summaryrefslogtreecommitdiffstats
path: root/arch/x86/net/bpf_jit.S
blob: 66870223f8c5e001e7fc5bbe02b659c8778def86 (plain)
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
/* 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

sk_load_word_ind:
	.globl	sk_load_word_ind

	add	%ebx,%esi	/* offset += X */
#	test    %esi,%esi	/* if (offset < 0) goto bpf_error; */
	js	bpf_error

sk_load_word:
	.globl	sk_load_word

	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_ind:
	.globl sk_load_half_ind

	add	%ebx,%esi	/* offset += X */
	js	bpf_error

sk_load_half:
	.globl	sk_load_half

	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_ind:
	.globl sk_load_byte_ind
	add	%ebx,%esi	/* offset += X */
	js	bpf_error

sk_load_byte:
	.globl	sk_load_byte

	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, already known positive
 */
ENTRY(sk_load_byte_msh)
	CFI_STARTPROC
	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
	CFI_ENDPROC
ENDPROC(sk_load_byte_msh)

bpf_error:
# force a return 0 from jit handler
	xor		%eax,%eax
	mov		-8(%rbp),%rbx
	leaveq
	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