MIPS: net: Add BPF JIT

This adds initial support for BPF-JIT on MIPS

Tested on mips32 LE/BE and mips64 BE/n64 using
dhcp, ping and various tcpdump filters.

Benchmarking:

Assuming the remote MIPS target uses 192.168.154.181
as its IP address, and the local host uses 192.168.154.136,
the following results can be obtained using the following
tcpdump filter (catches no frames) and a simple
'time ping -f -c 1000000' command.

[root@(none) ~]# tcpdump -p -n -s 0 -i eth0 net 10.0.0.0/24 -d
(000) ldh      [12]
(001) jeq      #0x800           jt 2	jf 8
(002) ld       [26]
(003) and      #0xffffff00
(004) jeq      #0xa000000       jt 16	jf 5
(005) ld       [30]
(006) and      #0xffffff00
(007) jeq      #0xa000000       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      #0xa000000       jt 16	jf 13
(013) ld       [38]
(014) and      #0xffffff00
(015) jeq      #0xa000000       jt 16	jf 17
(016) ret      #65535

- BPF-JIT Disabled

real    1m38.005s
user    0m1.510s
sys     0m6.710s

- BPF-JIT Enabled

real    1m35.215s
user    0m1.200s
sys     0m4.140s

[ralf@linux-mips.org: Resolved conflict.]
Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>

arch/mips/Kbuild

@@ -16,6 +16,7 @@ obj- := $(platform-)
 
 obj-y += kernel/
 obj-y += mm/
+obj-y += net/
 
 ifdef CONFIG_KVM
 obj-y += kvm/

arch/mips/net/Makefile

+# MIPS networking code
+
+obj-$(CONFIG_BPF_JIT) += bpf_jit.o

arch/mips/net/bpf_jit.h

+/*
+ * Just-In-Time compiler for BPF filters on MIPS
+ *
+ * Copyright (c) 2014 Imagination Technologies Ltd.
+ * Author: Markos Chandras <markos.chandras@imgtec.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.
+ */
+
+#ifndef BPF_JIT_MIPS_OP_H
+#define BPF_JIT_MIPS_OP_H
+
+/* Registers used by JIT */
+#define MIPS_R_ZERO	0
+#define MIPS_R_V0	2
+#define MIPS_R_V1	3
+#define MIPS_R_A0	4
+#define MIPS_R_A1	5
+#define MIPS_R_T6	14
+#define MIPS_R_T7	15
+#define MIPS_R_S0	16
+#define MIPS_R_S1	17
+#define MIPS_R_S2	18
+#define MIPS_R_S3	19
+#define MIPS_R_S4	20
+#define MIPS_R_S5	21
+#define MIPS_R_S6	22
+#define MIPS_R_S7	23
+#define MIPS_R_SP	29
+#define MIPS_R_RA	31
+
+/* Conditional codes */
+#define MIPS_COND_EQ	0x1
+#define MIPS_COND_GE	(0x1 << 1)
+#define MIPS_COND_GT	(0x1 << 2)
+#define MIPS_COND_NE	(0x1 << 3)
+#define MIPS_COND_ALL	(0x1 << 4)
+/* Conditionals on X register or K immediate */
+#define MIPS_COND_X	(0x1 << 5)
+#define MIPS_COND_K	(0x1 << 6)
+
+#endif /* BPF_JIT_MIPS_OP_H */