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/* 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>
/*
* 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 MAX_BPF_STACK (512 /* from filter.h */ + \
32 /* space for rbx,r13,r14,r15 */ + \
8 /* space for skb_copy_bits */)
#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) \
mov %rbx, %rdi; /* arg1 == skb */ \
push %r9; \
push SKBDATA; \
/* rsi already has offset */ \
mov $LEN,%ecx; /* len */ \
lea - MAX_BPF_STACK + 32(%rbp),%rdx; \
call skb_copy_bits; \
test %eax,%eax; \
pop SKBDATA; \
pop %r9;
bpf_slow_path_word:
bpf_slow_path_common(4)
js bpf_error
mov - MAX_BPF_STACK + 32(%rbp),%eax
bswap %eax
ret
bpf_slow_path_half:
bpf_slow_path_common(2)
js bpf_error
mov - MAX_BPF_STACK + 32(%rbp),%ax
rol $8,%ax
movzwl %ax,%eax
ret
bpf_slow_path_byte:
bpf_slow_path_common(1)
js bpf_error
movzbl - MAX_BPF_STACK + 32(%rbp),%eax
ret
#define sk_negative_common(SIZE) \
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; \
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 - MAX_BPF_STACK(%rbp),%rbx
mov - MAX_BPF_STACK + 8(%rbp),%r13
mov - MAX_BPF_STACK + 16(%rbp),%r14
mov - MAX_BPF_STACK + 24(%rbp),%r15
leaveq
ret
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