summaryrefslogtreecommitdiff
path: root/tools/bpf/bpftool/feature.c
blob: 7f36385aa9e2e3773b0c8c2bb092bdd9bb84d097 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
// SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
/* Copyright (c) 2019 Netronome Systems, Inc. */

#include <ctype.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>
#include <net/if.h>
#ifdef USE_LIBCAP
#include <sys/capability.h>
#endif
#include <sys/utsname.h>
#include <sys/vfs.h>

#include <linux/filter.h>
#include <linux/limits.h>

#include <bpf/bpf.h>
#include <bpf/libbpf.h>
#include <zlib.h>

#include "main.h"

#ifndef PROC_SUPER_MAGIC
# define PROC_SUPER_MAGIC	0x9fa0
#endif

enum probe_component {
	COMPONENT_UNSPEC,
	COMPONENT_KERNEL,
	COMPONENT_DEVICE,
};

#define BPF_HELPER_MAKE_ENTRY(name)	[BPF_FUNC_ ## name] = "bpf_" # name
static const char * const helper_name[] = {
	__BPF_FUNC_MAPPER(BPF_HELPER_MAKE_ENTRY)
};

#undef BPF_HELPER_MAKE_ENTRY

static bool full_mode;
#ifdef USE_LIBCAP
static bool run_as_unprivileged;
#endif

/* Miscellaneous utility functions */

static bool check_procfs(void)
{
	struct statfs st_fs;

	if (statfs("/proc", &st_fs) < 0)
		return false;
	if ((unsigned long)st_fs.f_type != PROC_SUPER_MAGIC)
		return false;

	return true;
}

static void uppercase(char *str, size_t len)
{
	size_t i;

	for (i = 0; i < len && str[i] != '\0'; i++)
		str[i] = toupper(str[i]);
}

/* Printing utility functions */

static void
print_bool_feature(const char *feat_name, const char *plain_name,
		   const char *define_name, bool res, const char *define_prefix)
{
	if (json_output)
		jsonw_bool_field(json_wtr, feat_name, res);
	else if (define_prefix)
		printf("#define %s%sHAVE_%s\n", define_prefix,
		       res ? "" : "NO_", define_name);
	else
		printf("%s is %savailable\n", plain_name, res ? "" : "NOT ");
}

static void print_kernel_option(const char *name, const char *value,
				const char *define_prefix)
{
	char *endptr;
	int res;

	if (json_output) {
		if (!value) {
			jsonw_null_field(json_wtr, name);
			return;
		}
		errno = 0;
		res = strtol(value, &endptr, 0);
		if (!errno && *endptr == '\n')
			jsonw_int_field(json_wtr, name, res);
		else
			jsonw_string_field(json_wtr, name, value);
	} else if (define_prefix) {
		if (value)
			printf("#define %s%s %s\n", define_prefix,
			       name, value);
		else
			printf("/* %s%s is not set */\n", define_prefix, name);
	} else {
		if (value)
			printf("%s is set to %s\n", name, value);
		else
			printf("%s is not set\n", name);
	}
}

static void
print_start_section(const char *json_title, const char *plain_title,
		    const char *define_comment, const char *define_prefix)
{
	if (json_output) {
		jsonw_name(json_wtr, json_title);
		jsonw_start_object(json_wtr);
	} else if (define_prefix) {
		printf("%s\n", define_comment);
	} else {
		printf("%s\n", plain_title);
	}
}

static void print_end_section(void)
{
	if (json_output)
		jsonw_end_object(json_wtr);
	else
		printf("\n");
}

/* Probing functions */

static int read_procfs(const char *path)
{
	char *endptr, *line = NULL;
	size_t len = 0;
	FILE *fd;
	int res;

	fd = fopen(path, "r");
	if (!fd)
		return -1;

	res = getline(&line, &len, fd);
	fclose(fd);
	if (res < 0)
		return -1;

	errno = 0;
	res = strtol(line, &endptr, 10);
	if (errno || *line == '\0' || *endptr != '\n')
		res = -1;
	free(line);

	return res;
}

static void probe_unprivileged_disabled(void)
{
	int res;

	/* No support for C-style ouptut */

	res = read_procfs("/proc/sys/kernel/unprivileged_bpf_disabled");
	if (json_output) {
		jsonw_int_field(json_wtr, "unprivileged_bpf_disabled", res);
	} else {
		switch (res) {
		case 0:
			printf("bpf() syscall for unprivileged users is enabled\n");
			break;
		case 1:
			printf("bpf() syscall restricted to privileged users\n");
			break;
		case -1:
			printf("Unable to retrieve required privileges for bpf() syscall\n");
			break;
		default:
			printf("bpf() syscall restriction has unknown value %d\n", res);
		}
	}
}

static void probe_jit_enable(void)
{
	int res;

	/* No support for C-style ouptut */

	res = read_procfs("/proc/sys/net/core/bpf_jit_enable");
	if (json_output) {
		jsonw_int_field(json_wtr, "bpf_jit_enable", res);
	} else {
		switch (res) {
		case 0:
			printf("JIT compiler is disabled\n");
			break;
		case 1:
			printf("JIT compiler is enabled\n");
			break;
		case 2:
			printf("JIT compiler is enabled with debugging traces in kernel logs\n");
			break;
		case -1:
			printf("Unable to retrieve JIT-compiler status\n");
			break;
		default:
			printf("JIT-compiler status has unknown value %d\n",
			       res);
		}
	}
}

static void probe_jit_harden(void)
{
	int res;

	/* No support for C-style ouptut */

	res = read_procfs("/proc/sys/net/core/bpf_jit_harden");
	if (json_output) {
		jsonw_int_field(json_wtr, "bpf_jit_harden", res);
	} else {
		switch (res) {
		case 0:
			printf("JIT compiler hardening is disabled\n");
			break;
		case 1:
			printf("JIT compiler hardening is enabled for unprivileged users\n");
			break;
		case 2:
			printf("JIT compiler hardening is enabled for all users\n");
			break;
		case -1:
			printf("Unable to retrieve JIT hardening status\n");
			break;
		default:
			printf("JIT hardening status has unknown value %d\n",
			       res);
		}
	}
}

static void probe_jit_kallsyms(void)
{
	int res;

	/* No support for C-style ouptut */

	res = read_procfs("/proc/sys/net/core/bpf_jit_kallsyms");
	if (json_output) {
		jsonw_int_field(json_wtr, "bpf_jit_kallsyms", res);
	} else {
		switch (res) {
		case 0:
			printf("JIT compiler kallsyms exports are disabled\n");
			break;
		case 1:
			printf("JIT compiler kallsyms exports are enabled for root\n");
			break;
		case -1:
			printf("Unable to retrieve JIT kallsyms export status\n");
			break;
		default:
			printf("JIT kallsyms exports status has unknown value %d\n", res);
		}
	}
}

static void probe_jit_limit(void)
{
	int res;

	/* No support for C-style ouptut */

	res = read_procfs("/proc/sys/net/core/bpf_jit_limit");
	if (json_output) {
		jsonw_int_field(json_wtr, "bpf_jit_limit", res);
	} else {
		switch (res) {
		case -1:
			printf("Unable to retrieve global memory limit for JIT compiler for unprivileged users\n");
			break;
		default:
			printf("Global memory limit for JIT compiler for unprivileged users is %d bytes\n", res);
		}
	}
}

static bool read_next_kernel_config_option(gzFile file, char *buf, size_t n,
					   char **value)
{
	char *sep;

	while (gzgets(file, buf, n)) {
		if (strncmp(buf, "CONFIG_", 7))
			continue;

		sep = strchr(buf, '=');
		if (!sep)
			continue;

		/* Trim ending '\n' */
		buf[strlen(buf) - 1] = '\0';

		/* Split on '=' and ensure that a value is present. */
		*sep = '\0';
		if (!sep[1])
			continue;

		*value = sep + 1;
		return true;
	}

	return false;
}

static void probe_kernel_image_config(const char *define_prefix)
{
	static const struct {
		const char * const name;
		bool macro_dump;
	} options[] = {
		/* Enable BPF */
		{ "CONFIG_BPF", },
		/* Enable bpf() syscall */
		{ "CONFIG_BPF_SYSCALL", },
		/* Does selected architecture support eBPF JIT compiler */
		{ "CONFIG_HAVE_EBPF_JIT", },
		/* Compile eBPF JIT compiler */
		{ "CONFIG_BPF_JIT", },
		/* Avoid compiling eBPF interpreter (use JIT only) */
		{ "CONFIG_BPF_JIT_ALWAYS_ON", },
		/* Kernel BTF debug information available */
		{ "CONFIG_DEBUG_INFO_BTF", },
		/* Kernel module BTF debug information available */
		{ "CONFIG_DEBUG_INFO_BTF_MODULES", },

		/* cgroups */
		{ "CONFIG_CGROUPS", },
		/* BPF programs attached to cgroups */
		{ "CONFIG_CGROUP_BPF", },
		/* bpf_get_cgroup_classid() helper */
		{ "CONFIG_CGROUP_NET_CLASSID", },
		/* bpf_skb_{,ancestor_}cgroup_id() helpers */
		{ "CONFIG_SOCK_CGROUP_DATA", },

		/* Tracing: attach BPF to kprobes, tracepoints, etc. */
		{ "CONFIG_BPF_EVENTS", },
		/* Kprobes */
		{ "CONFIG_KPROBE_EVENTS", },
		/* Uprobes */
		{ "CONFIG_UPROBE_EVENTS", },
		/* Tracepoints */
		{ "CONFIG_TRACING", },
		/* Syscall tracepoints */
		{ "CONFIG_FTRACE_SYSCALLS", },
		/* bpf_override_return() helper support for selected arch */
		{ "CONFIG_FUNCTION_ERROR_INJECTION", },
		/* bpf_override_return() helper */
		{ "CONFIG_BPF_KPROBE_OVERRIDE", },

		/* Network */
		{ "CONFIG_NET", },
		/* AF_XDP sockets */
		{ "CONFIG_XDP_SOCKETS", },
		/* BPF_PROG_TYPE_LWT_* and related helpers */
		{ "CONFIG_LWTUNNEL_BPF", },
		/* BPF_PROG_TYPE_SCHED_ACT, TC (traffic control) actions */
		{ "CONFIG_NET_ACT_BPF", },
		/* BPF_PROG_TYPE_SCHED_CLS, TC filters */
		{ "CONFIG_NET_CLS_BPF", },
		/* TC clsact qdisc */
		{ "CONFIG_NET_CLS_ACT", },
		/* Ingress filtering with TC */
		{ "CONFIG_NET_SCH_INGRESS", },
		/* bpf_skb_get_xfrm_state() helper */
		{ "CONFIG_XFRM", },
		/* bpf_get_route_realm() helper */
		{ "CONFIG_IP_ROUTE_CLASSID", },
		/* BPF_PROG_TYPE_LWT_SEG6_LOCAL and related helpers */
		{ "CONFIG_IPV6_SEG6_BPF", },
		/* BPF_PROG_TYPE_LIRC_MODE2 and related helpers */
		{ "CONFIG_BPF_LIRC_MODE2", },
		/* BPF stream parser and BPF socket maps */
		{ "CONFIG_BPF_STREAM_PARSER", },
		/* xt_bpf module for passing BPF programs to netfilter  */
		{ "CONFIG_NETFILTER_XT_MATCH_BPF", },
		/* bpfilter back-end for iptables */
		{ "CONFIG_BPFILTER", },
		/* bpftilter module with "user mode helper" */
		{ "CONFIG_BPFILTER_UMH", },

		/* test_bpf module for BPF tests */
		{ "CONFIG_TEST_BPF", },

		/* Misc configs useful in BPF C programs */
		/* jiffies <-> sec conversion for bpf_jiffies64() helper */
		{ "CONFIG_HZ", true, }
	};
	char *values[ARRAY_SIZE(options)] = { };
	struct utsname utsn;
	char path[PATH_MAX];
	gzFile file = NULL;
	char buf[4096];
	char *value;
	size_t i;

	if (!uname(&utsn)) {
		snprintf(path, sizeof(path), "/boot/config-%s", utsn.release);

		/* gzopen also accepts uncompressed files. */
		file = gzopen(path, "r");
	}

	if (!file) {
		/* Some distributions build with CONFIG_IKCONFIG=y and put the
		 * config file at /proc/config.gz.
		 */
		file = gzopen("/proc/config.gz", "r");
	}
	if (!file) {
		p_info("skipping kernel config, can't open file: %s",
		       strerror(errno));
		goto end_parse;
	}
	/* Sanity checks */
	if (!gzgets(file, buf, sizeof(buf)) ||
	    !gzgets(file, buf, sizeof(buf))) {
		p_info("skipping kernel config, can't read from file: %s",
		       strerror(errno));
		goto end_parse;
	}
	if (strcmp(buf, "# Automatically generated file; DO NOT EDIT.\n")) {
		p_info("skipping kernel config, can't find correct file");
		goto end_parse;
	}

	while (read_next_kernel_config_option(file, buf, sizeof(buf), &value)) {
		for (i = 0; i < ARRAY_SIZE(options); i++) {
			if ((define_prefix && !options[i].macro_dump) ||
			    values[i] || strcmp(buf, options[i].name))
				continue;

			values[i] = strdup(value);
		}
	}

end_parse:
	if (file)
		gzclose(file);

	for (i = 0; i < ARRAY_SIZE(options); i++) {
		if (define_prefix && !options[i].macro_dump)
			continue;
		print_kernel_option(options[i].name, values[i], define_prefix);
		free(values[i]);
	}
}

static bool probe_bpf_syscall(const char *define_prefix)
{
	bool res;

	bpf_load_program(BPF_PROG_TYPE_UNSPEC, NULL, 0, NULL, 0, NULL, 0);
	res = (errno != ENOSYS);

	print_bool_feature("have_bpf_syscall",
			   "bpf() syscall",
			   "BPF_SYSCALL",
			   res, define_prefix);

	return res;
}

static void
probe_prog_type(enum bpf_prog_type prog_type, bool *supported_types,
		const char *define_prefix, __u32 ifindex)
{
	char feat_name[128], plain_desc[128], define_name[128];
	const char *plain_comment = "eBPF program_type ";
	size_t maxlen;
	bool res;

	if (ifindex)
		/* Only test offload-able program types */
		switch (prog_type) {
		case BPF_PROG_TYPE_SCHED_CLS:
		case BPF_PROG_TYPE_XDP:
			break;
		default:
			return;
		}

	res = bpf_probe_prog_type(prog_type, ifindex);
#ifdef USE_LIBCAP
	/* Probe may succeed even if program load fails, for unprivileged users
	 * check that we did not fail because of insufficient permissions
	 */
	if (run_as_unprivileged && errno == EPERM)
		res = false;
#endif

	supported_types[prog_type] |= res;

	if (!prog_type_name[prog_type]) {
		p_info("program type name not found (type %d)", prog_type);
		return;
	}
	maxlen = sizeof(plain_desc) - strlen(plain_comment) - 1;
	if (strlen(prog_type_name[prog_type]) > maxlen) {
		p_info("program type name too long");
		return;
	}

	sprintf(feat_name, "have_%s_prog_type", prog_type_name[prog_type]);
	sprintf(define_name, "%s_prog_type", prog_type_name[prog_type]);
	uppercase(define_name, sizeof(define_name));
	sprintf(plain_desc, "%s%s", plain_comment, prog_type_name[prog_type]);
	print_bool_feature(feat_name, plain_desc, define_name, res,
			   define_prefix);
}

static void
probe_map_type(enum bpf_map_type map_type, const char *define_prefix,
	       __u32 ifindex)
{
	char feat_name[128], plain_desc[128], define_name[128];
	const char *plain_comment = "eBPF map_type ";
	size_t maxlen;
	bool res;

	res = bpf_probe_map_type(map_type, ifindex);

	/* Probe result depends on the success of map creation, no additional
	 * check required for unprivileged users
	 */

	if (!map_type_name[map_type]) {
		p_info("map type name not found (type %d)", map_type);
		return;
	}
	maxlen = sizeof(plain_desc) - strlen(plain_comment) - 1;
	if (strlen(map_type_name[map_type]) > maxlen) {
		p_info("map type name too long");
		return;
	}

	sprintf(feat_name, "have_%s_map_type", map_type_name[map_type]);
	sprintf(define_name, "%s_map_type", map_type_name[map_type]);
	uppercase(define_name, sizeof(define_name));
	sprintf(plain_desc, "%s%s", plain_comment, map_type_name[map_type]);
	print_bool_feature(feat_name, plain_desc, define_name, res,
			   define_prefix);
}

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)
{
	bool res = false;

	if (supported_type) {
		res = bpf_probe_helper(id, prog_type, ifindex);
#ifdef USE_LIBCAP
		/* Probe may succeed even if program load fails, for
		 * unprivileged users check that we did not fail because of
		 * insufficient permissions
		 */
		if (run_as_unprivileged && errno == EPERM)
			res = false;
#endif
	}

	if (json_output) {
		if (res)
			jsonw_string(json_wtr, helper_name[id]);
	} else if (define_prefix) {
		printf("#define %sBPF__PROG_TYPE_%s__HELPER_%s %s\n",
		       define_prefix, ptype_name, helper_name[id],
		       res ? "1" : "0");
	} else {
		if (res)
			printf("\n\t- %s", helper_name[id]);
	}
}

static void
probe_helpers_for_progtype(enum bpf_prog_type prog_type, bool supported_type,
			   const char *define_prefix, __u32 ifindex)
{
	const char *ptype_name = prog_type_name[prog_type];
	char feat_name[128];
	unsigned int id;

	if (ifindex)
		/* Only test helpers for offload-able program types */
		switch (prog_type) {
		case BPF_PROG_TYPE_SCHED_CLS:
		case BPF_PROG_TYPE_XDP:
			break;
		default:
			return;
		}

	if (json_output) {
		sprintf(feat_name, "%s_available_helpers", ptype_name);
		jsonw_name(json_wtr, feat_name);
		jsonw_start_array(json_wtr);
	} else if (!define_prefix) {
		printf("eBPF helpers supported for program type %s:",
		       ptype_name);
	}

	for (id = 1; id < ARRAY_SIZE(helper_name); id++) {
		/* Skip helper functions which emit dmesg messages when not in
		 * the full mode.
		 */
		switch (id) {
		case BPF_FUNC_trace_printk:
		case BPF_FUNC_probe_write_user:
			if (!full_mode)
				continue;
			/* fallthrough */
		default:
			probe_helper_for_progtype(prog_type, supported_type,
						  define_prefix, id, ptype_name,
						  ifindex);
		}
	}

	if (json_output)
		jsonw_end_array(json_wtr);
	else if (!define_prefix)
		printf("\n");
}

static void
probe_large_insn_limit(const char *define_prefix, __u32 ifindex)
{
	bool res;

	res = bpf_probe_large_insn_limit(ifindex);
	print_bool_feature("have_large_insn_limit",
			   "Large program size limit",
			   "LARGE_INSN_LIMIT",
			   res, define_prefix);
}

static void
section_system_config(enum probe_component target, const char *define_prefix)
{
	switch (target) {
	case COMPONENT_KERNEL:
	case COMPONENT_UNSPEC:
		print_start_section("system_config",
				    "Scanning system configuration...",
				    "/*** Misc kernel config items ***/",
				    define_prefix);
		if (!define_prefix) {
			if (check_procfs()) {
				probe_unprivileged_disabled();
				probe_jit_enable();
				probe_jit_harden();
				probe_jit_kallsyms();
				probe_jit_limit();
			} else {
				p_info("/* procfs not mounted, skipping related probes */");
			}
		}
		probe_kernel_image_config(define_prefix);
		print_end_section();
		break;
	default:
		break;
	}
}

static bool section_syscall_config(const char *define_prefix)
{
	bool res;

	print_start_section("syscall_config",
			    "Scanning system call availability...",
			    "/*** System call availability ***/",
			    define_prefix);
	res = probe_bpf_syscall(define_prefix);
	print_end_section();

	return res;
}

static void
section_program_types(bool *supported_types, const char *define_prefix,
		      __u32 ifindex)
{
	unsigned int i;

	print_start_section("program_types",
			    "Scanning eBPF program types...",
			    "/*** eBPF program types ***/",
			    define_prefix);

	for (i = BPF_PROG_TYPE_UNSPEC + 1; i < prog_type_name_size; i++)
		probe_prog_type(i, supported_types, define_prefix, ifindex);

	print_end_section();
}

static void section_map_types(const char *define_prefix, __u32 ifindex)
{
	unsigned int i;

	print_start_section("map_types",
			    "Scanning eBPF map types...",
			    "/*** eBPF map types ***/",
			    define_prefix);

	for (i = BPF_MAP_TYPE_UNSPEC + 1; i < map_type_name_size; i++)
		probe_map_type(i, define_prefix, ifindex);

	print_end_section();
}

static void
section_helpers(bool *supported_types, const char *define_prefix, __u32 ifindex)
{
	unsigned int i;

	print_start_section("helpers",
			    "Scanning eBPF helper functions...",
			    "/*** eBPF helper functions ***/",
			    define_prefix);

	if (define_prefix)
		printf("/*\n"
		       " * Use %sHAVE_PROG_TYPE_HELPER(prog_type_name, helper_name)\n"
		       " * to determine if <helper_name> is available for <prog_type_name>,\n"
		       " * e.g.\n"
		       " *	#if %sHAVE_PROG_TYPE_HELPER(xdp, bpf_redirect)\n"
		       " *		// do stuff with this helper\n"
		       " *	#elif\n"
		       " *		// use a workaround\n"
		       " *	#endif\n"
		       " */\n"
		       "#define %sHAVE_PROG_TYPE_HELPER(prog_type, helper)	\\\n"
		       "	%sBPF__PROG_TYPE_ ## prog_type ## __HELPER_ ## helper\n",
		       define_prefix, define_prefix, define_prefix,
		       define_prefix);
	for (i = BPF_PROG_TYPE_UNSPEC + 1; i < prog_type_name_size; i++)
		probe_helpers_for_progtype(i, supported_types[i], define_prefix,
					   ifindex);

	print_end_section();
}

static void section_misc(const char *define_prefix, __u32 ifindex)
{
	print_start_section("misc",
			    "Scanning miscellaneous eBPF features...",
			    "/*** eBPF misc features ***/",
			    define_prefix);
	probe_large_insn_limit(define_prefix, ifindex);
	print_end_section();
}

#ifdef USE_LIBCAP
#define capability(c) { c, false, #c }
#define capability_msg(a, i) a[i].set ? "" : a[i].name, a[i].set ? "" : ", "
#endif

static int handle_perms(void)
{
#ifdef USE_LIBCAP
	struct {
		cap_value_t cap;
		bool set;
		char name[14];	/* strlen("CAP_SYS_ADMIN") */
	} bpf_caps[] = {
		capability(CAP_SYS_ADMIN),
#ifdef CAP_BPF
		capability(CAP_BPF),
		capability(CAP_NET_ADMIN),
		capability(CAP_PERFMON),
#endif
	};
	cap_value_t cap_list[ARRAY_SIZE(bpf_caps)];
	unsigned int i, nb_bpf_caps = 0;
	bool cap_sys_admin_only = true;
	cap_flag_value_t val;
	int res = -1;
	cap_t caps;

	caps = cap_get_proc();
	if (!caps) {
		p_err("failed to get capabilities for process: %s",
		      strerror(errno));
		return -1;
	}

#ifdef CAP_BPF
	if (CAP_IS_SUPPORTED(CAP_BPF))
		cap_sys_admin_only = false;
#endif

	for (i = 0; i < ARRAY_SIZE(bpf_caps); i++) {
		const char *cap_name = bpf_caps[i].name;
		cap_value_t cap = bpf_caps[i].cap;

		if (cap_get_flag(caps, cap, CAP_EFFECTIVE, &val)) {
			p_err("bug: failed to retrieve %s status: %s", cap_name,
			      strerror(errno));
			goto exit_free;
		}

		if (val == CAP_SET) {
			bpf_caps[i].set = true;
			cap_list[nb_bpf_caps++] = cap;
		}

		if (cap_sys_admin_only)
			/* System does not know about CAP_BPF, meaning that
			 * CAP_SYS_ADMIN is the only capability required. We
			 * just checked it, break.
			 */
			break;
	}

	if ((run_as_unprivileged && !nb_bpf_caps) ||
	    (!run_as_unprivileged && nb_bpf_caps == ARRAY_SIZE(bpf_caps)) ||
	    (!run_as_unprivileged && cap_sys_admin_only && nb_bpf_caps)) {
		/* We are all good, exit now */
		res = 0;
		goto exit_free;
	}

	if (!run_as_unprivileged) {
		if (cap_sys_admin_only)
			p_err("missing %s, required for full feature probing; run as root or use 'unprivileged'",
			      bpf_caps[0].name);
		else
			p_err("missing %s%s%s%s%s%s%s%srequired for full feature probing; run as root or use 'unprivileged'",
			      capability_msg(bpf_caps, 0),
#ifdef CAP_BPF
			      capability_msg(bpf_caps, 1),
			      capability_msg(bpf_caps, 2),
			      capability_msg(bpf_caps, 3)
#else
				"", "", "", "", "", ""
#endif /* CAP_BPF */
				);
		goto exit_free;
	}

	/* if (run_as_unprivileged && nb_bpf_caps > 0), drop capabilities. */
	if (cap_set_flag(caps, CAP_EFFECTIVE, nb_bpf_caps, cap_list,
			 CAP_CLEAR)) {
		p_err("bug: failed to clear capabilities: %s", strerror(errno));
		goto exit_free;
	}

	if (cap_set_proc(caps)) {
		p_err("failed to drop capabilities: %s", strerror(errno));
		goto exit_free;
	}

	res = 0;

exit_free:
	if (cap_free(caps) && !res) {
		p_err("failed to clear storage object for capabilities: %s",
		      strerror(errno));
		res = -1;
	}

	return res;
#else
	/* Detection assumes user has specific privileges.
	 * We do not use libpcap so let's approximate, and restrict usage to
	 * root user only.
	 */
	if (geteuid()) {
		p_err("full feature probing requires root privileges");
		return -1;
	}

	return 0;
#endif /* USE_LIBCAP */
}

static int do_probe(int argc, char **argv)
{
	enum probe_component target = COMPONENT_UNSPEC;
	const char *define_prefix = NULL;
	bool supported_types[128] = {};
	__u32 ifindex = 0;
	char *ifname;

	set_max_rlimit();

	while (argc) {
		if (is_prefix(*argv, "kernel")) {
			if (target != COMPONENT_UNSPEC) {
				p_err("component to probe already specified");
				return -1;
			}
			target = COMPONENT_KERNEL;
			NEXT_ARG();
		} else if (is_prefix(*argv, "dev")) {
			NEXT_ARG();

			if (target != COMPONENT_UNSPEC || ifindex) {
				p_err("component to probe already specified");
				return -1;
			}
			if (!REQ_ARGS(1))
				return -1;

			target = COMPONENT_DEVICE;
			ifname = GET_ARG();
			ifindex = if_nametoindex(ifname);
			if (!ifindex) {
				p_err("unrecognized netdevice '%s': %s", ifname,
				      strerror(errno));
				return -1;
			}
		} else if (is_prefix(*argv, "full")) {
			full_mode = true;
			NEXT_ARG();
		} else if (is_prefix(*argv, "macros") && !define_prefix) {
			define_prefix = "";
			NEXT_ARG();
		} else if (is_prefix(*argv, "prefix")) {
			if (!define_prefix) {
				p_err("'prefix' argument can only be use after 'macros'");
				return -1;
			}
			if (strcmp(define_prefix, "")) {
				p_err("'prefix' already defined");
				return -1;
			}
			NEXT_ARG();

			if (!REQ_ARGS(1))
				return -1;
			define_prefix = GET_ARG();
		} else if (is_prefix(*argv, "unprivileged")) {
#ifdef USE_LIBCAP
			run_as_unprivileged = true;
			NEXT_ARG();
#else
			p_err("unprivileged run not supported, recompile bpftool with libcap");
			return -1;
#endif
		} else {
			p_err("expected no more arguments, 'kernel', 'dev', 'macros' or 'prefix', got: '%s'?",
			      *argv);
			return -1;
		}
	}

	/* Full feature detection requires specific privileges.
	 * Let's approximate, and warn if user is not root.
	 */
	if (handle_perms())
		return -1;

	if (json_output) {
		define_prefix = NULL;
		jsonw_start_object(json_wtr);
	}

	section_system_config(target, define_prefix);
	if (!section_syscall_config(define_prefix))
		/* bpf() syscall unavailable, don't probe other BPF features */
		goto exit_close_json;
	section_program_types(supported_types, define_prefix, ifindex);
	section_map_types(define_prefix, ifindex);
	section_helpers(supported_types, define_prefix, ifindex);
	section_misc(define_prefix, ifindex);

exit_close_json:
	if (json_output)
		/* End root object */
		jsonw_end_object(json_wtr);

	return 0;
}

static int do_help(int argc, char **argv)
{
	if (json_output) {
		jsonw_null(json_wtr);
		return 0;
	}

	fprintf(stderr,
		"Usage: %1$s %2$s probe [COMPONENT] [full] [unprivileged] [macros [prefix PREFIX]]\n"
		"       %1$s %2$s help\n"
		"\n"
		"       COMPONENT := { kernel | dev NAME }\n"
		"       " HELP_SPEC_OPTIONS " }\n"
		"",
		bin_name, argv[-2]);

	return 0;
}

static const struct cmd cmds[] = {
	{ "probe",	do_probe },
	{ "help",	do_help },
	{ 0 }
};

int do_feature(int argc, char **argv)
{
	return cmd_select(cmds, argc, argv, do_help);
}