Commit 03450e27 authored by Dominik Brodowski's avatar Dominik Brodowski
Browse files

fs: add ksys_fchmod() and do_fchmodat() helpers and ksys_chmod() wrapper;... 

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

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: default avatarDominik Brodowski <linux@dominikbrodowski.net>
parent 46ea89eb

fs/internal.h

+2 −0
Original line number Diff line number Diff line
@@ -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 *);

fs/open.c

+14 −3
Original line number Diff line number Diff line
@@ -551,7 +551,7 @@ out_unlock: 
	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 @@ retry: 
	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)

include/linux/syscalls.h

+8 −0
Original line number Diff line number Diff line
@@ -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

init/initramfs.c

+3 −3
Original line number Diff line number Diff line
@@ -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);

		}

	}

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