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

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Date:   Fri, 3 Jun 2022 13:34:19 -0400
From:   Peter Xu <peterx@...hat.com>
To:     Alejandro Colomar <alx.manpages@...il.com>
Cc:     linux-kernel@...r.kernel.org, linux-man@...r.kernel.org,
        linux-mm@...ck.org, 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

On Fri, Jun 03, 2022 at 07:11:05PM +0200, Alejandro Colomar wrote:
> 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/

Thanks Alex, I'll fix and repost the patchset soon.

-- 
Peter Xu