_chroot() again.

This patch is part of a series which removes in-kernel calls to syscalls.
On this basis, the syscall entry path can be streamlined. For details, see
http://lkml.kernel.org/r/20180325162527.GA17492@light.dominikbrodowski.net

Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>

1 files changed, 1 insertions, 1 deletions

diff --git a/init/do_mounts.c b/init/do_mounts.c
index eb768de..2f06f78 100644
--- a/init/do_mounts.c
+++ b/init/do_mounts.c
@@ -600,7 +600,7 @@ void __init prepare_namespace(void)
 out:
 	devtmpfs_mount("dev");
 	ksys_mount(".", "/", NULL, MS_MOVE, NULL);
-	sys_chroot(".");
+	ksys_chroot(".");
 }
 
 static bool is_tmpfs;