netdev - Re: [PATCH v6 net-next 4/6] bpf: enable bpf syscall on x64 and i386

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: <CAMEtUuy1DXFMABAg2Uup5HtqmiJHw0WR=or-z9CfpVMscrVcVg@mail.gmail.com>
Date:	Mon, 25 Aug 2014 18:43:55 -0700
From:	Alexei Starovoitov <ast@...mgrid.com>
To:	David Miller <davem@...emloft.net>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andy Lutomirski <luto@...capital.net>,
	Steven Rostedt <rostedt@...dmis.org>,
	Daniel Borkmann <dborkman@...hat.com>,
	Chema Gonzalez <chema@...gle.com>,
	Eric Dumazet <edumazet@...gle.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Brendan Gregg <brendan.d.gregg@...il.com>,
	Namhyung Kim <namhyung@...nel.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Kees Cook <keescook@...omium.org>,
	Linux API <linux-api@...r.kernel.org>,
	Network Development <netdev@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v6 net-next 4/6] bpf: enable bpf syscall on x64 and i386

On Mon, Aug 25, 2014 at 6:07 PM, David Miller <davem@...emloft.net> wrote:
> From: Alexei Starovoitov <ast@...mgrid.com>
> Date: Mon, 25 Aug 2014 18:00:56 -0700
>
>> -
>> +asmlinkage long sys_bpf(int cmd, unsigned long arg2, unsigned long arg3,
>> +                     unsigned long arg4, unsigned long arg5);
>
> Please do not add interfaces with opaque types as arguments.
>
> It is impossible for the compiler to type check the args at
> compile time when userspace tries to use this stuff.

I share this concern. I went with single BPF syscall, because
alternative is 6 syscalls for every command and more
syscalls in the future when we'd need to add another command.
I think type casting is much lesser evil.
We already have similar muxing syscalls.
It feels to me that single mux/demux syscall is easier to support,
document, add new commands. Type casting, yeah, not pretty.
Most users will be using wrappers similar to those I've defined in libbpf.h
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html