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Commit 0a14842f authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
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net: filter: Just In Time compiler for x86-64 



In order to speedup packet filtering, here is an implementation of a
JIT compiler for x86_64

It is disabled by default, and must be enabled by the admin.

echo 1 >/proc/sys/net/core/bpf_jit_enable

It uses module_alloc() and module_free() to get memory in the 2GB text
kernel range since we call helpers functions from the generated code.

EAX : BPF A accumulator
EBX : BPF X accumulator
RDI : pointer to skb   (first argument given to JIT function)
RBP : frame pointer (even if CONFIG_FRAME_POINTER=n)
r9d : skb->len - skb->data_len (headlen)
r8  : skb->data

To get a trace of generated code, use :

echo 2 >/proc/sys/net/core/bpf_jit_enable

Example of generated code :

# tcpdump -p -n -s 0 -i eth1 host 192.168.20.0/24

flen=18 proglen=147 pass=3 image=ffffffffa00b5000
JIT code: ffffffffa00b5000: 55 48 89 e5 48 83 ec 60 48 89 5d f8 44 8b 4f 60
JIT code: ffffffffa00b5010: 44 2b 4f 64 4c 8b 87 b8 00 00 00 be 0c 00 00 00
JIT code: ffffffffa00b5020: e8 24 7b f7 e0 3d 00 08 00 00 75 28 be 1a 00 00
JIT code: ffffffffa00b5030: 00 e8 fe 7a f7 e0 24 00 3d 00 14 a8 c0 74 49 be
JIT code: ffffffffa00b5040: 1e 00 00 00 e8 eb 7a f7 e0 24 00 3d 00 14 a8 c0
JIT code: ffffffffa00b5050: 74 36 eb 3b 3d 06 08 00 00 74 07 3d 35 80 00 00
JIT code: ffffffffa00b5060: 75 2d be 1c 00 00 00 e8 c8 7a f7 e0 24 00 3d 00
JIT code: ffffffffa00b5070: 14 a8 c0 74 13 be 26 00 00 00 e8 b5 7a f7 e0 24
JIT code: ffffffffa00b5080: 00 3d 00 14 a8 c0 75 07 b8 ff ff 00 00 eb 02 31
JIT code: ffffffffa00b5090: c0 c9 c3

BPF program is 144 bytes long, so native program is almost same size ;)

(000) ldh      [12]
(001) jeq      #0x800           jt 2    jf 8
(002) ld       [26]
(003) and      #0xffffff00
(004) jeq      #0xc0a81400      jt 16   jf 5
(005) ld       [30]
(006) and      #0xffffff00
(007) jeq      #0xc0a81400      jt 16   jf 17
(008) jeq      #0x806           jt 10   jf 9
(009) jeq      #0x8035          jt 10   jf 17
(010) ld       [28]
(011) and      #0xffffff00
(012) jeq      #0xc0a81400      jt 16   jf 13
(013) ld       [38]
(014) and      #0xffffff00
(015) jeq      #0xc0a81400      jt 16   jf 17
(016) ret      #65535
(017) ret      #0

Signed-off-by: default avatarEric Dumazet <eric.dumazet@gmail.com>
Cc: Arnaldo Carvalho de Melo <acme@infradead.org>
Cc: Ben Hutchings <bhutchings@solarflare.com>
Cc: Hagen Paul Pfeifer <hagen@jauu.net>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent b678027c

Documentation/sysctl/net.txt

+11 −0
Original line number Diff line number Diff line
@@ -32,6 +32,17 @@ Table : Subdirectories in /proc/sys/net 
1. /proc/sys/net/core - Network core options

-------------------------------------------------------



bpf_jit_enable

--------------



This enables Berkeley Packet Filter Just in Time compiler.

Currently supported on x86_64 architecture, bpf_jit provides a framework

to speed packet filtering, the one used by tcpdump/libpcap for example.

Values :

	0 - disable the JIT (default value)

	1 - enable the JIT

	2 - enable the JIT and ask the compiler to emit traces on kernel log.



rmem_default

------------

MAINTAINERS

+1 −0
Original line number Diff line number Diff line
@@ -4372,6 +4372,7 @@ S: Maintained 
F:	net/ipv4/

F:	net/ipv6/

F:	include/net/ip*

F:	arch/x86/net/*



NETWORKING [LABELED] (NetLabel, CIPSO, Labeled IPsec, SECMARK)

M:	Paul Moore <paul.moore@hp.com>

arch/x86/Kbuild

+1 −0
Original line number Diff line number Diff line
@@ -15,3 +15,4 @@ obj-y += vdso/ 
obj-$(CONFIG_IA32_EMULATION) += ia32/



obj-y += platform/

obj-y += net/

arch/x86/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -72,6 +72,7 @@ config X86 
	select IRQ_FORCED_THREADING

	select USE_GENERIC_SMP_HELPERS if SMP

	select ARCH_NO_SYSDEV_OPS

	select HAVE_BPF_JIT if X86_64



config INSTRUCTION_DECODER

	def_bool (KPROBES || PERF_EVENTS)

arch/x86/net/Makefile

0 → 100644
+4 −0
Original line number Diff line number Diff line 
#

# Arch-specific network modules

#

obj-$(CONFIG_BPF_JIT) += bpf_jit.o bpf_jit_comp.o