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author | 2011-04-20 09:27:32 +0000 | |
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committer | 2011-04-27 23:05:08 -0700 | |
commit | 0a14842f5a3c0e88a1e59fac5c3025db39721f74 (patch) | |
tree | 4d0832c4c9ced2503e2d899eb56952f87511d4ab /arch/x86/net/bpf_jit.S | |
parent | ipv4: Kill RTO_CONN. (diff) | |
download | linux-0a14842f5a3c0e88a1e59fac5c3025db39721f74.tar.gz linux-0a14842f5a3c0e88a1e59fac5c3025db39721f74.tar.bz2 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 'arch/x86/net/bpf_jit.S')
-rw-r--r-- | arch/x86/net/bpf_jit.S | 140 |
1 files changed, 140 insertions, 0 deletions
diff --git a/arch/x86/net/bpf_jit.S b/arch/x86/net/bpf_jit.S new file mode 100644 index 000000000000..66870223f8c5 --- /dev/null +++ b/arch/x86/net/bpf_jit.S @@ -0,0 +1,140 @@ +/* bpf_jit.S : BPF JIT helper functions + * + * Copyright (C) 2011 Eric Dumazet (eric.dumazet@gmail.com) + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation; version 2 + * of the License. + */ +#include <linux/linkage.h> +#include <asm/dwarf2.h> + +/* + * Calling convention : + * rdi : skb pointer + * esi : offset of byte(s) to fetch in skb (can be scratched) + * r8 : copy of skb->data + * r9d : hlen = skb->len - skb->data_len + */ +#define SKBDATA %r8 + +sk_load_word_ind: + .globl sk_load_word_ind + + add %ebx,%esi /* offset += X */ +# test %esi,%esi /* if (offset < 0) goto bpf_error; */ + js bpf_error + +sk_load_word: + .globl sk_load_word + + mov %r9d,%eax # hlen + sub %esi,%eax # hlen - offset + cmp $3,%eax + jle bpf_slow_path_word + mov (SKBDATA,%rsi),%eax + bswap %eax /* ntohl() */ + ret + + +sk_load_half_ind: + .globl sk_load_half_ind + + add %ebx,%esi /* offset += X */ + js bpf_error + +sk_load_half: + .globl sk_load_half + + mov %r9d,%eax + sub %esi,%eax # hlen - offset + cmp $1,%eax + jle bpf_slow_path_half + movzwl (SKBDATA,%rsi),%eax + rol $8,%ax # ntohs() + ret + +sk_load_byte_ind: + .globl sk_load_byte_ind + add %ebx,%esi /* offset += X */ + js bpf_error + +sk_load_byte: + .globl sk_load_byte + + cmp %esi,%r9d /* if (offset >= hlen) goto bpf_slow_path_byte */ + jle bpf_slow_path_byte + movzbl (SKBDATA,%rsi),%eax + ret + +/** + * sk_load_byte_msh - BPF_S_LDX_B_MSH helper + * + * Implements BPF_S_LDX_B_MSH : ldxb 4*([offset]&0xf) + * Must preserve A accumulator (%eax) + * Inputs : %esi is the offset value, already known positive + */ +ENTRY(sk_load_byte_msh) + CFI_STARTPROC + cmp %esi,%r9d /* if (offset >= hlen) goto bpf_slow_path_byte_msh */ + jle bpf_slow_path_byte_msh + movzbl (SKBDATA,%rsi),%ebx + and $15,%bl + shl $2,%bl + ret + CFI_ENDPROC +ENDPROC(sk_load_byte_msh) + +bpf_error: +# force a return 0 from jit handler + xor %eax,%eax + mov -8(%rbp),%rbx + leaveq + ret + +/* rsi contains offset and can be scratched */ +#define bpf_slow_path_common(LEN) \ + push %rdi; /* save skb */ \ + push %r9; \ + push SKBDATA; \ +/* rsi already has offset */ \ + mov $LEN,%ecx; /* len */ \ + lea -12(%rbp),%rdx; \ + call skb_copy_bits; \ + test %eax,%eax; \ + pop SKBDATA; \ + pop %r9; \ + pop %rdi + + +bpf_slow_path_word: + bpf_slow_path_common(4) + js bpf_error + mov -12(%rbp),%eax + bswap %eax + ret + +bpf_slow_path_half: + bpf_slow_path_common(2) + js bpf_error + mov -12(%rbp),%ax + rol $8,%ax + movzwl %ax,%eax + ret + +bpf_slow_path_byte: + bpf_slow_path_common(1) + js bpf_error + movzbl -12(%rbp),%eax + ret + +bpf_slow_path_byte_msh: + xchg %eax,%ebx /* dont lose A , X is about to be scratched */ + bpf_slow_path_common(1) + js bpf_error + movzbl -12(%rbp),%eax + and $15,%al + shl $2,%al + xchg %eax,%ebx + ret |