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

Alexei Starovoitov
2021-05-04T14:12:19Z

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>