Re: [RFC v2] bpf.2: Use standard types and attributes

Greg KH
2021-05-04T14:24:33Z

On Tue, May 04, 2021 at 07:12:01AM -0700, Alexei Starovoitov wrote:
> On Tue, May 4, 2021 at 4:05 AM 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 C11 keywords such as 'alignas()' when possible, and C2x
> > syntax '[[gnu::xxx]]' elsewhere, 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.
> >
> > The standard isn't very clear on how to use alignas() or
> > [[]]-style attributes, so the following link is useful in the case
> > of 'alignas()' and '[[gnu::aligned()]]':
> > <https://stackoverflow.com/q/67271825/6872717>
> >
> > Signed-off-by: Alejandro Colomar <alx.manpages@gmail.com>
> > Cc: LKML <linux-kernel@vger.kernel.org>
> > Cc: glibc <libc-alpha@sourceware.org>
> > Cc: GCC <gcc-patches@gcc.gnu.org>
> > Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>
> > Cc: bpf <bpf@vger.kernel.org>
> > Cc: David Laight <David.Laight@ACULAB.COM>
> > Cc: Zack Weinberg <zackw@panix.com>
> > Cc: Joseph Myers <joseph@codesourcery.com>
> > ---
> > man2/bpf.2 | 49 ++++++++++++++++++++++++-------------------------
> > 1 file changed, 24 insertions(+), 25 deletions(-)
> >
> > diff --git a/man2/bpf.2 b/man2/bpf.2
> > index 6e1ffa198..04b8fbcef 100644
> > --- a/man2/bpf.2
> > +++ b/man2/bpf.2
> > @@ -186,41 +186,40 @@ commands:
> > .PP
> > .in +4n
> > .EX
> > -union bpf_attr {
> > +union [[gnu::aligned(8)]] 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 */
>
> For the same reasons as explained earlier:
> Nacked-by: Alexei Starovoitov <ast@kernel.org>

I agree, the two are not the same type at all, this change should not be
accepted.

thanks,

greg k-h