Using this helper allows us to avoid the in-kernel calls to the sys_unshare() 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_unshare(). 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> Cc: Ingo Molnar <mingo@xxxxxxxxxx> Signed-off-by: Dominik Brodowski <linux@xxxxxxxxxxxxxxxxxxxx> --- drivers/base/devtmpfs.c | 2 +- include/linux/syscalls.h | 1 + init/do_mounts_initrd.c | 2 +- kernel/fork.c | 7 ++++++- 4 files changed, 9 insertions(+), 3 deletions(-) diff --git a/drivers/base/devtmpfs.c b/drivers/base/devtmpfs.c index 3f7ee954fd2c..f7768077e817 100644 --- a/drivers/base/devtmpfs.c +++ b/drivers/base/devtmpfs.c @@ -380,7 +380,7 @@ static int devtmpfsd(void *p) { char options[] = "mode=0755"; int *err = p; - *err = sys_unshare(CLONE_NEWNS); + *err = ksys_unshare(CLONE_NEWNS); if (*err) goto out; *err = ksys_mount("devtmpfs", "/", "devtmpfs", MS_SILENT, options); diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h index 0a9942b3e718..e724dda509e0 100644 --- a/include/linux/syscalls.h +++ b/include/linux/syscalls.h @@ -961,6 +961,7 @@ int ksys_ioctl(unsigned int fd, unsigned int cmd, unsigned long arg); off_t ksys_lseek(unsigned int fd, off_t offset, unsigned int whence); ssize_t ksys_read(unsigned int fd, char __user *buf, size_t count); void ksys_sync(void); +int ksys_unshare(unsigned long unshare_flags); /* * The following kernel syscall equivalents are just wrappers to fs-internal diff --git a/init/do_mounts_initrd.c b/init/do_mounts_initrd.c index 03ec0c1b7553..d1d3e53bdeef 100644 --- a/init/do_mounts_initrd.c +++ b/init/do_mounts_initrd.c @@ -36,7 +36,7 @@ __setup("noinitrd", no_initrd); static int init_linuxrc(struct subprocess_info *info, struct cred *new) { - sys_unshare(CLONE_FS | CLONE_FILES); + ksys_unshare(CLONE_FS | CLONE_FILES); /* stdin/stdout/stderr for /linuxrc */ ksys_open("/dev/console", O_RDWR, 0); ksys_dup(0); diff --git a/kernel/fork.c b/kernel/fork.c index b1e031aac9db..f71b67dc156d 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -2354,7 +2354,7 @@ static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp * constructed. Here we are modifying the current, active, * task_struct. */ -SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags) +int ksys_unshare(unsigned long unshare_flags) { struct fs_struct *fs, *new_fs = NULL; struct files_struct *fd, *new_fd = NULL; @@ -2470,6 +2470,11 @@ SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags) return err; } +SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags) +{ + return ksys_unshare(unshare_flags); +} + /* * Helper to unshare the files of the current task. * We don't want to expose copy_files internals to -- 2.16.3
