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authorKay Sievers <kay.sievers@vrfy.org>2009-04-30 15:23:42 +0200
committerGreg Kroah-Hartman <gregkh@suse.de>2009-09-15 09:50:49 -0700
commit2b2af54a5bb6f7e80ccf78f20084b93c398c3a8b (patch)
treebb27e3b16a2a8fadeea869033a406f0a19b63e29 /init
parentea5ffff57dce2f4c85ab056f4b0a202f71db2bdf (diff)
Driver Core: devtmpfs - kernel-maintained tmpfs-based /dev
Devtmpfs lets the kernel create a tmpfs instance called devtmpfs very early at kernel initialization, before any driver-core device is registered. Every device with a major/minor will provide a device node in devtmpfs. Devtmpfs can be changed and altered by userspace at any time, and in any way needed - just like today's udev-mounted tmpfs. Unmodified udev versions will run just fine on top of it, and will recognize an already existing kernel-created device node and use it. The default node permissions are root:root 0600. Proper permissions and user/group ownership, meaningful symlinks, all other policy still needs to be applied by userspace. If a node is created by devtmps, devtmpfs will remove the device node when the device goes away. If the device node was created by userspace, or the devtmpfs created node was replaced by userspace, it will no longer be removed by devtmpfs. If it is requested to auto-mount it, it makes init=/bin/sh work without any further userspace support. /dev will be fully populated and dynamic, and always reflect the current device state of the kernel. With the commonly used dynamic device numbers, it solves the problem where static devices nodes may point to the wrong devices. It is intended to make the initial bootup logic simpler and more robust, by de-coupling the creation of the inital environment, to reliably run userspace processes, from a complex userspace bootstrap logic to provide a working /dev. Signed-off-by: Kay Sievers <kay.sievers@vrfy.org> Signed-off-by: Jan Blunck <jblunck@suse.de> Tested-By: Harald Hoyer <harald@redhat.com> Tested-By: Scott James Remnant <scott@ubuntu.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'init')
-rw-r--r--init/do_mounts.c2
-rw-r--r--init/main.c2
2 files changed, 3 insertions, 1 deletions
diff --git a/init/do_mounts.c b/init/do_mounts.c
index 093f6591550..bb008d064c1 100644
--- a/init/do_mounts.c
+++ b/init/do_mounts.c
@@ -415,7 +415,7 @@ void __init prepare_namespace(void)
mount_root();
out:
+ devtmpfs_mount("dev");
sys_mount(".", "/", NULL, MS_MOVE, NULL);
sys_chroot(".");
}
-
diff --git a/init/main.c b/init/main.c
index b34fd8e5ede..8e6a7846bd0 100644
--- a/init/main.c
+++ b/init/main.c
@@ -68,6 +68,7 @@
#include <linux/async.h>
#include <linux/kmemcheck.h>
#include <linux/kmemtrace.h>
+#include <linux/shmem_fs.h>
#include <trace/boot.h>
#include <asm/io.h>
@@ -809,6 +810,7 @@ static void __init do_basic_setup(void)
init_workqueues();
cpuset_init_smp();
usermodehelper_init();
+ init_tmpfs();
driver_init();
init_irq_proc();
do_ctors();