From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) by ozlabs.org (Postfix) with ESMTP id C57962C00AB for ; Wed, 4 Sep 2013 06:52:42 +1000 (EST) Message-ID: <52264C0D.3000409@redhat.com> Date: Tue, 03 Sep 2013 22:52:29 +0200 From: Daniel Borkmann MIME-Version: 1.0 To: Vladimir Murzin Subject: Re: [PATCH] ppc: bpf_jit: support MOD operation References: <1377643792-10327-1-git-send-email-murzin.v@gmail.com> <20130902174842.GA1866@hp530> <1378154750.3978.43.camel@pasglop> <20130903195819.GA1971@hp530> In-Reply-To: <20130903195819.GA1971@hp530> Content-Type: text/plain; charset=KOI8-R; format=flowed Cc: Matt Evans , paulus@samba.org, netdev , linuxppc-dev@lists.ozlabs.org, davem@davemloft.net List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On 09/03/2013 09:58 PM, Vladimir Murzin wrote: > On Tue, Sep 03, 2013 at 06:45:50AM +1000, Benjamin Herrenschmidt wrote: >> On Mon, 2013-09-02 at 19:48 +0200, Vladimir Murzin wrote: >>> Ping >>> >>> On Wed, Aug 28, 2013 at 02:49:52AM +0400, Vladimir Murzin wrote: >>>> commit b6069a9570 (filter: add MOD operation) added generic >>>> support for modulus operation in BPF. >>>> >> Sorry, nobody got a chance to review that yet. Unfortunately Matt >> doesn't work for us anymore and none of us has experience with the >> BPF code, so somebody (possibly me) will need to spend a bit of time >> figuring it out before verifying that is correct. >> >> Do you have a test case/suite by any chance ? >> >> Ben. >> > > Hi Ben! > > Thanks for your feedback. > > This patch is only compile tested. I have no real hardware, but I'll > probably bring up qemu ppc64 till end of the week... > Meanwhile, I've made simple how-to for testing. You can use it if you wish. > It is mainly based on the [1] and rechecked on x86-64. Please also cc netdev on BPF related changes. Actually, your test plan can be further simplified ... For retrieving and disassembling the JIT image, we have bpf_jit_disasm [1]. 1) echo 2 > /proc/sys/net/core/bpf_jit_enable 2) ... attach filter ... 3) bpf_jit_disasm -o For generating a simple stupid test filter, you can use bpfc [2] (also see its man page). E.g. ... # cat blub ldi #10 mod #8 ret a # bpfc blub { 0x0, 0, 0, 0x0000000a }, { 0x94, 0, 0, 0x00000008 }, { 0x16, 0, 0, 0x00000000 }, And load this array e.g. either into a small C program that attaches this as BPF filter, or simply do bpfc blub > blub2 and run netsniff-ng -f blub2\ -s -i eth0, that should also do it. Then, when attached, the kernel should truncate incoming frames for pf_packet into max length of 2, just as an example. [1] kernel tree, tools/net/bpf_jit_disasm.c [2] git clone git://github.com/borkmann/netsniff-ng.git > 1. get the tcpdump utility (git clone git://bpf.tcpdump.org/tcpdump) > 2. get the libcap library (git clone git://bpf.tcpdump.org/libpcap) > 2.1. apply patch for libcap [2] (against libcap-1.3 branch) > 2.2. build libcap (./configure && make && ln -s libcap.so.1.3.0 libcap.so) > 3. build tcpdump (LDFLAGS="-L/path/to/libcap" ./configure && make) > 4. run > > # ./tcpdump -d "(ip[2:2] - 20) % 5 != 0 && ip[6] & 0x20 = 0x20" > (000) ldh [14] > (001) jeq #0x800 jt 2 jf 10 > (002) ldh [18] > (003) sub #20 > (004) mod #5 > (005) jeq #0x0 jt 10 jf 6 > (006) ldb [22] > (007) and #0x20 > (008) jeq #0x20 jt 9 jf 10 > (009) ret #65535 > (010) ret #0 > > to get pseudo code (we are interested the most into line #4) > > 5. enable bpf jit compiler > > # echo 2 > /proc/sys/net/core/bpf_jit_enable > > 6. run > > ./tcpdump -nv "(ip[2:2] - 20) % 5 != 0 && ip[6] & 0x20 = 0x20" > > 7. check dmesg for lines starting with (output for x86-64 is provided as an example) > > [ 3768.329253] flen=11 proglen=99 pass=3 image=ffffffffa003c000 > [ 3768.329254] JIT code: ffffffffa003c000: 55 48 89 e5 48 83 ec 60 48 89 5d f8 44 8b 4f 60 > [ 3768.329255] JIT code: ffffffffa003c010: 44 2b 4f 64 4c 8b 87 c0 00 00 00 0f b7 47 76 86 > [ 3768.329256] JIT code: ffffffffa003c020: c4 3d 00 08 00 00 75 37 be 02 00 00 00 e8 9f 3e > [ 3768.329257] JIT code: ffffffffa003c030: 02 e1 83 e8 14 31 d2 b9 05 00 00 00 f7 f1 89 d0 > [ 3768.329258] JIT code: ffffffffa003c040: 85 c0 74 1b be 06 00 00 00 e8 9f 3e 02 e1 25 20 > [ 3768.329259] JIT code: ffffffffa003c050: 00 00 00 83 f8 20 75 07 b8 ff ff 00 00 eb 02 31 > [ 3768.329259] JIT code: ffffffffa003c060: c0 c9 c3 > > 8. make sure generated opcodes (JIT code) implement pseudo code form step 4. > > Reference > [1] http://comments.gmane.org/gmane.linux.network/242456 > [2] http://permalink.gmane.org/gmane.network.tcpdump.devel/5973 > > P.S. > I hope net people will corect me if I'm wrong there > > Cheers > Vladimir Murzin > >>>> This patch brings JIT support for PPC64 >>>> >>>> Signed-off-by: Vladimir Murzin