fs: add ksys_mount() helper; remove in-kernel calls to sys_mount()
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@light.dominikbrodowski.net Cc: Alexander Viro <viro@zeniv.linux.org.uk> Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>
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@ -356,7 +356,8 @@ int devtmpfs_mount(const char *mntdir)
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if (!thread)
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return 0;
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err = sys_mount("devtmpfs", (char *)mntdir, "devtmpfs", MS_SILENT, NULL);
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err = ksys_mount("devtmpfs", (char *)mntdir, "devtmpfs", MS_SILENT,
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NULL);
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if (err)
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printk(KERN_INFO "devtmpfs: error mounting %i\n", err);
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else
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@ -382,7 +383,7 @@ static int devtmpfsd(void *p)
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*err = sys_unshare(CLONE_NEWNS);
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if (*err)
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goto out;
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*err = sys_mount("devtmpfs", "/", "devtmpfs", MS_SILENT, options);
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*err = ksys_mount("devtmpfs", "/", "devtmpfs", MS_SILENT, options);
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if (*err)
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goto out;
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sys_chdir("/.."); /* will traverse into overmounted root */
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@ -3032,8 +3032,8 @@ struct dentry *mount_subtree(struct vfsmount *mnt, const char *name)
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}
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EXPORT_SYMBOL(mount_subtree);
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SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name,
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char __user *, type, unsigned long, flags, void __user *, data)
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int ksys_mount(char __user *dev_name, char __user *dir_name, char __user *type,
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unsigned long flags, void __user *data)
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{
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int ret;
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char *kernel_type;
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@ -3066,6 +3066,12 @@ out_type:
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return ret;
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}
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SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name,
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char __user *, type, unsigned long, flags, void __user *, data)
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{
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return ksys_mount(dev_name, dir_name, type, flags, data);
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}
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/*
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* Return true if path is reachable from root
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*
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@ -946,4 +946,7 @@ asmlinkage long sys_statx(int dfd, const char __user *path, unsigned flags,
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* the ksys_xyzyyz() functions prototyped below.
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*/
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int ksys_mount(char __user *dev_name, char __user *dir_name, char __user *type,
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unsigned long flags, void __user *data);
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#endif
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@ -363,7 +363,7 @@ static void __init get_fs_names(char *page)
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static int __init do_mount_root(char *name, char *fs, int flags, void *data)
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{
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struct super_block *s;
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int err = sys_mount(name, "/root", fs, flags, data);
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int err = ksys_mount(name, "/root", fs, flags, data);
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if (err)
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return err;
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@ -599,7 +599,7 @@ void __init prepare_namespace(void)
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mount_root();
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out:
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devtmpfs_mount("dev");
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sys_mount(".", "/", NULL, MS_MOVE, NULL);
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ksys_mount(".", "/", NULL, MS_MOVE, NULL);
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sys_chroot(".");
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}
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@ -43,7 +43,7 @@ static int init_linuxrc(struct subprocess_info *info, struct cred *new)
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sys_dup(0);
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/* move initrd over / and chdir/chroot in initrd root */
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sys_chdir("/root");
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sys_mount(".", "/", NULL, MS_MOVE, NULL);
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ksys_mount(".", "/", NULL, MS_MOVE, NULL);
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sys_chroot(".");
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sys_setsid();
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return 0;
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@ -81,7 +81,7 @@ static void __init handle_initrd(void)
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current->flags &= ~PF_FREEZER_SKIP;
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/* move initrd to rootfs' /old */
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sys_mount("..", ".", NULL, MS_MOVE, NULL);
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ksys_mount("..", ".", NULL, MS_MOVE, NULL);
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/* switch root and cwd back to / of rootfs */
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sys_chroot("..");
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@ -95,7 +95,7 @@ static void __init handle_initrd(void)
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mount_root();
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printk(KERN_NOTICE "Trying to move old root to /initrd ... ");
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error = sys_mount("/old", "/root/initrd", NULL, MS_MOVE, NULL);
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error = ksys_mount("/old", "/root/initrd", NULL, MS_MOVE, NULL);
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if (!error)
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printk("okay\n");
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else {
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