linux-kernel - Re: [PATCH 5/5] usefaultfd.2: add brief description of "non-cooperative" mode

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Date:   Wed, 26 Apr 2017 09:18:14 +0200
From:   "Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>
To:     Mike Rapoport <rppt@...ux.vnet.ibm.com>
Cc:     mtk.manpages@...il.com, Andrea Arcangeli <aarcange@...hat.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-man@...r.kernel.org
Subject: Re: [PATCH 5/5] usefaultfd.2: add brief description of
 "non-cooperative" mode

On 04/25/2017 06:29 PM, Mike Rapoport wrote:
> Signed-off-by: Mike Rapoport <rppt@...ux.vnet.ibm.com>

Thanks, Mike. Applied.

Cheers,

Michael

> ---
>  man2/userfaultfd.2 | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
> 
> diff --git a/man2/userfaultfd.2 b/man2/userfaultfd.2
> index dc37319..291dd10 100644
> --- a/man2/userfaultfd.2
> +++ b/man2/userfaultfd.2
> @@ -89,6 +89,20 @@ them using the operations described in
>  .BR ioctl_userfaultfd (2).
>  When servicing the page fault events,
>  the fault-handling thread can trigger a wake-up for the sleeping thread.
> +
> +It is possible for the faulting threads and the fault-handling threads
> +to run in the context of different processes.
> +In this case, these threads may belong to different programs,
> +and the program that executes the faulting threads
> +will not necessarily cooperate with the program that handles the page faults.
> +In such non-cooperative mode,
> +the process that monitors userfaultfd and handles page faults,
> +needs to be aware of the changes in the virtual memory layout
> +of the faulting process to avoid memory corruption.
> +.\" FIXME elaborate about non-cooperating mode, describe its limitations
> +.\" for kerneles before 4.11, features added in 4.11
> +.\" and limitations remaining in 4.11
> +.\" Maybe it's worth adding a dedicated sub-section...
>  .\"
>  .SS Userfaultfd operation
>  After the userfaultfd object is created with
> 


-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/