2020-07-09 15:19:39

by Christoph Hellwig

Subject: [PATCH 16/17] init: open code setting up stdin/stdout/stderr

Don't rely on the implicit set_fs(KERNEL_DS) for ksys_open to work, but
instead open a struct file for /dev/console and then install it as FD
0/1/2 manually.

Signed-off-by: Christoph Hellwig <[email protected]>
---
fs/file.c | 7 +------
include/linux/syscalls.h | 1 -
init/main.c | 16 ++++++++++------
3 files changed, 11 insertions(+), 13 deletions(-)

diff --git a/fs/file.c b/fs/file.c
index abb8b7081d7a44..85b7993165dd2f 100644
--- a/fs/file.c
+++ b/fs/file.c
@@ -985,7 +985,7 @@ SYSCALL_DEFINE2(dup2, unsigned int, oldfd, unsigned int, newfd)
return ksys_dup3(oldfd, newfd, 0);
}

-int ksys_dup(unsigned int fildes)
+SYSCALL_DEFINE1(dup, unsigned int, fildes)
{
int ret = -EBADF;
struct file *file = fget_raw(fildes);
@@ -1000,11 +1000,6 @@ int ksys_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 e8810d75efa9b0..59af62090ac400 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -1237,7 +1237,6 @@ asmlinkage long sys_ni_syscall(void);
*/

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);
diff --git a/init/main.c b/init/main.c
index 0ead83e86b5aa2..db0621dfbb0468 100644
--- a/init/main.c
+++ b/init/main.c
@@ -1457,15 +1457,19 @@ static int __ref kernel_init(void *unused)
"See Linux Documentation/admin-guide/init.rst for guidance.");
}

+/* Open /dev/console, for stdin/stdout/stderr, this should never fail */
void console_on_rootfs(void)
{
- /* Open the /dev/console as stdin, this should never fail */
- if (ksys_open((const char __user *) "/dev/console", O_RDWR, 0) < 0)
- pr_err("Warning: unable to open an initial console.\n");
+ struct file *file = filp_open("/dev/console", O_RDWR, 0);

- /* create stdout/stderr */
- (void) ksys_dup(0);
- (void) ksys_dup(0);
+ if (IS_ERR(file)) {
+ pr_err("Warning: unable to open an initial console.\n");
+ return;
+ }
+ get_file_rcu_many(file, 2);
+ fd_install(get_unused_fd_flags(0), file);
+ fd_install(get_unused_fd_flags(0), file);
+ fd_install(get_unused_fd_flags(0), file);
}

static noinline void __init kernel_init_freeable(void)
--
2.26.2

2020-07-09 18:33:48

by Brian Gerst

Subject: Re: [PATCH 16/17] init: open code setting up stdin/stdout/stderr

On Thu, Jul 9, 2020 at 11:19 AM Christoph Hellwig <[email protected]> wrote:
>
> Don't rely on the implicit set_fs(KERNEL_DS) for ksys_open to work, but
> instead open a struct file for /dev/console and then install it as FD
> 0/1/2 manually.
>
> Signed-off-by: Christoph Hellwig <[email protected]>
> ---
> fs/file.c | 7 +------
> include/linux/syscalls.h | 1 -
> init/main.c | 16 ++++++++++------
> 3 files changed, 11 insertions(+), 13 deletions(-)
>
> diff --git a/fs/file.c b/fs/file.c
> index abb8b7081d7a44..85b7993165dd2f 100644
> --- a/fs/file.c
> +++ b/fs/file.c
> @@ -985,7 +985,7 @@ SYSCALL_DEFINE2(dup2, unsigned int, oldfd, unsigned int, newfd)
> return ksys_dup3(oldfd, newfd, 0);
> }
>
> -int ksys_dup(unsigned int fildes)
> +SYSCALL_DEFINE1(dup, unsigned int, fildes)
> {
> int ret = -EBADF;
> struct file *file = fget_raw(fildes);
> @@ -1000,11 +1000,6 @@ int ksys_dup(unsigned int fildes)
> return ret;
> }
>
> -SYSCALL_DEFINE1(dup, unsigned int, fildes)
> -{
> - return ksys_dup(fildes);
> -}
> -

Please split the removal of the now unused ksys_*() functions into a
separate patch.

--
Brian Gerst