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_load() loads "test_pkt_access.o" with BPF_F_TEST_RND_HI32 77 * which randomizes upper 32 bits after BPF_ALU32 insns. 78 * Hence after 'w0 <<= 1' upper bits of $rax are random. 79 * That is 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 __u32 eth_proto; 124 __u32 nh_off; 125 126 /* check that BPF extension can read packet via direct packet access */ 127 if (data + 14 + sizeof(ip6) > data_end) 128 return 0; 129 ip6p = data + 14; 130 131 if (ip6p->nexthdr != 6 || ip6p->payload_len != __bpf_constant_htons(123)) 132 return 0; 133 134 /* check that legacy packet access helper works too */ 135 if (bpf_skb_load_bytes(skb, 14, &ip6, sizeof(ip6)) < 0) 136 return 0; 137 ip6p = &ip6; 138 if (ip6p->nexthdr != 6 || ip6p->payload_len != __bpf_constant_htons(123)) 139 return 0; 140 141 if (ifindex != 1 || val != 3 || var != 1) 142 return 0; 143 test_get_skb_ifindex = 1; 144 return 3; /* original get_skb_ifindex() returns val * ifindex * var */ 145 } 146 147 volatile __u64 test_get_constant = 0; 148 SEC("freplace/get_constant") 149 int new_get_constant(long val) 150 { 151 if (val != 123) 152 return 0; 153 test_get_constant = 1; 154 return test_get_constant; /* original get_constant() returns val - 122 */ 155 } 156 157 __u64 test_pkt_write_access_subprog = 0; 158 SEC("freplace/test_pkt_write_access_subprog") 159 int new_test_pkt_write_access_subprog(struct __sk_buff *skb, __u32 off) 160 { 161 162 void *data = (void *)(long)skb->data; 163 void *data_end = (void *)(long)skb->data_end; 164 struct tcphdr *tcp; 165 166 if (off > sizeof(struct ethhdr) + sizeof(struct ipv6hdr)) 167 return -1; 168 169 tcp = data + off; 170 if (tcp + 1 > data_end) 171 return -1; 172 173 /* make modifications to the packet data */ 174 tcp->check++; 175 tcp->syn = 0; 176 177 test_pkt_write_access_subprog = 1; 178 return 0; 179 } 180 181 char _license[] SEC("license") = "GPL"; 182