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1 | /* bpf_jit.S : BPF JIT helper functions |
2 | * | |
3 | * Copyright (C) 2011 Eric Dumazet (eric.dumazet@gmail.com) | |
4 | * | |
5 | * This program is free software; you can redistribute it and/or | |
6 | * modify it under the terms of the GNU General Public License | |
7 | * as published by the Free Software Foundation; version 2 | |
8 | * of the License. | |
9 | */ | |
10 | #include <linux/linkage.h> | |
0a14842f ED |
11 | |
12 | /* | |
13 | * Calling convention : | |
62258278 | 14 | * rbx : skb pointer (callee saved) |
0a14842f | 15 | * esi : offset of byte(s) to fetch in skb (can be scratched) |
62258278 | 16 | * r10 : copy of skb->data |
0a14842f ED |
17 | * r9d : hlen = skb->len - skb->data_len |
18 | */ | |
62258278 | 19 | #define SKBDATA %r10 |
a998d434 | 20 | #define SKF_MAX_NEG_OFF $(-0x200000) /* SKF_LL_OFF from filter.h */ |
62258278 AS |
21 | #define MAX_BPF_STACK (512 /* from filter.h */ + \ |
22 | 32 /* space for rbx,r13,r14,r15 */ + \ | |
23 | 8 /* space for skb_copy_bits */) | |
0a14842f ED |
24 | |
25 | sk_load_word: | |
26 | .globl sk_load_word | |
27 | ||
a998d434 JS |
28 | test %esi,%esi |
29 | js bpf_slow_path_word_neg | |
30 | ||
31 | sk_load_word_positive_offset: | |
32 | .globl sk_load_word_positive_offset | |
33 | ||
0a14842f ED |
34 | mov %r9d,%eax # hlen |
35 | sub %esi,%eax # hlen - offset | |
36 | cmp $3,%eax | |
37 | jle bpf_slow_path_word | |
38 | mov (SKBDATA,%rsi),%eax | |
39 | bswap %eax /* ntohl() */ | |
40 | ret | |
41 | ||
0a14842f ED |
42 | sk_load_half: |
43 | .globl sk_load_half | |
44 | ||
a998d434 JS |
45 | test %esi,%esi |
46 | js bpf_slow_path_half_neg | |
47 | ||
48 | sk_load_half_positive_offset: | |
49 | .globl sk_load_half_positive_offset | |
50 | ||
0a14842f ED |
51 | mov %r9d,%eax |
52 | sub %esi,%eax # hlen - offset | |
53 | cmp $1,%eax | |
54 | jle bpf_slow_path_half | |
55 | movzwl (SKBDATA,%rsi),%eax | |
56 | rol $8,%ax # ntohs() | |
57 | ret | |
58 | ||
0a14842f ED |
59 | sk_load_byte: |
60 | .globl sk_load_byte | |
61 | ||
a998d434 JS |
62 | test %esi,%esi |
63 | js bpf_slow_path_byte_neg | |
64 | ||
65 | sk_load_byte_positive_offset: | |
66 | .globl sk_load_byte_positive_offset | |
67 | ||
0a14842f ED |
68 | cmp %esi,%r9d /* if (offset >= hlen) goto bpf_slow_path_byte */ |
69 | jle bpf_slow_path_byte | |
70 | movzbl (SKBDATA,%rsi),%eax | |
71 | ret | |
72 | ||
0a14842f ED |
73 | /* rsi contains offset and can be scratched */ |
74 | #define bpf_slow_path_common(LEN) \ | |
62258278 | 75 | mov %rbx, %rdi; /* arg1 == skb */ \ |
0a14842f ED |
76 | push %r9; \ |
77 | push SKBDATA; \ | |
78 | /* rsi already has offset */ \ | |
79 | mov $LEN,%ecx; /* len */ \ | |
62258278 | 80 | lea - MAX_BPF_STACK + 32(%rbp),%rdx; \ |
0a14842f ED |
81 | call skb_copy_bits; \ |
82 | test %eax,%eax; \ | |
83 | pop SKBDATA; \ | |
62258278 | 84 | pop %r9; |
0a14842f ED |
85 | |
86 | ||
87 | bpf_slow_path_word: | |
88 | bpf_slow_path_common(4) | |
89 | js bpf_error | |
62258278 | 90 | mov - MAX_BPF_STACK + 32(%rbp),%eax |
0a14842f ED |
91 | bswap %eax |
92 | ret | |
93 | ||
94 | bpf_slow_path_half: | |
95 | bpf_slow_path_common(2) | |
96 | js bpf_error | |
62258278 | 97 | mov - MAX_BPF_STACK + 32(%rbp),%ax |
0a14842f ED |
98 | rol $8,%ax |
99 | movzwl %ax,%eax | |
100 | ret | |
101 | ||
102 | bpf_slow_path_byte: | |
103 | bpf_slow_path_common(1) | |
104 | js bpf_error | |
62258278 | 105 | movzbl - MAX_BPF_STACK + 32(%rbp),%eax |
0a14842f | 106 | ret |
a998d434 JS |
107 | |
108 | #define sk_negative_common(SIZE) \ | |
62258278 | 109 | mov %rbx, %rdi; /* arg1 == skb */ \ |
a998d434 JS |
110 | push %r9; \ |
111 | push SKBDATA; \ | |
112 | /* rsi already has offset */ \ | |
fdfaf64e | 113 | mov $SIZE,%edx; /* size */ \ |
a998d434 JS |
114 | call bpf_internal_load_pointer_neg_helper; \ |
115 | test %rax,%rax; \ | |
116 | pop SKBDATA; \ | |
117 | pop %r9; \ | |
a998d434 JS |
118 | jz bpf_error |
119 | ||
a998d434 JS |
120 | bpf_slow_path_word_neg: |
121 | cmp SKF_MAX_NEG_OFF, %esi /* test range */ | |
122 | jl bpf_error /* offset lower -> error */ | |
123 | sk_load_word_negative_offset: | |
124 | .globl sk_load_word_negative_offset | |
125 | sk_negative_common(4) | |
126 | mov (%rax), %eax | |
127 | bswap %eax | |
128 | ret | |
129 | ||
130 | bpf_slow_path_half_neg: | |
131 | cmp SKF_MAX_NEG_OFF, %esi | |
132 | jl bpf_error | |
133 | sk_load_half_negative_offset: | |
134 | .globl sk_load_half_negative_offset | |
135 | sk_negative_common(2) | |
136 | mov (%rax),%ax | |
137 | rol $8,%ax | |
138 | movzwl %ax,%eax | |
139 | ret | |
140 | ||
141 | bpf_slow_path_byte_neg: | |
142 | cmp SKF_MAX_NEG_OFF, %esi | |
143 | jl bpf_error | |
144 | sk_load_byte_negative_offset: | |
145 | .globl sk_load_byte_negative_offset | |
146 | sk_negative_common(1) | |
147 | movzbl (%rax), %eax | |
148 | ret | |
149 | ||
a998d434 JS |
150 | bpf_error: |
151 | # force a return 0 from jit handler | |
62258278 AS |
152 | xor %eax,%eax |
153 | mov - MAX_BPF_STACK(%rbp),%rbx | |
154 | mov - MAX_BPF_STACK + 8(%rbp),%r13 | |
155 | mov - MAX_BPF_STACK + 16(%rbp),%r14 | |
156 | mov - MAX_BPF_STACK + 24(%rbp),%r15 | |
a998d434 JS |
157 | leaveq |
158 | ret |