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Message-ID: <20130911161553.GB1967@hp530>
Date: Wed, 11 Sep 2013 18:15:57 +0200
From: Vladimir Murzin <murzin.v@...il.com>
To: Daniel Borkmann <dborkman@...hat.com>
Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>,
linuxppc-dev@...ts.ozlabs.org, paulus@...ba.org,
davem@...emloft.net, Matt Evans <matt@...abs.org>,
netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH] ppc: bpf_jit: support MOD operation
On Wed, Sep 04, 2013 at 09:04:04AM +0200, Daniel Borkmann wrote:
> On 09/03/2013 10:52 PM, Daniel Borkmann wrote:
> > On 09/03/2013 09:58 PM, Vladimir Murzin wrote:
> [...]
> >>> 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.
Finally I've managed to bring up qemu ppc64 and done simple testing. As a
result I could see difference in opcodes for divide instruction - I've just
sent the patch for that.
WRT mod instruction result is:
For BPF program
(000) ldh [12]
(001) jeq #0x800 jt 2 jf 10
(002) ldh [16]
(003) sub #20
(004) mod #5
(005) jeq #0x0 jt 10 jf 6
(006) ldb [20]
(007) and #0x20
(008) jeq #0x20 jt 9 jf 10
(009) ret #65535
(010) ret #0
The following code is generated (with patch divw to divwu applied)
244 bytes emitted from JIT compiler (pass:3, flen:11)
d0000000015c0018 + <x>:
0: mflr r0
4: std r0,16(r1)
8: std r14,-144(r1)
c: std r15,-136(r1)
10: stdu r1,-288(r1)
14: lwz r7,108(r3)
18: lwz r15,104(r3)
1c: subf r15,r7,r15
20: ld r14,216(r3)
24: lis r7,-16384
28: rldicr r7,r7,32,31
2c: oris r7,r7,9
30: ori r7,r7,43428
34: mtlr r7
38: li r6,12
3c: blrl
40: blt- 0x00000000000000dc
44: nop
48: cmplwi r4,2048
4c: bne- 0x00000000000000d8
50: nop
54: lis r7,-16384
58: rldicr r7,r7,32,31
5c: oris r7,r7,9
60: ori r7,r7,43428
64: mtlr r7
68: li r6,16
6c: blrl
70: blt- 0x00000000000000dc
74: nop
78: addi r4,r4,-20
7c: li r8,5
80: divwu r7,r4,r8
84: mullw r7,r8,r7
88: subf r4,r7,r4
8c: cmplwi r4,0
90: beq- 0x00000000000000d8
94: nop
98: lis r7,-16384
9c: rldicr r7,r7,32,31
a0: oris r7,r7,9
a4: ori r7,r7,43456
a8: mtlr r7
ac: li r6,20
b0: blrl
b4: blt- 0x00000000000000dc
b8: nop
bc: andi. r4,r4,32
c0: cmplwi r4,32
c4: bne- 0x00000000000000d8
c8: nop
cc: li r3,-1
d0: addis r3,r3,1
d4: b 0x00000000000000dc
d8: li r3,0
dc: addi r1,r1,288
e0: ld r0,16(r1)
e4: mtlr r0
e8: ld r14,-144(r1)
ec: ld r15,-136(r1)
f0: blr
Raw codes are
flen=11 proglen=244 pass=3 image=d0000000015c0018
JIT code: 00000000: 7c 08 02 a6 f8 01 00 10 f9 c1 ff 70 f9 e1 ff 78
JIT code: 00000010: f8 21 fe e1 80 e3 00 6c 81 e3 00 68 7d e7 78 50
JIT code: 00000020: e9 c3 00 d8 3c e0 c0 00 78 e7 07 c6 64 e7 00 09
JIT code: 00000030: 60 e7 a9 a4 7c e8 03 a6 38 c0 00 0c 4e 80 00 21
JIT code: 00000040: 41 80 00 9c 60 00 00 00 28 04 08 00 40 82 00 8c
JIT code: 00000050: 60 00 00 00 3c e0 c0 00 78 e7 07 c6 64 e7 00 09
JIT code: 00000060: 60 e7 a9 a4 7c e8 03 a6 38 c0 00 10 4e 80 00 21
JIT code: 00000070: 41 80 00 6c 60 00 00 00 38 84 ff ec 39 00 00 05
JIT code: 00000080: 7c e4 43 96 7c e8 39 d6 7c 87 20 50 28 04 00 00
JIT code: 00000090: 41 82 00 48 60 00 00 00 3c e0 c0 00 78 e7 07 c6
JIT code: 000000a0: 64 e7 00 09 60 e7 a9 c0 7c e8 03 a6 38 c0 00 14
JIT code: 000000b0: 4e 80 00 21 41 80 00 28 60 00 00 00 70 84 00 20
JIT code: 000000c0: 28 04 00 20 40 82 00 14 60 00 00 00 38 60 ff ff
JIT code: 000000d0: 3c 63 00 01 48 00 00 08 38 60 00 00 38 21 01 20
JIT code: 000000e0: e8 01 00 10 7c 08 03 a6 e9 c1 ff 70 e9 e1 ff 78
JIT code: 000000f0: 4e 80 00 20
Ben,
How do you feel about it?
> >
> > 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 },
>
> Plus something like ...
>
> ldxi #0
> mod x
> ret a
>
Thanks Daniel!
Unfortunately, I couldn't trigger JIT compiler with the pair bpfc/netsniff-ng
(even for x86-64). I guess I missed something. I'd be very grateful if you
point at my mistakes.
> For longer-term testing, also trinity has BPF support. ;)
>
Wow! Could do give some hint how to run this for BPF only?
> > 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
Thanks
Vladimir
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