Using this helper allows us to avoid the in-kernel calls to the sys_chdir() 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_chdir(). 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> --- drivers/base/devtmpfs.c | 2 +- fs/open.c | 7 ++++++- include/linux/syscalls.h | 1 + init/do_mounts.c | 2 +- init/do_mounts_initrd.c | 8 ++++---- 5 files changed, 13 insertions(+), 7 deletions(-) diff --git a/drivers/base/devtmpfs.c b/drivers/base/devtmpfs.c index 5743f04014ca..3f7ee954fd2c 100644 --- a/drivers/base/devtmpfs.c +++ b/drivers/base/devtmpfs.c @@ -386,7 +386,7 @@ static int devtmpfsd(void *p) *err = ksys_mount("devtmpfs", "/", "devtmpfs", MS_SILENT, options); if (*err) goto out; - sys_chdir("/.."); /* will traverse into overmounted root */ + ksys_chdir("/.."); /* will traverse into overmounted root */ ksys_chroot("."); complete(&setup_done); while (1) { diff --git a/fs/open.c b/fs/open.c index 7a475e8a2e41..a19b8277c439 100644 --- a/fs/open.c +++ b/fs/open.c @@ -431,7 +431,7 @@ SYSCALL_DEFINE2(access, const char __user *, filename, int, mode) return sys_faccessat(AT_FDCWD, filename, mode); } -SYSCALL_DEFINE1(chdir, const char __user *, filename) +int ksys_chdir(const char __user *filename) { struct path path; int error; @@ -457,6 +457,11 @@ SYSCALL_DEFINE1(chdir, const char __user *, filename) return error; } +SYSCALL_DEFINE1(chdir, const char __user *, filename) +{ + return ksys_chdir(filename); +} + SYSCALL_DEFINE1(fchdir, unsigned int, fd) { struct fd f = fdget_raw(fd); diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h index 80524faa9664..090645b48447 100644 --- a/include/linux/syscalls.h +++ b/include/linux/syscalls.h @@ -952,5 +952,6 @@ int ksys_umount(char __user *name, int flags); int ksys_dup(unsigned int fildes); int ksys_chroot(const char __user *filename); ssize_t ksys_write(unsigned int fd, const char __user *buf, size_t count); +int ksys_chdir(const char __user *filename); #endif diff --git a/init/do_mounts.c b/init/do_mounts.c index 2f06f7827b0c..89f18985fa90 100644 --- a/init/do_mounts.c +++ b/init/do_mounts.c @@ -367,7 +367,7 @@ static int __init do_mount_root(char *name, char *fs, int flags, void *data) if (err) return err; - sys_chdir("/root"); + ksys_chdir("/root"); s = current->fs->pwd.dentry->d_sb; ROOT_DEV = s->s_dev; printk(KERN_INFO diff --git a/init/do_mounts_initrd.c b/init/do_mounts_initrd.c index 71293265ac4b..83f396d30b9a 100644 --- a/init/do_mounts_initrd.c +++ b/init/do_mounts_initrd.c @@ -42,7 +42,7 @@ static int init_linuxrc(struct subprocess_info *info, struct cred *new) ksys_dup(0); ksys_dup(0); /* move initrd over / and chdir/chroot in initrd root */ - sys_chdir("/root"); + ksys_chdir("/root"); ksys_mount(".", "/", NULL, MS_MOVE, NULL); ksys_chroot("."); sys_setsid(); @@ -61,7 +61,7 @@ static void __init handle_initrd(void) /* mount initrd on rootfs' /root */ mount_block_root("/dev/root.old", root_mountflags & ~MS_RDONLY); sys_mkdir("/old", 0700); - sys_chdir("/old"); + ksys_chdir("/old"); /* try loading default modules from initrd */ load_default_modules(); @@ -86,11 +86,11 @@ static void __init handle_initrd(void) ksys_chroot(".."); if (new_decode_dev(real_root_dev) == Root_RAM0) { - sys_chdir("/old"); + ksys_chdir("/old"); return; } - sys_chdir("/"); + ksys_chdir("/"); ROOT_DEV = new_decode_dev(real_root_dev); mount_root(); -- 2.16.3
