linux-kernel - Re: [PATCH v3 2/3] ioctl_userfaultfd.2: fix / update UFFDIO

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Message-ID: <ZS8XglFnkdMdILaw@debian>
Date:   Wed, 18 Oct 2023 01:23:46 +0200
From:   Alejandro Colomar <alx@...nel.org>
To:     Axel Rasmussen <axelrasmussen@...gle.com>
Cc:     Mike Rapoport <rppt@...nel.org>, Peter Xu <peterx@...hat.com>,
        linux-man@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/3] ioctl_userfaultfd.2: fix / update UFFDIO_REGISTER
 error code list

Hi Axel, Mike,

On Tue, Oct 17, 2023 at 04:01:09PM -0700, Axel Rasmussen wrote:
> The list of error codes in the man page was out of date with respect to
> the current state of the kernel. Some errors were partially /
> incorrectly described.
> 
> Update the error code listing, so it matches the current state of the
> kernel, and correctly describes all the errors.
> 
> Signed-off-by: Axel Rasmussen <axelrasmussen@...gle.com>

I'll wait a bit before applying this one, in case Mike (or Peter) want
to review it.

The other two, you can find them here, as usual:
<https://www.alejandro-colomar.es/src/alx/linux/man-pages/man-pages.git/commit/?h=contrib&id=9ae03d21383151794b118ac8dd98b4d6e26c9689>
<https://www.alejandro-colomar.es/src/alx/linux/man-pages/man-pages.git/commit/?h=contrib&id=5f1acc81e55540d1276977e66d64649c6ca7b58b>

And BTW, while running `make lint build check`, I caught some accidents
from a previous patch from yours:
<https://www.alejandro-colomar.es/src/alx/linux/man-pages/man-pages.git/commit/?h=contrib&id=bf8647d1d82205934776b474fe89e5f30e03ad25>

Cheers,
Alex

> ---
>  man2/ioctl_userfaultfd.2 | 33 +++++++++++++++++++--------------
>  1 file changed, 19 insertions(+), 14 deletions(-)
> 
> diff --git a/man2/ioctl_userfaultfd.2 b/man2/ioctl_userfaultfd.2
> index 82aee667c..40528001e 100644
> --- a/man2/ioctl_userfaultfd.2
> +++ b/man2/ioctl_userfaultfd.2
> @@ -413,8 +413,6 @@ On error, \-1 is returned and
>  .I errno
>  is set to indicate the error.
>  Possible errors include:
> -.\" FIXME Is the following error list correct?
> -.\"
>  .TP
>  .B EBUSY
>  A mapping in the specified range is registered with another
> @@ -433,21 +431,28 @@ field; or the
>  field was zero.
>  .TP
>  .B EINVAL
> -There is no mapping in the specified address range.
> -.TP
> -.B EINVAL
> -.I range.start
> +The specified address range was invalid.
> +More specifically,
> +no mapping exists in the given range,
> +or the mapping that exists there is invalid
> +(e.g. unsupported type of memory),
> +or the range values
> +.RI ( range.start
> +or
> +.IR range.len )
> +are not multiples of the relevant page size,
>  or
>  .I range.len
> -is not a multiple of the system page size; or,
> -.I range.len
> -is zero; or these fields are otherwise invalid.
> +is zero.
>  .TP
> -.B EINVAL
> -There as an incompatible mapping in the specified address range.
> -.\" Mike Rapoport:
> -.\" ENOMEM if the process is exiting and the
> -.\" mm_struct has gone by the time userfault grabs it.
> +.B ENOMEM
> +The process is exiting,
> +and its address space has already been torn down
> +when userfaultfd attempts to reference it.
> +.TP
> +.B EPERM
> +The userfaultfd would allow writing to a file backing the mapping,
> +but the calling process lacks such write permissions.
>  .SS UFFDIO_UNREGISTER
>  (Since Linux 4.3.)
>  Unregister a memory address range from userfaultfd.
> -- 
> 2.42.0.655.g421f12c284-goog
> 

-- 
<https://www.alejandro-colomar.es/>

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