Merge branch 'remove-ksys-mount-dup' of git://git.kernel.org/pub/scm/linux/kernel/git/brodo/linux

Pull ksys_mount() and ksys_dup() removal from Dominik Brodowski:
 "This small series replaces all in-kernel calls to the
  userspace-focused ksys_mount() and ksys_dup() with calls to
  kernel-centric functions:

  For each replacement of ksys_mount() with do_mount(), one needs to
  verify that the first and third parameter (char *dev_name, char *type)
  are strings allocated in kernelspace and that the fifth parameter
  (void *data) is either NULL or refers to a full page (only occurence
  in init/do_mounts.c::do_mount_root()). The second and fourth
  parameters (char *dir_name, unsigned long flags) are passed by
  ksys_mount() to do_mount() unchanged, and therefore do not require
  particular care.

  Moreover, instead of pretending to be userspace, the opening of
  /dev/console as stdin/stdout/stderr can be implemented using in-kernel
  functions as well. Thereby, ksys_dup() can be removed for good"

[ This doesn't get rid of the special "kernel init runs with KERNEL_DS"
  case, but it at least removes _some_ of the users of "treat kernel
  pointers as user pointers for our magical init sequence".

  One day we'll hopefully be rid of it all, and can initialize our
  init_thread addr_limit to USER_DS.    - Linus ]

* 'remove-ksys-mount-dup' of git://git.kernel.org/pub/scm/linux/kernel/git/brodo/linux:
  fs: remove ksys_dup()
  init: unify opening /dev/console as stdin/stdout/stderr
  init: use do_mount() instead of ksys_mount()
  initrd: use do_mount() instead of ksys_mount()
  devtmpfs: use do_mount() instead of ksys_mount()

Author: torvalds

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 */

fs/file.c

@@ -960,7 +960,7 @@ SYSCALL_DEFINE2(dup2, unsigned int, oldfd, unsigned int, newfd)
 	return ksys_dup3(oldfd, newfd, 0);
 }
 
-int ksys_dup(unsigned int fildes)
+SYSCALL_DEFINE1(dup, unsigned int, fildes)
 {
 	int ret = -EBADF;
 	struct file *file = fget_raw(fildes);
@@ -975,11 +975,6 @@ int ksys_dup(unsigned int fildes)
 	return ret;
 }
 
-SYSCALL_DEFINE1(dup, unsigned int, fildes)
-{
-	return ksys_dup(fildes);
-}
-
 int f_dupfd(unsigned int from, struct file *file, unsigned flags)
 {
 	int err;

fs/namespace.c

@@ -3325,8 +3325,8 @@ struct dentry *mount_subtree(struct vfsmount *m, const char *name)
 }
 EXPORT_SYMBOL(mount_subtree);
 
-int ksys_mount(const char __user *dev_name, const char __user *dir_name,
-	       const char __user *type, unsigned long flags, void __user *data)
+SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name,
+		char __user *, type, unsigned long, flags, void __user *, data)
 {
 	int ret;
 	char *kernel_type;
@@ -3359,12 +3359,6 @@ int ksys_mount(const char __user *dev_name, const 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);
-}
-
 /*
  * Create a kernel mount representation for a new, prepared superblock
  * (specified by fs_fd) and attach to an open_tree-like file descriptor.

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 */

include/linux/initrd.h

@@ -28,3 +28,5 @@ extern unsigned int real_root_dev;
 
 extern char __initramfs_start[];
 extern unsigned long __initramfs_size;
+
+void console_on_rootfs(void);

include/linux/syscalls.h

@@ -1231,10 +1231,7 @@ asmlinkage long sys_ni_syscall(void);
  * the ksys_xyzyyz() functions prototyped below.
  */
 
-int ksys_mount(const char __user *dev_name, const char __user *dir_name,
-	       const char __user *type, unsigned long flags, void __user *data);
 int ksys_umount(char __user *name, int flags);
-int ksys_dup(unsigned int fildes);
 int ksys_chroot(const char __user *filename);
 ssize_t ksys_write(unsigned int fd, const char __user *buf, size_t count);
 int ksys_chdir(const char __user *filename);

init/do_mounts.c

@@ -387,12 +387,25 @@ static void __init get_fs_names(char *page)
 	*s = '\0';
 }
 
-static int __init do_mount_root(char *name, char *fs, int flags, void *data)
+static int __init do_mount_root(const char *name, const char *fs,
+				 const int flags, const void *data)
 {
 	struct super_block *s;
-	int err = ksys_mount(name, "/root", fs, flags, data);
-	if (err)
-		return err;
+	char *data_page;
+	struct page *p;
+	int ret;
+
+	/* do_mount() requires a full page as fifth argument */
+	p = alloc_page(GFP_KERNEL);
+	if (!p)
+		return -ENOMEM;
+
+	data_page = page_address(p);
+	strncpy(data_page, data, PAGE_SIZE - 1);
+
+	ret = do_mount(name, "/root", fs, flags, data_page);
+	if (ret)
+		goto out;
 
 	ksys_chdir("/root");
 	s = current->fs->pwd.dentry->d_sb;
@@ -402,7 +415,10 @@ static int __init do_mount_root(char *name, char *fs, int flags, void *data)
 	       s->s_type->name,
 	       sb_rdonly(s) ? " readonly" : "",
 	       MAJOR(ROOT_DEV), MINOR(ROOT_DEV));
-	return 0;
+
+out:
+	put_page(p);
+	return ret;
 }
 
 void __init mount_block_root(char *name, int flags)
@@ -670,8 +686,8 @@ void __init prepare_namespace(void)
 
 	mount_root();
 out:
-	devtmpfs_mount("dev");
-	ksys_mount(".", "/", NULL, MS_MOVE, NULL);
+	devtmpfs_mount();
+	do_mount(".", "/", NULL, MS_MOVE, NULL);
 	ksys_chroot(".");
 }
 

init/do_mounts_initrd.c

@@ -48,13 +48,10 @@ early_param("initrd", early_initrd);
 static int init_linuxrc(struct subprocess_info *info, struct cred *new)
 {
 	ksys_unshare(CLONE_FS | CLONE_FILES);
-	/* stdin/stdout/stderr for /linuxrc */
-	ksys_open("/dev/console", O_RDWR, 0);
-	ksys_dup(0);
-	ksys_dup(0);
+	console_on_rootfs();
 	/* move initrd over / and chdir/chroot in initrd root */
 	ksys_chdir("/root");
-	ksys_mount(".", "/", NULL, MS_MOVE, NULL);
+	do_mount(".", "/", NULL, MS_MOVE, NULL);
 	ksys_chroot(".");
 	ksys_setsid();
 	return 0;
@@ -89,7 +86,7 @@ static void __init handle_initrd(void)
 	current->flags &= ~PF_FREEZER_SKIP;
 
 	/* move initrd to rootfs' /old */
-	ksys_mount("..", ".", NULL, MS_MOVE, NULL);
+	do_mount("..", ".", NULL, MS_MOVE, NULL);
 	/* switch root and cwd back to / of rootfs */
 	ksys_chroot("..");
 
@@ -103,7 +100,7 @@ static void __init handle_initrd(void)
 	mount_root();
 
 	printk(KERN_NOTICE "Trying to move old root to /initrd ... ");
-	error = ksys_mount("/old", "/root/initrd", NULL, MS_MOVE, NULL);
+	error = do_mount("/old", "/root/initrd", NULL, MS_MOVE, NULL);
 	if (!error)
 		printk("okay\n");
 	else {

init/main.c

@@ -93,6 +93,7 @@
 #include <linux/rodata_test.h>
 #include <linux/jump_label.h>
 #include <linux/mem_encrypt.h>
+#include <linux/file.h>
 
 #include <asm/io.h>
 #include <asm/bugs.h>
@@ -1155,6 +1156,30 @@ static int __ref kernel_init(void *unused)
 	      "See Linux Documentation/admin-guide/init.rst for guidance.");
 }
 
+void console_on_rootfs(void)
+{
+	struct file *file;
+	unsigned int i;
+
+	/* Open /dev/console in kernelspace, this should never fail */
+	file = filp_open("/dev/console", O_RDWR, 0);
+	if (!file)
+		goto err_out;
+
+	/* create stdin/stdout/stderr, this should never fail */
+	for (i = 0; i < 3; i++) {
+		if (f_dupfd(i, file, 0) != i)
+			goto err_out;
+	}
+
+	return;
+
+err_out:
+	/* no panic -- this might not be fatal */
+	pr_err("Warning: unable to open an initial console.\n");
+	return;
+}
+
 static noinline void __init kernel_init_freeable(void)
 {
 	/*
@@ -1190,12 +1215,8 @@ static noinline void __init kernel_init_freeable(void)
 
 	do_basic_setup();
 
-	/* Open the /dev/console on the rootfs, this should never fail */
-	if (ksys_open((const char __user *) "/dev/console", O_RDWR, 0) < 0)
-		pr_err("Warning: unable to open an initial console.\n");
+	console_on_rootfs();
 
-	(void) ksys_dup(0);
-	(void) ksys_dup(0);
 	/*
 	 * check if there is an early userspace init.  If yes, let it do all
 	 * the work