linux-kernel - Re: [PATCH bpf-next 1/3] libbpf: add asm/unistd.h to xsk to get __NR

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Message-ID: <20190814092403.GA4142@khorivan>
Date:   Wed, 14 Aug 2019 12:24:05 +0300
From:   Ivan Khoronzhuk <ivan.khoronzhuk@...aro.org>
To:     Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc:     Magnus Karlsson <magnus.karlsson@...el.com>,
        Björn Töpel <bjorn.topel@...el.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        john fastabend <john.fastabend@...il.com>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        xdp-newbies@...r.kernel.org,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH bpf-next 1/3] libbpf: add asm/unistd.h to xsk to get
 __NR_mmap2

On Tue, Aug 13, 2019 at 04:38:13PM -0700, Andrii Nakryiko wrote:

Hi, Andrii

>On Tue, Aug 13, 2019 at 3:24 AM Ivan Khoronzhuk
><ivan.khoronzhuk@...aro.org> wrote:
>>
>> That's needed to get __NR_mmap2 when mmap2 syscall is used.
>>
>> Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@...aro.org>
>> ---
>>  tools/lib/bpf/xsk.c | 1 +
>>  1 file changed, 1 insertion(+)
>>
>> diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c
>> index 5007b5d4fd2c..f2fc40f9804c 100644
>> --- a/tools/lib/bpf/xsk.c
>> +++ b/tools/lib/bpf/xsk.c
>> @@ -12,6 +12,7 @@
>>  #include <stdlib.h>
>>  #include <string.h>
>>  #include <unistd.h>
>> +#include <asm/unistd.h>
>
>asm/unistd.h is not present in Github libbpf projection. Is there any

Look on includes from
tools/lib/bpf/libpf.c
tools/lib/bpf/bpf.c

That's how it's done... Copping headers to arch/arm will not
solve this, it includes both of them anyway, and anyway it needs
asm/unistd.h inclusion here, only because xsk.c needs __NR_*


>way to avoid including this header? Generally, libbpf can't easily use
>all of kernel headers, we need to re-implemented all the extra used
>stuff for Github version of libbpf, so we try to minimize usage of new
>headers that are not just plain uapi headers from include/uapi.

Yes I know, it's far away from real number of changes needed.
I faced enough about this already and kernel headers, especially
for arm32 it's a bit decency problem. But this patch it's part of
normal one. I have couple issues despite this normally fixed mmap2
that is the same even if uapi includes are coppied to tools/arch/arm.

In continuation of kernel headers inclusion and arm build:

For instance, what about this rough "kernel headers" hack:
https://github.com/ikhorn/af_xdp_stuff/commit/aa645ccca4d844f404ec3c2b27402d4d7848d1b5

or this one related for arm32 only:
https://github.com/ikhorn/af_xdp_stuff/commit/2c6c6d538605aac39600dcb3c9b66de11c70b963

I have more...

>
>>  #include <arpa/inet.h>
>>  #include <asm/barrier.h>
>>  #include <linux/compiler.h>
>> --
>> 2.17.1
>>

-- 
Regards,
Ivan Khoronzhuk