Commit b724e846 authored by Dominik Brodowski's avatar Dominik Brodowski
Browse files

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

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

Introducing the ksys_symlink() wrapper allows us to avoid the in-kernel
calls to the sys_symlink() 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_symlink().

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 0101db7a

fs/internal.h

+2 −0
Original line number Diff line number Diff line
@@ -58,6 +58,8 @@ extern int vfs_path_lookup(struct dentry *, struct vfsmount *, 
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);

long do_symlinkat(const char __user *oldname, int newdfd,

		  const char __user *newname);



/*

 * namespace.c

fs/namei.c

+9 −3
Original line number Diff line number Diff line
@@ -4113,8 +4113,8 @@ int vfs_symlink(struct inode *dir, struct dentry *dentry, const char *oldname) 
}

EXPORT_SYMBOL(vfs_symlink);



SYSCALL_DEFINE3(symlinkat, const char __user *, oldname,

		int, newdfd, const char __user *, newname)

long do_symlinkat(const char __user *oldname, int newdfd,

		  const char __user *newname)

{

	int error;

	struct filename *from;
@@ -4144,9 +4144,15 @@ out_putname: 
	return error;

}



SYSCALL_DEFINE3(symlinkat, const char __user *, oldname,

		int, newdfd, const char __user *, newname)

{

	return do_symlinkat(oldname, newdfd, newname);

}



SYSCALL_DEFINE2(symlink, const char __user *, oldname, const char __user *, newname)

{

	return sys_symlinkat(oldname, AT_FDCWD, newname);

	return do_symlinkat(oldname, AT_FDCWD, newname);

}



/**

include/linux/syscalls.h

+9 −0
Original line number Diff line number Diff line
@@ -979,4 +979,13 @@ static inline long ksys_mkdir(const char __user *pathname, umode_t mode) 
	return do_mkdirat(AT_FDCWD, pathname, mode);

}



extern long do_symlinkat(const char __user *oldname, int newdfd,

			 const char __user *newname);



static inline long ksys_symlink(const char __user *oldname,

				const char __user *newname)

{

	return do_symlinkat(oldname, AT_FDCWD, newname);

}



#endif

init/initramfs.c

+1 −1
Original line number Diff line number Diff line
@@ -392,7 +392,7 @@ static int __init do_symlink(void) 
{

	collected[N_ALIGN(name_len) + body_len] = '\0';

	clean_path(collected, 0);

	sys_symlink(collected + N_ALIGN(name_len), collected);

	ksys_symlink(collected + N_ALIGN(name_len), collected);

	sys_lchown(collected, uid, gid);

	do_utime(collected, mtime);

	state = SkipIt;

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