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

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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: Dominik Brodowski <linux@dominikbrodowski.net>
This commit is contained in:
Dominik Brodowski 2018-03-11 11:34:50 +01:00
parent b724e846b4
commit 87c4e19262
6 changed files with 23 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
fs/internal.h
View File

@ -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);

12
fs/namei.c
View File

@ -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)

9
include/linux/syscalls.h
View File

@ -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

2
init/do_mounts.h
View File

@ -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)

2
init/initramfs.c
View File

@ -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);

2
init/noinitramfs.c
View File

@ -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)