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
check_procfs(void)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
uppercase(char * str,size_t len)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
print_bool_feature(const char * feat_name,const char * plain_name,const char * define_name,bool res,const char * define_prefix)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
print_kernel_option(const char * name,const char * value,const char * define_prefix)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
print_start_section(const char * json_title,const char * plain_title,const char * define_comment,const char * define_prefix)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
print_end_section(void)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
read_procfs(const char * path)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
probe_unprivileged_disabled(void)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
probe_jit_enable(void)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
probe_jit_harden(void)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
probe_jit_kallsyms(void)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
probe_jit_limit(void)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
read_next_kernel_config_option(gzFile file,char * buf,size_t n,char ** value)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
probe_kernel_image_config(const char * define_prefix)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 /* Kernel BTF debug information available */
340 { "CONFIG_DEBUG_INFO_BTF", },
341 /* Kernel module BTF debug information available */
342 { "CONFIG_DEBUG_INFO_BTF_MODULES", },
343
344 /* cgroups */
345 { "CONFIG_CGROUPS", },
346 /* BPF programs attached to cgroups */
347 { "CONFIG_CGROUP_BPF", },
348 /* bpf_get_cgroup_classid() helper */
349 { "CONFIG_CGROUP_NET_CLASSID", },
350 /* bpf_skb_{,ancestor_}cgroup_id() helpers */
351 { "CONFIG_SOCK_CGROUP_DATA", },
352
353 /* Tracing: attach BPF to kprobes, tracepoints, etc. */
354 { "CONFIG_BPF_EVENTS", },
355 /* Kprobes */
356 { "CONFIG_KPROBE_EVENTS", },
357 /* Uprobes */
358 { "CONFIG_UPROBE_EVENTS", },
359 /* Tracepoints */
360 { "CONFIG_TRACING", },
361 /* Syscall tracepoints */
362 { "CONFIG_FTRACE_SYSCALLS", },
363 /* bpf_override_return() helper support for selected arch */
364 { "CONFIG_FUNCTION_ERROR_INJECTION", },
365 /* bpf_override_return() helper */
366 { "CONFIG_BPF_KPROBE_OVERRIDE", },
367
368 /* Network */
369 { "CONFIG_NET", },
370 /* AF_XDP sockets */
371 { "CONFIG_XDP_SOCKETS", },
372 /* BPF_PROG_TYPE_LWT_* and related helpers */
373 { "CONFIG_LWTUNNEL_BPF", },
374 /* BPF_PROG_TYPE_SCHED_ACT, TC (traffic control) actions */
375 { "CONFIG_NET_ACT_BPF", },
376 /* BPF_PROG_TYPE_SCHED_CLS, TC filters */
377 { "CONFIG_NET_CLS_BPF", },
378 /* TC clsact qdisc */
379 { "CONFIG_NET_CLS_ACT", },
380 /* Ingress filtering with TC */
381 { "CONFIG_NET_SCH_INGRESS", },
382 /* bpf_skb_get_xfrm_state() helper */
383 { "CONFIG_XFRM", },
384 /* bpf_get_route_realm() helper */
385 { "CONFIG_IP_ROUTE_CLASSID", },
386 /* BPF_PROG_TYPE_LWT_SEG6_LOCAL and related helpers */
387 { "CONFIG_IPV6_SEG6_BPF", },
388 /* BPF_PROG_TYPE_LIRC_MODE2 and related helpers */
389 { "CONFIG_BPF_LIRC_MODE2", },
390 /* BPF stream parser and BPF socket maps */
391 { "CONFIG_BPF_STREAM_PARSER", },
392 /* xt_bpf module for passing BPF programs to netfilter */
393 { "CONFIG_NETFILTER_XT_MATCH_BPF", },
394 /* bpfilter back-end for iptables */
395 { "CONFIG_BPFILTER", },
396 /* bpftilter module with "user mode helper" */
397 { "CONFIG_BPFILTER_UMH", },
398
399 /* test_bpf module for BPF tests */
400 { "CONFIG_TEST_BPF", },
401
402 /* Misc configs useful in BPF C programs */
403 /* jiffies <-> sec conversion for bpf_jiffies64() helper */
404 { "CONFIG_HZ", true, }
405 };
406 char *values[ARRAY_SIZE(options)] = { };
407 struct utsname utsn;
408 char path[PATH_MAX];
409 gzFile file = NULL;
410 char buf[4096];
411 char *value;
412 size_t i;
413
414 if (!uname(&utsn)) {
415 snprintf(path, sizeof(path), "/boot/config-%s", utsn.release);
416
417 /* gzopen also accepts uncompressed files. */
418 file = gzopen(path, "r");
419 }
420
421 if (!file) {
422 /* Some distributions build with CONFIG_IKCONFIG=y and put the
423 * config file at /proc/config.gz.
424 */
425 file = gzopen("/proc/config.gz", "r");
426 }
427 if (!file) {
428 p_info("skipping kernel config, can't open file: %s",
429 strerror(errno));
430 goto end_parse;
431 }
432 /* Sanity checks */
433 if (!gzgets(file, buf, sizeof(buf)) ||
434 !gzgets(file, buf, sizeof(buf))) {
435 p_info("skipping kernel config, can't read from file: %s",
436 strerror(errno));
437 goto end_parse;
438 }
439 if (strcmp(buf, "# Automatically generated file; DO NOT EDIT.\n")) {
440 p_info("skipping kernel config, can't find correct file");
441 goto end_parse;
442 }
443
444 while (read_next_kernel_config_option(file, buf, sizeof(buf), &value)) {
445 for (i = 0; i < ARRAY_SIZE(options); i++) {
446 if ((define_prefix && !options[i].macro_dump) ||
447 values[i] || strcmp(buf, options[i].name))
448 continue;
449
450 values[i] = strdup(value);
451 }
452 }
453
454 end_parse:
455 if (file)
456 gzclose(file);
457
458 for (i = 0; i < ARRAY_SIZE(options); i++) {
459 if (define_prefix && !options[i].macro_dump)
460 continue;
461 print_kernel_option(options[i].name, values[i], define_prefix);
462 free(values[i]);
463 }
464 }
465
probe_bpf_syscall(const char * define_prefix)466 static bool probe_bpf_syscall(const char *define_prefix)
467 {
468 bool res;
469
470 bpf_load_program(BPF_PROG_TYPE_UNSPEC, NULL, 0, NULL, 0, NULL, 0);
471 res = (errno != ENOSYS);
472
473 print_bool_feature("have_bpf_syscall",
474 "bpf() syscall",
475 "BPF_SYSCALL",
476 res, define_prefix);
477
478 return res;
479 }
480
481 static void
probe_prog_type(enum bpf_prog_type prog_type,bool * supported_types,const char * define_prefix,__u32 ifindex)482 probe_prog_type(enum bpf_prog_type prog_type, bool *supported_types,
483 const char *define_prefix, __u32 ifindex)
484 {
485 char feat_name[128], plain_desc[128], define_name[128];
486 const char *plain_comment = "eBPF program_type ";
487 size_t maxlen;
488 bool res;
489
490 if (ifindex)
491 /* Only test offload-able program types */
492 switch (prog_type) {
493 case BPF_PROG_TYPE_SCHED_CLS:
494 case BPF_PROG_TYPE_XDP:
495 break;
496 default:
497 return;
498 }
499
500 res = bpf_probe_prog_type(prog_type, ifindex);
501 #ifdef USE_LIBCAP
502 /* Probe may succeed even if program load fails, for unprivileged users
503 * check that we did not fail because of insufficient permissions
504 */
505 if (run_as_unprivileged && errno == EPERM)
506 res = false;
507 #endif
508
509 supported_types[prog_type] |= res;
510
511 if (!prog_type_name[prog_type]) {
512 p_info("program type name not found (type %d)", prog_type);
513 return;
514 }
515 maxlen = sizeof(plain_desc) - strlen(plain_comment) - 1;
516 if (strlen(prog_type_name[prog_type]) > maxlen) {
517 p_info("program type name too long");
518 return;
519 }
520
521 sprintf(feat_name, "have_%s_prog_type", prog_type_name[prog_type]);
522 sprintf(define_name, "%s_prog_type", prog_type_name[prog_type]);
523 uppercase(define_name, sizeof(define_name));
524 sprintf(plain_desc, "%s%s", plain_comment, prog_type_name[prog_type]);
525 print_bool_feature(feat_name, plain_desc, define_name, res,
526 define_prefix);
527 }
528
529 static void
probe_map_type(enum bpf_map_type map_type,const char * define_prefix,__u32 ifindex)530 probe_map_type(enum bpf_map_type map_type, const char *define_prefix,
531 __u32 ifindex)
532 {
533 char feat_name[128], plain_desc[128], define_name[128];
534 const char *plain_comment = "eBPF map_type ";
535 size_t maxlen;
536 bool res;
537
538 res = bpf_probe_map_type(map_type, ifindex);
539
540 /* Probe result depends on the success of map creation, no additional
541 * check required for unprivileged users
542 */
543
544 if (!map_type_name[map_type]) {
545 p_info("map type name not found (type %d)", map_type);
546 return;
547 }
548 maxlen = sizeof(plain_desc) - strlen(plain_comment) - 1;
549 if (strlen(map_type_name[map_type]) > maxlen) {
550 p_info("map type name too long");
551 return;
552 }
553
554 sprintf(feat_name, "have_%s_map_type", map_type_name[map_type]);
555 sprintf(define_name, "%s_map_type", map_type_name[map_type]);
556 uppercase(define_name, sizeof(define_name));
557 sprintf(plain_desc, "%s%s", plain_comment, map_type_name[map_type]);
558 print_bool_feature(feat_name, plain_desc, define_name, res,
559 define_prefix);
560 }
561
562 static void
probe_helper_for_progtype(enum bpf_prog_type prog_type,bool supported_type,const char * define_prefix,unsigned int id,const char * ptype_name,__u32 ifindex)563 probe_helper_for_progtype(enum bpf_prog_type prog_type, bool supported_type,
564 const char *define_prefix, unsigned int id,
565 const char *ptype_name, __u32 ifindex)
566 {
567 bool res = false;
568
569 if (supported_type) {
570 res = bpf_probe_helper(id, prog_type, ifindex);
571 #ifdef USE_LIBCAP
572 /* Probe may succeed even if program load fails, for
573 * unprivileged users check that we did not fail because of
574 * insufficient permissions
575 */
576 if (run_as_unprivileged && errno == EPERM)
577 res = false;
578 #endif
579 }
580
581 if (json_output) {
582 if (res)
583 jsonw_string(json_wtr, helper_name[id]);
584 } else if (define_prefix) {
585 printf("#define %sBPF__PROG_TYPE_%s__HELPER_%s %s\n",
586 define_prefix, ptype_name, helper_name[id],
587 res ? "1" : "0");
588 } else {
589 if (res)
590 printf("\n\t- %s", helper_name[id]);
591 }
592 }
593
594 static void
probe_helpers_for_progtype(enum bpf_prog_type prog_type,bool supported_type,const char * define_prefix,__u32 ifindex)595 probe_helpers_for_progtype(enum bpf_prog_type prog_type, bool supported_type,
596 const char *define_prefix, __u32 ifindex)
597 {
598 const char *ptype_name = prog_type_name[prog_type];
599 char feat_name[128];
600 unsigned int id;
601
602 if (ifindex)
603 /* Only test helpers for offload-able program types */
604 switch (prog_type) {
605 case BPF_PROG_TYPE_SCHED_CLS:
606 case BPF_PROG_TYPE_XDP:
607 break;
608 default:
609 return;
610 }
611
612 if (json_output) {
613 sprintf(feat_name, "%s_available_helpers", ptype_name);
614 jsonw_name(json_wtr, feat_name);
615 jsonw_start_array(json_wtr);
616 } else if (!define_prefix) {
617 printf("eBPF helpers supported for program type %s:",
618 ptype_name);
619 }
620
621 for (id = 1; id < ARRAY_SIZE(helper_name); id++) {
622 /* Skip helper functions which emit dmesg messages when not in
623 * the full mode.
624 */
625 switch (id) {
626 case BPF_FUNC_trace_printk:
627 case BPF_FUNC_trace_vprintk:
628 case BPF_FUNC_probe_write_user:
629 if (!full_mode)
630 continue;
631 /* fallthrough */
632 default:
633 probe_helper_for_progtype(prog_type, supported_type,
634 define_prefix, id, ptype_name,
635 ifindex);
636 }
637 }
638
639 if (json_output)
640 jsonw_end_array(json_wtr);
641 else if (!define_prefix)
642 printf("\n");
643 }
644
645 static void
probe_large_insn_limit(const char * define_prefix,__u32 ifindex)646 probe_large_insn_limit(const char *define_prefix, __u32 ifindex)
647 {
648 bool res;
649
650 res = bpf_probe_large_insn_limit(ifindex);
651 print_bool_feature("have_large_insn_limit",
652 "Large program size limit",
653 "LARGE_INSN_LIMIT",
654 res, define_prefix);
655 }
656
657 static void
section_system_config(enum probe_component target,const char * define_prefix)658 section_system_config(enum probe_component target, const char *define_prefix)
659 {
660 switch (target) {
661 case COMPONENT_KERNEL:
662 case COMPONENT_UNSPEC:
663 print_start_section("system_config",
664 "Scanning system configuration...",
665 "/*** Misc kernel config items ***/",
666 define_prefix);
667 if (!define_prefix) {
668 if (check_procfs()) {
669 probe_unprivileged_disabled();
670 probe_jit_enable();
671 probe_jit_harden();
672 probe_jit_kallsyms();
673 probe_jit_limit();
674 } else {
675 p_info("/* procfs not mounted, skipping related probes */");
676 }
677 }
678 probe_kernel_image_config(define_prefix);
679 print_end_section();
680 break;
681 default:
682 break;
683 }
684 }
685
section_syscall_config(const char * define_prefix)686 static bool section_syscall_config(const char *define_prefix)
687 {
688 bool res;
689
690 print_start_section("syscall_config",
691 "Scanning system call availability...",
692 "/*** System call availability ***/",
693 define_prefix);
694 res = probe_bpf_syscall(define_prefix);
695 print_end_section();
696
697 return res;
698 }
699
700 static void
section_program_types(bool * supported_types,const char * define_prefix,__u32 ifindex)701 section_program_types(bool *supported_types, const char *define_prefix,
702 __u32 ifindex)
703 {
704 unsigned int i;
705
706 print_start_section("program_types",
707 "Scanning eBPF program types...",
708 "/*** eBPF program types ***/",
709 define_prefix);
710
711 for (i = BPF_PROG_TYPE_UNSPEC + 1; i < prog_type_name_size; i++)
712 probe_prog_type(i, supported_types, define_prefix, ifindex);
713
714 print_end_section();
715 }
716
section_map_types(const char * define_prefix,__u32 ifindex)717 static void section_map_types(const char *define_prefix, __u32 ifindex)
718 {
719 unsigned int i;
720
721 print_start_section("map_types",
722 "Scanning eBPF map types...",
723 "/*** eBPF map types ***/",
724 define_prefix);
725
726 for (i = BPF_MAP_TYPE_UNSPEC + 1; i < map_type_name_size; i++)
727 probe_map_type(i, define_prefix, ifindex);
728
729 print_end_section();
730 }
731
732 static void
section_helpers(bool * supported_types,const char * define_prefix,__u32 ifindex)733 section_helpers(bool *supported_types, const char *define_prefix, __u32 ifindex)
734 {
735 unsigned int i;
736
737 print_start_section("helpers",
738 "Scanning eBPF helper functions...",
739 "/*** eBPF helper functions ***/",
740 define_prefix);
741
742 if (define_prefix)
743 printf("/*\n"
744 " * Use %sHAVE_PROG_TYPE_HELPER(prog_type_name, helper_name)\n"
745 " * to determine if <helper_name> is available for <prog_type_name>,\n"
746 " * e.g.\n"
747 " * #if %sHAVE_PROG_TYPE_HELPER(xdp, bpf_redirect)\n"
748 " * // do stuff with this helper\n"
749 " * #elif\n"
750 " * // use a workaround\n"
751 " * #endif\n"
752 " */\n"
753 "#define %sHAVE_PROG_TYPE_HELPER(prog_type, helper) \\\n"
754 " %sBPF__PROG_TYPE_ ## prog_type ## __HELPER_ ## helper\n",
755 define_prefix, define_prefix, define_prefix,
756 define_prefix);
757 for (i = BPF_PROG_TYPE_UNSPEC + 1; i < prog_type_name_size; i++)
758 probe_helpers_for_progtype(i, supported_types[i], define_prefix,
759 ifindex);
760
761 print_end_section();
762 }
763
section_misc(const char * define_prefix,__u32 ifindex)764 static void section_misc(const char *define_prefix, __u32 ifindex)
765 {
766 print_start_section("misc",
767 "Scanning miscellaneous eBPF features...",
768 "/*** eBPF misc features ***/",
769 define_prefix);
770 probe_large_insn_limit(define_prefix, ifindex);
771 print_end_section();
772 }
773
774 #ifdef USE_LIBCAP
775 #define capability(c) { c, false, #c }
776 #define capability_msg(a, i) a[i].set ? "" : a[i].name, a[i].set ? "" : ", "
777 #endif
778
handle_perms(void)779 static int handle_perms(void)
780 {
781 #ifdef USE_LIBCAP
782 struct {
783 cap_value_t cap;
784 bool set;
785 char name[14]; /* strlen("CAP_SYS_ADMIN") */
786 } bpf_caps[] = {
787 capability(CAP_SYS_ADMIN),
788 #ifdef CAP_BPF
789 capability(CAP_BPF),
790 capability(CAP_NET_ADMIN),
791 capability(CAP_PERFMON),
792 #endif
793 };
794 cap_value_t cap_list[ARRAY_SIZE(bpf_caps)];
795 unsigned int i, nb_bpf_caps = 0;
796 bool cap_sys_admin_only = true;
797 cap_flag_value_t val;
798 int res = -1;
799 cap_t caps;
800
801 caps = cap_get_proc();
802 if (!caps) {
803 p_err("failed to get capabilities for process: %s",
804 strerror(errno));
805 return -1;
806 }
807
808 #ifdef CAP_BPF
809 if (CAP_IS_SUPPORTED(CAP_BPF))
810 cap_sys_admin_only = false;
811 #endif
812
813 for (i = 0; i < ARRAY_SIZE(bpf_caps); i++) {
814 const char *cap_name = bpf_caps[i].name;
815 cap_value_t cap = bpf_caps[i].cap;
816
817 if (cap_get_flag(caps, cap, CAP_EFFECTIVE, &val)) {
818 p_err("bug: failed to retrieve %s status: %s", cap_name,
819 strerror(errno));
820 goto exit_free;
821 }
822
823 if (val == CAP_SET) {
824 bpf_caps[i].set = true;
825 cap_list[nb_bpf_caps++] = cap;
826 }
827
828 if (cap_sys_admin_only)
829 /* System does not know about CAP_BPF, meaning that
830 * CAP_SYS_ADMIN is the only capability required. We
831 * just checked it, break.
832 */
833 break;
834 }
835
836 if ((run_as_unprivileged && !nb_bpf_caps) ||
837 (!run_as_unprivileged && nb_bpf_caps == ARRAY_SIZE(bpf_caps)) ||
838 (!run_as_unprivileged && cap_sys_admin_only && nb_bpf_caps)) {
839 /* We are all good, exit now */
840 res = 0;
841 goto exit_free;
842 }
843
844 if (!run_as_unprivileged) {
845 if (cap_sys_admin_only)
846 p_err("missing %s, required for full feature probing; run as root or use 'unprivileged'",
847 bpf_caps[0].name);
848 else
849 p_err("missing %s%s%s%s%s%s%s%srequired for full feature probing; run as root or use 'unprivileged'",
850 capability_msg(bpf_caps, 0),
851 #ifdef CAP_BPF
852 capability_msg(bpf_caps, 1),
853 capability_msg(bpf_caps, 2),
854 capability_msg(bpf_caps, 3)
855 #else
856 "", "", "", "", "", ""
857 #endif /* CAP_BPF */
858 );
859 goto exit_free;
860 }
861
862 /* if (run_as_unprivileged && nb_bpf_caps > 0), drop capabilities. */
863 if (cap_set_flag(caps, CAP_EFFECTIVE, nb_bpf_caps, cap_list,
864 CAP_CLEAR)) {
865 p_err("bug: failed to clear capabilities: %s", strerror(errno));
866 goto exit_free;
867 }
868
869 if (cap_set_proc(caps)) {
870 p_err("failed to drop capabilities: %s", strerror(errno));
871 goto exit_free;
872 }
873
874 res = 0;
875
876 exit_free:
877 if (cap_free(caps) && !res) {
878 p_err("failed to clear storage object for capabilities: %s",
879 strerror(errno));
880 res = -1;
881 }
882
883 return res;
884 #else
885 /* Detection assumes user has specific privileges.
886 * We do not use libpcap so let's approximate, and restrict usage to
887 * root user only.
888 */
889 if (geteuid()) {
890 p_err("full feature probing requires root privileges");
891 return -1;
892 }
893
894 return 0;
895 #endif /* USE_LIBCAP */
896 }
897
do_probe(int argc,char ** argv)898 static int do_probe(int argc, char **argv)
899 {
900 enum probe_component target = COMPONENT_UNSPEC;
901 const char *define_prefix = NULL;
902 bool supported_types[128] = {};
903 __u32 ifindex = 0;
904 char *ifname;
905
906 set_max_rlimit();
907
908 while (argc) {
909 if (is_prefix(*argv, "kernel")) {
910 if (target != COMPONENT_UNSPEC) {
911 p_err("component to probe already specified");
912 return -1;
913 }
914 target = COMPONENT_KERNEL;
915 NEXT_ARG();
916 } else if (is_prefix(*argv, "dev")) {
917 NEXT_ARG();
918
919 if (target != COMPONENT_UNSPEC || ifindex) {
920 p_err("component to probe already specified");
921 return -1;
922 }
923 if (!REQ_ARGS(1))
924 return -1;
925
926 target = COMPONENT_DEVICE;
927 ifname = GET_ARG();
928 ifindex = if_nametoindex(ifname);
929 if (!ifindex) {
930 p_err("unrecognized netdevice '%s': %s", ifname,
931 strerror(errno));
932 return -1;
933 }
934 } else if (is_prefix(*argv, "full")) {
935 full_mode = true;
936 NEXT_ARG();
937 } else if (is_prefix(*argv, "macros") && !define_prefix) {
938 define_prefix = "";
939 NEXT_ARG();
940 } else if (is_prefix(*argv, "prefix")) {
941 if (!define_prefix) {
942 p_err("'prefix' argument can only be use after 'macros'");
943 return -1;
944 }
945 if (strcmp(define_prefix, "")) {
946 p_err("'prefix' already defined");
947 return -1;
948 }
949 NEXT_ARG();
950
951 if (!REQ_ARGS(1))
952 return -1;
953 define_prefix = GET_ARG();
954 } else if (is_prefix(*argv, "unprivileged")) {
955 #ifdef USE_LIBCAP
956 run_as_unprivileged = true;
957 NEXT_ARG();
958 #else
959 p_err("unprivileged run not supported, recompile bpftool with libcap");
960 return -1;
961 #endif
962 } else {
963 p_err("expected no more arguments, 'kernel', 'dev', 'macros' or 'prefix', got: '%s'?",
964 *argv);
965 return -1;
966 }
967 }
968
969 /* Full feature detection requires specific privileges.
970 * Let's approximate, and warn if user is not root.
971 */
972 if (handle_perms())
973 return -1;
974
975 if (json_output) {
976 define_prefix = NULL;
977 jsonw_start_object(json_wtr);
978 }
979
980 section_system_config(target, define_prefix);
981 if (!section_syscall_config(define_prefix))
982 /* bpf() syscall unavailable, don't probe other BPF features */
983 goto exit_close_json;
984 section_program_types(supported_types, define_prefix, ifindex);
985 section_map_types(define_prefix, ifindex);
986 section_helpers(supported_types, define_prefix, ifindex);
987 section_misc(define_prefix, ifindex);
988
989 exit_close_json:
990 if (json_output)
991 /* End root object */
992 jsonw_end_object(json_wtr);
993
994 return 0;
995 }
996
do_help(int argc,char ** argv)997 static int do_help(int argc, char **argv)
998 {
999 if (json_output) {
1000 jsonw_null(json_wtr);
1001 return 0;
1002 }
1003
1004 fprintf(stderr,
1005 "Usage: %1$s %2$s probe [COMPONENT] [full] [unprivileged] [macros [prefix PREFIX]]\n"
1006 " %1$s %2$s help\n"
1007 "\n"
1008 " COMPONENT := { kernel | dev NAME }\n"
1009 " " HELP_SPEC_OPTIONS " }\n"
1010 "",
1011 bin_name, argv[-2]);
1012
1013 return 0;
1014 }
1015
1016 static const struct cmd cmds[] = {
1017 { "probe", do_probe },
1018 { "help", do_help },
1019 { 0 }
1020 };
1021
do_feature(int argc,char ** argv)1022 int do_feature(int argc, char **argv)
1023 {
1024 return cmd_select(cmds, argc, argv, do_help);
1025 }
1026