From 87c4e19262d81862886207be3c8795f6576d5a52 Mon Sep 17 00:00:00 2001 From: Dominik Brodowski Date: Sun, 11 Mar 2018 11:34:50 +0100 Subject: [PATCH] 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 Cc: Andrew Morton Signed-off-by: Dominik Brodowski --- fs/internal.h | 2 ++ fs/namei.c | 12 +++++++++--- include/linux/syscalls.h | 9 +++++++++ init/do_mounts.h | 2 +- init/initramfs.c | 2 +- init/noinitramfs.c | 2 +- 6 files changed, 23 insertions(+), 6 deletions(-) diff --git a/fs/internal.h b/fs/internal.h index a3f04ca2a08b..4f0b67054c54 100644 --- a/fs/internal.h +++ b/fs/internal.h @@ -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); diff --git a/fs/namei.c b/fs/namei.c index e15da92209d5..8459a18cdd18 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -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 @@ SYSCALL_DEFINE4(mknodat, int, dfd, const char __user *, filename, umode_t, mode, 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) diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h index 39c5cef86a10..0b4fd684f0f1 100644 --- a/include/linux/syscalls.h +++ b/include/linux/syscalls.h @@ -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 diff --git a/init/do_mounts.h b/init/do_mounts.h index 401f90ee1eeb..0bb0806de4ce 100644 --- a/init/do_mounts.h +++ b/init/do_mounts.h @@ -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) diff --git a/init/initramfs.c b/init/initramfs.c index cd9571a113b6..2972ed0ab399 100644 --- a/init/initramfs.c +++ b/init/initramfs.c @@ -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); diff --git a/init/noinitramfs.c b/init/noinitramfs.c index a08a9d937e60..f4bad8436c93 100644 --- a/init/noinitramfs.c +++ b/init/noinitramfs.c @@ -33,7 +33,7 @@ static int __init default_rootfs(void) if (err < 0) goto out; - err = sys_mknod((const char __user __force *) "/dev/console", + err = ksys_mknod((const char __user __force *) "/dev/console", S_IFCHR | S_IRUSR | S_IWUSR, new_encode_dev(MKDEV(5, 1))); if (err < 0) -- GitLab