tools/lib/bpf/libbpf_probes.c

   1 // SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
   2 /* Copyright (c) 2019 Netronome Systems, Inc. */
   3
   4 #include <errno.h>
   5 #include <fcntl.h>
   6 #include <string.h>
   7 #include <stdlib.h>
   8 #include <unistd.h>
   9 #include <net/if.h>
  10 #include <sys/utsname.h>
  11
  12 #include <linux/btf.h>
  13 #include <linux/filter.h>
  14 #include <linux/kernel.h>
  15
  16 #include "bpf.h"
  17 #include "libbpf.h"
  18 #include "libbpf_internal.h"
  19
  20 static int probe_prog_load(enum bpf_prog_type prog_type,
  21                            const struct bpf_insn *insns, size_t insns_cnt,
  22                            char *log_buf, size_t log_buf_sz)
  23 {
  24         LIBBPF_OPTS(bpf_prog_load_opts, opts,
  25                 .log_buf = log_buf,
  26                 .log_size = log_buf_sz,
  27                 .log_level = log_buf ? 1 : 0,
  28         );
  29         int fd, err, exp_err = 0;
  30         const char *exp_msg = NULL;
  31         char buf[4096];
  32
  33         switch (prog_type) {
  34         case BPF_PROG_TYPE_CGROUP_SOCK_ADDR:
  35                 opts.expected_attach_type = BPF_CGROUP_INET4_CONNECT;
  36                 break;
  37         case BPF_PROG_TYPE_CGROUP_SOCKOPT:
  38                 opts.expected_attach_type = BPF_CGROUP_GETSOCKOPT;
  39                 break;
  40         case BPF_PROG_TYPE_SK_LOOKUP:
  41                 opts.expected_attach_type = BPF_SK_LOOKUP;
  42                 break;
  43         case BPF_PROG_TYPE_KPROBE:
  44                 opts.kern_version = get_kernel_version();
  45                 break;
  46         case BPF_PROG_TYPE_LIRC_MODE2:
  47                 opts.expected_attach_type = BPF_LIRC_MODE2;
  48                 break;
  49         case BPF_PROG_TYPE_TRACING:
  50         case BPF_PROG_TYPE_LSM:
  51                 opts.log_buf = buf;
  52                 opts.log_size = sizeof(buf);
  53                 opts.log_level = 1;
  54                 if (prog_type == BPF_PROG_TYPE_TRACING)
  55                         opts.expected_attach_type = BPF_TRACE_FENTRY;
  56                 else
  57                         opts.expected_attach_type = BPF_MODIFY_RETURN;
  58                 opts.attach_btf_id = 1;
  59
  60                 exp_err = -EINVAL;
  61                 exp_msg = "attach_btf_id 1 is not a function";
  62                 break;
  63         case BPF_PROG_TYPE_EXT:
  64                 opts.log_buf = buf;
  65                 opts.log_size = sizeof(buf);
  66                 opts.log_level = 1;
  67                 opts.attach_btf_id = 1;
  68
  69                 exp_err = -EINVAL;
  70                 exp_msg = "Cannot replace kernel functions";
  71                 break;
  72         case BPF_PROG_TYPE_SYSCALL:
  73                 opts.prog_flags = BPF_F_SLEEPABLE;
  74                 break;
  75         case BPF_PROG_TYPE_STRUCT_OPS:
  76                 exp_err = -524; /* -ENOTSUPP */
  77                 break;
  78         case BPF_PROG_TYPE_UNSPEC:
  79         case BPF_PROG_TYPE_SOCKET_FILTER:
  80         case BPF_PROG_TYPE_SCHED_CLS:
  81         case BPF_PROG_TYPE_SCHED_ACT:
  82         case BPF_PROG_TYPE_TRACEPOINT:
  83         case BPF_PROG_TYPE_XDP:
  84         case BPF_PROG_TYPE_PERF_EVENT:
  85         case BPF_PROG_TYPE_CGROUP_SKB:
  86         case BPF_PROG_TYPE_CGROUP_SOCK:
  87         case BPF_PROG_TYPE_LWT_IN:
  88         case BPF_PROG_TYPE_LWT_OUT:
  89         case BPF_PROG_TYPE_LWT_XMIT:
  90         case BPF_PROG_TYPE_SOCK_OPS:
  91         case BPF_PROG_TYPE_SK_SKB:
  92         case BPF_PROG_TYPE_CGROUP_DEVICE:
  93         case BPF_PROG_TYPE_SK_MSG:
  94         case BPF_PROG_TYPE_RAW_TRACEPOINT:
  95         case BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE:
  96         case BPF_PROG_TYPE_LWT_SEG6LOCAL:
  97         case BPF_PROG_TYPE_SK_REUSEPORT:
  98         case BPF_PROG_TYPE_FLOW_DISSECTOR:
  99         case BPF_PROG_TYPE_CGROUP_SYSCTL:
 100                 break;
 101         default:
 102                 return -EOPNOTSUPP;
 103         }
 104
 105         fd = bpf_prog_load(prog_type, NULL, "GPL", insns, insns_cnt, &opts);
 106         err = -errno;
 107         if (fd >= 0)
 108                 close(fd);
 109         if (exp_err) {
 110                 if (fd >= 0 || err != exp_err)
 111                         return 0;
 112                 if (exp_msg && !strstr(buf, exp_msg))
 113                         return 0;
 114                 return 1;
 115         }
 116         return fd >= 0 ? 1 : 0;
 117 }
 118
 119 int libbpf_probe_bpf_prog_type(enum bpf_prog_type prog_type, const void *opts)
 120 {
 121         struct bpf_insn insns[] = {
 122                 BPF_MOV64_IMM(BPF_REG_0, 0),
 123                 BPF_EXIT_INSN()
 124         };
 125         const size_t insn_cnt = ARRAY_SIZE(insns);
 126         int ret;
 127
 128         if (opts)
 129                 return libbpf_err(-EINVAL);
 130
 131         ret = probe_prog_load(prog_type, insns, insn_cnt, NULL, 0);
 132         return libbpf_err(ret);
 133 }
 134
 135 int libbpf__load_raw_btf(const char *raw_types, size_t types_len,
 136                          const char *str_sec, size_t str_len)
 137 {
 138         struct btf_header hdr = {
 139                 .magic = BTF_MAGIC,
 140                 .version = BTF_VERSION,
 141                 .hdr_len = sizeof(struct btf_header),
 142                 .type_len = types_len,
 143                 .str_off = types_len,
 144                 .str_len = str_len,
 145         };
 146         int btf_fd, btf_len;
 147         __u8 *raw_btf;
 148
 149         btf_len = hdr.hdr_len + hdr.type_len + hdr.str_len;
 150         raw_btf = malloc(btf_len);
 151         if (!raw_btf)
 152                 return -ENOMEM;
 153
 154         memcpy(raw_btf, &hdr, sizeof(hdr));
 155         memcpy(raw_btf + hdr.hdr_len, raw_types, hdr.type_len);
 156         memcpy(raw_btf + hdr.hdr_len + hdr.type_len, str_sec, hdr.str_len);
 157
 158         btf_fd = bpf_btf_load(raw_btf, btf_len, NULL);
 159
 160         free(raw_btf);
 161         return btf_fd;
 162 }
 163
 164 static int load_local_storage_btf(void)
 165 {
 166         const char strs[] = "\0bpf_spin_lock\0val\0cnt\0l";
 167         /* struct bpf_spin_lock {
 168          *   int val;
 169          * };
 170          * struct val {
 171          *   int cnt;
 172          *   struct bpf_spin_lock l;
 173          * };
 174          */
 175         __u32 types[] = {
 176                 /* int */
 177                 BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4),  /* [1] */
 178                 /* struct bpf_spin_lock */                      /* [2] */
 179                 BTF_TYPE_ENC(1, BTF_INFO_ENC(BTF_KIND_STRUCT, 0, 1), 4),
 180                 BTF_MEMBER_ENC(15, 1, 0), /* int val; */
 181                 /* struct val */                                /* [3] */
 182                 BTF_TYPE_ENC(15, BTF_INFO_ENC(BTF_KIND_STRUCT, 0, 2), 8),
 183                 BTF_MEMBER_ENC(19, 1, 0), /* int cnt; */
 184                 BTF_MEMBER_ENC(23, 2, 32),/* struct bpf_spin_lock l; */
 185         };
 186
 187         return libbpf__load_raw_btf((char *)types, sizeof(types),
 188                                      strs, sizeof(strs));
 189 }
 190
 191 static int probe_map_create(enum bpf_map_type map_type)
 192 {
 193         LIBBPF_OPTS(bpf_map_create_opts, opts);
 194         int key_size, value_size, max_entries;
 195         __u32 btf_key_type_id = 0, btf_value_type_id = 0;
 196         int fd = -1, btf_fd = -1, fd_inner = -1, exp_err = 0, err = 0;
 197
 198         key_size        = sizeof(__u32);
 199         value_size      = sizeof(__u32);
 200         max_entries     = 1;
 201
 202         switch (map_type) {
 203         case BPF_MAP_TYPE_STACK_TRACE:
 204                 value_size      = sizeof(__u64);
 205                 break;
 206         case BPF_MAP_TYPE_LPM_TRIE:
 207                 key_size        = sizeof(__u64);
 208                 value_size      = sizeof(__u64);
 209                 opts.map_flags  = BPF_F_NO_PREALLOC;
 210                 break;
 211         case BPF_MAP_TYPE_CGROUP_STORAGE:
 212         case BPF_MAP_TYPE_PERCPU_CGROUP_STORAGE:
 213                 key_size        = sizeof(struct bpf_cgroup_storage_key);
 214                 value_size      = sizeof(__u64);
 215                 max_entries     = 0;
 216                 break;
 217         case BPF_MAP_TYPE_QUEUE:
 218         case BPF_MAP_TYPE_STACK:
 219                 key_size        = 0;
 220                 break;
 221         case BPF_MAP_TYPE_SK_STORAGE:
 222         case BPF_MAP_TYPE_INODE_STORAGE:
 223         case BPF_MAP_TYPE_TASK_STORAGE:
 224         case BPF_MAP_TYPE_CGRP_STORAGE:
 225                 btf_key_type_id = 1;
 226                 btf_value_type_id = 3;
 227                 value_size = 8;
 228                 max_entries = 0;
 229                 opts.map_flags = BPF_F_NO_PREALLOC;
 230                 btf_fd = load_local_storage_btf();
 231                 if (btf_fd < 0)
 232                         return btf_fd;
 233                 break;
 234         case BPF_MAP_TYPE_RINGBUF:
 235         case BPF_MAP_TYPE_USER_RINGBUF:
 236                 key_size = 0;
 237                 value_size = 0;
 238                 max_entries = sysconf(_SC_PAGE_SIZE);
 239                 break;
 240         case BPF_MAP_TYPE_STRUCT_OPS:
 241                 /* we'll get -ENOTSUPP for invalid BTF type ID for struct_ops */
 242                 opts.btf_vmlinux_value_type_id = 1;
 243                 exp_err = -524; /* -ENOTSUPP */
 244                 break;
 245         case BPF_MAP_TYPE_BLOOM_FILTER:
 246                 key_size = 0;
 247                 max_entries = 1;
 248                 break;
 249         case BPF_MAP_TYPE_HASH:
 250         case BPF_MAP_TYPE_ARRAY:
 251         case BPF_MAP_TYPE_PROG_ARRAY:
 252         case BPF_MAP_TYPE_PERF_EVENT_ARRAY:
 253         case BPF_MAP_TYPE_PERCPU_HASH:
 254         case BPF_MAP_TYPE_PERCPU_ARRAY:
 255         case BPF_MAP_TYPE_CGROUP_ARRAY:
 256         case BPF_MAP_TYPE_LRU_HASH:
 257         case BPF_MAP_TYPE_LRU_PERCPU_HASH:
 258         case BPF_MAP_TYPE_ARRAY_OF_MAPS:
 259         case BPF_MAP_TYPE_HASH_OF_MAPS:
 260         case BPF_MAP_TYPE_DEVMAP:
 261         case BPF_MAP_TYPE_DEVMAP_HASH:
 262         case BPF_MAP_TYPE_SOCKMAP:
 263         case BPF_MAP_TYPE_CPUMAP:
 264         case BPF_MAP_TYPE_XSKMAP:
 265         case BPF_MAP_TYPE_SOCKHASH:
 266         case BPF_MAP_TYPE_REUSEPORT_SOCKARRAY:
 267                 break;
 268         case BPF_MAP_TYPE_UNSPEC:
 269         default:
 270                 return -EOPNOTSUPP;
 271         }
 272
 273         if (map_type == BPF_MAP_TYPE_ARRAY_OF_MAPS ||
 274             map_type == BPF_MAP_TYPE_HASH_OF_MAPS) {
 275                 fd_inner = bpf_map_create(BPF_MAP_TYPE_HASH, NULL,
 276                                           sizeof(__u32), sizeof(__u32), 1, NULL);
 277                 if (fd_inner < 0)
 278                         goto cleanup;
 279
 280                 opts.inner_map_fd = fd_inner;
 281         }
 282
 283         if (btf_fd >= 0) {
 284                 opts.btf_fd = btf_fd;
 285                 opts.btf_key_type_id = btf_key_type_id;
 286                 opts.btf_value_type_id = btf_value_type_id;
 287         }
 288
 289         fd = bpf_map_create(map_type, NULL, key_size, value_size, max_entries, &opts);
 290         err = -errno;
 291
 292 cleanup:
 293         if (fd >= 0)
 294                 close(fd);
 295         if (fd_inner >= 0)
 296                 close(fd_inner);
 297         if (btf_fd >= 0)
 298                 close(btf_fd);
 299
 300         if (exp_err)
 301                 return fd < 0 && err == exp_err ? 1 : 0;
 302         else
 303                 return fd >= 0 ? 1 : 0;
 304 }
 305
 306 int libbpf_probe_bpf_map_type(enum bpf_map_type map_type, const void *opts)
 307 {
 308         int ret;
 309
 310         if (opts)
 311                 return libbpf_err(-EINVAL);
 312
 313         ret = probe_map_create(map_type);
 314         return libbpf_err(ret);
 315 }
 316
 317 int libbpf_probe_bpf_helper(enum bpf_prog_type prog_type, enum bpf_func_id helper_id,
 318                             const void *opts)
 319 {
 320         struct bpf_insn insns[] = {
 321                 BPF_EMIT_CALL((__u32)helper_id),
 322                 BPF_EXIT_INSN(),
 323         };
 324         const size_t insn_cnt = ARRAY_SIZE(insns);
 325         char buf[4096];
 326         int ret;
 327
 328         if (opts)
 329                 return libbpf_err(-EINVAL);
 330
 331         /* we can't successfully load all prog types to check for BPF helper
 332          * support, so bail out with -EOPNOTSUPP error
 333          */
 334         switch (prog_type) {
 335         case BPF_PROG_TYPE_TRACING:
 336         case BPF_PROG_TYPE_EXT:
 337         case BPF_PROG_TYPE_LSM:
 338         case BPF_PROG_TYPE_STRUCT_OPS:
 339                 return -EOPNOTSUPP;
 340         default:
 341                 break;
 342         }
 343
 344         buf[0] = '\0';
 345         ret = probe_prog_load(prog_type, insns, insn_cnt, buf, sizeof(buf));
 346         if (ret < 0)
 347                 return libbpf_err(ret);
 348
 349         /* If BPF verifier doesn't recognize BPF helper ID (enum bpf_func_id)
 350          * at all, it will emit something like "invalid func unknown#181".
 351          * If BPF verifier recognizes BPF helper but it's not supported for
 352          * given BPF program type, it will emit "unknown func bpf_sys_bpf#166".
 353          * In both cases, provided combination of BPF program type and BPF
 354          * helper is not supported by the kernel.
 355          * In all other cases, probe_prog_load() above will either succeed (e.g.,
 356          * because BPF helper happens to accept no input arguments or it
 357          * accepts one input argument and initial PTR_TO_CTX is fine for
 358          * that), or we'll get some more specific BPF verifier error about
 359          * some unsatisfied conditions.
 360          */
 361         if (ret == 0 && (strstr(buf, "invalid func ") || strstr(buf, "unknown func ")))
 362                 return 0;
 363         return 1; /* assume supported */
 364 }