1 #include <sys/socket.h>
2 #include <sysexits.h>
3 #include <unistd.h>
4
5 #include <bpf/btf.h>
6 #include <bpf/libbpf.h>
7
8 #include <cstdlib>
9 #include <sstream>
10
11 constexpr int kERROR_BPF_OBJECT_OPEN = 1;
12 constexpr int kERROR_BTF_NOT_FOUND = 2;
13 constexpr int kERROR_LOAD_BTF = 3;
14 constexpr int kERROR_SEND_BTF_FD = 4;
15 constexpr int kERROR_BTF_TYPE_IDS = 5;
16
no_print(enum libbpf_print_level,const char *,va_list)17 static int no_print(enum libbpf_print_level , const char *, va_list ) {
18 return 0;
19 }
20
sendBtfFd(int socket,int fd)21 int sendBtfFd(int socket, int fd) {
22 char buf[CMSG_SPACE(sizeof(fd))];
23
24 struct msghdr msg;
25 memset(&msg, 0, sizeof(msg));
26 msg.msg_control = buf;
27 msg.msg_controllen = sizeof(buf);
28
29 struct cmsghdr *cmsg = CMSG_FIRSTHDR(&msg);
30 cmsg->cmsg_level = SOL_SOCKET;
31 cmsg->cmsg_type = SCM_RIGHTS;
32 cmsg->cmsg_len = CMSG_LEN(sizeof(fd));
33
34 *(int*)CMSG_DATA(cmsg) = fd;
35 return sendmsg(socket, &msg, 0);
36 }
37
main(int argc,char ** argv)38 int main(int argc, char **argv) {
39 int ret = 0, socketFd, pipeFd, btfFd;
40 if (argc != 4) return EX_USAGE;
41
42 socketFd = atoi(argv[1]);
43 pipeFd = atoi(argv[2]);
44
45 auto path(argv[3]);
46 ret = libbpf_set_strict_mode(LIBBPF_STRICT_CLEAN_PTRS);
47 if (ret) return EX_SOFTWARE;
48
49 libbpf_set_print(no_print);
50
51 struct bpf_object_open_opts opts = {
52 .relaxed_maps = true,
53 .sz = sizeof(struct bpf_object_open_opts),
54 };
55 struct bpf_object *obj = bpf_object__open_file(path, &opts);
56 if (!obj) return kERROR_BPF_OBJECT_OPEN;
57
58 struct btf *btf = bpf_object__btf(obj);
59 if (!btf) return kERROR_BTF_NOT_FOUND;
60
61 ret = btf__load_into_kernel(btf);
62 if (ret) {
63 if (errno != EINVAL) return kERROR_LOAD_BTF;
64 // For BTF_KIND_FUNC, newer kernels can read the BTF_INFO_VLEN bits of
65 // struct btf_type to distinguish static vs. global vs. extern
66 // functions, but older kernels enforce that only the BTF_INFO_KIND bits
67 // can be set. Retry with non-BTF_INFO_KIND bits zeroed out to handle
68 // this case.
69 for (unsigned int i = 1; i < btf__type_cnt(btf); ++i) {
70 struct btf_type *bt = (struct btf_type *)btf__type_by_id(btf, i);
71 if (btf_is_func(bt)) {
72 bt->info = (BTF_INFO_KIND(bt->info)) << 24;
73 }
74 }
75 if (btf__load_into_kernel(btf)) return kERROR_LOAD_BTF;
76 }
77
78 btfFd = btf__fd(btf);
79 if (sendBtfFd(socketFd, btf__fd(btf))) return kERROR_SEND_BTF_FD;
80
81 std::ostringstream oss;
82 struct bpf_map *m;
83 bpf_object__for_each_map(m, obj) {
84 unsigned kTid, vTid;
85 auto mapName = bpf_map__name(m);
86 if (btf__get_map_kv_tids(btf, mapName, bpf_map__key_size(m),
87 bpf_map__value_size(m), &kTid, &vTid))
88 return kERROR_BTF_TYPE_IDS;
89 oss << mapName << ' ' << kTid << ' ' << vTid << '\n';
90 }
91 write(pipeFd, oss.str().c_str(), oss.str().size());
92
93 return EX_OK;
94 }
95