linux/tools/bpf/bpftool/feature.c
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   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
  28enum 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
  35static const char * const helper_name[] = {
  36        __BPF_FUNC_MAPPER(BPF_HELPER_MAKE_ENTRY)
  37};
  38
  39#undef BPF_HELPER_MAKE_ENTRY
  40
  41static bool full_mode;
  42#ifdef USE_LIBCAP
  43static bool run_as_unprivileged;
  44#endif
  45
  46/* Miscellaneous utility functions */
  47
  48static 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
  60static 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
  70static void
  71print_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
  83static 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
 114static void
 115print_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
 128static 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
 138static 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
 163static 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
 189static 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
 219static 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
 249static 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
 275static 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
 295static 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
 323static 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
 450end_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
 462static 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
 477static void
 478probe_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
 525static void
 526probe_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
 558static void
 559probe_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
 590static void
 591probe_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
 640static void
 641probe_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
 652static void
 653section_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
 681static 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
 695static void
 696section_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
 712static 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
 727static void
 728section_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
 759static 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
 774static 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
 866exit_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
 888static 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
 979exit_close_json:
 980        if (json_output)
 981                /* End root object */
 982                jsonw_end_object(json_wtr);
 983
 984        return 0;
 985}
 986
 987static 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
1005static const struct cmd cmds[] = {
1006        { "probe",      do_probe },
1007        { "help",       do_help },
1008        { 0 }
1009};
1010
1011int do_feature(int argc, char **argv)
1012{
1013        return cmd_select(cmds, argc, argv, do_help);
1014}
1015