Commit 87c4e192 authored by Dominik Brodowski's avatar Dominik Brodowski
Browse files

fs: add do_mknodat() helper and ksys_mknod() wrapper; remove in-kernel calls to syscall 

Using the fs-internal do_mknodat() helper allows us to get rid of
fs-internal calls to the sys_mknodat() syscall.

Introducing the ksys_mknod() wrapper allows us to avoid the in-kernel
calls to sys_mknod() 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_mknod().

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: Al Viro <viro@zeniv.linux.org.uk>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarDominik Brodowski <linux@dominikbrodowski.net>
parent b724e846

fs/internal.h

+2 −0
Original line number Diff line number Diff line
@@ -55,6 +55,8 @@ extern void __init chrdev_init(void); 
extern int user_path_mountpoint_at(int, const char __user *, unsigned int, struct path *);

extern int vfs_path_lookup(struct dentry *, struct vfsmount *,

			   const char *, unsigned int, struct path *);

long do_mknodat(int dfd, const char __user *filename, umode_t mode,

		unsigned int dev);

long do_mkdirat(int dfd, const char __user *pathname, umode_t mode);

long do_rmdir(int dfd, const char __user *pathname);

long do_unlinkat(int dfd, struct filename *name);

fs/namei.c

+9 −3
Original line number Diff line number Diff line
@@ -3728,8 +3728,8 @@ static int may_mknod(umode_t mode) 
	}

}



SYSCALL_DEFINE4(mknodat, int, dfd, const char __user *, filename, umode_t, mode,

		unsigned, dev)

long do_mknodat(int dfd, const char __user *filename, umode_t mode,

		unsigned int dev)

{

	struct dentry *dentry;

	struct path path;
@@ -3772,9 +3772,15 @@ out: 
	return error;

}



SYSCALL_DEFINE4(mknodat, int, dfd, const char __user *, filename, umode_t, mode,

		unsigned int, dev)

{

	return do_mknodat(dfd, filename, mode, dev);

}



SYSCALL_DEFINE3(mknod, const char __user *, filename, umode_t, mode, unsigned, dev)

{

	return sys_mknodat(AT_FDCWD, filename, mode, dev);

	return do_mknodat(AT_FDCWD, filename, mode, dev);

}



int vfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)

include/linux/syscalls.h

+9 −0
Original line number Diff line number Diff line
@@ -988,4 +988,13 @@ static inline long ksys_symlink(const char __user *oldname, 
	return do_symlinkat(oldname, AT_FDCWD, newname);

}



extern long do_mknodat(int dfd, const char __user *filename, umode_t mode,

		       unsigned int dev);



static inline long ksys_mknod(const char __user *filename, umode_t mode,

			      unsigned int dev)

{

	return do_mknodat(AT_FDCWD, filename, mode, dev);

}



#endif

init/do_mounts.h

+1 −1
Original line number Diff line number Diff line
@@ -17,7 +17,7 @@ extern int root_mountflags; 
static inline int create_dev(char *name, dev_t dev)

{

	ksys_unlink(name);

	return sys_mknod(name, S_IFBLK|0600, new_encode_dev(dev));

	return ksys_mknod(name, S_IFBLK|0600, new_encode_dev(dev));

}



static inline u32 bstat(char *name)

init/initramfs.c

+1 −1
Original line number Diff line number Diff line
@@ -359,7 +359,7 @@ static int __init do_name(void) 
	} else if (S_ISBLK(mode) || S_ISCHR(mode) ||

		   S_ISFIFO(mode) || S_ISSOCK(mode)) {

		if (maybe_link() == 0) {

			sys_mknod(collected, mode, rdev);

			ksys_mknod(collected, mode, rdev);

			sys_chown(collected, uid, gid);

			sys_chmod(collected, mode);

			do_utime(collected, mtime);

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