From b724e846b491ef8db943be8086226c9d8da31877 Mon Sep 17 00:00:00 2001 From: Dominik Brodowski Date: Sun, 11 Mar 2018 11:34:49 +0100 Subject: [PATCH] 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 Cc: Andrew Morton Signed-off-by: Dominik Brodowski --- fs/internal.h | 2 ++ fs/namei.c | 12 +++++++++--- include/linux/syscalls.h | 9 +++++++++ init/initramfs.c | 2 +- 4 files changed, 21 insertions(+), 4 deletions(-) diff --git a/fs/internal.h b/fs/internal.h index 53846bd..a3f04ca 100644 --- a/fs/internal.h +++ b/fs/internal.h @@ -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 diff --git a/fs/namei.c b/fs/namei.c index dcf5062..e15da92 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -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); } /** diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h index c982cb5..39c5cef 100644 --- a/include/linux/syscalls.h +++ b/include/linux/syscalls.h @@ -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 diff --git a/init/initramfs.c b/init/initramfs.c index ca538a5..cd9571a 100644 --- a/init/initramfs.c +++ b/init/initramfs.c @@ -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; -- 2.7.4