1 // SPDX-License-Identifier: GPL-2.0
2 /* Copyright (c) 2019 Facebook */
3 #include <linux/stddef.h>
4 #include <linux/if_ether.h>
5 #include <linux/ipv6.h>
6 #include <linux/bpf.h>
7 #include <linux/tcp.h>
8 #include <bpf/bpf_helpers.h>
9 #include <bpf/bpf_endian.h>
10 #include <bpf/bpf_tracing.h>
11
12 struct sk_buff {
13 unsigned int len;
14 };
15
16 __u64 test_result = 0;
17 SEC("fexit/test_pkt_access")
18 int BPF_PROG(test_main, struct sk_buff *skb, int ret)
19 {
20 int len;
21
22 __builtin_preserve_access_index(({
23 len = skb->len;
24 }));
25 if (len != 74 || ret != 0)
26 return 0;
27 test_result = 1;
28 return 0;
29 }
30
31 __u64 test_result_subprog1 = 0;
32 SEC("fexit/test_pkt_access_subprog1")
33 int BPF_PROG(test_subprog1, struct sk_buff *skb, int ret)
34 {
35 int len;
36
37 __builtin_preserve_access_index(({
38 len = skb->len;
39 }));
40 if (len != 74 || ret != 148)
41 return 0;
42 test_result_subprog1 = 1;
43 return 0;
44 }
45
46 /* Though test_pkt_access_subprog2() is defined in C as:
47 * static __attribute__ ((noinline))
48 * int test_pkt_access_subprog2(int val, volatile struct __sk_buff *skb)
49 * {
50 * return skb->len * val;
51 * }
52 * llvm optimizations remove 'int val' argument and generate BPF assembly:
53 * r0 = *(u32 *)(r1 + 0)
54 * w0 <<= 1
55 * exit
56 * In such case the verifier falls back to conservative and
57 * tracing program can access arguments and return value as u64
58 * instead of accurate types.
59 */
60 struct args_subprog2 {
61 __u64 args[5];
62 __u64 ret;
63 };
64 __u64 test_result_subprog2 = 0;
65 SEC("fexit/test_pkt_access_subprog2")
66 int test_subprog2(struct args_subprog2 *ctx)
67 {
68 struct sk_buff *skb = (void *)ctx->args[0];
69 __u64 ret;
70 int len;
71
72 bpf_probe_read_kernel(&len, sizeof(len),
73 __builtin_preserve_access_index(&skb->len));
74
75 ret = ctx->ret;
76 /* bpf_prog_test_load() loads "test_pkt_access.bpf.o" with
77 * BPF_F_TEST_RND_HI32 which randomizes upper 32 bits after BPF_ALU32
78 * insns. Hence after 'w0 <<= 1' upper bits of $rax are random. That is
79 * expected and correct. Trim them.
80 */
81 ret = (__u32) ret;
82 if (len != 74 || ret != 148)
83 return 0;
84 test_result_subprog2 = 1;
85 return 0;
86 }
87
88 __u64 test_result_subprog3 = 0;
89 SEC("fexit/test_pkt_access_subprog3")
90 int BPF_PROG(test_subprog3, int val, struct sk_buff *skb, int ret)
91 {
92 int len;
93
94 __builtin_preserve_access_index(({
95 len = skb->len;
96 }));
97 if (len != 74 || ret != 74 * val || val != 3)
98 return 0;
99 test_result_subprog3 = 1;
100 return 0;
101 }
102
103 __u64 test_get_skb_len = 0;
104 SEC("freplace/get_skb_len")
105 int new_get_skb_len(struct __sk_buff *skb)
106 {
107 int len = skb->len;
108
109 if (len != 74)
110 return 0;
111 test_get_skb_len = 1;
112 return 74; /* original get_skb_len() returns skb->len */
113 }
114
115 __u64 test_get_skb_ifindex = 0;
116 SEC("freplace/get_skb_ifindex")
117 int new_get_skb_ifindex(int val, struct __sk_buff *skb, int var)
118 {
119 void *data_end = (void *)(long)skb->data_end;
120 void *data = (void *)(long)skb->data;
121 struct ipv6hdr ip6, *ip6p;
122 int ifindex = skb->ifindex;
123
124 /* check that BPF extension can read packet via direct packet access */
125 if (data + 14 + sizeof(ip6) > data_end)
126 return 0;
127 ip6p = data + 14;
128
129 if (ip6p->nexthdr != 6 || ip6p->payload_len != __bpf_constant_htons(123))
130 return 0;
131
132 /* check that legacy packet access helper works too */
133 if (bpf_skb_load_bytes(skb, 14, &ip6, sizeof(ip6)) < 0)
134 return 0;
135 ip6p = &ip6;
136 if (ip6p->nexthdr != 6 || ip6p->payload_len != __bpf_constant_htons(123))
137 return 0;
138
139 if (ifindex != 1 || val != 3 || var != 1)
140 return 0;
141 test_get_skb_ifindex = 1;
142 return 3; /* original get_skb_ifindex() returns val * ifindex * var */
143 }
144
145 volatile __u64 test_get_constant = 0;
146 SEC("freplace/get_constant")
147 int new_get_constant(long val)
148 {
149 if (val != 123)
150 return 0;
151 test_get_constant = 1;
152 return test_get_constant; /* original get_constant() returns val - 122 */
153 }
154
155 __u64 test_pkt_write_access_subprog = 0;
156 SEC("freplace/test_pkt_write_access_subprog")
157 int new_test_pkt_write_access_subprog(struct __sk_buff *skb, __u32 off)
158 {
159
160 void *data = (void *)(long)skb->data;
161 void *data_end = (void *)(long)skb->data_end;
162 struct tcphdr *tcp;
163
164 if (off > sizeof(struct ethhdr) + sizeof(struct ipv6hdr))
165 return -1;
166
167 tcp = data + off;
168 if (tcp + 1 > data_end)
169 return -1;
170
171 /* make modifications to the packet data */
172 tcp->check++;
173 tcp->syn = 0;
174
175 test_pkt_write_access_subprog = 1;
176 return 0;
177 }
178
179 char _license[] SEC("license") = "GPL";
180
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