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Subject[PATCH 1/3] devtmpfs: use do_mount() instead of ksys_mount()
Date
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>
---
drivers/base/devtmpfs.c | 6 +++---
include/linux/device.h | 4 ++--
init/do_mounts.c | 2 +-
3 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/base/devtmpfs.c b/drivers/base/devtmpfs.c
index 30d0523014e0..6cdbf1531238 100644
--- 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 e226030c1df3..96ff76731e93 100644
--- 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 af9cda887a23..43f6d098c880 100644
--- 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(".");
}
--
2.24.1
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