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

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

Introducing the ksys_mkdir() wrapper allows us to avoid the in-kernel calls
to the sys_mkdir() 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_mkdir().

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 11:34:49 +01:00
parent f459dffae1
commit 0101db7a30
6 changed files with 19 additions and 6 deletions
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1
fs/internal.h
View File

@ -55,6 +55,7 @@ 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_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);

9
fs/namei.c
View File

@ -3803,7 +3803,7 @@ int vfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
}
EXPORT_SYMBOL(vfs_mkdir);
SYSCALL_DEFINE3(mkdirat, int, dfd, const char __user *, pathname, umode_t, mode)
long do_mkdirat(int dfd, const char __user *pathname, umode_t mode)
{
struct dentry *dentry;
struct path path;
@ -3828,9 +3828,14 @@ SYSCALL_DEFINE3(mkdirat, int, dfd, const char __user *, pathname, umode_t, mode)
return error;
}
SYSCALL_DEFINE3(mkdirat, int, dfd, const char __user *, pathname, umode_t, mode)
{
return do_mkdirat(dfd, pathname, mode);
}
SYSCALL_DEFINE2(mkdir, const char __user *, pathname, umode_t, mode)
{
return sys_mkdirat(AT_FDCWD, pathname, mode);
return do_mkdirat(AT_FDCWD, pathname, mode);
}
int vfs_rmdir(struct inode *dir, struct dentry *dentry)

7
include/linux/syscalls.h
View File

@ -972,4 +972,11 @@ static inline long ksys_rmdir(const char __user *pathname)
return do_rmdir(AT_FDCWD, pathname);
}
extern long do_mkdirat(int dfd, const char __user *pathname, umode_t mode);
static inline long ksys_mkdir(const char __user *pathname, umode_t mode)
{
return do_mkdirat(AT_FDCWD, pathname, mode);
}
#endif

2
init/do_mounts_initrd.c
View File

@ -60,7 +60,7 @@ static void __init handle_initrd(void)
create_dev("/dev/root.old", Root_RAM0);
/* mount initrd on rootfs' /root */
mount_block_root("/dev/root.old", root_mountflags & ~MS_RDONLY);
sys_mkdir("/old", 0700);
ksys_mkdir("/old", 0700);
ksys_chdir("/old");
/* try loading default modules from initrd */

2
init/initramfs.c
View File

@ -352,7 +352,7 @@ static int __init do_name(void)
}
}
} else if (S_ISDIR(mode)) {
sys_mkdir(collected, mode);
ksys_mkdir(collected, mode);
sys_chown(collected, uid, gid);
sys_chmod(collected, mode);
dir_add(collected, mtime);

4
init/noinitramfs.c
View File

@ -29,7 +29,7 @@ static int __init default_rootfs(void)
{
int err;
err = sys_mkdir((const char __user __force *) "/dev", 0755);
err = ksys_mkdir((const char __user __force *) "/dev", 0755);
if (err < 0)
goto out;
@ -39,7 +39,7 @@ static int __init default_rootfs(void)
if (err < 0)
goto out;
err = sys_mkdir((const char __user __force *) "/root", 0700);
err = ksys_mkdir((const char __user __force *) "/root", 0700);
if (err < 0)
goto out;