BPF Archive on lore.kernel.org
 help / color / Atom feed
From: David Laight <David.Laight@ACULAB.COM>
To: 'Alexei Starovoitov' <alexei.starovoitov@gmail.com>,
	Alejandro Colomar <alx.manpages@gmail.com>,
	bpf <bpf@vger.kernel.org>
Cc: "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com>,
	linux-man <linux-man@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	"libc-alpha@sourceware.org" <libc-alpha@sourceware.org>,
	"gcc-patches@gcc.gnu.org" <gcc-patches@gcc.gnu.org>
Subject: RE: [RFC] bpf.2: Use standard types and attributes
Date: Sat, 24 Apr 2021 20:43:30 +0000
Message-ID: <78af3c302dd5447887f4a14cd4629119@AcuMS.aculab.com> (raw)
In-Reply-To: <CAADnVQLf4qe3Hj7cjBUCY4wXb9t2ZjUt=Z=JuygRY0LNNHWAoA@mail.gmail.com>

From: Alexei Starovoitov
> Sent: 24 April 2021 00:20
> 
> On Fri, Apr 23, 2021 at 4:15 PM Alejandro Colomar
> <alx.manpages@gmail.com> wrote:
> >
> > Some manual pages are already using C99 syntax for integral
> > types 'uint32_t', but some aren't.  There are some using kernel
> > syntax '__u32'.  Fix those.
> >
> > Some pages also document attributes, using GNU syntax
> > '__attribute__((xxx))'.  Update those to use the shorter and more
> > portable C2x syntax, which hasn't been standardized yet, but is
> > already implemented in GCC, and available through either --std=c2x
> > or any of the --std=gnu... options.
> >
> > Signed-off-by: Alejandro Colomar <alx.manpages@gmail.com>
> > ---
> >  man2/bpf.2 | 47 +++++++++++++++++++++++------------------------
> >  1 file changed, 23 insertions(+), 24 deletions(-)
> >
> > diff --git a/man2/bpf.2 b/man2/bpf.2
> > index 6e1ffa198..204f01bfc 100644
> > --- a/man2/bpf.2
> > +++ b/man2/bpf.2
> > @@ -188,39 +188,38 @@ commands:
> >  .EX
> >  union bpf_attr {
> >      struct {    /* Used by BPF_MAP_CREATE */
> > -        __u32         map_type;
> > -        __u32         key_size;    /* size of key in bytes */
> > -        __u32         value_size;  /* size of value in bytes */
> > -        __u32         max_entries; /* maximum number of entries
> > -                                      in a map */
> > +        uint32_t    map_type;
> > +        uint32_t    key_size;    /* size of key in bytes */
> > +        uint32_t    value_size;  /* size of value in bytes */
> > +        uint32_t    max_entries; /* maximum number of entries
> > +                                    in a map */
> 
> Nack.
> The man page should describe the kernel api the way it is in .h file.

And the code below is no more portable that a #pragma'.
It is probably worse than __attribute__((aligned(8)))
+            uint64_t [[gnu::aligned(8)]] value;
The standards committee are smoking dope again.
At least the '__aligned_u64 value;' form stands a reasonable
chance of being converted by cpp into whatever your compiler supports.

OTOH the bfp developers want shooting for defining a structure
with hidden padding fields.
It they ensured that all 64bit fields were aligned they wouldn't
need the __aligned_u64 at all.
And would be much less likely to leak kernel stack to userspace.

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)

  parent reply index

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20210423230609.13519-1-alx.manpages@gmail.com>
2021-04-23 23:20 ` Alexei Starovoitov
2021-04-24 17:56   ` Alejandro Colomar (man-pages)
2021-04-25 16:52     ` Alexei Starovoitov
2021-04-25 19:12       ` Zack Weinberg
2021-04-24 20:43   ` David Laight [this message]
2021-04-25 19:16     ` Zack Weinberg
2021-04-25 21:09       ` David Laight
2021-05-04 11:05 ` [RFC v2] " Alejandro Colomar
2021-05-04 14:12   ` Alexei Starovoitov
2021-05-04 14:24     ` Greg KH
2021-05-04 15:53       ` Alejandro Colomar (man-pages)
2021-05-04 16:06         ` Greg KH
2021-05-04 18:37           ` Zack Weinberg
2021-05-04 18:54             ` Alejandro Colomar (man-pages)
2021-05-04 19:45               ` Florian Weimer
2021-05-04 19:59                 ` Alejandro Colomar (man-pages)
2021-05-05  8:23                 ` David Laight
2021-05-05 22:22                   ` Joseph Myers
2021-05-04 20:06               ` Daniel Borkmann
2021-05-04 20:16                 ` Alejandro Colomar (man-pages)
2021-05-04 20:33                 ` Zack Weinberg
2021-05-04 21:23                   ` Alexei Starovoitov
2021-05-15 19:01               ` [PATCH v3] " Alejandro Colomar
2021-05-16  9:16                 ` Alejandro Colomar (man-pages)
2021-05-17 18:56                   ` Daniel Borkmann
2021-05-21 11:12                     ` Alejandro Colomar
2021-05-04 16:08         ` [RFC v2] " Daniel Borkmann

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=78af3c302dd5447887f4a14cd4629119@AcuMS.aculab.com \
    --to=david.laight@aculab.com \
    --cc=alexei.starovoitov@gmail.com \
    --cc=alx.manpages@gmail.com \
    --cc=bpf@vger.kernel.org \
    --cc=gcc-patches@gcc.gnu.org \
    --cc=libc-alpha@sourceware.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-man@vger.kernel.org \
    --cc=mtk.manpages@gmail.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

BPF Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/bpf/0 bpf/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 bpf bpf/ https://lore.kernel.org/bpf \
		bpf@vger.kernel.org
	public-inbox-index bpf

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.bpf


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git