netdev - Re: [PATCH bpf-next v2] libbpf: use implicit XSKMAP lookup from AF

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAJ+HfNgWeY7oLwun2Lt4nbT-Mh2yETZfHOGcYhvD=A+-UxWVOw@mail.gmail.com>
Date:   Mon, 21 Oct 2019 15:37:54 +0200
From:   Björn Töpel <bjorn.topel@...il.com>
To:     Toke Høiland-Jørgensen <toke@...hat.com>
Cc:     Netdev <netdev@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Björn Töpel <bjorn.topel@...el.com>,
        bpf <bpf@...r.kernel.org>,
        Magnus Karlsson <magnus.karlsson@...il.com>,
        "Karlsson, Magnus" <magnus.karlsson@...el.com>,
        "Samudrala, Sridhar" <sridhar.samudrala@...el.com>
Subject: Re: [PATCH bpf-next v2] libbpf: use implicit XSKMAP lookup from
 AF_XDP XDP program

On Mon, 21 Oct 2019 at 14:19, Toke Høiland-Jørgensen <toke@...hat.com> wrote:
>
> Björn Töpel <bjorn.topel@...il.com> writes:
>
[...]
> >
> > bpf_redirect_map() returns a 32-bit signed int, so the upper 32-bit
> > will need to be cleared. Having an explicit AND is one instruction
> > less than two shifts. So, it's an optimization (every instruction is
> > sacred).
>
> OIC. Well, a comment explaining that might be nice (since you're doing
> per-instruction comments anyway)? :)
>

Sure, I can do a v3 with a comment, unless someone has a better idea
avoiding both shifts and AND.

Thanks for taking a look!


Björn


> -Toke
>