Using the fs-internal do_linkat() helper allows us to get rid of fs-internal calls to the sys_linkat() syscall. Introducing the ksys_link() wrapper allows us to avoid the in-kernel calls to sys_link() 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_link(). In the near future, the only fs-external user of ksys_link() should be converted to use vfs_link() instead. 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@xxxxxxxxxxxxxxxxxxxxxxxxxx Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Dominik Brodowski <linux@xxxxxxxxxxxxxxxxxxxx> --- 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 4f0b67054c54..91e6fc93fcb5 100644 --- a/fs/internal.h +++ b/fs/internal.h @@ -62,6 +62,8 @@ 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); +int do_linkat(int olddfd, const char __user *oldname, int newdfd, + const char __user *newname, int flags); /* * namespace.c diff --git a/fs/namei.c b/fs/namei.c index 8459a18cdd18..10148235829f 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -4250,8 +4250,8 @@ EXPORT_SYMBOL(vfs_link); * with linux 2.0, and to avoid hard-linking to directories * and other special files. --ADM */ -SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname, - int, newdfd, const char __user *, newname, int, flags) +int do_linkat(int olddfd, const char __user *oldname, int newdfd, + const char __user *newname, int flags) { struct dentry *new_dentry; struct path old_path, new_path; @@ -4315,9 +4315,15 @@ SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname, return error; } +SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname, + int, newdfd, const char __user *, newname, int, flags) +{ + return do_linkat(olddfd, oldname, newdfd, newname, flags); +} + SYSCALL_DEFINE2(link, const char __user *, oldname, const char __user *, newname) { - return sys_linkat(AT_FDCWD, oldname, AT_FDCWD, newname, 0); + return do_linkat(AT_FDCWD, oldname, AT_FDCWD, newname, 0); } /** diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h index 0b4fd684f0f1..827ed917630c 100644 --- a/include/linux/syscalls.h +++ b/include/linux/syscalls.h @@ -997,4 +997,13 @@ static inline long ksys_mknod(const char __user *filename, umode_t mode, return do_mknodat(AT_FDCWD, filename, mode, dev); } +extern int do_linkat(int olddfd, const char __user *oldname, int newdfd, + const char __user *newname, int flags); + +static inline long ksys_link(const char __user *oldname, + const char __user *newname) +{ + return do_linkat(AT_FDCWD, oldname, AT_FDCWD, newname, 0); +} + #endif diff --git a/init/initramfs.c b/init/initramfs.c index 2972ed0ab399..5855ab632b4e 100644 --- a/init/initramfs.c +++ b/init/initramfs.c @@ -306,7 +306,7 @@ static int __init maybe_link(void) if (nlink >= 2) { char *old = find_link(major, minor, ino, mode, collected); if (old) - return (sys_link(old, collected) < 0) ? -1 : 1; + return (ksys_link(old, collected) < 0) ? -1 : 1; } return 0; } -- 2.16.3
