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 <murzi...@gmail.com>
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