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#include <sys/socket.h>
#include <sysexits.h>
#include <unistd.h>
#include <bpf/btf.h>
#include <bpf/libbpf.h>
#include <cstdlib>
#include <sstream>
constexpr int kERROR_BPF_OBJECT_OPEN = 1;
constexpr int kERROR_BTF_NOT_FOUND = 2;
constexpr int kERROR_LOAD_BTF = 3;
constexpr int kERROR_SEND_BTF_FD = 4;
constexpr int kERROR_BTF_TYPE_IDS = 5;
static int no_print(enum libbpf_print_level , const char *, va_list ) {
return 0;
}
int sendBtfFd(int socket, int fd) {
char buf[CMSG_SPACE(sizeof(fd))];
struct msghdr msg;
memset(&msg, 0, sizeof(msg));
msg.msg_control = buf;
msg.msg_controllen = sizeof(buf);
struct cmsghdr *cmsg = CMSG_FIRSTHDR(&msg);
cmsg->cmsg_level = SOL_SOCKET;
cmsg->cmsg_type = SCM_RIGHTS;
cmsg->cmsg_len = CMSG_LEN(sizeof(fd));
*(int*)CMSG_DATA(cmsg) = fd;
return sendmsg(socket, &msg, 0);
}
int main(int argc, char **argv) {
int ret = 0, socketFd, pipeFd, btfFd;
if (argc != 4) return EX_USAGE;
socketFd = atoi(argv[1]);
pipeFd = atoi(argv[2]);
auto path(argv[3]);
ret = libbpf_set_strict_mode(LIBBPF_STRICT_CLEAN_PTRS);
if (ret) return EX_SOFTWARE;
libbpf_set_print(no_print);
struct bpf_object_open_opts opts = {
.relaxed_maps = true,
.sz = sizeof(struct bpf_object_open_opts),
};
struct bpf_object *obj = bpf_object__open_file(path, &opts);
if (!obj) return kERROR_BPF_OBJECT_OPEN;
struct btf *btf = bpf_object__btf(obj);
if (!btf) return kERROR_BTF_NOT_FOUND;
ret = btf__load_into_kernel(btf);
if (ret) {
if (errno != EINVAL) return kERROR_LOAD_BTF;
// For BTF_KIND_FUNC, newer kernels can read the BTF_INFO_VLEN bits of
// struct btf_type to distinguish static vs. global vs. extern
// functions, but older kernels enforce that only the BTF_INFO_KIND bits
// can be set. Retry with non-BTF_INFO_KIND bits zeroed out to handle
// this case.
for (unsigned int i = 1; i < btf__type_cnt(btf); ++i) {
struct btf_type *bt = (struct btf_type *)btf__type_by_id(btf, i);
if (btf_is_func(bt)) {
bt->info = (BTF_INFO_KIND(bt->info)) << 24;
}
}
if (btf__load_into_kernel(btf)) return kERROR_LOAD_BTF;
}
btfFd = btf__fd(btf);
if (sendBtfFd(socketFd, btf__fd(btf))) return kERROR_SEND_BTF_FD;
std::ostringstream oss;
struct bpf_map *m;
bpf_object__for_each_map(m, obj) {
unsigned kTid, vTid;
auto mapName = bpf_map__name(m);
if (btf__get_map_kv_tids(btf, mapName, bpf_map__key_size(m),
bpf_map__value_size(m), &kTid, &vTid))
return kERROR_BTF_TYPE_IDS;
oss << mapName << ' ' << kTid << ' ' << vTid << '\n';
}
write(pipeFd, oss.str().c_str(), oss.str().size());
return EX_OK;
}
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