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1#!/usr/bin/env python3
2# SPDX-License-Identifier: GPL-2.0-only
3#
4# Copyright (C) 2018-2019 Netronome Systems, Inc.
5# Copyright (C) 2021 Isovalent, Inc.
6
7# In case user attempts to run with Python 2.
8from __future__ import print_function
9
10import argparse
11import re
12import sys, os
13import subprocess
14
15helpersDocStart = 'Start of BPF helper function descriptions:'
16
17class NoHelperFound(BaseException):
18 pass
19
20class NoSyscallCommandFound(BaseException):
21 pass
22
23class ParsingError(BaseException):
24 def __init__(self, line='<line not provided>', reader=None):
25 if reader:
26 BaseException.__init__(self,
27 'Error at file offset %d, parsing line: %s' %
28 (reader.tell(), line))
29 else:
30 BaseException.__init__(self, 'Error parsing line: %s' % line)
31
32
33class APIElement(object):
34 """
35 An object representing the description of an aspect of the eBPF API.
36 @proto: prototype of the API symbol
37 @desc: textual description of the symbol
38 @ret: (optional) description of any associated return value
39 """
40 def __init__(self, proto='', desc='', ret='', attrs=[]):
41 self.proto = proto
42 self.desc = desc
43 self.ret = ret
44 self.attrs = attrs
45
46
47class Helper(APIElement):
48 """
49 An object representing the description of an eBPF helper function.
50 @proto: function prototype of the helper function
51 @desc: textual description of the helper function
52 @ret: description of the return value of the helper function
53 """
54 def __init__(self, *args, **kwargs):
55 super().__init__(*args, **kwargs)
56 self.enum_val = None
57
58 def proto_break_down(self):
59 """
60 Break down helper function protocol into smaller chunks: return type,
61 name, distincts arguments.
62 """
63 arg_re = re.compile(r'((\w+ )*?(\w+|...))( (\**)(\w+))?$')
64 res = {}
65 proto_re = re.compile(r'(.+) (\**)(\w+)\(((([^,]+)(, )?){1,5})\)$')
66
67 capture = proto_re.match(self.proto)
68 res['ret_type'] = capture.group(1)
69 res['ret_star'] = capture.group(2)
70 res['name'] = capture.group(3)
71 res['args'] = []
72
73 args = capture.group(4).split(', ')
74 for a in args:
75 capture = arg_re.match(a)
76 res['args'].append({
77 'type' : capture.group(1),
78 'star' : capture.group(5),
79 'name' : capture.group(6)
80 })
81
82 return res
83
84
85ATTRS = {
86 '__bpf_fastcall': 'bpf_fastcall'
87}
88
89
90class HeaderParser(object):
91 """
92 An object used to parse a file in order to extract the documentation of a
93 list of eBPF helper functions. All the helpers that can be retrieved are
94 stored as Helper object, in the self.helpers() array.
95 @filename: name of file to parse, usually include/uapi/linux/bpf.h in the
96 kernel tree
97 """
98 def __init__(self, filename):
99 self.reader = open(filename, 'r')
100 self.line = ''
101 self.helpers = []
102 self.commands = []
103 self.desc_unique_helpers = set()
104 self.define_unique_helpers = []
105 self.helper_enum_vals = {}
106 self.helper_enum_pos = {}
107 self.desc_syscalls = []
108 self.enum_syscalls = []
109
110 def parse_element(self):
111 proto = self.parse_symbol()
112 desc = self.parse_desc(proto)
113 ret = self.parse_ret(proto)
114 return APIElement(proto=proto, desc=desc, ret=ret)
115
116 def parse_helper(self):
117 proto = self.parse_proto()
118 desc = self.parse_desc(proto)
119 ret = self.parse_ret(proto)
120 attrs = self.parse_attrs(proto)
121 return Helper(proto=proto, desc=desc, ret=ret, attrs=attrs)
122
123 def parse_symbol(self):
124 p = re.compile(r' \* ?(BPF\w+)$')
125 capture = p.match(self.line)
126 if not capture:
127 raise NoSyscallCommandFound
128 end_re = re.compile(r' \* ?NOTES$')
129 end = end_re.match(self.line)
130 if end:
131 raise NoSyscallCommandFound
132 self.line = self.reader.readline()
133 return capture.group(1)
134
135 def parse_proto(self):
136 # Argument can be of shape:
137 # - "void"
138 # - "type name"
139 # - "type *name"
140 # - Same as above, with "const" and/or "struct" in front of type
141 # - "..." (undefined number of arguments, for bpf_trace_printk())
142 # There is at least one term ("void"), and at most five arguments.
143 p = re.compile(r' \* ?((.+) \**\w+\((((const )?(struct )?(\w+|\.\.\.)( \**\w+)?)(, )?){1,5}\))$')
144 capture = p.match(self.line)
145 if not capture:
146 raise NoHelperFound
147 self.line = self.reader.readline()
148 return capture.group(1)
149
150 def parse_desc(self, proto):
151 p = re.compile(r' \* ?(?:\t| {5,8})Description$')
152 capture = p.match(self.line)
153 if not capture:
154 raise Exception("No description section found for " + proto)
155 # Description can be several lines, some of them possibly empty, and it
156 # stops when another subsection title is met.
157 desc = ''
158 desc_present = False
159 while True:
160 self.line = self.reader.readline()
161 if self.line == ' *\n':
162 desc += '\n'
163 else:
164 p = re.compile(r' \* ?(?:\t| {5,8})(?:\t| {8})(.*)')
165 capture = p.match(self.line)
166 if capture:
167 desc_present = True
168 desc += capture.group(1) + '\n'
169 else:
170 break
171
172 if not desc_present:
173 raise Exception("No description found for " + proto)
174 return desc
175
176 def parse_ret(self, proto):
177 p = re.compile(r' \* ?(?:\t| {5,8})Return$')
178 capture = p.match(self.line)
179 if not capture:
180 raise Exception("No return section found for " + proto)
181 # Return value description can be several lines, some of them possibly
182 # empty, and it stops when another subsection title is met.
183 ret = ''
184 ret_present = False
185 while True:
186 self.line = self.reader.readline()
187 if self.line == ' *\n':
188 ret += '\n'
189 else:
190 p = re.compile(r' \* ?(?:\t| {5,8})(?:\t| {8})(.*)')
191 capture = p.match(self.line)
192 if capture:
193 ret_present = True
194 ret += capture.group(1) + '\n'
195 else:
196 break
197
198 if not ret_present:
199 raise Exception("No return found for " + proto)
200 return ret
201
202 def parse_attrs(self, proto):
203 p = re.compile(r' \* ?(?:\t| {5,8})Attributes$')
204 capture = p.match(self.line)
205 if not capture:
206 return []
207 # Expect a single line with mnemonics for attributes separated by spaces
208 self.line = self.reader.readline()
209 p = re.compile(r' \* ?(?:\t| {5,8})(?:\t| {8})(.*)')
210 capture = p.match(self.line)
211 if not capture:
212 raise Exception("Incomplete 'Attributes' section for " + proto)
213 attrs = capture.group(1).split(' ')
214 for attr in attrs:
215 if attr not in ATTRS:
216 raise Exception("Unexpected attribute '" + attr + "' specified for " + proto)
217 self.line = self.reader.readline()
218 if self.line != ' *\n':
219 raise Exception("Expecting empty line after 'Attributes' section for " + proto)
220 # Prepare a line for next self.parse_* to consume
221 self.line = self.reader.readline()
222 return attrs
223
224 def seek_to(self, target, help_message, discard_lines = 1):
225 self.reader.seek(0)
226 offset = self.reader.read().find(target)
227 if offset == -1:
228 raise Exception(help_message)
229 self.reader.seek(offset)
230 self.reader.readline()
231 for _ in range(discard_lines):
232 self.reader.readline()
233 self.line = self.reader.readline()
234
235 def parse_desc_syscall(self):
236 self.seek_to('* DOC: eBPF Syscall Commands',
237 'Could not find start of eBPF syscall descriptions list')
238 while True:
239 try:
240 command = self.parse_element()
241 self.commands.append(command)
242 self.desc_syscalls.append(command.proto)
243
244 except NoSyscallCommandFound:
245 break
246
247 def parse_enum_syscall(self):
248 self.seek_to('enum bpf_cmd {',
249 'Could not find start of bpf_cmd enum', 0)
250 # Searches for either one or more BPF\w+ enums
251 bpf_p = re.compile(r'\s*(BPF\w+)+')
252 # Searches for an enum entry assigned to another entry,
253 # for e.g. BPF_PROG_RUN = BPF_PROG_TEST_RUN, which is
254 # not documented hence should be skipped in check to
255 # determine if the right number of syscalls are documented
256 assign_p = re.compile(r'\s*(BPF\w+)\s*=\s*(BPF\w+)')
257 bpf_cmd_str = ''
258 while True:
259 capture = assign_p.match(self.line)
260 if capture:
261 # Skip line if an enum entry is assigned to another entry
262 self.line = self.reader.readline()
263 continue
264 capture = bpf_p.match(self.line)
265 if capture:
266 bpf_cmd_str += self.line
267 else:
268 break
269 self.line = self.reader.readline()
270 # Find the number of occurences of BPF\w+
271 self.enum_syscalls = re.findall(r'(BPF\w+)+', bpf_cmd_str)
272
273 def parse_desc_helpers(self):
274 self.seek_to(helpersDocStart,
275 'Could not find start of eBPF helper descriptions list')
276 while True:
277 try:
278 helper = self.parse_helper()
279 self.helpers.append(helper)
280 proto = helper.proto_break_down()
281 self.desc_unique_helpers.add(proto['name'])
282 except NoHelperFound:
283 break
284
285 def parse_define_helpers(self):
286 # Parse FN(...) in #define ___BPF_FUNC_MAPPER to compare later with the
287 # number of unique function names present in description and use the
288 # correct enumeration value.
289 # Note: seek_to(..) discards the first line below the target search text,
290 # resulting in FN(unspec, 0, ##ctx) being skipped and not added to
291 # self.define_unique_helpers.
292 self.seek_to('#define ___BPF_FUNC_MAPPER(FN, ctx...)',
293 'Could not find start of eBPF helper definition list')
294 # Searches for one FN(\w+) define or a backslash for newline
295 p = re.compile(r'\s*FN\((\w+), (\d+), ##ctx\)|\\\\')
296 fn_defines_str = ''
297 i = 0
298 while True:
299 capture = p.match(self.line)
300 if capture:
301 fn_defines_str += self.line
302 helper_name = capture.expand(r'bpf_\1')
303 self.helper_enum_vals[helper_name] = int(capture.group(2))
304 self.helper_enum_pos[helper_name] = i
305 i += 1
306 else:
307 break
308 self.line = self.reader.readline()
309 # Find the number of occurences of FN(\w+)
310 self.define_unique_helpers = re.findall(r'FN\(\w+, \d+, ##ctx\)', fn_defines_str)
311
312 def validate_helpers(self):
313 last_helper = ''
314 seen_helpers = set()
315 seen_enum_vals = set()
316 i = 0
317 for helper in self.helpers:
318 proto = helper.proto_break_down()
319 name = proto['name']
320 try:
321 enum_val = self.helper_enum_vals[name]
322 enum_pos = self.helper_enum_pos[name]
323 except KeyError:
324 raise Exception("Helper %s is missing from enum bpf_func_id" % name)
325
326 if name in seen_helpers:
327 if last_helper != name:
328 raise Exception("Helper %s has multiple descriptions which are not grouped together" % name)
329 continue
330
331 # Enforce current practice of having the descriptions ordered
332 # by enum value.
333 if enum_pos != i:
334 raise Exception("Helper %s (ID %d) comment order (#%d) must be aligned with its position (#%d) in enum bpf_func_id" % (name, enum_val, i + 1, enum_pos + 1))
335 if enum_val in seen_enum_vals:
336 raise Exception("Helper %s has duplicated value %d" % (name, enum_val))
337
338 seen_helpers.add(name)
339 last_helper = name
340 seen_enum_vals.add(enum_val)
341
342 helper.enum_val = enum_val
343 i += 1
344
345 def run(self):
346 self.parse_desc_syscall()
347 self.parse_enum_syscall()
348 self.parse_desc_helpers()
349 self.parse_define_helpers()
350 self.validate_helpers()
351 self.reader.close()
352
353###############################################################################
354
355class Printer(object):
356 """
357 A generic class for printers. Printers should be created with an array of
358 Helper objects, and implement a way to print them in the desired fashion.
359 @parser: A HeaderParser with objects to print to standard output
360 """
361 def __init__(self, parser):
362 self.parser = parser
363 self.elements = []
364
365 def print_header(self):
366 pass
367
368 def print_footer(self):
369 pass
370
371 def print_one(self, helper):
372 pass
373
374 def print_all(self):
375 self.print_header()
376 for elem in self.elements:
377 self.print_one(elem)
378 self.print_footer()
379
380 def elem_number_check(self, desc_unique_elem, define_unique_elem, type, instance):
381 """
382 Checks the number of helpers/syscalls documented within the header file
383 description with those defined as part of enum/macro and raise an
384 Exception if they don't match.
385 """
386 nr_desc_unique_elem = len(desc_unique_elem)
387 nr_define_unique_elem = len(define_unique_elem)
388 if nr_desc_unique_elem != nr_define_unique_elem:
389 exception_msg = '''
390The number of unique %s in description (%d) doesn\'t match the number of unique %s defined in %s (%d)
391''' % (type, nr_desc_unique_elem, type, instance, nr_define_unique_elem)
392 if nr_desc_unique_elem < nr_define_unique_elem:
393 # Function description is parsed until no helper is found (which can be due to
394 # misformatting). Hence, only print the first missing/misformatted helper/enum.
395 exception_msg += '''
396The description for %s is not present or formatted correctly.
397''' % (define_unique_elem[nr_desc_unique_elem])
398 raise Exception(exception_msg)
399
400class PrinterRST(Printer):
401 """
402 A generic class for printers that print ReStructured Text. Printers should
403 be created with a HeaderParser object, and implement a way to print API
404 elements in the desired fashion.
405 @parser: A HeaderParser with objects to print to standard output
406 """
407 def __init__(self, parser):
408 self.parser = parser
409
410 def print_license(self):
411 license = '''\
412.. Copyright (C) All BPF authors and contributors from 2014 to present.
413.. See git log include/uapi/linux/bpf.h in kernel tree for details.
414..
415.. SPDX-License-Identifier: Linux-man-pages-copyleft
416..
417.. Please do not edit this file. It was generated from the documentation
418.. located in file include/uapi/linux/bpf.h of the Linux kernel sources
419.. (helpers description), and from scripts/bpf_doc.py in the same
420.. repository (header and footer).
421'''
422 print(license)
423
424 def print_elem(self, elem):
425 if (elem.desc):
426 print('\tDescription')
427 # Do not strip all newline characters: formatted code at the end of
428 # a section must be followed by a blank line.
429 for line in re.sub('\n$', '', elem.desc, count=1).split('\n'):
430 print('{}{}'.format('\t\t' if line else '', line))
431
432 if (elem.ret):
433 print('\tReturn')
434 for line in elem.ret.rstrip().split('\n'):
435 print('{}{}'.format('\t\t' if line else '', line))
436
437 print('')
438
439 def get_kernel_version(self):
440 try:
441 version = subprocess.run(['git', 'describe'], cwd=linuxRoot,
442 capture_output=True, check=True)
443 version = version.stdout.decode().rstrip()
444 except:
445 try:
446 version = subprocess.run(['make', '-s', '--no-print-directory', 'kernelversion'],
447 cwd=linuxRoot, capture_output=True, check=True)
448 version = version.stdout.decode().rstrip()
449 except:
450 return 'Linux'
451 return 'Linux {version}'.format(version=version)
452
453 def get_last_doc_update(self, delimiter):
454 try:
455 cmd = ['git', 'log', '-1', '--pretty=format:%cs', '--no-patch',
456 '-L',
457 '/{}/,/\\*\\//:include/uapi/linux/bpf.h'.format(delimiter)]
458 date = subprocess.run(cmd, cwd=linuxRoot,
459 capture_output=True, check=True)
460 return date.stdout.decode().rstrip()
461 except:
462 return ''
463
464class PrinterHelpersRST(PrinterRST):
465 """
466 A printer for dumping collected information about helpers as a ReStructured
467 Text page compatible with the rst2man program, which can be used to
468 generate a manual page for the helpers.
469 @parser: A HeaderParser with Helper objects to print to standard output
470 """
471 def __init__(self, parser):
472 self.elements = parser.helpers
473 self.elem_number_check(parser.desc_unique_helpers, parser.define_unique_helpers, 'helper', '___BPF_FUNC_MAPPER')
474
475 def print_header(self):
476 header = '''\
477===========
478BPF-HELPERS
479===========
480-------------------------------------------------------------------------------
481list of eBPF helper functions
482-------------------------------------------------------------------------------
483
484:Manual section: 7
485:Version: {version}
486{date_field}{date}
487
488DESCRIPTION
489===========
490
491The extended Berkeley Packet Filter (eBPF) subsystem consists in programs
492written in a pseudo-assembly language, then attached to one of the several
493kernel hooks and run in reaction of specific events. This framework differs
494from the older, "classic" BPF (or "cBPF") in several aspects, one of them being
495the ability to call special functions (or "helpers") from within a program.
496These functions are restricted to a white-list of helpers defined in the
497kernel.
498
499These helpers are used by eBPF programs to interact with the system, or with
500the context in which they work. For instance, they can be used to print
501debugging messages, to get the time since the system was booted, to interact
502with eBPF maps, or to manipulate network packets. Since there are several eBPF
503program types, and that they do not run in the same context, each program type
504can only call a subset of those helpers.
505
506Due to eBPF conventions, a helper can not have more than five arguments.
507
508Internally, eBPF programs call directly into the compiled helper functions
509without requiring any foreign-function interface. As a result, calling helpers
510introduces no overhead, thus offering excellent performance.
511
512This document is an attempt to list and document the helpers available to eBPF
513developers. They are sorted by chronological order (the oldest helpers in the
514kernel at the top).
515
516HELPERS
517=======
518'''
519 kernelVersion = self.get_kernel_version()
520 lastUpdate = self.get_last_doc_update(helpersDocStart)
521
522 PrinterRST.print_license(self)
523 print(header.format(version=kernelVersion,
524 date_field = ':Date: ' if lastUpdate else '',
525 date=lastUpdate))
526
527 def print_footer(self):
528 footer = '''
529EXAMPLES
530========
531
532Example usage for most of the eBPF helpers listed in this manual page are
533available within the Linux kernel sources, at the following locations:
534
535* *samples/bpf/*
536* *tools/testing/selftests/bpf/*
537
538LICENSE
539=======
540
541eBPF programs can have an associated license, passed along with the bytecode
542instructions to the kernel when the programs are loaded. The format for that
543string is identical to the one in use for kernel modules (Dual licenses, such
544as "Dual BSD/GPL", may be used). Some helper functions are only accessible to
545programs that are compatible with the GNU General Public License (GNU GPL).
546
547In order to use such helpers, the eBPF program must be loaded with the correct
548license string passed (via **attr**) to the **bpf**\\ () system call, and this
549generally translates into the C source code of the program containing a line
550similar to the following:
551
552::
553
554 char ____license[] __attribute__((section("license"), used)) = "GPL";
555
556IMPLEMENTATION
557==============
558
559This manual page is an effort to document the existing eBPF helper functions.
560But as of this writing, the BPF sub-system is under heavy development. New eBPF
561program or map types are added, along with new helper functions. Some helpers
562are occasionally made available for additional program types. So in spite of
563the efforts of the community, this page might not be up-to-date. If you want to
564check by yourself what helper functions exist in your kernel, or what types of
565programs they can support, here are some files among the kernel tree that you
566may be interested in:
567
568* *include/uapi/linux/bpf.h* is the main BPF header. It contains the full list
569 of all helper functions, as well as many other BPF definitions including most
570 of the flags, structs or constants used by the helpers.
571* *net/core/filter.c* contains the definition of most network-related helper
572 functions, and the list of program types from which they can be used.
573* *kernel/trace/bpf_trace.c* is the equivalent for most tracing program-related
574 helpers.
575* *kernel/bpf/verifier.c* contains the functions used to check that valid types
576 of eBPF maps are used with a given helper function.
577* *kernel/bpf/* directory contains other files in which additional helpers are
578 defined (for cgroups, sockmaps, etc.).
579* The bpftool utility can be used to probe the availability of helper functions
580 on the system (as well as supported program and map types, and a number of
581 other parameters). To do so, run **bpftool feature probe** (see
582 **bpftool-feature**\\ (8) for details). Add the **unprivileged** keyword to
583 list features available to unprivileged users.
584
585Compatibility between helper functions and program types can generally be found
586in the files where helper functions are defined. Look for the **struct
587bpf_func_proto** objects and for functions returning them: these functions
588contain a list of helpers that a given program type can call. Note that the
589**default:** label of the **switch ... case** used to filter helpers can call
590other functions, themselves allowing access to additional helpers. The
591requirement for GPL license is also in those **struct bpf_func_proto**.
592
593Compatibility between helper functions and map types can be found in the
594**check_map_func_compatibility**\\ () function in file *kernel/bpf/verifier.c*.
595
596Helper functions that invalidate the checks on **data** and **data_end**
597pointers for network processing are listed in function
598**bpf_helper_changes_pkt_data**\\ () in file *net/core/filter.c*.
599
600SEE ALSO
601========
602
603**bpf**\\ (2),
604**bpftool**\\ (8),
605**cgroups**\\ (7),
606**ip**\\ (8),
607**perf_event_open**\\ (2),
608**sendmsg**\\ (2),
609**socket**\\ (7),
610**tc-bpf**\\ (8)'''
611 print(footer)
612
613 def print_proto(self, helper):
614 """
615 Format function protocol with bold and italics markers. This makes RST
616 file less readable, but gives nice results in the manual page.
617 """
618 proto = helper.proto_break_down()
619
620 print('**%s %s%s(' % (proto['ret_type'],
621 proto['ret_star'].replace('*', '\\*'),
622 proto['name']),
623 end='')
624
625 comma = ''
626 for a in proto['args']:
627 one_arg = '{}{}'.format(comma, a['type'])
628 if a['name']:
629 if a['star']:
630 one_arg += ' {}**\\ '.format(a['star'].replace('*', '\\*'))
631 else:
632 one_arg += '** '
633 one_arg += '*{}*\\ **'.format(a['name'])
634 comma = ', '
635 print(one_arg, end='')
636
637 print(')**')
638
639 def print_one(self, helper):
640 self.print_proto(helper)
641 self.print_elem(helper)
642
643
644class PrinterSyscallRST(PrinterRST):
645 """
646 A printer for dumping collected information about the syscall API as a
647 ReStructured Text page compatible with the rst2man program, which can be
648 used to generate a manual page for the syscall.
649 @parser: A HeaderParser with APIElement objects to print to standard
650 output
651 """
652 def __init__(self, parser):
653 self.elements = parser.commands
654 self.elem_number_check(parser.desc_syscalls, parser.enum_syscalls, 'syscall', 'bpf_cmd')
655
656 def print_header(self):
657 header = '''\
658===
659bpf
660===
661-------------------------------------------------------------------------------
662Perform a command on an extended BPF object
663-------------------------------------------------------------------------------
664
665:Manual section: 2
666
667COMMANDS
668========
669'''
670 PrinterRST.print_license(self)
671 print(header)
672
673 def print_one(self, command):
674 print('**%s**' % (command.proto))
675 self.print_elem(command)
676
677
678class PrinterHelpers(Printer):
679 """
680 A printer for dumping collected information about helpers as C header to
681 be included from BPF program.
682 @parser: A HeaderParser with Helper objects to print to standard output
683 """
684 def __init__(self, parser):
685 self.elements = parser.helpers
686 self.elem_number_check(parser.desc_unique_helpers, parser.define_unique_helpers, 'helper', '___BPF_FUNC_MAPPER')
687
688 type_fwds = [
689 'struct bpf_fib_lookup',
690 'struct bpf_sk_lookup',
691 'struct bpf_perf_event_data',
692 'struct bpf_perf_event_value',
693 'struct bpf_pidns_info',
694 'struct bpf_redir_neigh',
695 'struct bpf_sock',
696 'struct bpf_sock_addr',
697 'struct bpf_sock_ops',
698 'struct bpf_sock_tuple',
699 'struct bpf_spin_lock',
700 'struct bpf_sysctl',
701 'struct bpf_tcp_sock',
702 'struct bpf_tunnel_key',
703 'struct bpf_xfrm_state',
704 'struct linux_binprm',
705 'struct pt_regs',
706 'struct sk_reuseport_md',
707 'struct sockaddr',
708 'struct tcphdr',
709 'struct seq_file',
710 'struct tcp6_sock',
711 'struct tcp_sock',
712 'struct tcp_timewait_sock',
713 'struct tcp_request_sock',
714 'struct udp6_sock',
715 'struct unix_sock',
716 'struct task_struct',
717 'struct cgroup',
718
719 'struct __sk_buff',
720 'struct sk_msg_md',
721 'struct xdp_md',
722 'struct path',
723 'struct btf_ptr',
724 'struct inode',
725 'struct socket',
726 'struct file',
727 'struct bpf_timer',
728 'struct mptcp_sock',
729 'struct bpf_dynptr',
730 'struct iphdr',
731 'struct ipv6hdr',
732 ]
733 known_types = {
734 '...',
735 'void',
736 'const void',
737 'char',
738 'const char',
739 'int',
740 'long',
741 'unsigned long',
742
743 '__be16',
744 '__be32',
745 '__wsum',
746
747 'struct bpf_fib_lookup',
748 'struct bpf_perf_event_data',
749 'struct bpf_perf_event_value',
750 'struct bpf_pidns_info',
751 'struct bpf_redir_neigh',
752 'struct bpf_sk_lookup',
753 'struct bpf_sock',
754 'struct bpf_sock_addr',
755 'struct bpf_sock_ops',
756 'struct bpf_sock_tuple',
757 'struct bpf_spin_lock',
758 'struct bpf_sysctl',
759 'struct bpf_tcp_sock',
760 'struct bpf_tunnel_key',
761 'struct bpf_xfrm_state',
762 'struct linux_binprm',
763 'struct pt_regs',
764 'struct sk_reuseport_md',
765 'struct sockaddr',
766 'struct tcphdr',
767 'struct seq_file',
768 'struct tcp6_sock',
769 'struct tcp_sock',
770 'struct tcp_timewait_sock',
771 'struct tcp_request_sock',
772 'struct udp6_sock',
773 'struct unix_sock',
774 'struct task_struct',
775 'struct cgroup',
776 'struct path',
777 'struct btf_ptr',
778 'struct inode',
779 'struct socket',
780 'struct file',
781 'struct bpf_timer',
782 'struct mptcp_sock',
783 'struct bpf_dynptr',
784 'const struct bpf_dynptr',
785 'struct iphdr',
786 'struct ipv6hdr',
787 }
788 mapped_types = {
789 'u8': '__u8',
790 'u16': '__u16',
791 'u32': '__u32',
792 'u64': '__u64',
793 's8': '__s8',
794 's16': '__s16',
795 's32': '__s32',
796 's64': '__s64',
797 'size_t': 'unsigned long',
798 'struct bpf_map': 'void',
799 'struct sk_buff': 'struct __sk_buff',
800 'const struct sk_buff': 'const struct __sk_buff',
801 'struct sk_msg_buff': 'struct sk_msg_md',
802 'struct xdp_buff': 'struct xdp_md',
803 }
804 # Helpers overloaded for different context types.
805 overloaded_helpers = [
806 'bpf_get_socket_cookie',
807 'bpf_sk_assign',
808 ]
809
810 def print_header(self):
811 header = '''\
812/* This is auto-generated file. See bpf_doc.py for details. */
813
814/* Forward declarations of BPF structs */'''
815
816 print(header)
817 for fwd in self.type_fwds:
818 print('%s;' % fwd)
819 print('')
820
821 used_attrs = set()
822 for helper in self.elements:
823 for attr in helper.attrs:
824 used_attrs.add(attr)
825 for attr in sorted(used_attrs):
826 print('#ifndef %s' % attr)
827 print('#if __has_attribute(%s)' % ATTRS[attr])
828 print('#define %s __attribute__((%s))' % (attr, ATTRS[attr]))
829 print('#else')
830 print('#define %s' % attr)
831 print('#endif')
832 print('#endif')
833 if used_attrs:
834 print('')
835
836 def print_footer(self):
837 footer = ''
838 print(footer)
839
840 def map_type(self, t):
841 if t in self.known_types:
842 return t
843 if t in self.mapped_types:
844 return self.mapped_types[t]
845 print("Unrecognized type '%s', please add it to known types!" % t,
846 file=sys.stderr)
847 sys.exit(1)
848
849 seen_helpers = set()
850
851 def print_one(self, helper):
852 proto = helper.proto_break_down()
853
854 if proto['name'] in self.seen_helpers:
855 return
856 self.seen_helpers.add(proto['name'])
857
858 print('/*')
859 print(" * %s" % proto['name'])
860 print(" *")
861 if (helper.desc):
862 # Do not strip all newline characters: formatted code at the end of
863 # a section must be followed by a blank line.
864 for line in re.sub('\n$', '', helper.desc, count=1).split('\n'):
865 print(' *{}{}'.format(' \t' if line else '', line))
866
867 if (helper.ret):
868 print(' *')
869 print(' * Returns')
870 for line in helper.ret.rstrip().split('\n'):
871 print(' *{}{}'.format(' \t' if line else '', line))
872
873 print(' */')
874 print('static ', end='')
875 if helper.attrs:
876 print('%s ' % (" ".join(helper.attrs)), end='')
877 print('%s %s(* const %s)(' % (self.map_type(proto['ret_type']),
878 proto['ret_star'], proto['name']), end='')
879 comma = ''
880 for i, a in enumerate(proto['args']):
881 t = a['type']
882 n = a['name']
883 if proto['name'] in self.overloaded_helpers and i == 0:
884 t = 'void'
885 n = 'ctx'
886 one_arg = '{}{}'.format(comma, self.map_type(t))
887 if n:
888 if a['star']:
889 one_arg += ' {}'.format(a['star'])
890 else:
891 one_arg += ' '
892 one_arg += '{}'.format(n)
893 comma = ', '
894 print(one_arg, end='')
895
896 print(') = (void *) %d;' % helper.enum_val)
897 print('')
898
899###############################################################################
900
901# If script is launched from scripts/ from kernel tree and can access
902# ../include/uapi/linux/bpf.h, use it as a default name for the file to parse,
903# otherwise the --filename argument will be required from the command line.
904script = os.path.abspath(sys.argv[0])
905linuxRoot = os.path.dirname(os.path.dirname(script))
906bpfh = os.path.join(linuxRoot, 'include/uapi/linux/bpf.h')
907
908printers = {
909 'helpers': PrinterHelpersRST,
910 'syscall': PrinterSyscallRST,
911}
912
913argParser = argparse.ArgumentParser(description="""
914Parse eBPF header file and generate documentation for the eBPF API.
915The RST-formatted output produced can be turned into a manual page with the
916rst2man utility.
917""")
918argParser.add_argument('--header', action='store_true',
919 help='generate C header file')
920if (os.path.isfile(bpfh)):
921 argParser.add_argument('--filename', help='path to include/uapi/linux/bpf.h',
922 default=bpfh)
923else:
924 argParser.add_argument('--filename', help='path to include/uapi/linux/bpf.h')
925argParser.add_argument('target', nargs='?', default='helpers',
926 choices=printers.keys(), help='eBPF API target')
927args = argParser.parse_args()
928
929# Parse file.
930headerParser = HeaderParser(args.filename)
931headerParser.run()
932
933# Print formatted output to standard output.
934if args.header:
935 if args.target != 'helpers':
936 raise NotImplementedError('Only helpers header generation is supported')
937 printer = PrinterHelpers(headerParser)
938else:
939 printer = printers[args.target](headerParser)
940printer.print_all()
1#!/usr/bin/env python3
2# SPDX-License-Identifier: GPL-2.0-only
3#
4# Copyright (C) 2018-2019 Netronome Systems, Inc.
5# Copyright (C) 2021 Isovalent, Inc.
6
7# In case user attempts to run with Python 2.
8from __future__ import print_function
9
10import argparse
11import re
12import sys, os
13import subprocess
14
15helpersDocStart = 'Start of BPF helper function descriptions:'
16
17class NoHelperFound(BaseException):
18 pass
19
20class NoSyscallCommandFound(BaseException):
21 pass
22
23class ParsingError(BaseException):
24 def __init__(self, line='<line not provided>', reader=None):
25 if reader:
26 BaseException.__init__(self,
27 'Error at file offset %d, parsing line: %s' %
28 (reader.tell(), line))
29 else:
30 BaseException.__init__(self, 'Error parsing line: %s' % line)
31
32
33class APIElement(object):
34 """
35 An object representing the description of an aspect of the eBPF API.
36 @proto: prototype of the API symbol
37 @desc: textual description of the symbol
38 @ret: (optional) description of any associated return value
39 """
40 def __init__(self, proto='', desc='', ret=''):
41 self.proto = proto
42 self.desc = desc
43 self.ret = ret
44
45
46class Helper(APIElement):
47 """
48 An object representing the description of an eBPF helper function.
49 @proto: function prototype of the helper function
50 @desc: textual description of the helper function
51 @ret: description of the return value of the helper function
52 """
53 def __init__(self, *args, **kwargs):
54 super().__init__(*args, **kwargs)
55 self.enum_val = None
56
57 def proto_break_down(self):
58 """
59 Break down helper function protocol into smaller chunks: return type,
60 name, distincts arguments.
61 """
62 arg_re = re.compile(r'((\w+ )*?(\w+|...))( (\**)(\w+))?$')
63 res = {}
64 proto_re = re.compile(r'(.+) (\**)(\w+)\(((([^,]+)(, )?){1,5})\)$')
65
66 capture = proto_re.match(self.proto)
67 res['ret_type'] = capture.group(1)
68 res['ret_star'] = capture.group(2)
69 res['name'] = capture.group(3)
70 res['args'] = []
71
72 args = capture.group(4).split(', ')
73 for a in args:
74 capture = arg_re.match(a)
75 res['args'].append({
76 'type' : capture.group(1),
77 'star' : capture.group(5),
78 'name' : capture.group(6)
79 })
80
81 return res
82
83
84class HeaderParser(object):
85 """
86 An object used to parse a file in order to extract the documentation of a
87 list of eBPF helper functions. All the helpers that can be retrieved are
88 stored as Helper object, in the self.helpers() array.
89 @filename: name of file to parse, usually include/uapi/linux/bpf.h in the
90 kernel tree
91 """
92 def __init__(self, filename):
93 self.reader = open(filename, 'r')
94 self.line = ''
95 self.helpers = []
96 self.commands = []
97 self.desc_unique_helpers = set()
98 self.define_unique_helpers = []
99 self.helper_enum_vals = {}
100 self.helper_enum_pos = {}
101 self.desc_syscalls = []
102 self.enum_syscalls = []
103
104 def parse_element(self):
105 proto = self.parse_symbol()
106 desc = self.parse_desc(proto)
107 ret = self.parse_ret(proto)
108 return APIElement(proto=proto, desc=desc, ret=ret)
109
110 def parse_helper(self):
111 proto = self.parse_proto()
112 desc = self.parse_desc(proto)
113 ret = self.parse_ret(proto)
114 return Helper(proto=proto, desc=desc, ret=ret)
115
116 def parse_symbol(self):
117 p = re.compile(r' \* ?(BPF\w+)$')
118 capture = p.match(self.line)
119 if not capture:
120 raise NoSyscallCommandFound
121 end_re = re.compile(r' \* ?NOTES$')
122 end = end_re.match(self.line)
123 if end:
124 raise NoSyscallCommandFound
125 self.line = self.reader.readline()
126 return capture.group(1)
127
128 def parse_proto(self):
129 # Argument can be of shape:
130 # - "void"
131 # - "type name"
132 # - "type *name"
133 # - Same as above, with "const" and/or "struct" in front of type
134 # - "..." (undefined number of arguments, for bpf_trace_printk())
135 # There is at least one term ("void"), and at most five arguments.
136 p = re.compile(r' \* ?((.+) \**\w+\((((const )?(struct )?(\w+|\.\.\.)( \**\w+)?)(, )?){1,5}\))$')
137 capture = p.match(self.line)
138 if not capture:
139 raise NoHelperFound
140 self.line = self.reader.readline()
141 return capture.group(1)
142
143 def parse_desc(self, proto):
144 p = re.compile(r' \* ?(?:\t| {5,8})Description$')
145 capture = p.match(self.line)
146 if not capture:
147 raise Exception("No description section found for " + proto)
148 # Description can be several lines, some of them possibly empty, and it
149 # stops when another subsection title is met.
150 desc = ''
151 desc_present = False
152 while True:
153 self.line = self.reader.readline()
154 if self.line == ' *\n':
155 desc += '\n'
156 else:
157 p = re.compile(r' \* ?(?:\t| {5,8})(?:\t| {8})(.*)')
158 capture = p.match(self.line)
159 if capture:
160 desc_present = True
161 desc += capture.group(1) + '\n'
162 else:
163 break
164
165 if not desc_present:
166 raise Exception("No description found for " + proto)
167 return desc
168
169 def parse_ret(self, proto):
170 p = re.compile(r' \* ?(?:\t| {5,8})Return$')
171 capture = p.match(self.line)
172 if not capture:
173 raise Exception("No return section found for " + proto)
174 # Return value description can be several lines, some of them possibly
175 # empty, and it stops when another subsection title is met.
176 ret = ''
177 ret_present = False
178 while True:
179 self.line = self.reader.readline()
180 if self.line == ' *\n':
181 ret += '\n'
182 else:
183 p = re.compile(r' \* ?(?:\t| {5,8})(?:\t| {8})(.*)')
184 capture = p.match(self.line)
185 if capture:
186 ret_present = True
187 ret += capture.group(1) + '\n'
188 else:
189 break
190
191 if not ret_present:
192 raise Exception("No return found for " + proto)
193 return ret
194
195 def seek_to(self, target, help_message, discard_lines = 1):
196 self.reader.seek(0)
197 offset = self.reader.read().find(target)
198 if offset == -1:
199 raise Exception(help_message)
200 self.reader.seek(offset)
201 self.reader.readline()
202 for _ in range(discard_lines):
203 self.reader.readline()
204 self.line = self.reader.readline()
205
206 def parse_desc_syscall(self):
207 self.seek_to('* DOC: eBPF Syscall Commands',
208 'Could not find start of eBPF syscall descriptions list')
209 while True:
210 try:
211 command = self.parse_element()
212 self.commands.append(command)
213 self.desc_syscalls.append(command.proto)
214
215 except NoSyscallCommandFound:
216 break
217
218 def parse_enum_syscall(self):
219 self.seek_to('enum bpf_cmd {',
220 'Could not find start of bpf_cmd enum', 0)
221 # Searches for either one or more BPF\w+ enums
222 bpf_p = re.compile(r'\s*(BPF\w+)+')
223 # Searches for an enum entry assigned to another entry,
224 # for e.g. BPF_PROG_RUN = BPF_PROG_TEST_RUN, which is
225 # not documented hence should be skipped in check to
226 # determine if the right number of syscalls are documented
227 assign_p = re.compile(r'\s*(BPF\w+)\s*=\s*(BPF\w+)')
228 bpf_cmd_str = ''
229 while True:
230 capture = assign_p.match(self.line)
231 if capture:
232 # Skip line if an enum entry is assigned to another entry
233 self.line = self.reader.readline()
234 continue
235 capture = bpf_p.match(self.line)
236 if capture:
237 bpf_cmd_str += self.line
238 else:
239 break
240 self.line = self.reader.readline()
241 # Find the number of occurences of BPF\w+
242 self.enum_syscalls = re.findall(r'(BPF\w+)+', bpf_cmd_str)
243
244 def parse_desc_helpers(self):
245 self.seek_to(helpersDocStart,
246 'Could not find start of eBPF helper descriptions list')
247 while True:
248 try:
249 helper = self.parse_helper()
250 self.helpers.append(helper)
251 proto = helper.proto_break_down()
252 self.desc_unique_helpers.add(proto['name'])
253 except NoHelperFound:
254 break
255
256 def parse_define_helpers(self):
257 # Parse FN(...) in #define ___BPF_FUNC_MAPPER to compare later with the
258 # number of unique function names present in description and use the
259 # correct enumeration value.
260 # Note: seek_to(..) discards the first line below the target search text,
261 # resulting in FN(unspec, 0, ##ctx) being skipped and not added to
262 # self.define_unique_helpers.
263 self.seek_to('#define ___BPF_FUNC_MAPPER(FN, ctx...)',
264 'Could not find start of eBPF helper definition list')
265 # Searches for one FN(\w+) define or a backslash for newline
266 p = re.compile(r'\s*FN\((\w+), (\d+), ##ctx\)|\\\\')
267 fn_defines_str = ''
268 i = 0
269 while True:
270 capture = p.match(self.line)
271 if capture:
272 fn_defines_str += self.line
273 helper_name = capture.expand(r'bpf_\1')
274 self.helper_enum_vals[helper_name] = int(capture.group(2))
275 self.helper_enum_pos[helper_name] = i
276 i += 1
277 else:
278 break
279 self.line = self.reader.readline()
280 # Find the number of occurences of FN(\w+)
281 self.define_unique_helpers = re.findall(r'FN\(\w+, \d+, ##ctx\)', fn_defines_str)
282
283 def validate_helpers(self):
284 last_helper = ''
285 seen_helpers = set()
286 seen_enum_vals = set()
287 i = 0
288 for helper in self.helpers:
289 proto = helper.proto_break_down()
290 name = proto['name']
291 try:
292 enum_val = self.helper_enum_vals[name]
293 enum_pos = self.helper_enum_pos[name]
294 except KeyError:
295 raise Exception("Helper %s is missing from enum bpf_func_id" % name)
296
297 if name in seen_helpers:
298 if last_helper != name:
299 raise Exception("Helper %s has multiple descriptions which are not grouped together" % name)
300 continue
301
302 # Enforce current practice of having the descriptions ordered
303 # by enum value.
304 if enum_pos != i:
305 raise Exception("Helper %s (ID %d) comment order (#%d) must be aligned with its position (#%d) in enum bpf_func_id" % (name, enum_val, i + 1, enum_pos + 1))
306 if enum_val in seen_enum_vals:
307 raise Exception("Helper %s has duplicated value %d" % (name, enum_val))
308
309 seen_helpers.add(name)
310 last_helper = name
311 seen_enum_vals.add(enum_val)
312
313 helper.enum_val = enum_val
314 i += 1
315
316 def run(self):
317 self.parse_desc_syscall()
318 self.parse_enum_syscall()
319 self.parse_desc_helpers()
320 self.parse_define_helpers()
321 self.validate_helpers()
322 self.reader.close()
323
324###############################################################################
325
326class Printer(object):
327 """
328 A generic class for printers. Printers should be created with an array of
329 Helper objects, and implement a way to print them in the desired fashion.
330 @parser: A HeaderParser with objects to print to standard output
331 """
332 def __init__(self, parser):
333 self.parser = parser
334 self.elements = []
335
336 def print_header(self):
337 pass
338
339 def print_footer(self):
340 pass
341
342 def print_one(self, helper):
343 pass
344
345 def print_all(self):
346 self.print_header()
347 for elem in self.elements:
348 self.print_one(elem)
349 self.print_footer()
350
351 def elem_number_check(self, desc_unique_elem, define_unique_elem, type, instance):
352 """
353 Checks the number of helpers/syscalls documented within the header file
354 description with those defined as part of enum/macro and raise an
355 Exception if they don't match.
356 """
357 nr_desc_unique_elem = len(desc_unique_elem)
358 nr_define_unique_elem = len(define_unique_elem)
359 if nr_desc_unique_elem != nr_define_unique_elem:
360 exception_msg = '''
361The number of unique %s in description (%d) doesn\'t match the number of unique %s defined in %s (%d)
362''' % (type, nr_desc_unique_elem, type, instance, nr_define_unique_elem)
363 if nr_desc_unique_elem < nr_define_unique_elem:
364 # Function description is parsed until no helper is found (which can be due to
365 # misformatting). Hence, only print the first missing/misformatted helper/enum.
366 exception_msg += '''
367The description for %s is not present or formatted correctly.
368''' % (define_unique_elem[nr_desc_unique_elem])
369 raise Exception(exception_msg)
370
371class PrinterRST(Printer):
372 """
373 A generic class for printers that print ReStructured Text. Printers should
374 be created with a HeaderParser object, and implement a way to print API
375 elements in the desired fashion.
376 @parser: A HeaderParser with objects to print to standard output
377 """
378 def __init__(self, parser):
379 self.parser = parser
380
381 def print_license(self):
382 license = '''\
383.. Copyright (C) All BPF authors and contributors from 2014 to present.
384.. See git log include/uapi/linux/bpf.h in kernel tree for details.
385..
386.. SPDX-License-Identifier: Linux-man-pages-copyleft
387..
388.. Please do not edit this file. It was generated from the documentation
389.. located in file include/uapi/linux/bpf.h of the Linux kernel sources
390.. (helpers description), and from scripts/bpf_doc.py in the same
391.. repository (header and footer).
392'''
393 print(license)
394
395 def print_elem(self, elem):
396 if (elem.desc):
397 print('\tDescription')
398 # Do not strip all newline characters: formatted code at the end of
399 # a section must be followed by a blank line.
400 for line in re.sub('\n$', '', elem.desc, count=1).split('\n'):
401 print('{}{}'.format('\t\t' if line else '', line))
402
403 if (elem.ret):
404 print('\tReturn')
405 for line in elem.ret.rstrip().split('\n'):
406 print('{}{}'.format('\t\t' if line else '', line))
407
408 print('')
409
410 def get_kernel_version(self):
411 try:
412 version = subprocess.run(['git', 'describe'], cwd=linuxRoot,
413 capture_output=True, check=True)
414 version = version.stdout.decode().rstrip()
415 except:
416 try:
417 version = subprocess.run(['make', 'kernelversion'], cwd=linuxRoot,
418 capture_output=True, check=True)
419 version = version.stdout.decode().rstrip()
420 except:
421 return 'Linux'
422 return 'Linux {version}'.format(version=version)
423
424 def get_last_doc_update(self, delimiter):
425 try:
426 cmd = ['git', 'log', '-1', '--pretty=format:%cs', '--no-patch',
427 '-L',
428 '/{}/,/\\*\\//:include/uapi/linux/bpf.h'.format(delimiter)]
429 date = subprocess.run(cmd, cwd=linuxRoot,
430 capture_output=True, check=True)
431 return date.stdout.decode().rstrip()
432 except:
433 return ''
434
435class PrinterHelpersRST(PrinterRST):
436 """
437 A printer for dumping collected information about helpers as a ReStructured
438 Text page compatible with the rst2man program, which can be used to
439 generate a manual page for the helpers.
440 @parser: A HeaderParser with Helper objects to print to standard output
441 """
442 def __init__(self, parser):
443 self.elements = parser.helpers
444 self.elem_number_check(parser.desc_unique_helpers, parser.define_unique_helpers, 'helper', '___BPF_FUNC_MAPPER')
445
446 def print_header(self):
447 header = '''\
448===========
449BPF-HELPERS
450===========
451-------------------------------------------------------------------------------
452list of eBPF helper functions
453-------------------------------------------------------------------------------
454
455:Manual section: 7
456:Version: {version}
457{date_field}{date}
458
459DESCRIPTION
460===========
461
462The extended Berkeley Packet Filter (eBPF) subsystem consists in programs
463written in a pseudo-assembly language, then attached to one of the several
464kernel hooks and run in reaction of specific events. This framework differs
465from the older, "classic" BPF (or "cBPF") in several aspects, one of them being
466the ability to call special functions (or "helpers") from within a program.
467These functions are restricted to a white-list of helpers defined in the
468kernel.
469
470These helpers are used by eBPF programs to interact with the system, or with
471the context in which they work. For instance, they can be used to print
472debugging messages, to get the time since the system was booted, to interact
473with eBPF maps, or to manipulate network packets. Since there are several eBPF
474program types, and that they do not run in the same context, each program type
475can only call a subset of those helpers.
476
477Due to eBPF conventions, a helper can not have more than five arguments.
478
479Internally, eBPF programs call directly into the compiled helper functions
480without requiring any foreign-function interface. As a result, calling helpers
481introduces no overhead, thus offering excellent performance.
482
483This document is an attempt to list and document the helpers available to eBPF
484developers. They are sorted by chronological order (the oldest helpers in the
485kernel at the top).
486
487HELPERS
488=======
489'''
490 kernelVersion = self.get_kernel_version()
491 lastUpdate = self.get_last_doc_update(helpersDocStart)
492
493 PrinterRST.print_license(self)
494 print(header.format(version=kernelVersion,
495 date_field = ':Date: ' if lastUpdate else '',
496 date=lastUpdate))
497
498 def print_footer(self):
499 footer = '''
500EXAMPLES
501========
502
503Example usage for most of the eBPF helpers listed in this manual page are
504available within the Linux kernel sources, at the following locations:
505
506* *samples/bpf/*
507* *tools/testing/selftests/bpf/*
508
509LICENSE
510=======
511
512eBPF programs can have an associated license, passed along with the bytecode
513instructions to the kernel when the programs are loaded. The format for that
514string is identical to the one in use for kernel modules (Dual licenses, such
515as "Dual BSD/GPL", may be used). Some helper functions are only accessible to
516programs that are compatible with the GNU General Public License (GNU GPL).
517
518In order to use such helpers, the eBPF program must be loaded with the correct
519license string passed (via **attr**) to the **bpf**\\ () system call, and this
520generally translates into the C source code of the program containing a line
521similar to the following:
522
523::
524
525 char ____license[] __attribute__((section("license"), used)) = "GPL";
526
527IMPLEMENTATION
528==============
529
530This manual page is an effort to document the existing eBPF helper functions.
531But as of this writing, the BPF sub-system is under heavy development. New eBPF
532program or map types are added, along with new helper functions. Some helpers
533are occasionally made available for additional program types. So in spite of
534the efforts of the community, this page might not be up-to-date. If you want to
535check by yourself what helper functions exist in your kernel, or what types of
536programs they can support, here are some files among the kernel tree that you
537may be interested in:
538
539* *include/uapi/linux/bpf.h* is the main BPF header. It contains the full list
540 of all helper functions, as well as many other BPF definitions including most
541 of the flags, structs or constants used by the helpers.
542* *net/core/filter.c* contains the definition of most network-related helper
543 functions, and the list of program types from which they can be used.
544* *kernel/trace/bpf_trace.c* is the equivalent for most tracing program-related
545 helpers.
546* *kernel/bpf/verifier.c* contains the functions used to check that valid types
547 of eBPF maps are used with a given helper function.
548* *kernel/bpf/* directory contains other files in which additional helpers are
549 defined (for cgroups, sockmaps, etc.).
550* The bpftool utility can be used to probe the availability of helper functions
551 on the system (as well as supported program and map types, and a number of
552 other parameters). To do so, run **bpftool feature probe** (see
553 **bpftool-feature**\\ (8) for details). Add the **unprivileged** keyword to
554 list features available to unprivileged users.
555
556Compatibility between helper functions and program types can generally be found
557in the files where helper functions are defined. Look for the **struct
558bpf_func_proto** objects and for functions returning them: these functions
559contain a list of helpers that a given program type can call. Note that the
560**default:** label of the **switch ... case** used to filter helpers can call
561other functions, themselves allowing access to additional helpers. The
562requirement for GPL license is also in those **struct bpf_func_proto**.
563
564Compatibility between helper functions and map types can be found in the
565**check_map_func_compatibility**\\ () function in file *kernel/bpf/verifier.c*.
566
567Helper functions that invalidate the checks on **data** and **data_end**
568pointers for network processing are listed in function
569**bpf_helper_changes_pkt_data**\\ () in file *net/core/filter.c*.
570
571SEE ALSO
572========
573
574**bpf**\\ (2),
575**bpftool**\\ (8),
576**cgroups**\\ (7),
577**ip**\\ (8),
578**perf_event_open**\\ (2),
579**sendmsg**\\ (2),
580**socket**\\ (7),
581**tc-bpf**\\ (8)'''
582 print(footer)
583
584 def print_proto(self, helper):
585 """
586 Format function protocol with bold and italics markers. This makes RST
587 file less readable, but gives nice results in the manual page.
588 """
589 proto = helper.proto_break_down()
590
591 print('**%s %s%s(' % (proto['ret_type'],
592 proto['ret_star'].replace('*', '\\*'),
593 proto['name']),
594 end='')
595
596 comma = ''
597 for a in proto['args']:
598 one_arg = '{}{}'.format(comma, a['type'])
599 if a['name']:
600 if a['star']:
601 one_arg += ' {}**\\ '.format(a['star'].replace('*', '\\*'))
602 else:
603 one_arg += '** '
604 one_arg += '*{}*\\ **'.format(a['name'])
605 comma = ', '
606 print(one_arg, end='')
607
608 print(')**')
609
610 def print_one(self, helper):
611 self.print_proto(helper)
612 self.print_elem(helper)
613
614
615class PrinterSyscallRST(PrinterRST):
616 """
617 A printer for dumping collected information about the syscall API as a
618 ReStructured Text page compatible with the rst2man program, which can be
619 used to generate a manual page for the syscall.
620 @parser: A HeaderParser with APIElement objects to print to standard
621 output
622 """
623 def __init__(self, parser):
624 self.elements = parser.commands
625 self.elem_number_check(parser.desc_syscalls, parser.enum_syscalls, 'syscall', 'bpf_cmd')
626
627 def print_header(self):
628 header = '''\
629===
630bpf
631===
632-------------------------------------------------------------------------------
633Perform a command on an extended BPF object
634-------------------------------------------------------------------------------
635
636:Manual section: 2
637
638COMMANDS
639========
640'''
641 PrinterRST.print_license(self)
642 print(header)
643
644 def print_one(self, command):
645 print('**%s**' % (command.proto))
646 self.print_elem(command)
647
648
649class PrinterHelpers(Printer):
650 """
651 A printer for dumping collected information about helpers as C header to
652 be included from BPF program.
653 @parser: A HeaderParser with Helper objects to print to standard output
654 """
655 def __init__(self, parser):
656 self.elements = parser.helpers
657 self.elem_number_check(parser.desc_unique_helpers, parser.define_unique_helpers, 'helper', '___BPF_FUNC_MAPPER')
658
659 type_fwds = [
660 'struct bpf_fib_lookup',
661 'struct bpf_sk_lookup',
662 'struct bpf_perf_event_data',
663 'struct bpf_perf_event_value',
664 'struct bpf_pidns_info',
665 'struct bpf_redir_neigh',
666 'struct bpf_sock',
667 'struct bpf_sock_addr',
668 'struct bpf_sock_ops',
669 'struct bpf_sock_tuple',
670 'struct bpf_spin_lock',
671 'struct bpf_sysctl',
672 'struct bpf_tcp_sock',
673 'struct bpf_tunnel_key',
674 'struct bpf_xfrm_state',
675 'struct linux_binprm',
676 'struct pt_regs',
677 'struct sk_reuseport_md',
678 'struct sockaddr',
679 'struct tcphdr',
680 'struct seq_file',
681 'struct tcp6_sock',
682 'struct tcp_sock',
683 'struct tcp_timewait_sock',
684 'struct tcp_request_sock',
685 'struct udp6_sock',
686 'struct unix_sock',
687 'struct task_struct',
688 'struct cgroup',
689
690 'struct __sk_buff',
691 'struct sk_msg_md',
692 'struct xdp_md',
693 'struct path',
694 'struct btf_ptr',
695 'struct inode',
696 'struct socket',
697 'struct file',
698 'struct bpf_timer',
699 'struct mptcp_sock',
700 'struct bpf_dynptr',
701 'struct iphdr',
702 'struct ipv6hdr',
703 ]
704 known_types = {
705 '...',
706 'void',
707 'const void',
708 'char',
709 'const char',
710 'int',
711 'long',
712 'unsigned long',
713
714 '__be16',
715 '__be32',
716 '__wsum',
717
718 'struct bpf_fib_lookup',
719 'struct bpf_perf_event_data',
720 'struct bpf_perf_event_value',
721 'struct bpf_pidns_info',
722 'struct bpf_redir_neigh',
723 'struct bpf_sk_lookup',
724 'struct bpf_sock',
725 'struct bpf_sock_addr',
726 'struct bpf_sock_ops',
727 'struct bpf_sock_tuple',
728 'struct bpf_spin_lock',
729 'struct bpf_sysctl',
730 'struct bpf_tcp_sock',
731 'struct bpf_tunnel_key',
732 'struct bpf_xfrm_state',
733 'struct linux_binprm',
734 'struct pt_regs',
735 'struct sk_reuseport_md',
736 'struct sockaddr',
737 'struct tcphdr',
738 'struct seq_file',
739 'struct tcp6_sock',
740 'struct tcp_sock',
741 'struct tcp_timewait_sock',
742 'struct tcp_request_sock',
743 'struct udp6_sock',
744 'struct unix_sock',
745 'struct task_struct',
746 'struct cgroup',
747 'struct path',
748 'struct btf_ptr',
749 'struct inode',
750 'struct socket',
751 'struct file',
752 'struct bpf_timer',
753 'struct mptcp_sock',
754 'struct bpf_dynptr',
755 'const struct bpf_dynptr',
756 'struct iphdr',
757 'struct ipv6hdr',
758 }
759 mapped_types = {
760 'u8': '__u8',
761 'u16': '__u16',
762 'u32': '__u32',
763 'u64': '__u64',
764 's8': '__s8',
765 's16': '__s16',
766 's32': '__s32',
767 's64': '__s64',
768 'size_t': 'unsigned long',
769 'struct bpf_map': 'void',
770 'struct sk_buff': 'struct __sk_buff',
771 'const struct sk_buff': 'const struct __sk_buff',
772 'struct sk_msg_buff': 'struct sk_msg_md',
773 'struct xdp_buff': 'struct xdp_md',
774 }
775 # Helpers overloaded for different context types.
776 overloaded_helpers = [
777 'bpf_get_socket_cookie',
778 'bpf_sk_assign',
779 ]
780
781 def print_header(self):
782 header = '''\
783/* This is auto-generated file. See bpf_doc.py for details. */
784
785/* Forward declarations of BPF structs */'''
786
787 print(header)
788 for fwd in self.type_fwds:
789 print('%s;' % fwd)
790 print('')
791
792 def print_footer(self):
793 footer = ''
794 print(footer)
795
796 def map_type(self, t):
797 if t in self.known_types:
798 return t
799 if t in self.mapped_types:
800 return self.mapped_types[t]
801 print("Unrecognized type '%s', please add it to known types!" % t,
802 file=sys.stderr)
803 sys.exit(1)
804
805 seen_helpers = set()
806
807 def print_one(self, helper):
808 proto = helper.proto_break_down()
809
810 if proto['name'] in self.seen_helpers:
811 return
812 self.seen_helpers.add(proto['name'])
813
814 print('/*')
815 print(" * %s" % proto['name'])
816 print(" *")
817 if (helper.desc):
818 # Do not strip all newline characters: formatted code at the end of
819 # a section must be followed by a blank line.
820 for line in re.sub('\n$', '', helper.desc, count=1).split('\n'):
821 print(' *{}{}'.format(' \t' if line else '', line))
822
823 if (helper.ret):
824 print(' *')
825 print(' * Returns')
826 for line in helper.ret.rstrip().split('\n'):
827 print(' *{}{}'.format(' \t' if line else '', line))
828
829 print(' */')
830 print('static %s %s(*%s)(' % (self.map_type(proto['ret_type']),
831 proto['ret_star'], proto['name']), end='')
832 comma = ''
833 for i, a in enumerate(proto['args']):
834 t = a['type']
835 n = a['name']
836 if proto['name'] in self.overloaded_helpers and i == 0:
837 t = 'void'
838 n = 'ctx'
839 one_arg = '{}{}'.format(comma, self.map_type(t))
840 if n:
841 if a['star']:
842 one_arg += ' {}'.format(a['star'])
843 else:
844 one_arg += ' '
845 one_arg += '{}'.format(n)
846 comma = ', '
847 print(one_arg, end='')
848
849 print(') = (void *) %d;' % helper.enum_val)
850 print('')
851
852###############################################################################
853
854# If script is launched from scripts/ from kernel tree and can access
855# ../include/uapi/linux/bpf.h, use it as a default name for the file to parse,
856# otherwise the --filename argument will be required from the command line.
857script = os.path.abspath(sys.argv[0])
858linuxRoot = os.path.dirname(os.path.dirname(script))
859bpfh = os.path.join(linuxRoot, 'include/uapi/linux/bpf.h')
860
861printers = {
862 'helpers': PrinterHelpersRST,
863 'syscall': PrinterSyscallRST,
864}
865
866argParser = argparse.ArgumentParser(description="""
867Parse eBPF header file and generate documentation for the eBPF API.
868The RST-formatted output produced can be turned into a manual page with the
869rst2man utility.
870""")
871argParser.add_argument('--header', action='store_true',
872 help='generate C header file')
873if (os.path.isfile(bpfh)):
874 argParser.add_argument('--filename', help='path to include/uapi/linux/bpf.h',
875 default=bpfh)
876else:
877 argParser.add_argument('--filename', help='path to include/uapi/linux/bpf.h')
878argParser.add_argument('target', nargs='?', default='helpers',
879 choices=printers.keys(), help='eBPF API target')
880args = argParser.parse_args()
881
882# Parse file.
883headerParser = HeaderParser(args.filename)
884headerParser.run()
885
886# Print formatted output to standard output.
887if args.header:
888 if args.target != 'helpers':
889 raise NotImplementedError('Only helpers header generation is supported')
890 printer = PrinterHelpers(headerParser)
891else:
892 printer = printers[args.target](headerParser)
893printer.print_all()