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From:   Dmitry Safonov <0x7f454c46@gmail.com>
Date:   Mon, 27 Feb 2023 16:02:54 +0000
Message-ID: <CAJwJo6YnELNhU8RmR-z37vDZ=xb0CmUUBgrPGgHP2dqjVm=O2g@mail.gmail.com>
Subject: Re: [PATCH v12 2/3] ptrace,syscall_user_dispatch: checkpoint/restore
 support for SUD
To:     Gregory Price <gourry.memverge@gmail.com>
Cc:     linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
        oleg@redhat.com, avagin@gmail.com, peterz@infradead.org,
        luto@kernel.org, krisman@collabora.com, tglx@linutronix.de,
        corbet@lwn.net, shuah@kernel.org,
        Gregory Price <gregory.price@memverge.com>
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Hi Gragory,

On Fri, 24 Feb 2023 at 23:40, Gregory Price <gourry.memverge@gmail.com> wrote:
>
> Implement ptrace getter/setter interface for syscall user dispatch.
>
> These prctl settings are presently write-only, making it impossible to
> implement transparent checkpoint/restore via software like CRIU.
>
> 'on_dispatch' field is not exposed because it is a kernel-internal
> only field that cannot be 'true' when returning to userland.
>
> Signed-off-by: Gregory Price <gregory.price@memverge.com>
> ---
[..]
> +int syscall_user_dispatch_set_config(struct task_struct *task, unsigned long size,
> +                                    void __user *data)
> +{
> +       int rc;
> +       struct ptrace_sud_config cfg;
> +
> +       if (size != sizeof(struct ptrace_sud_config))
> +               return -EINVAL;
> +
> +       if (copy_from_user(&cfg, data, sizeof(struct ptrace_sud_config)))
> +               return -EFAULT;

It seems that the tool you want here would be copy_struct_from_user(),
which is designed for extendable syscalls.

Thanks,
             Dmitry