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    Subject[PATCH 16/17] init: open code setting up stdin/stdout/stderr
    Date
    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 <hch@lst.de>
    ---
    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
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