devtmpfs: use do_mount() instead of ksys_mount()

In devtmpfs, do_mount() can be called directly instead of complex wrapping
by ksys_mount():
- the first and third arguments are const strings in the kernel,
  and do not need to be copied over from userspace;
- the fifth argument is NULL, and therefore no page needs to be
  copied over from userspace;
- the second and fourth argument are passed through anyway.

Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>

diff --git a/drivers/base/devtmpfs.c b/drivers/base/devtmpfs.c
index 30d0523..6cdbf15 100644 (file)
--- a/drivers/base/devtmpfs.c
+++ b/drivers/base/devtmpfs.c
@@ -359,7 +359,7 @@ static int handle_remove(const char *nodename, struct device *dev)
  * If configured, or requested by the commandline, devtmpfs will be
  * auto-mounted after the kernel mounted the root filesystem.
  */
-int devtmpfs_mount(const char *mntdir)
+int devtmpfs_mount(void)
 {
        int err;
 
@@ -369,7 +369,7 @@ int devtmpfs_mount(const char *mntdir)
        if (!thread)
                return 0;
 
-       err = ksys_mount("devtmpfs", mntdir, "devtmpfs", MS_SILENT, NULL);
+       err = do_mount("devtmpfs", "dev", "devtmpfs", MS_SILENT, NULL);
        if (err)
                printk(KERN_INFO "devtmpfs: error mounting %i\n", err);
        else
@@ -394,7 +394,7 @@ static int devtmpfsd(void *p)
        *err = ksys_unshare(CLONE_NEWNS);
        if (*err)
                goto out;
-       *err = ksys_mount("devtmpfs", "/", "devtmpfs", MS_SILENT, NULL);
+       *err = do_mount("devtmpfs", "/", "devtmpfs", MS_SILENT, NULL);
        if (*err)
                goto out;
        ksys_chdir("/.."); /* will traverse into overmounted root */

diff --git a/include/linux/device.h b/include/linux/device.h
index e226030..96ff767 100644 (file)
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -1666,11 +1666,11 @@ extern bool kill_device(struct device *dev);
 #ifdef CONFIG_DEVTMPFS
 extern int devtmpfs_create_node(struct device *dev);
 extern int devtmpfs_delete_node(struct device *dev);
-extern int devtmpfs_mount(const char *mntdir);
+extern int devtmpfs_mount(void);
 #else
 static inline int devtmpfs_create_node(struct device *dev) { return 0; }
 static inline int devtmpfs_delete_node(struct device *dev) { return 0; }
-static inline int devtmpfs_mount(const char *mountpoint) { return 0; }
+static inline int devtmpfs_mount(void) { return 0; }
 #endif
 
 /* drivers/base/power/shutdown.c */

diff --git a/init/do_mounts.c b/init/do_mounts.c
index af9cda8..43f6d09 100644 (file)
--- a/init/do_mounts.c
+++ b/init/do_mounts.c
@@ -670,7 +670,7 @@ void __init prepare_namespace(void)
 
        mount_root();
 out:
-       devtmpfs_mount("dev");
+       devtmpfs_mount();
        ksys_mount(".", "/", NULL, MS_MOVE, NULL);
        ksys_chroot(".");
 }