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fs: add ksys_fchmod() and do_fchmodat() helpers and ksys_chmod() wrapper; remove in-kernel calls to syscall

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

Introducing the ksys_fchmod() helper and the ksys_chmod() wrapper allows
us to avoid the in-kernel calls to the sys_fchmod() and sys_chmod()
syscalls. The ksys_ prefix denotes that these functions are meant as a
drop-in replacement for the syscalls. In particular, they use the same
calling convention as sys_fchmod() and sys_chmod().

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 11:34:53 +01:00
parent 46ea89eb65
commit 03450e271a
4 changed files with 27 additions and 6 deletions
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2
fs/internal.h
View File

@ -119,6 +119,8 @@ extern struct file *do_filp_open(int dfd, struct filename *pathname,
extern struct file *do_file_open_root(struct dentry *, struct vfsmount *,
const char *, const struct open_flags *);
int do_fchmodat(int dfd, const char __user *filename, umode_t mode);
extern int open_check_o_direct(struct file *f);
extern int vfs_open(const struct path *, struct file *, const struct cred *);
extern struct file *filp_clone_open(struct file *);

17
fs/open.c
View File

@ -551,7 +551,7 @@ static int chmod_common(const struct path *path, umode_t mode)
return error;
}
SYSCALL_DEFINE2(fchmod, unsigned int, fd, umode_t, mode)
int ksys_fchmod(unsigned int fd, umode_t mode)
{
struct fd f = fdget(fd);
int err = -EBADF;
@ -564,7 +564,12 @@ SYSCALL_DEFINE2(fchmod, unsigned int, fd, umode_t, mode)
return err;
}
SYSCALL_DEFINE3(fchmodat, int, dfd, const char __user *, filename, umode_t, mode)
SYSCALL_DEFINE2(fchmod, unsigned int, fd, umode_t, mode)
{
return ksys_fchmod(fd, mode);
}
int do_fchmodat(int dfd, const char __user *filename, umode_t mode)
{
struct path path;
int error;
@ -582,9 +587,15 @@ SYSCALL_DEFINE3(fchmodat, int, dfd, const char __user *, filename, umode_t, mode
return error;
}
SYSCALL_DEFINE3(fchmodat, int, dfd, const char __user *, filename,
umode_t, mode)
{
return do_fchmodat(dfd, filename, mode);
}
SYSCALL_DEFINE2(chmod, const char __user *, filename, umode_t, mode)
{
return sys_fchmodat(AT_FDCWD, filename, mode);
return do_fchmodat(AT_FDCWD, filename, mode);
}
static int chown_common(const struct path *path, uid_t user, gid_t group)

8
include/linux/syscalls.h
View File

@ -953,6 +953,7 @@ 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);
int ksys_fchmod(unsigned int fd, umode_t mode);
/*
* The following kernel syscall equivalents are just wrappers to fs-internal
@ -1006,4 +1007,11 @@ static inline long ksys_link(const char __user *oldname,
return do_linkat(AT_FDCWD, oldname, AT_FDCWD, newname, 0);
}
extern int do_fchmodat(int dfd, const char __user *filename, umode_t mode);
static inline int ksys_chmod(const char __user *filename, umode_t mode)
{
return do_fchmodat(AT_FDCWD, filename, mode);
}
#endif

6
init/initramfs.c
View File

@ -344,7 +344,7 @@ static int __init do_name(void)
if (wfd >= 0) {
sys_fchown(wfd, uid, gid);
sys_fchmod(wfd, mode);
ksys_fchmod(wfd, mode);
if (body_len)
sys_ftruncate(wfd, body_len);
vcollected = kstrdup(collected, GFP_KERNEL);
@ -354,14 +354,14 @@ static int __init do_name(void)
} else if (S_ISDIR(mode)) {
ksys_mkdir(collected, mode);
sys_chown(collected, uid, gid);
sys_chmod(collected, mode);
ksys_chmod(collected, mode);
dir_add(collected, mtime);
} else if (S_ISBLK(mode) || S_ISCHR(mode) ||
S_ISFIFO(mode) || S_ISSOCK(mode)) {
if (maybe_link() == 0) {
ksys_mknod(collected, mode, rdev);
sys_chown(collected, uid, gid);
sys_chmod(collected, mode);
ksys_chmod(collected, mode);
do_utime(collected, mtime);
}
}