Using this helper allows us to avoid the in-kernel calls to the sys_mount() 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_mount(). In the near future, all callers of ksys_mount() should be converted to call do_mount() directly. 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@xxxxxxxxxxxxxxxxxxxxxxxxxx Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx> Signed-off-by: Dominik Brodowski <linux@xxxxxxxxxxxxxxxxxxxx> --- drivers/base/devtmpfs.c | 5 +++-- fs/namespace.c | 10 ++++++++-- include/linux/syscalls.h | 3 +++ init/do_mounts.c | 4 ++-- init/do_mounts_initrd.c | 6 +++--- 5 files changed, 19 insertions(+), 9 deletions(-) diff --git a/drivers/base/devtmpfs.c b/drivers/base/devtmpfs.c index 50025d7959cb..4afb04686c8e 100644 --- a/drivers/base/devtmpfs.c +++ b/drivers/base/devtmpfs.c @@ -356,7 +356,8 @@ int devtmpfs_mount(const char *mntdir) if (!thread) return 0; - err = sys_mount("devtmpfs", (char *)mntdir, "devtmpfs", MS_SILENT, NULL); + err = ksys_mount("devtmpfs", (char *)mntdir, "devtmpfs", MS_SILENT, + NULL); if (err) printk(KERN_INFO "devtmpfs: error mounting %i\n", err); else @@ -382,7 +383,7 @@ static int devtmpfsd(void *p) *err = sys_unshare(CLONE_NEWNS); if (*err) goto out; - *err = sys_mount("devtmpfs", "/", "devtmpfs", MS_SILENT, options); + *err = ksys_mount("devtmpfs", "/", "devtmpfs", MS_SILENT, options); if (*err) goto out; sys_chdir("/.."); /* will traverse into overmounted root */ diff --git a/fs/namespace.c b/fs/namespace.c index 9d1374ab6e06..642b8b229944 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -3032,8 +3032,8 @@ struct dentry *mount_subtree(struct vfsmount *mnt, const char *name) } EXPORT_SYMBOL(mount_subtree); -SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name, - char __user *, type, unsigned long, flags, void __user *, data) +int ksys_mount(char __user *dev_name, char __user *dir_name, char __user *type, + unsigned long flags, void __user *data) { int ret; char *kernel_type; @@ -3066,6 +3066,12 @@ SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name, return ret; } +SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name, + char __user *, type, unsigned long, flags, void __user *, data) +{ + return ksys_mount(dev_name, dir_name, type, flags, data); +} + /* * Return true if path is reachable from root * diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h index 6ab7ed71a8b6..3a9f9c534624 100644 --- a/include/linux/syscalls.h +++ b/include/linux/syscalls.h @@ -946,4 +946,7 @@ asmlinkage long sys_statx(int dfd, const char __user *path, unsigned flags, * the ksys_xyzyyz() functions prototyped below. */ +int ksys_mount(char __user *dev_name, char __user *dir_name, char __user *type, + unsigned long flags, void __user *data); + #endif diff --git a/init/do_mounts.c b/init/do_mounts.c index 7cf4f6dafd5f..eb768de43d84 100644 --- a/init/do_mounts.c +++ b/init/do_mounts.c @@ -363,7 +363,7 @@ static void __init get_fs_names(char *page) static int __init do_mount_root(char *name, char *fs, int flags, void *data) { struct super_block *s; - int err = sys_mount(name, "/root", fs, flags, data); + int err = ksys_mount(name, "/root", fs, flags, data); if (err) return err; @@ -599,7 +599,7 @@ void __init prepare_namespace(void) mount_root(); out: devtmpfs_mount("dev"); - sys_mount(".", "/", NULL, MS_MOVE, NULL); + ksys_mount(".", "/", NULL, MS_MOVE, NULL); sys_chroot("."); } diff --git a/init/do_mounts_initrd.c b/init/do_mounts_initrd.c index 53d4f0f326e7..7868a6039fb4 100644 --- a/init/do_mounts_initrd.c +++ b/init/do_mounts_initrd.c @@ -43,7 +43,7 @@ static int init_linuxrc(struct subprocess_info *info, struct cred *new) sys_dup(0); /* move initrd over / and chdir/chroot in initrd root */ sys_chdir("/root"); - sys_mount(".", "/", NULL, MS_MOVE, NULL); + ksys_mount(".", "/", NULL, MS_MOVE, NULL); sys_chroot("."); sys_setsid(); return 0; @@ -81,7 +81,7 @@ static void __init handle_initrd(void) current->flags &= ~PF_FREEZER_SKIP; /* move initrd to rootfs' /old */ - sys_mount("..", ".", NULL, MS_MOVE, NULL); + ksys_mount("..", ".", NULL, MS_MOVE, NULL); /* switch root and cwd back to / of rootfs */ sys_chroot(".."); @@ -95,7 +95,7 @@ static void __init handle_initrd(void) mount_root(); printk(KERN_NOTICE "Trying to move old root to /initrd ... "); - error = sys_mount("/old", "/root/initrd", NULL, MS_MOVE, NULL); + error = ksys_mount("/old", "/root/initrd", NULL, MS_MOVE, NULL); if (!error) printk("okay\n"); else { -- 2.16.3
