diff options
| author | Eric Dumazet <eric.dumazet@gmail.com> | 2011-04-20 11:27:32 +0200 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2011-04-28 08:05:08 +0200 |
| commit | 0a14842f5a3c0e88a1e59fac5c3025db39721f74 (patch) | |
| tree | 4d0832c4c9ced2503e2d899eb56952f87511d4ab /Documentation/sysctl/net.txt | |
| parent | ipv4: Kill RTO_CONN. (diff) | |
| download | linux-0a14842f5a3c0e88a1e59fac5c3025db39721f74.tar.xz linux-0a14842f5a3c0e88a1e59fac5c3025db39721f74.zip | |
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: Eric 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: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'Documentation/sysctl/net.txt')
| -rw-r--r-- | Documentation/sysctl/net.txt | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/Documentation/sysctl/net.txt b/Documentation/sysctl/net.txt index cbd05ffc606b..3201a7097e4d 100644 --- a/Documentation/sysctl/net.txt +++ b/Documentation/sysctl/net.txt @@ -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 ------------ |