1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
|
/* 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
#define SKF_MAX_NEG_OFF $(-0x200000) /* SKF_LL_OFF from filter.h */
sk_load_word:
.globl sk_load_word
test %esi,%esi
js bpf_slow_path_word_neg
sk_load_word_positive_offset:
.globl sk_load_word_positive_offset
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:
.globl sk_load_half
test %esi,%esi
js bpf_slow_path_half_neg
sk_load_half_positive_offset:
.globl sk_load_half_positive_offset
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:
.globl sk_load_byte
test %esi,%esi
js bpf_slow_path_byte_neg
sk_load_byte_positive_offset:
.globl sk_load_byte_positive_offset
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
*/
sk_load_byte_msh:
.globl sk_load_byte_msh
test %esi,%esi
js bpf_slow_path_byte_msh_neg
sk_load_byte_msh_positive_offset:
.globl sk_load_byte_msh_positive_offset
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
/* 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
#define sk_negative_common(SIZE) \
push %rdi; /* save skb */ \
push %r9; \
push SKBDATA; \
/* rsi already has offset */ \
mov $SIZE,%edx; /* size */ \
call bpf_internal_load_pointer_neg_helper; \
test %rax,%rax; \
pop SKBDATA; \
pop %r9; \
pop %rdi; \
jz bpf_error
bpf_slow_path_word_neg:
cmp SKF_MAX_NEG_OFF, %esi /* test range */
jl bpf_error /* offset lower -> error */
sk_load_word_negative_offset:
.globl sk_load_word_negative_offset
sk_negative_common(4)
mov (%rax), %eax
bswap %eax
ret
bpf_slow_path_half_neg:
cmp SKF_MAX_NEG_OFF, %esi
jl bpf_error
sk_load_half_negative_offset:
.globl sk_load_half_negative_offset
sk_negative_common(2)
mov (%rax),%ax
rol $8,%ax
movzwl %ax,%eax
ret
bpf_slow_path_byte_neg:
cmp SKF_MAX_NEG_OFF, %esi
jl bpf_error
sk_load_byte_negative_offset:
.globl sk_load_byte_negative_offset
sk_negative_common(1)
movzbl (%rax), %eax
ret
bpf_slow_path_byte_msh_neg:
cmp SKF_MAX_NEG_OFF, %esi
jl bpf_error
sk_load_byte_msh_negative_offset:
.globl sk_load_byte_msh_negative_offset
xchg %eax,%ebx /* dont lose A , X is about to be scratched */
sk_negative_common(1)
movzbl (%rax),%eax
and $15,%al
shl $2,%al
xchg %eax,%ebx
ret
bpf_error:
# force a return 0 from jit handler
xor %eax,%eax
mov -8(%rbp),%rbx
leaveq
ret
|
