linux-kernel - Re: [PATCH 1/2] userfaultfd.2: Add section for UFFD_USER_MODE

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Date:   Fri, 3 Jun 2022 19:11:05 +0200
From:   Alejandro Colomar <alx.manpages@...il.com>
To:     Peter Xu <peterx@...hat.com>, linux-kernel@...r.kernel.org,
        linux-man@...r.kernel.org, linux-mm@...ck.org
Cc:     Axel Rasmussen <axelrasmussen@...gle.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Nadav Amit <nadav.amit@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 1/2] userfaultfd.2: Add section for UFFD_USER_MODE_ONLY

Hi Peter,

On 5/31/22 03:11, Peter Xu wrote:
> Add a paragraph for UFFD_USER_MODE_ONLY flag that was introduced in
> Linux 5.11.
> 
> Signed-off-by: Peter Xu <peterx@...hat.com>

See some minor comments below.

Cheers,

Alex

> ---
>   man2/userfaultfd.2 | 14 ++++++++++++--
>   1 file changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/man2/userfaultfd.2 b/man2/userfaultfd.2
> index cee7c01d2..0928a76d2 100644
> --- a/man2/userfaultfd.2
> +++ b/man2/userfaultfd.2
> @@ -29,8 +29,9 @@
>   userfaultfd \- create a file descriptor for handling page faults in user space
>   .SH SYNOPSIS
>   .nf
> -.BR "#include <fcntl.h>" "            /* Definition of " O_* " constants */"
> -.BR "#include <sys/syscall.h>" "      /* Definition of " SYS_* " constants */"
> +.BR "#include <fcntl.h>" "             /* Definition of " O_* " constants */"
> +.BR "#include <sys/syscall.h>" "       /* Definition of " SYS_* " constants */"
> +.BR "#include <linux/userfaultfd.h>" " /* Definition of " UFFD_* " constants */"
>   .B #include <unistd.h>
>   .PP
>   .BI "int syscall(SYS_userfaultfd, int " flags );
> @@ -76,6 +77,15 @@ See the description of the
>   .BR O_NONBLOCK
>   flag in
>   .BR open (2).
> +.TP
> +.BR UFFD_USER_MODE_ONLY


s/BR/B/

see groff_man(7):

[
	[...]

        .B [text]
               Set text in bold.  If the macro is given no  argu‐
               ments,  the  text of the next input line is set in
               bold.

	[...]

        .BR bold‐text roman‐text ...
               Set each argument in bold and roman, alternately.
]

> +This is an userfaultfd specific flag that was introduced since Linux 5.11.
> +When set, the userfaultfd object will only be able to handle page faults
> +originated from the userspace on the registered regions.
> +When a kernel originated fault was triggered on the registered range with
> +this userfaultfd, a
> +.BR SIGBUS

s/BR/B/

> +signal will be delivered.
>   .PP
>   When the last file descriptor referring to a userfaultfd object is closed,
>   all memory ranges that were registered with the object are unregistered

-- 
Alejandro Colomar
<http://www.alejandro-colomar.es/>

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