2 * bpf_jib_asm.S: Packet/header access helper functions for MIPS/MIPS64 BPF
5 * Copyright (C) 2015 Imagination Technologies Ltd.
6 * Author: Markos Chandras <markos.chandras@imgtec.com>
8 * This program is free software; you can redistribute it and/or modify it
9 * under the terms of the GNU General Public License as published by the
10 * Free Software Foundation; version 2 of the License.
14 #include <asm/regdef.h>
19 * r_skb_hl skb header length
21 * r_off(a1) offset register
27 * r_s0 Scratch register 0
28 * r_s1 Scratch register 1
32 * a1: offset (imm or imm + X)
34 * All non-BPF-ABI registers are free for use. On return, we only
35 * care about r_ret. The BPF-ABI registers are assumed to remain
36 * unmodified during the entire filter operation.
41 #define SKF_LL_OFF (-0x200000) /* Can't include linux/filter.h in assembly */
43 /* We know better :) so prevent assembler reordering etc */
46 #define is_offset_negative(TYPE) \
47 /* If offset is negative we have more work to do */ \
49 bgtz t0, bpf_slow_path_##TYPE##_neg; \
50 /* Be careful what follows in DS. */
52 #define is_offset_in_header(SIZE, TYPE) \
53 /* Reading from header? */ \
54 addiu $r_s0, $r_skb_hl, -SIZE; \
55 slt t0, $r_s0, offset; \
56 bgtz t0, bpf_slow_path_##TYPE; \
59 is_offset_negative(word)
60 FEXPORT(sk_load_word_positive)
61 is_offset_in_header(4, word)
62 /* Offset within header boundaries */
63 PTR_ADDU t1, $r_skb_data, offset
65 #ifdef CONFIG_CPU_LITTLE_ENDIAN
66 # if defined(__mips_isa_rev) && (__mips_isa_rev >= 2)
86 is_offset_negative(half)
87 FEXPORT(sk_load_half_positive)
88 is_offset_in_header(2, half)
89 /* Offset within header boundaries */
90 PTR_ADDU t1, $r_skb_data, offset
92 #ifdef CONFIG_CPU_LITTLE_ENDIAN
93 # if defined(__mips_isa_rev) && (__mips_isa_rev >= 2)
109 is_offset_negative(byte)
110 FEXPORT(sk_load_byte_positive)
111 is_offset_in_header(1, byte)
112 /* Offset within header boundaries */
113 PTR_ADDU t1, $r_skb_data, offset
120 * call skb_copy_bits:
121 * (prototype in linux/skbuff.h)
123 * int skb_copy_bits(sk_buff *skb, int offset, void *to, int len)
125 * o32 mandates we leave 4 spaces for argument registers in case
126 * the callee needs to use them. Even though we don't care about
127 * the argument registers ourselves, we need to allocate that space
128 * to remain ABI compliant since the callee may want to use that space.
129 * We also allocate 2 more spaces for $r_ra and our return register (*to).
131 * n64 is a bit different. The *caller* will allocate the space to preserve
132 * the arguments. So in 64-bit kernels, we allocate the 4-arg space for no
133 * good reason but it does not matter that much really.
135 * (void *to) is returned in r_s0
138 #define bpf_slow_path_common(SIZE) \
139 /* Quick check. Are we within reasonable boundaries? */ \
140 LONG_ADDIU $r_s1, $r_skb_len, -SIZE; \
141 sltu $r_s0, offset, $r_s1; \
143 /* Load 4th argument in DS */ \
144 LONG_ADDIU a3, zero, SIZE; \
145 PTR_ADDIU $r_sp, $r_sp, -(6 * SZREG); \
146 PTR_LA t0, skb_copy_bits; \
147 PTR_S $r_ra, (5 * SZREG)($r_sp); \
148 /* Assign low slot to a2 */ \
151 /* Reset our destination slot (DS but it's ok) */ \
152 INT_S zero, (4 * SZREG)($r_sp); \
154 * skb_copy_bits returns 0 on success and -EFAULT \
155 * on error. Our data live in a2. Do not bother with \
156 * our data if an error has been returned. \
158 /* Restore our frame */ \
159 PTR_L $r_ra, (5 * SZREG)($r_sp); \
160 INT_L $r_s0, (4 * SZREG)($r_sp); \
162 PTR_ADDIU $r_sp, $r_sp, 6 * SZREG; \
165 NESTED(bpf_slow_path_word, (6 * SZREG), $r_sp)
166 bpf_slow_path_common(4)
167 #ifdef CONFIG_CPU_LITTLE_ENDIAN
168 # if defined(__mips_isa_rev) && (__mips_isa_rev >= 2)
178 andi t1, $r_s0, 0xff00
189 END(bpf_slow_path_word)
191 NESTED(bpf_slow_path_half, (6 * SZREG), $r_sp)
192 bpf_slow_path_common(2)
193 #ifdef CONFIG_CPU_LITTLE_ENDIAN
194 # if defined(__mips_isa_rev) && (__mips_isa_rev >= 2)
199 andi t1, $r_s0, 0xff00
210 END(bpf_slow_path_half)
212 NESTED(bpf_slow_path_byte, (6 * SZREG), $r_sp)
213 bpf_slow_path_common(1)
217 END(bpf_slow_path_byte)
220 * Negative entry points
222 .macro bpf_is_end_of_data
224 /* Reading link layer data? */
227 /* Be careful what follows in DS. */
230 * call skb_copy_bits:
231 * (prototype in linux/filter.h)
233 * void *bpf_internal_load_pointer_neg_helper(const struct sk_buff *skb,
234 * int k, unsigned int size)
236 * see above (bpf_slow_path_common) for ABI restrictions
238 #define bpf_negative_common(SIZE) \
239 PTR_ADDIU $r_sp, $r_sp, -(6 * SZREG); \
240 PTR_LA t0, bpf_internal_load_pointer_neg_helper; \
241 PTR_S $r_ra, (5 * SZREG)($r_sp); \
244 PTR_L $r_ra, (5 * SZREG)($r_sp); \
245 /* Check return pointer */ \
247 PTR_ADDIU $r_sp, $r_sp, 6 * SZREG; \
248 /* Preserve our pointer */ \
250 /* Set return value */ \
253 bpf_slow_path_word_neg:
255 NESTED(sk_load_word_negative, (6 * SZREG), $r_sp)
256 bpf_negative_common(4)
259 END(sk_load_word_negative)
261 bpf_slow_path_half_neg:
263 NESTED(sk_load_half_negative, (6 * SZREG), $r_sp)
264 bpf_negative_common(2)
267 END(sk_load_half_negative)
269 bpf_slow_path_byte_neg:
271 NESTED(sk_load_byte_negative, (6 * SZREG), $r_sp)
272 bpf_negative_common(1)
275 END(sk_load_byte_negative)
279 addiu $r_ret, zero, 1