From c7248321a3d42ffba78db0dde88d1c49ca1c045f Mon Sep 17 00:00:00 2001 From: Dominik Brodowski Date: Sun, 11 Mar 2018 11:34:40 +0100 Subject: [PATCH] fs: add ksys_dup{,3}() helper; remove in-kernel calls to sys_dup{,3}() Using ksys_dup() and ksys_dup3() as helper functions allows us to avoid the in-kernel calls to the sys_dup() and sys_dup3() syscalls. The ksys_ prefix denotes that these functions are meant as a drop-in replacement for the syscalls. In particular, they use the same calling convention as sys_dup{,3}(). In the near future, the fs-external callers of ksys_dup{,3}() should be converted to call do_dup2() directly. Then, ksys_dup{,3}() can be moved within sys_dup{,3}() again. 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: Alexander Viro Signed-off-by: Dominik Brodowski --- fs/file.c | 16 +++++++++++++--- include/linux/syscalls.h | 1 + init/do_mounts_initrd.c | 4 ++-- init/main.c | 4 ++-- 4 files changed, 18 insertions(+), 7 deletions(-) diff --git a/fs/file.c b/fs/file.c index 42f0db4bd0fb..d304004f0b65 100644 --- a/fs/file.c +++ b/fs/file.c @@ -870,7 +870,7 @@ int replace_fd(unsigned fd, struct file *file, unsigned flags) return err; } -SYSCALL_DEFINE3(dup3, unsigned int, oldfd, unsigned int, newfd, int, flags) +static int ksys_dup3(unsigned int oldfd, unsigned int newfd, int flags) { int err = -EBADF; struct file *file; @@ -904,6 +904,11 @@ SYSCALL_DEFINE3(dup3, unsigned int, oldfd, unsigned int, newfd, int, flags) return err; } +SYSCALL_DEFINE3(dup3, unsigned int, oldfd, unsigned int, newfd, int, flags) +{ + return ksys_dup3(oldfd, newfd, flags); +} + SYSCALL_DEFINE2(dup2, unsigned int, oldfd, unsigned int, newfd) { if (unlikely(newfd == oldfd)) { /* corner case */ @@ -916,10 +921,10 @@ SYSCALL_DEFINE2(dup2, unsigned int, oldfd, unsigned int, newfd) rcu_read_unlock(); return retval; } - return sys_dup3(oldfd, newfd, 0); + return ksys_dup3(oldfd, newfd, 0); } -SYSCALL_DEFINE1(dup, unsigned int, fildes) +int ksys_dup(unsigned int fildes) { int ret = -EBADF; struct file *file = fget_raw(fildes); @@ -934,6 +939,11 @@ SYSCALL_DEFINE1(dup, unsigned int, fildes) return ret; } +SYSCALL_DEFINE1(dup, unsigned int, fildes) +{ + return ksys_dup(fildes); +} + int f_dupfd(unsigned int from, struct file *file, unsigned flags) { int err; diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h index 48964c408c7b..50876ae1d17b 100644 --- a/include/linux/syscalls.h +++ b/include/linux/syscalls.h @@ -949,5 +949,6 @@ asmlinkage long sys_statx(int dfd, const char __user *path, unsigned flags, int ksys_mount(char __user *dev_name, char __user *dir_name, char __user *type, unsigned long flags, void __user *data); int ksys_umount(char __user *name, int flags); +int ksys_dup(unsigned int fildes); #endif diff --git a/init/do_mounts_initrd.c b/init/do_mounts_initrd.c index 1c4da8353332..e8573e1776f6 100644 --- a/init/do_mounts_initrd.c +++ b/init/do_mounts_initrd.c @@ -39,8 +39,8 @@ static int init_linuxrc(struct subprocess_info *info, struct cred *new) sys_unshare(CLONE_FS | CLONE_FILES); /* stdin/stdout/stderr for /linuxrc */ sys_open("/dev/console", O_RDWR, 0); - sys_dup(0); - sys_dup(0); + ksys_dup(0); + ksys_dup(0); /* move initrd over / and chdir/chroot in initrd root */ sys_chdir("/root"); ksys_mount(".", "/", NULL, MS_MOVE, NULL); diff --git a/init/main.c b/init/main.c index 969eaf140ef0..b8649d1466e1 100644 --- a/init/main.c +++ b/init/main.c @@ -1077,8 +1077,8 @@ static noinline void __init kernel_init_freeable(void) if (sys_open((const char __user *) "/dev/console", O_RDWR, 0) < 0) pr_err("Warning: unable to open an initial console.\n"); - (void) sys_dup(0); - (void) sys_dup(0); + (void) ksys_dup(0); + (void) ksys_dup(0); /* * check if there is an early userspace init. If yes, let it do all * the work