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

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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: Dominik Brodowski <linux@dominikbrodowski.net>
This commit is contained in:
Dominik Brodowski 2018-03-11 11:34:49 +01:00
parent 0101db7a30
commit b724e846b4
4 changed files with 21 additions and 4 deletions
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2
fs/internal.h
View File

@ -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

12
fs/namei.c
View File

@ -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 @@ SYSCALL_DEFINE3(symlinkat, const char __user *, oldname,
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);
}
/**

9
include/linux/syscalls.h
View File

@ -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

2
init/initramfs.c
View File

@ -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;