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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 | /* 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/frame.h>
/*
* Calling convention :
* rbx : skb pointer (callee saved)
* esi : offset of byte(s) to fetch in skb (can be scratched)
* r10 : copy of skb->data
* r9d : hlen = skb->len - skb->data_len
*/
#define SKBDATA %r10
#define SKF_MAX_NEG_OFF $(-0x200000) /* SKF_LL_OFF from filter.h */
#define FUNC(name) \
.globl name; \
.type name, @function; \
name:
FUNC(sk_load_word)
test %esi,%esi
js bpf_slow_path_word_neg
FUNC(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
FUNC(sk_load_half)
test %esi,%esi
js bpf_slow_path_half_neg
FUNC(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
FUNC(sk_load_byte)
test %esi,%esi
js bpf_slow_path_byte_neg
FUNC(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
/* rsi contains offset and can be scratched */
#define bpf_slow_path_common(LEN) \
lea 32(%rbp), %rdx;\
FRAME_BEGIN; \
mov %rbx, %rdi; /* arg1 == skb */ \
push %r9; \
push SKBDATA; \
/* rsi already has offset */ \
mov $LEN,%ecx; /* len */ \
call skb_copy_bits; \
test %eax,%eax; \
pop SKBDATA; \
pop %r9; \
FRAME_END
bpf_slow_path_word:
bpf_slow_path_common(4)
js bpf_error
mov 32(%rbp),%eax
bswap %eax
ret
bpf_slow_path_half:
bpf_slow_path_common(2)
js bpf_error
mov 32(%rbp),%ax
rol $8,%ax
movzwl %ax,%eax
ret
bpf_slow_path_byte:
bpf_slow_path_common(1)
js bpf_error
movzbl 32(%rbp),%eax
ret
#define sk_negative_common(SIZE) \
FRAME_BEGIN; \
mov %rbx, %rdi; /* arg1 == 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; \
FRAME_END; \
jz bpf_error
bpf_slow_path_word_neg:
cmp SKF_MAX_NEG_OFF, %esi /* test range */
jl bpf_error /* offset lower -> error */
FUNC(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
FUNC(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
FUNC(sk_load_byte_negative_offset)
sk_negative_common(1)
movzbl (%rax), %eax
ret
bpf_error:
# force a return 0 from jit handler
xor %eax,%eax
mov (%rbp),%rbx
mov 8(%rbp),%r13
mov 16(%rbp),%r14
mov 24(%rbp),%r15
add $40, %rbp
leaveq
ret
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