1 // SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) 2 /* Copyright (c) 2019 Netronome Systems, Inc. */ 3 4 #include <ctype.h> 5 #include <errno.h> 6 #include <string.h> 7 #include <unistd.h> 8 #include <net/if.h> 9 #ifdef USE_LIBCAP 10 #include <sys/capability.h> 11 #endif 12 #include <sys/utsname.h> 13 #include <sys/vfs.h> 14 15 #include <linux/filter.h> 16 #include <linux/limits.h> 17 18 #include <bpf/bpf.h> 19 #include <bpf/libbpf.h> 20 #include <zlib.h> 21 22 #include "main.h" 23 24 #ifndef PROC_SUPER_MAGIC 25 # define PROC_SUPER_MAGIC 0x9fa0 26 #endif 27 28 enum probe_component { 29 COMPONENT_UNSPEC, 30 COMPONENT_KERNEL, 31 COMPONENT_DEVICE, 32 }; 33 34 #define BPF_HELPER_MAKE_ENTRY(name) [BPF_FUNC_ ## name] = "bpf_" # name 35 static const char * const helper_name[] = { 36 __BPF_FUNC_MAPPER(BPF_HELPER_MAKE_ENTRY) 37 }; 38 39 #undef BPF_HELPER_MAKE_ENTRY 40 41 static bool full_mode; 42 #ifdef USE_LIBCAP 43 static bool run_as_unprivileged; 44 #endif 45 46 /* Miscellaneous utility functions */ 47 48 static bool check_procfs(void) 49 { 50 struct statfs st_fs; 51 52 if (statfs("/proc", &st_fs) < 0) 53 return false; 54 if ((unsigned long)st_fs.f_type != PROC_SUPER_MAGIC) 55 return false; 56 57 return true; 58 } 59 60 static void uppercase(char *str, size_t len) 61 { 62 size_t i; 63 64 for (i = 0; i < len && str[i] != '\0'; i++) 65 str[i] = toupper(str[i]); 66 } 67 68 /* Printing utility functions */ 69 70 static void 71 print_bool_feature(const char *feat_name, const char *plain_name, 72 const char *define_name, bool res, const char *define_prefix) 73 { 74 if (json_output) 75 jsonw_bool_field(json_wtr, feat_name, res); 76 else if (define_prefix) 77 printf("#define %s%sHAVE_%s\n", define_prefix, 78 res ? "" : "NO_", define_name); 79 else 80 printf("%s is %savailable\n", plain_name, res ? "" : "NOT "); 81 } 82 83 static void print_kernel_option(const char *name, const char *value, 84 const char *define_prefix) 85 { 86 char *endptr; 87 int res; 88 89 if (json_output) { 90 if (!value) { 91 jsonw_null_field(json_wtr, name); 92 return; 93 } 94 errno = 0; 95 res = strtol(value, &endptr, 0); 96 if (!errno && *endptr == '\n') 97 jsonw_int_field(json_wtr, name, res); 98 else 99 jsonw_string_field(json_wtr, name, value); 100 } else if (define_prefix) { 101 if (value) 102 printf("#define %s%s %s\n", define_prefix, 103 name, value); 104 else 105 printf("/* %s%s is not set */\n", define_prefix, name); 106 } else { 107 if (value) 108 printf("%s is set to %s\n", name, value); 109 else 110 printf("%s is not set\n", name); 111 } 112 } 113 114 static void 115 print_start_section(const char *json_title, const char *plain_title, 116 const char *define_comment, const char *define_prefix) 117 { 118 if (json_output) { 119 jsonw_name(json_wtr, json_title); 120 jsonw_start_object(json_wtr); 121 } else if (define_prefix) { 122 printf("%s\n", define_comment); 123 } else { 124 printf("%s\n", plain_title); 125 } 126 } 127 128 static void print_end_section(void) 129 { 130 if (json_output) 131 jsonw_end_object(json_wtr); 132 else 133 printf("\n"); 134 } 135 136 /* Probing functions */ 137 138 static int read_procfs(const char *path) 139 { 140 char *endptr, *line = NULL; 141 size_t len = 0; 142 FILE *fd; 143 int res; 144 145 fd = fopen(path, "r"); 146 if (!fd) 147 return -1; 148 149 res = getline(&line, &len, fd); 150 fclose(fd); 151 if (res < 0) 152 return -1; 153 154 errno = 0; 155 res = strtol(line, &endptr, 10); 156 if (errno || *line == '\0' || *endptr != '\n') 157 res = -1; 158 free(line); 159 160 return res; 161 } 162 163 static void probe_unprivileged_disabled(void) 164 { 165 int res; 166 167 /* No support for C-style ouptut */ 168 169 res = read_procfs("/proc/sys/kernel/unprivileged_bpf_disabled"); 170 if (json_output) { 171 jsonw_int_field(json_wtr, "unprivileged_bpf_disabled", res); 172 } else { 173 switch (res) { 174 case 0: 175 printf("bpf() syscall for unprivileged users is enabled\n"); 176 break; 177 case 1: 178 printf("bpf() syscall restricted to privileged users\n"); 179 break; 180 case -1: 181 printf("Unable to retrieve required privileges for bpf() syscall\n"); 182 break; 183 default: 184 printf("bpf() syscall restriction has unknown value %d\n", res); 185 } 186 } 187 } 188 189 static void probe_jit_enable(void) 190 { 191 int res; 192 193 /* No support for C-style ouptut */ 194 195 res = read_procfs("/proc/sys/net/core/bpf_jit_enable"); 196 if (json_output) { 197 jsonw_int_field(json_wtr, "bpf_jit_enable", res); 198 } else { 199 switch (res) { 200 case 0: 201 printf("JIT compiler is disabled\n"); 202 break; 203 case 1: 204 printf("JIT compiler is enabled\n"); 205 break; 206 case 2: 207 printf("JIT compiler is enabled with debugging traces in kernel logs\n"); 208 break; 209 case -1: 210 printf("Unable to retrieve JIT-compiler status\n"); 211 break; 212 default: 213 printf("JIT-compiler status has unknown value %d\n", 214 res); 215 } 216 } 217 } 218 219 static void probe_jit_harden(void) 220 { 221 int res; 222 223 /* No support for C-style ouptut */ 224 225 res = read_procfs("/proc/sys/net/core/bpf_jit_harden"); 226 if (json_output) { 227 jsonw_int_field(json_wtr, "bpf_jit_harden", res); 228 } else { 229 switch (res) { 230 case 0: 231 printf("JIT compiler hardening is disabled\n"); 232 break; 233 case 1: 234 printf("JIT compiler hardening is enabled for unprivileged users\n"); 235 break; 236 case 2: 237 printf("JIT compiler hardening is enabled for all users\n"); 238 break; 239 case -1: 240 printf("Unable to retrieve JIT hardening status\n"); 241 break; 242 default: 243 printf("JIT hardening status has unknown value %d\n", 244 res); 245 } 246 } 247 } 248 249 static void probe_jit_kallsyms(void) 250 { 251 int res; 252 253 /* No support for C-style ouptut */ 254 255 res = read_procfs("/proc/sys/net/core/bpf_jit_kallsyms"); 256 if (json_output) { 257 jsonw_int_field(json_wtr, "bpf_jit_kallsyms", res); 258 } else { 259 switch (res) { 260 case 0: 261 printf("JIT compiler kallsyms exports are disabled\n"); 262 break; 263 case 1: 264 printf("JIT compiler kallsyms exports are enabled for root\n"); 265 break; 266 case -1: 267 printf("Unable to retrieve JIT kallsyms export status\n"); 268 break; 269 default: 270 printf("JIT kallsyms exports status has unknown value %d\n", res); 271 } 272 } 273 } 274 275 static void probe_jit_limit(void) 276 { 277 int res; 278 279 /* No support for C-style ouptut */ 280 281 res = read_procfs("/proc/sys/net/core/bpf_jit_limit"); 282 if (json_output) { 283 jsonw_int_field(json_wtr, "bpf_jit_limit", res); 284 } else { 285 switch (res) { 286 case -1: 287 printf("Unable to retrieve global memory limit for JIT compiler for unprivileged users\n"); 288 break; 289 default: 290 printf("Global memory limit for JIT compiler for unprivileged users is %d bytes\n", res); 291 } 292 } 293 } 294 295 static bool read_next_kernel_config_option(gzFile file, char *buf, size_t n, 296 char **value) 297 { 298 char *sep; 299 300 while (gzgets(file, buf, n)) { 301 if (strncmp(buf, "CONFIG_", 7)) 302 continue; 303 304 sep = strchr(buf, '='); 305 if (!sep) 306 continue; 307 308 /* Trim ending '\n' */ 309 buf[strlen(buf) - 1] = '\0'; 310 311 /* Split on '=' and ensure that a value is present. */ 312 *sep = '\0'; 313 if (!sep[1]) 314 continue; 315 316 *value = sep + 1; 317 return true; 318 } 319 320 return false; 321 } 322 323 static void probe_kernel_image_config(const char *define_prefix) 324 { 325 static const struct { 326 const char * const name; 327 bool macro_dump; 328 } options[] = { 329 /* Enable BPF */ 330 { "CONFIG_BPF", }, 331 /* Enable bpf() syscall */ 332 { "CONFIG_BPF_SYSCALL", }, 333 /* Does selected architecture support eBPF JIT compiler */ 334 { "CONFIG_HAVE_EBPF_JIT", }, 335 /* Compile eBPF JIT compiler */ 336 { "CONFIG_BPF_JIT", }, 337 /* Avoid compiling eBPF interpreter (use JIT only) */ 338 { "CONFIG_BPF_JIT_ALWAYS_ON", }, 339 340 /* cgroups */ 341 { "CONFIG_CGROUPS", }, 342 /* BPF programs attached to cgroups */ 343 { "CONFIG_CGROUP_BPF", }, 344 /* bpf_get_cgroup_classid() helper */ 345 { "CONFIG_CGROUP_NET_CLASSID", }, 346 /* bpf_skb_{,ancestor_}cgroup_id() helpers */ 347 { "CONFIG_SOCK_CGROUP_DATA", }, 348 349 /* Tracing: attach BPF to kprobes, tracepoints, etc. */ 350 { "CONFIG_BPF_EVENTS", }, 351 /* Kprobes */ 352 { "CONFIG_KPROBE_EVENTS", }, 353 /* Uprobes */ 354 { "CONFIG_UPROBE_EVENTS", }, 355 /* Tracepoints */ 356 { "CONFIG_TRACING", }, 357 /* Syscall tracepoints */ 358 { "CONFIG_FTRACE_SYSCALLS", }, 359 /* bpf_override_return() helper support for selected arch */ 360 { "CONFIG_FUNCTION_ERROR_INJECTION", }, 361 /* bpf_override_return() helper */ 362 { "CONFIG_BPF_KPROBE_OVERRIDE", }, 363 364 /* Network */ 365 { "CONFIG_NET", }, 366 /* AF_XDP sockets */ 367 { "CONFIG_XDP_SOCKETS", }, 368 /* BPF_PROG_TYPE_LWT_* and related helpers */ 369 { "CONFIG_LWTUNNEL_BPF", }, 370 /* BPF_PROG_TYPE_SCHED_ACT, TC (traffic control) actions */ 371 { "CONFIG_NET_ACT_BPF", }, 372 /* BPF_PROG_TYPE_SCHED_CLS, TC filters */ 373 { "CONFIG_NET_CLS_BPF", }, 374 /* TC clsact qdisc */ 375 { "CONFIG_NET_CLS_ACT", }, 376 /* Ingress filtering with TC */ 377 { "CONFIG_NET_SCH_INGRESS", }, 378 /* bpf_skb_get_xfrm_state() helper */ 379 { "CONFIG_XFRM", }, 380 /* bpf_get_route_realm() helper */ 381 { "CONFIG_IP_ROUTE_CLASSID", }, 382 /* BPF_PROG_TYPE_LWT_SEG6_LOCAL and related helpers */ 383 { "CONFIG_IPV6_SEG6_BPF", }, 384 /* BPF_PROG_TYPE_LIRC_MODE2 and related helpers */ 385 { "CONFIG_BPF_LIRC_MODE2", }, 386 /* BPF stream parser and BPF socket maps */ 387 { "CONFIG_BPF_STREAM_PARSER", }, 388 /* xt_bpf module for passing BPF programs to netfilter */ 389 { "CONFIG_NETFILTER_XT_MATCH_BPF", }, 390 /* bpfilter back-end for iptables */ 391 { "CONFIG_BPFILTER", }, 392 /* bpftilter module with "user mode helper" */ 393 { "CONFIG_BPFILTER_UMH", }, 394 395 /* test_bpf module for BPF tests */ 396 { "CONFIG_TEST_BPF", }, 397 398 /* Misc configs useful in BPF C programs */ 399 /* jiffies <-> sec conversion for bpf_jiffies64() helper */ 400 { "CONFIG_HZ", true, } 401 }; 402 char *values[ARRAY_SIZE(options)] = { }; 403 struct utsname utsn; 404 char path[PATH_MAX]; 405 gzFile file = NULL; 406 char buf[4096]; 407 char *value; 408 size_t i; 409 410 if (!uname(&utsn)) { 411 snprintf(path, sizeof(path), "/boot/config-%s", utsn.release); 412 413 /* gzopen also accepts uncompressed files. */ 414 file = gzopen(path, "r"); 415 } 416 417 if (!file) { 418 /* Some distributions build with CONFIG_IKCONFIG=y and put the 419 * config file at /proc/config.gz. 420 */ 421 file = gzopen("/proc/config.gz", "r"); 422 } 423 if (!file) { 424 p_info("skipping kernel config, can't open file: %s", 425 strerror(errno)); 426 goto end_parse; 427 } 428 /* Sanity checks */ 429 if (!gzgets(file, buf, sizeof(buf)) || 430 !gzgets(file, buf, sizeof(buf))) { 431 p_info("skipping kernel config, can't read from file: %s", 432 strerror(errno)); 433 goto end_parse; 434 } 435 if (strcmp(buf, "# Automatically generated file; DO NOT EDIT.\n")) { 436 p_info("skipping kernel config, can't find correct file"); 437 goto end_parse; 438 } 439 440 while (read_next_kernel_config_option(file, buf, sizeof(buf), &value)) { 441 for (i = 0; i < ARRAY_SIZE(options); i++) { 442 if ((define_prefix && !options[i].macro_dump) || 443 values[i] || strcmp(buf, options[i].name)) 444 continue; 445 446 values[i] = strdup(value); 447 } 448 } 449 450 end_parse: 451 if (file) 452 gzclose(file); 453 454 for (i = 0; i < ARRAY_SIZE(options); i++) { 455 if (define_prefix && !options[i].macro_dump) 456 continue; 457 print_kernel_option(options[i].name, values[i], define_prefix); 458 free(values[i]); 459 } 460 } 461 462 static bool probe_bpf_syscall(const char *define_prefix) 463 { 464 bool res; 465 466 bpf_load_program(BPF_PROG_TYPE_UNSPEC, NULL, 0, NULL, 0, NULL, 0); 467 res = (errno != ENOSYS); 468 469 print_bool_feature("have_bpf_syscall", 470 "bpf() syscall", 471 "BPF_SYSCALL", 472 res, define_prefix); 473 474 return res; 475 } 476 477 static void 478 probe_prog_type(enum bpf_prog_type prog_type, bool *supported_types, 479 const char *define_prefix, __u32 ifindex) 480 { 481 char feat_name[128], plain_desc[128], define_name[128]; 482 const char *plain_comment = "eBPF program_type "; 483 size_t maxlen; 484 bool res; 485 486 if (ifindex) 487 /* Only test offload-able program types */ 488 switch (prog_type) { 489 case BPF_PROG_TYPE_SCHED_CLS: 490 case BPF_PROG_TYPE_XDP: 491 break; 492 default: 493 return; 494 } 495 496 res = bpf_probe_prog_type(prog_type, ifindex); 497 #ifdef USE_LIBCAP 498 /* Probe may succeed even if program load fails, for unprivileged users 499 * check that we did not fail because of insufficient permissions 500 */ 501 if (run_as_unprivileged && errno == EPERM) 502 res = false; 503 #endif 504 505 supported_types[prog_type] |= res; 506 507 if (!prog_type_name[prog_type]) { 508 p_info("program type name not found (type %d)", prog_type); 509 return; 510 } 511 maxlen = sizeof(plain_desc) - strlen(plain_comment) - 1; 512 if (strlen(prog_type_name[prog_type]) > maxlen) { 513 p_info("program type name too long"); 514 return; 515 } 516 517 sprintf(feat_name, "have_%s_prog_type", prog_type_name[prog_type]); 518 sprintf(define_name, "%s_prog_type", prog_type_name[prog_type]); 519 uppercase(define_name, sizeof(define_name)); 520 sprintf(plain_desc, "%s%s", plain_comment, prog_type_name[prog_type]); 521 print_bool_feature(feat_name, plain_desc, define_name, res, 522 define_prefix); 523 } 524 525 static void 526 probe_map_type(enum bpf_map_type map_type, const char *define_prefix, 527 __u32 ifindex) 528 { 529 char feat_name[128], plain_desc[128], define_name[128]; 530 const char *plain_comment = "eBPF map_type "; 531 size_t maxlen; 532 bool res; 533 534 res = bpf_probe_map_type(map_type, ifindex); 535 536 /* Probe result depends on the success of map creation, no additional 537 * check required for unprivileged users 538 */ 539 540 if (!map_type_name[map_type]) { 541 p_info("map type name not found (type %d)", map_type); 542 return; 543 } 544 maxlen = sizeof(plain_desc) - strlen(plain_comment) - 1; 545 if (strlen(map_type_name[map_type]) > maxlen) { 546 p_info("map type name too long"); 547 return; 548 } 549 550 sprintf(feat_name, "have_%s_map_type", map_type_name[map_type]); 551 sprintf(define_name, "%s_map_type", map_type_name[map_type]); 552 uppercase(define_name, sizeof(define_name)); 553 sprintf(plain_desc, "%s%s", plain_comment, map_type_name[map_type]); 554 print_bool_feature(feat_name, plain_desc, define_name, res, 555 define_prefix); 556 } 557 558 static void 559 probe_helper_for_progtype(enum bpf_prog_type prog_type, bool supported_type, 560 const char *define_prefix, unsigned int id, 561 const char *ptype_name, __u32 ifindex) 562 { 563 bool res = false; 564 565 if (supported_type) { 566 res = bpf_probe_helper(id, prog_type, ifindex); 567 #ifdef USE_LIBCAP 568 /* Probe may succeed even if program load fails, for 569 * unprivileged users check that we did not fail because of 570 * insufficient permissions 571 */ 572 if (run_as_unprivileged && errno == EPERM) 573 res = false; 574 #endif 575 } 576 577 if (json_output) { 578 if (res) 579 jsonw_string(json_wtr, helper_name[id]); 580 } else if (define_prefix) { 581 printf("#define %sBPF__PROG_TYPE_%s__HELPER_%s %s\n", 582 define_prefix, ptype_name, helper_name[id], 583 res ? "1" : "0"); 584 } else { 585 if (res) 586 printf("\n\t- %s", helper_name[id]); 587 } 588 } 589 590 static void 591 probe_helpers_for_progtype(enum bpf_prog_type prog_type, bool supported_type, 592 const char *define_prefix, __u32 ifindex) 593 { 594 const char *ptype_name = prog_type_name[prog_type]; 595 char feat_name[128]; 596 unsigned int id; 597 598 if (ifindex) 599 /* Only test helpers for offload-able program types */ 600 switch (prog_type) { 601 case BPF_PROG_TYPE_SCHED_CLS: 602 case BPF_PROG_TYPE_XDP: 603 break; 604 default: 605 return; 606 } 607 608 if (json_output) { 609 sprintf(feat_name, "%s_available_helpers", ptype_name); 610 jsonw_name(json_wtr, feat_name); 611 jsonw_start_array(json_wtr); 612 } else if (!define_prefix) { 613 printf("eBPF helpers supported for program type %s:", 614 ptype_name); 615 } 616 617 for (id = 1; id < ARRAY_SIZE(helper_name); id++) { 618 /* Skip helper functions which emit dmesg messages when not in 619 * the full mode. 620 */ 621 switch (id) { 622 case BPF_FUNC_trace_printk: 623 case BPF_FUNC_probe_write_user: 624 if (!full_mode) 625 continue; 626 /* fallthrough */ 627 default: 628 probe_helper_for_progtype(prog_type, supported_type, 629 define_prefix, id, ptype_name, 630 ifindex); 631 } 632 } 633 634 if (json_output) 635 jsonw_end_array(json_wtr); 636 else if (!define_prefix) 637 printf("\n"); 638 } 639 640 static void 641 probe_large_insn_limit(const char *define_prefix, __u32 ifindex) 642 { 643 bool res; 644 645 res = bpf_probe_large_insn_limit(ifindex); 646 print_bool_feature("have_large_insn_limit", 647 "Large program size limit", 648 "LARGE_INSN_LIMIT", 649 res, define_prefix); 650 } 651 652 static void 653 section_system_config(enum probe_component target, const char *define_prefix) 654 { 655 switch (target) { 656 case COMPONENT_KERNEL: 657 case COMPONENT_UNSPEC: 658 print_start_section("system_config", 659 "Scanning system configuration...", 660 "/*** Misc kernel config items ***/", 661 define_prefix); 662 if (!define_prefix) { 663 if (check_procfs()) { 664 probe_unprivileged_disabled(); 665 probe_jit_enable(); 666 probe_jit_harden(); 667 probe_jit_kallsyms(); 668 probe_jit_limit(); 669 } else { 670 p_info("/* procfs not mounted, skipping related probes */"); 671 } 672 } 673 probe_kernel_image_config(define_prefix); 674 print_end_section(); 675 break; 676 default: 677 break; 678 } 679 } 680 681 static bool section_syscall_config(const char *define_prefix) 682 { 683 bool res; 684 685 print_start_section("syscall_config", 686 "Scanning system call availability...", 687 "/*** System call availability ***/", 688 define_prefix); 689 res = probe_bpf_syscall(define_prefix); 690 print_end_section(); 691 692 return res; 693 } 694 695 static void 696 section_program_types(bool *supported_types, const char *define_prefix, 697 __u32 ifindex) 698 { 699 unsigned int i; 700 701 print_start_section("program_types", 702 "Scanning eBPF program types...", 703 "/*** eBPF program types ***/", 704 define_prefix); 705 706 for (i = BPF_PROG_TYPE_UNSPEC + 1; i < prog_type_name_size; i++) 707 probe_prog_type(i, supported_types, define_prefix, ifindex); 708 709 print_end_section(); 710 } 711 712 static void section_map_types(const char *define_prefix, __u32 ifindex) 713 { 714 unsigned int i; 715 716 print_start_section("map_types", 717 "Scanning eBPF map types...", 718 "/*** eBPF map types ***/", 719 define_prefix); 720 721 for (i = BPF_MAP_TYPE_UNSPEC + 1; i < map_type_name_size; i++) 722 probe_map_type(i, define_prefix, ifindex); 723 724 print_end_section(); 725 } 726 727 static void 728 section_helpers(bool *supported_types, const char *define_prefix, __u32 ifindex) 729 { 730 unsigned int i; 731 732 print_start_section("helpers", 733 "Scanning eBPF helper functions...", 734 "/*** eBPF helper functions ***/", 735 define_prefix); 736 737 if (define_prefix) 738 printf("/*\n" 739 " * Use %sHAVE_PROG_TYPE_HELPER(prog_type_name, helper_name)\n" 740 " * to determine if <helper_name> is available for <prog_type_name>,\n" 741 " * e.g.\n" 742 " * #if %sHAVE_PROG_TYPE_HELPER(xdp, bpf_redirect)\n" 743 " * // do stuff with this helper\n" 744 " * #elif\n" 745 " * // use a workaround\n" 746 " * #endif\n" 747 " */\n" 748 "#define %sHAVE_PROG_TYPE_HELPER(prog_type, helper) \\\n" 749 " %sBPF__PROG_TYPE_ ## prog_type ## __HELPER_ ## helper\n", 750 define_prefix, define_prefix, define_prefix, 751 define_prefix); 752 for (i = BPF_PROG_TYPE_UNSPEC + 1; i < prog_type_name_size; i++) 753 probe_helpers_for_progtype(i, supported_types[i], define_prefix, 754 ifindex); 755 756 print_end_section(); 757 } 758 759 static void section_misc(const char *define_prefix, __u32 ifindex) 760 { 761 print_start_section("misc", 762 "Scanning miscellaneous eBPF features...", 763 "/*** eBPF misc features ***/", 764 define_prefix); 765 probe_large_insn_limit(define_prefix, ifindex); 766 print_end_section(); 767 } 768 769 #ifdef USE_LIBCAP 770 #define capability(c) { c, false, #c } 771 #define capability_msg(a, i) a[i].set ? "" : a[i].name, a[i].set ? "" : ", " 772 #endif 773 774 static int handle_perms(void) 775 { 776 #ifdef USE_LIBCAP 777 struct { 778 cap_value_t cap; 779 bool set; 780 char name[14]; /* strlen("CAP_SYS_ADMIN") */ 781 } bpf_caps[] = { 782 capability(CAP_SYS_ADMIN), 783 #ifdef CAP_BPF 784 capability(CAP_BPF), 785 capability(CAP_NET_ADMIN), 786 capability(CAP_PERFMON), 787 #endif 788 }; 789 cap_value_t cap_list[ARRAY_SIZE(bpf_caps)]; 790 unsigned int i, nb_bpf_caps = 0; 791 bool cap_sys_admin_only = true; 792 cap_flag_value_t val; 793 int res = -1; 794 cap_t caps; 795 796 caps = cap_get_proc(); 797 if (!caps) { 798 p_err("failed to get capabilities for process: %s", 799 strerror(errno)); 800 return -1; 801 } 802 803 #ifdef CAP_BPF 804 if (CAP_IS_SUPPORTED(CAP_BPF)) 805 cap_sys_admin_only = false; 806 #endif 807 808 for (i = 0; i < ARRAY_SIZE(bpf_caps); i++) { 809 const char *cap_name = bpf_caps[i].name; 810 cap_value_t cap = bpf_caps[i].cap; 811 812 if (cap_get_flag(caps, cap, CAP_EFFECTIVE, &val)) { 813 p_err("bug: failed to retrieve %s status: %s", cap_name, 814 strerror(errno)); 815 goto exit_free; 816 } 817 818 if (val == CAP_SET) { 819 bpf_caps[i].set = true; 820 cap_list[nb_bpf_caps++] = cap; 821 } 822 823 if (cap_sys_admin_only) 824 /* System does not know about CAP_BPF, meaning that 825 * CAP_SYS_ADMIN is the only capability required. We 826 * just checked it, break. 827 */ 828 break; 829 } 830 831 if ((run_as_unprivileged && !nb_bpf_caps) || 832 (!run_as_unprivileged && nb_bpf_caps == ARRAY_SIZE(bpf_caps)) || 833 (!run_as_unprivileged && cap_sys_admin_only && nb_bpf_caps)) { 834 /* We are all good, exit now */ 835 res = 0; 836 goto exit_free; 837 } 838 839 if (!run_as_unprivileged) { 840 if (cap_sys_admin_only) 841 p_err("missing %s, required for full feature probing; run as root or use 'unprivileged'", 842 bpf_caps[0].name); 843 else 844 p_err("missing %s%s%s%s%s%s%s%srequired for full feature probing; run as root or use 'unprivileged'", 845 capability_msg(bpf_caps, 0), 846 capability_msg(bpf_caps, 1), 847 capability_msg(bpf_caps, 2), 848 capability_msg(bpf_caps, 3)); 849 goto exit_free; 850 } 851 852 /* if (run_as_unprivileged && nb_bpf_caps > 0), drop capabilities. */ 853 if (cap_set_flag(caps, CAP_EFFECTIVE, nb_bpf_caps, cap_list, 854 CAP_CLEAR)) { 855 p_err("bug: failed to clear capabilities: %s", strerror(errno)); 856 goto exit_free; 857 } 858 859 if (cap_set_proc(caps)) { 860 p_err("failed to drop capabilities: %s", strerror(errno)); 861 goto exit_free; 862 } 863 864 res = 0; 865 866 exit_free: 867 if (cap_free(caps) && !res) { 868 p_err("failed to clear storage object for capabilities: %s", 869 strerror(errno)); 870 res = -1; 871 } 872 873 return res; 874 #else 875 /* Detection assumes user has specific privileges. 876 * We do not use libpcap so let's approximate, and restrict usage to 877 * root user only. 878 */ 879 if (geteuid()) { 880 p_err("full feature probing requires root privileges"); 881 return -1; 882 } 883 884 return 0; 885 #endif /* USE_LIBCAP */ 886 } 887 888 static int do_probe(int argc, char **argv) 889 { 890 enum probe_component target = COMPONENT_UNSPEC; 891 const char *define_prefix = NULL; 892 bool supported_types[128] = {}; 893 __u32 ifindex = 0; 894 char *ifname; 895 896 set_max_rlimit(); 897 898 while (argc) { 899 if (is_prefix(*argv, "kernel")) { 900 if (target != COMPONENT_UNSPEC) { 901 p_err("component to probe already specified"); 902 return -1; 903 } 904 target = COMPONENT_KERNEL; 905 NEXT_ARG(); 906 } else if (is_prefix(*argv, "dev")) { 907 NEXT_ARG(); 908 909 if (target != COMPONENT_UNSPEC || ifindex) { 910 p_err("component to probe already specified"); 911 return -1; 912 } 913 if (!REQ_ARGS(1)) 914 return -1; 915 916 target = COMPONENT_DEVICE; 917 ifname = GET_ARG(); 918 ifindex = if_nametoindex(ifname); 919 if (!ifindex) { 920 p_err("unrecognized netdevice '%s': %s", ifname, 921 strerror(errno)); 922 return -1; 923 } 924 } else if (is_prefix(*argv, "full")) { 925 full_mode = true; 926 NEXT_ARG(); 927 } else if (is_prefix(*argv, "macros") && !define_prefix) { 928 define_prefix = ""; 929 NEXT_ARG(); 930 } else if (is_prefix(*argv, "prefix")) { 931 if (!define_prefix) { 932 p_err("'prefix' argument can only be use after 'macros'"); 933 return -1; 934 } 935 if (strcmp(define_prefix, "")) { 936 p_err("'prefix' already defined"); 937 return -1; 938 } 939 NEXT_ARG(); 940 941 if (!REQ_ARGS(1)) 942 return -1; 943 define_prefix = GET_ARG(); 944 } else if (is_prefix(*argv, "unprivileged")) { 945 #ifdef USE_LIBCAP 946 run_as_unprivileged = true; 947 NEXT_ARG(); 948 #else 949 p_err("unprivileged run not supported, recompile bpftool with libcap"); 950 return -1; 951 #endif 952 } else { 953 p_err("expected no more arguments, 'kernel', 'dev', 'macros' or 'prefix', got: '%s'?", 954 *argv); 955 return -1; 956 } 957 } 958 959 /* Full feature detection requires specific privileges. 960 * Let's approximate, and warn if user is not root. 961 */ 962 if (handle_perms()) 963 return -1; 964 965 if (json_output) { 966 define_prefix = NULL; 967 jsonw_start_object(json_wtr); 968 } 969 970 section_system_config(target, define_prefix); 971 if (!section_syscall_config(define_prefix)) 972 /* bpf() syscall unavailable, don't probe other BPF features */ 973 goto exit_close_json; 974 section_program_types(supported_types, define_prefix, ifindex); 975 section_map_types(define_prefix, ifindex); 976 section_helpers(supported_types, define_prefix, ifindex); 977 section_misc(define_prefix, ifindex); 978 979 exit_close_json: 980 if (json_output) 981 /* End root object */ 982 jsonw_end_object(json_wtr); 983 984 return 0; 985 } 986 987 static int do_help(int argc, char **argv) 988 { 989 if (json_output) { 990 jsonw_null(json_wtr); 991 return 0; 992 } 993 994 fprintf(stderr, 995 "Usage: %1$s %2$s probe [COMPONENT] [full] [unprivileged] [macros [prefix PREFIX]]\n" 996 " %1$s %2$s help\n" 997 "\n" 998 " COMPONENT := { kernel | dev NAME }\n" 999 "", 1000 bin_name, argv[-2]); 1001 1002 return 0; 1003 } 1004 1005 static const struct cmd cmds[] = { 1006 { "probe", do_probe }, 1007 { "help", do_help }, 1008 { 0 } 1009 }; 1010 1011 int do_feature(int argc, char **argv) 1012 { 1013 return cmd_select(cmds, argc, argv, do_help); 1014 } 1015