scripts/bpf_doc.py

   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.
   8 from __future__ import print_function
   9
  10 import argparse
  11 import re
  12 import sys, os
  13
  14 class NoHelperFound(BaseException):
  15     pass
  16
  17 class NoSyscallCommandFound(BaseException):
  18     pass
  19
  20 class ParsingError(BaseException):
  21     def __init__(self, line='<line not provided>', reader=None):
  22         if reader:
  23             BaseException.__init__(self,
  24                                    'Error at file offset %d, parsing line: %s' %
  25                                    (reader.tell(), line))
  26         else:
  27             BaseException.__init__(self, 'Error parsing line: %s' % line)
  28
  29
  30 class APIElement(object):
  31     """
  32     An object representing the description of an aspect of the eBPF API.
  33     @proto: prototype of the API symbol
  34     @desc: textual description of the symbol
  35     @ret: (optional) description of any associated return value
  36     """
  37     def __init__(self, proto='', desc='', ret=''):
  38         self.proto = proto
  39         self.desc = desc
  40         self.ret = ret
  41
  42
  43 class Helper(APIElement):
  44     """
  45     An object representing the description of an eBPF helper function.
  46     @proto: function prototype of the helper function
  47     @desc: textual description of the helper function
  48     @ret: description of the return value of the helper function
  49     """
  50     def proto_break_down(self):
  51         """
  52         Break down helper function protocol into smaller chunks: return type,
  53         name, distincts arguments.
  54         """
  55         arg_re = re.compile('((\w+ )*?(\w+|...))( (\**)(\w+))?$')
  56         res = {}
  57         proto_re = re.compile('(.+) (\**)(\w+)\(((([^,]+)(, )?){1,5})\)$')
  58
  59         capture = proto_re.match(self.proto)
  60         res['ret_type'] = capture.group(1)
  61         res['ret_star'] = capture.group(2)
  62         res['name']     = capture.group(3)
  63         res['args'] = []
  64
  65         args    = capture.group(4).split(', ')
  66         for a in args:
  67             capture = arg_re.match(a)
  68             res['args'].append({
  69                 'type' : capture.group(1),
  70                 'star' : capture.group(5),
  71                 'name' : capture.group(6)
  72             })
  73
  74         return res
  75
  76
  77 class HeaderParser(object):
  78     """
  79     An object used to parse a file in order to extract the documentation of a
  80     list of eBPF helper functions. All the helpers that can be retrieved are
  81     stored as Helper object, in the self.helpers() array.
  82     @filename: name of file to parse, usually include/uapi/linux/bpf.h in the
  83                kernel tree
  84     """
  85     def __init__(self, filename):
  86         self.reader = open(filename, 'r')
  87         self.line = ''
  88         self.helpers = []
  89         self.commands = []
  90
  91     def parse_element(self):
  92         proto    = self.parse_symbol()
  93         desc     = self.parse_desc()
  94         ret      = self.parse_ret()
  95         return APIElement(proto=proto, desc=desc, ret=ret)
  96
  97     def parse_helper(self):
  98         proto    = self.parse_proto()
  99         desc     = self.parse_desc()
 100         ret      = self.parse_ret()
 101         return Helper(proto=proto, desc=desc, ret=ret)
 102
 103     def parse_symbol(self):
 104         p = re.compile(' \* ?(.+)$')
 105         capture = p.match(self.line)
 106         if not capture:
 107             raise NoSyscallCommandFound
 108         end_re = re.compile(' \* ?NOTES$')
 109         end = end_re.match(self.line)
 110         if end:
 111             raise NoSyscallCommandFound
 112         self.line = self.reader.readline()
 113         return capture.group(1)
 114
 115     def parse_proto(self):
 116         # Argument can be of shape:
 117         #   - "void"
 118         #   - "type  name"
 119         #   - "type *name"
 120         #   - Same as above, with "const" and/or "struct" in front of type
 121         #   - "..." (undefined number of arguments, for bpf_trace_printk())
 122         # There is at least one term ("void"), and at most five arguments.
 123         p = re.compile(' \* ?((.+) \**\w+\((((const )?(struct )?(\w+|\.\.\.)( \**\w+)?)(, )?){1,5}\))$')
 124         capture = p.match(self.line)
 125         if not capture:
 126             raise NoHelperFound
 127         self.line = self.reader.readline()
 128         return capture.group(1)
 129
 130     def parse_desc(self):
 131         p = re.compile(' \* ?(?:\t| {5,8})Description$')
 132         capture = p.match(self.line)
 133         if not capture:
 134             # Helper can have empty description and we might be parsing another
 135             # attribute: return but do not consume.
 136             return ''
 137         # Description can be several lines, some of them possibly empty, and it
 138         # stops when another subsection title is met.
 139         desc = ''
 140         while True:
 141             self.line = self.reader.readline()
 142             if self.line == ' *\n':
 143                 desc += '\n'
 144             else:
 145                 p = re.compile(' \* ?(?:\t| {5,8})(?:\t| {8})(.*)')
 146                 capture = p.match(self.line)
 147                 if capture:
 148                     desc += capture.group(1) + '\n'
 149                 else:
 150                     break
 151         return desc
 152
 153     def parse_ret(self):
 154         p = re.compile(' \* ?(?:\t| {5,8})Return$')
 155         capture = p.match(self.line)
 156         if not capture:
 157             # Helper can have empty retval and we might be parsing another
 158             # attribute: return but do not consume.
 159             return ''
 160         # Return value description can be several lines, some of them possibly
 161         # empty, and it stops when another subsection title is met.
 162         ret = ''
 163         while True:
 164             self.line = self.reader.readline()
 165             if self.line == ' *\n':
 166                 ret += '\n'
 167             else:
 168                 p = re.compile(' \* ?(?:\t| {5,8})(?:\t| {8})(.*)')
 169                 capture = p.match(self.line)
 170                 if capture:
 171                     ret += capture.group(1) + '\n'
 172                 else:
 173                     break
 174         return ret
 175
 176     def seek_to(self, target, help_message):
 177         self.reader.seek(0)
 178         offset = self.reader.read().find(target)
 179         if offset == -1:
 180             raise Exception(help_message)
 181         self.reader.seek(offset)
 182         self.reader.readline()
 183         self.reader.readline()
 184         self.line = self.reader.readline()
 185
 186     def parse_syscall(self):
 187         self.seek_to('* DOC: eBPF Syscall Commands',
 188                      'Could not find start of eBPF syscall descriptions list')
 189         while True:
 190             try:
 191                 command = self.parse_element()
 192                 self.commands.append(command)
 193             except NoSyscallCommandFound:
 194                 break
 195
 196     def parse_helpers(self):
 197         self.seek_to('* Start of BPF helper function descriptions:',
 198                      'Could not find start of eBPF helper descriptions list')
 199         while True:
 200             try:
 201                 helper = self.parse_helper()
 202                 self.helpers.append(helper)
 203             except NoHelperFound:
 204                 break
 205
 206     def run(self):
 207         self.parse_syscall()
 208         self.parse_helpers()
 209         self.reader.close()
 210
 211 ###############################################################################
 212
 213 class Printer(object):
 214     """
 215     A generic class for printers. Printers should be created with an array of
 216     Helper objects, and implement a way to print them in the desired fashion.
 217     @parser: A HeaderParser with objects to print to standard output
 218     """
 219     def __init__(self, parser):
 220         self.parser = parser
 221         self.elements = []
 222
 223     def print_header(self):
 224         pass
 225
 226     def print_footer(self):
 227         pass
 228
 229     def print_one(self, helper):
 230         pass
 231
 232     def print_all(self):
 233         self.print_header()
 234         for elem in self.elements:
 235             self.print_one(elem)
 236         self.print_footer()
 237
 238
 239 class PrinterRST(Printer):
 240     """
 241     A generic class for printers that print ReStructured Text. Printers should
 242     be created with a HeaderParser object, and implement a way to print API
 243     elements in the desired fashion.
 244     @parser: A HeaderParser with objects to print to standard output
 245     """
 246     def __init__(self, parser):
 247         self.parser = parser
 248
 249     def print_license(self):
 250         license = '''\
 251 .. Copyright (C) All BPF authors and contributors from 2014 to present.
 252 .. See git log include/uapi/linux/bpf.h in kernel tree for details.
 253 ..
 254 .. %%%LICENSE_START(VERBATIM)
 255 .. Permission is granted to make and distribute verbatim copies of this
 256 .. manual provided the copyright notice and this permission notice are
 257 .. preserved on all copies.
 258 ..
 259 .. Permission is granted to copy and distribute modified versions of this
 260 .. manual under the conditions for verbatim copying, provided that the
 261 .. entire resulting derived work is distributed under the terms of a
 262 .. permission notice identical to this one.
 263 ..
 264 .. Since the Linux kernel and libraries are constantly changing, this
 265 .. manual page may be incorrect or out-of-date.  The author(s) assume no
 266 .. responsibility for errors or omissions, or for damages resulting from
 267 .. the use of the information contained herein.  The author(s) may not
 268 .. have taken the same level of care in the production of this manual,
 269 .. which is licensed free of charge, as they might when working
 270 .. professionally.
 271 ..
 272 .. Formatted or processed versions of this manual, if unaccompanied by
 273 .. the source, must acknowledge the copyright and authors of this work.
 274 .. %%%LICENSE_END
 275 ..
 276 .. Please do not edit this file. It was generated from the documentation
 277 .. located in file include/uapi/linux/bpf.h of the Linux kernel sources
 278 .. (helpers description), and from scripts/bpf_doc.py in the same
 279 .. repository (header and footer).
 280 '''
 281         print(license)
 282
 283     def print_elem(self, elem):
 284         if (elem.desc):
 285             print('\tDescription')
 286             # Do not strip all newline characters: formatted code at the end of
 287             # a section must be followed by a blank line.
 288             for line in re.sub('\n$', '', elem.desc, count=1).split('\n'):
 289                 print('{}{}'.format('\t\t' if line else '', line))
 290
 291         if (elem.ret):
 292             print('\tReturn')
 293             for line in elem.ret.rstrip().split('\n'):
 294                 print('{}{}'.format('\t\t' if line else '', line))
 295
 296         print('')
 297
 298
 299 class PrinterHelpersRST(PrinterRST):
 300     """
 301     A printer for dumping collected information about helpers as a ReStructured
 302     Text page compatible with the rst2man program, which can be used to
 303     generate a manual page for the helpers.
 304     @parser: A HeaderParser with Helper objects to print to standard output
 305     """
 306     def __init__(self, parser):
 307         self.elements = parser.helpers
 308
 309     def print_header(self):
 310         header = '''\
 311 ===========
 312 BPF-HELPERS
 313 ===========
 314 -------------------------------------------------------------------------------
 315 list of eBPF helper functions
 316 -------------------------------------------------------------------------------
 317
 318 :Manual section: 7
 319
 320 DESCRIPTION
 321 ===========
 322
 323 The extended Berkeley Packet Filter (eBPF) subsystem consists in programs
 324 written in a pseudo-assembly language, then attached to one of the several
 325 kernel hooks and run in reaction of specific events. This framework differs
 326 from the older, "classic" BPF (or "cBPF") in several aspects, one of them being
 327 the ability to call special functions (or "helpers") from within a program.
 328 These functions are restricted to a white-list of helpers defined in the
 329 kernel.
 330
 331 These helpers are used by eBPF programs to interact with the system, or with
 332 the context in which they work. For instance, they can be used to print
 333 debugging messages, to get the time since the system was booted, to interact
 334 with eBPF maps, or to manipulate network packets. Since there are several eBPF
 335 program types, and that they do not run in the same context, each program type
 336 can only call a subset of those helpers.
 337
 338 Due to eBPF conventions, a helper can not have more than five arguments.
 339
 340 Internally, eBPF programs call directly into the compiled helper functions
 341 without requiring any foreign-function interface. As a result, calling helpers
 342 introduces no overhead, thus offering excellent performance.
 343
 344 This document is an attempt to list and document the helpers available to eBPF
 345 developers. They are sorted by chronological order (the oldest helpers in the
 346 kernel at the top).
 347
 348 HELPERS
 349 =======
 350 '''
 351         PrinterRST.print_license(self)
 352         print(header)
 353
 354     def print_footer(self):
 355         footer = '''
 356 EXAMPLES
 357 ========
 358
 359 Example usage for most of the eBPF helpers listed in this manual page are
 360 available within the Linux kernel sources, at the following locations:
 361
 362 * *samples/bpf/*
 363 * *tools/testing/selftests/bpf/*
 364
 365 LICENSE
 366 =======
 367
 368 eBPF programs can have an associated license, passed along with the bytecode
 369 instructions to the kernel when the programs are loaded. The format for that
 370 string is identical to the one in use for kernel modules (Dual licenses, such
 371 as "Dual BSD/GPL", may be used). Some helper functions are only accessible to
 372 programs that are compatible with the GNU Privacy License (GPL).
 373
 374 In order to use such helpers, the eBPF program must be loaded with the correct
 375 license string passed (via **attr**) to the **bpf**\ () system call, and this
 376 generally translates into the C source code of the program containing a line
 377 similar to the following:
 378
 379 ::
 380
 381         char ____license[] __attribute__((section("license"), used)) = "GPL";
 382
 383 IMPLEMENTATION
 384 ==============
 385
 386 This manual page is an effort to document the existing eBPF helper functions.
 387 But as of this writing, the BPF sub-system is under heavy development. New eBPF
 388 program or map types are added, along with new helper functions. Some helpers
 389 are occasionally made available for additional program types. So in spite of
 390 the efforts of the community, this page might not be up-to-date. If you want to
 391 check by yourself what helper functions exist in your kernel, or what types of
 392 programs they can support, here are some files among the kernel tree that you
 393 may be interested in:
 394
 395 * *include/uapi/linux/bpf.h* is the main BPF header. It contains the full list
 396   of all helper functions, as well as many other BPF definitions including most
 397   of the flags, structs or constants used by the helpers.
 398 * *net/core/filter.c* contains the definition of most network-related helper
 399   functions, and the list of program types from which they can be used.
 400 * *kernel/trace/bpf_trace.c* is the equivalent for most tracing program-related
 401   helpers.
 402 * *kernel/bpf/verifier.c* contains the functions used to check that valid types
 403   of eBPF maps are used with a given helper function.
 404 * *kernel/bpf/* directory contains other files in which additional helpers are
 405   defined (for cgroups, sockmaps, etc.).
 406 * The bpftool utility can be used to probe the availability of helper functions
 407   on the system (as well as supported program and map types, and a number of
 408   other parameters). To do so, run **bpftool feature probe** (see
 409   **bpftool-feature**\ (8) for details). Add the **unprivileged** keyword to
 410   list features available to unprivileged users.
 411
 412 Compatibility between helper functions and program types can generally be found
 413 in the files where helper functions are defined. Look for the **struct
 414 bpf_func_proto** objects and for functions returning them: these functions
 415 contain a list of helpers that a given program type can call. Note that the
 416 **default:** label of the **switch ... case** used to filter helpers can call
 417 other functions, themselves allowing access to additional helpers. The
 418 requirement for GPL license is also in those **struct bpf_func_proto**.
 419
 420 Compatibility between helper functions and map types can be found in the
 421 **check_map_func_compatibility**\ () function in file *kernel/bpf/verifier.c*.
 422
 423 Helper functions that invalidate the checks on **data** and **data_end**
 424 pointers for network processing are listed in function
 425 **bpf_helper_changes_pkt_data**\ () in file *net/core/filter.c*.
 426
 427 SEE ALSO
 428 ========
 429
 430 **bpf**\ (2),
 431 **bpftool**\ (8),
 432 **cgroups**\ (7),
 433 **ip**\ (8),
 434 **perf_event_open**\ (2),
 435 **sendmsg**\ (2),
 436 **socket**\ (7),
 437 **tc-bpf**\ (8)'''
 438         print(footer)
 439
 440     def print_proto(self, helper):
 441         """
 442         Format function protocol with bold and italics markers. This makes RST
 443         file less readable, but gives nice results in the manual page.
 444         """
 445         proto = helper.proto_break_down()
 446
 447         print('**%s %s%s(' % (proto['ret_type'],
 448                               proto['ret_star'].replace('*', '\\*'),
 449                               proto['name']),
 450               end='')
 451
 452         comma = ''
 453         for a in proto['args']:
 454             one_arg = '{}{}'.format(comma, a['type'])
 455             if a['name']:
 456                 if a['star']:
 457                     one_arg += ' {}**\ '.format(a['star'].replace('*', '\\*'))
 458                 else:
 459                     one_arg += '** '
 460                 one_arg += '*{}*\\ **'.format(a['name'])
 461             comma = ', '
 462             print(one_arg, end='')
 463
 464         print(')**')
 465
 466     def print_one(self, helper):
 467         self.print_proto(helper)
 468         self.print_elem(helper)
 469
 470
 471 class PrinterSyscallRST(PrinterRST):
 472     """
 473     A printer for dumping collected information about the syscall API as a
 474     ReStructured Text page compatible with the rst2man program, which can be
 475     used to generate a manual page for the syscall.
 476     @parser: A HeaderParser with APIElement objects to print to standard
 477              output
 478     """
 479     def __init__(self, parser):
 480         self.elements = parser.commands
 481
 482     def print_header(self):
 483         header = '''\
 484 ===
 485 bpf
 486 ===
 487 -------------------------------------------------------------------------------
 488 Perform a command on an extended BPF object
 489 -------------------------------------------------------------------------------
 490
 491 :Manual section: 2
 492
 493 COMMANDS
 494 ========
 495 '''
 496         PrinterRST.print_license(self)
 497         print(header)
 498
 499     def print_one(self, command):
 500         print('**%s**' % (command.proto))
 501         self.print_elem(command)
 502
 503
 504 class PrinterHelpers(Printer):
 505     """
 506     A printer for dumping collected information about helpers as C header to
 507     be included from BPF program.
 508     @parser: A HeaderParser with Helper objects to print to standard output
 509     """
 510     def __init__(self, parser):
 511         self.elements = parser.helpers
 512
 513     type_fwds = [
 514             'struct bpf_fib_lookup',
 515             'struct bpf_sk_lookup',
 516             'struct bpf_perf_event_data',
 517             'struct bpf_perf_event_value',
 518             'struct bpf_pidns_info',
 519             'struct bpf_redir_neigh',
 520             'struct bpf_sock',
 521             'struct bpf_sock_addr',
 522             'struct bpf_sock_ops',
 523             'struct bpf_sock_tuple',
 524             'struct bpf_spin_lock',
 525             'struct bpf_sysctl',
 526             'struct bpf_tcp_sock',
 527             'struct bpf_tunnel_key',
 528             'struct bpf_xfrm_state',
 529             'struct linux_binprm',
 530             'struct pt_regs',
 531             'struct sk_reuseport_md',
 532             'struct sockaddr',
 533             'struct tcphdr',
 534             'struct seq_file',
 535             'struct tcp6_sock',
 536             'struct tcp_sock',
 537             'struct tcp_timewait_sock',
 538             'struct tcp_request_sock',
 539             'struct udp6_sock',
 540             'struct task_struct',
 541
 542             'struct __sk_buff',
 543             'struct sk_msg_md',
 544             'struct xdp_md',
 545             'struct path',
 546             'struct btf_ptr',
 547             'struct inode',
 548             'struct socket',
 549             'struct file',
 550             'struct bpf_timer',
 551     ]
 552     known_types = {
 553             '...',
 554             'void',
 555             'const void',
 556             'char',
 557             'const char',
 558             'int',
 559             'long',
 560             'unsigned long',
 561
 562             '__be16',
 563             '__be32',
 564             '__wsum',
 565
 566             'struct bpf_fib_lookup',
 567             'struct bpf_perf_event_data',
 568             'struct bpf_perf_event_value',
 569             'struct bpf_pidns_info',
 570             'struct bpf_redir_neigh',
 571             'struct bpf_sk_lookup',
 572             'struct bpf_sock',
 573             'struct bpf_sock_addr',
 574             'struct bpf_sock_ops',
 575             'struct bpf_sock_tuple',
 576             'struct bpf_spin_lock',
 577             'struct bpf_sysctl',
 578             'struct bpf_tcp_sock',
 579             'struct bpf_tunnel_key',
 580             'struct bpf_xfrm_state',
 581             'struct linux_binprm',
 582             'struct pt_regs',
 583             'struct sk_reuseport_md',
 584             'struct sockaddr',
 585             'struct tcphdr',
 586             'struct seq_file',
 587             'struct tcp6_sock',
 588             'struct tcp_sock',
 589             'struct tcp_timewait_sock',
 590             'struct tcp_request_sock',
 591             'struct udp6_sock',
 592             'struct task_struct',
 593             'struct path',
 594             'struct btf_ptr',
 595             'struct inode',
 596             'struct socket',
 597             'struct file',
 598             'struct bpf_timer',
 599     }
 600     mapped_types = {
 601             'u8': '__u8',
 602             'u16': '__u16',
 603             'u32': '__u32',
 604             'u64': '__u64',
 605             's8': '__s8',
 606             's16': '__s16',
 607             's32': '__s32',
 608             's64': '__s64',
 609             'size_t': 'unsigned long',
 610             'struct bpf_map': 'void',
 611             'struct sk_buff': 'struct __sk_buff',
 612             'const struct sk_buff': 'const struct __sk_buff',
 613             'struct sk_msg_buff': 'struct sk_msg_md',
 614             'struct xdp_buff': 'struct xdp_md',
 615     }
 616     # Helpers overloaded for different context types.
 617     overloaded_helpers = [
 618         'bpf_get_socket_cookie',
 619         'bpf_sk_assign',
 620     ]
 621
 622     def print_header(self):
 623         header = '''\
 624 /* This is auto-generated file. See bpf_doc.py for details. */
 625
 626 /* Forward declarations of BPF structs */'''
 627
 628         print(header)
 629         for fwd in self.type_fwds:
 630             print('%s;' % fwd)
 631         print('')
 632
 633     def print_footer(self):
 634         footer = ''
 635         print(footer)
 636
 637     def map_type(self, t):
 638         if t in self.known_types:
 639             return t
 640         if t in self.mapped_types:
 641             return self.mapped_types[t]
 642         print("Unrecognized type '%s', please add it to known types!" % t,
 643               file=sys.stderr)
 644         sys.exit(1)
 645
 646     seen_helpers = set()
 647
 648     def print_one(self, helper):
 649         proto = helper.proto_break_down()
 650
 651         if proto['name'] in self.seen_helpers:
 652             return
 653         self.seen_helpers.add(proto['name'])
 654
 655         print('/*')
 656         print(" * %s" % proto['name'])
 657         print(" *")
 658         if (helper.desc):
 659             # Do not strip all newline characters: formatted code at the end of
 660             # a section must be followed by a blank line.
 661             for line in re.sub('\n$', '', helper.desc, count=1).split('\n'):
 662                 print(' *{}{}'.format(' \t' if line else '', line))
 663
 664         if (helper.ret):
 665             print(' *')
 666             print(' * Returns')
 667             for line in helper.ret.rstrip().split('\n'):
 668                 print(' *{}{}'.format(' \t' if line else '', line))
 669
 670         print(' */')
 671         print('static %s %s(*%s)(' % (self.map_type(proto['ret_type']),
 672                                       proto['ret_star'], proto['name']), end='')
 673         comma = ''
 674         for i, a in enumerate(proto['args']):
 675             t = a['type']
 676             n = a['name']
 677             if proto['name'] in self.overloaded_helpers and i == 0:
 678                     t = 'void'
 679                     n = 'ctx'
 680             one_arg = '{}{}'.format(comma, self.map_type(t))
 681             if n:
 682                 if a['star']:
 683                     one_arg += ' {}'.format(a['star'])
 684                 else:
 685                     one_arg += ' '
 686                 one_arg += '{}'.format(n)
 687             comma = ', '
 688             print(one_arg, end='')
 689
 690         print(') = (void *) %d;' % len(self.seen_helpers))
 691         print('')
 692
 693 ###############################################################################
 694
 695 # If script is launched from scripts/ from kernel tree and can access
 696 # ../include/uapi/linux/bpf.h, use it as a default name for the file to parse,
 697 # otherwise the --filename argument will be required from the command line.
 698 script = os.path.abspath(sys.argv[0])
 699 linuxRoot = os.path.dirname(os.path.dirname(script))
 700 bpfh = os.path.join(linuxRoot, 'include/uapi/linux/bpf.h')
 701
 702 printers = {
 703         'helpers': PrinterHelpersRST,
 704         'syscall': PrinterSyscallRST,
 705 }
 706
 707 argParser = argparse.ArgumentParser(description="""
 708 Parse eBPF header file and generate documentation for the eBPF API.
 709 The RST-formatted output produced can be turned into a manual page with the
 710 rst2man utility.
 711 """)
 712 argParser.add_argument('--header', action='store_true',
 713                        help='generate C header file')
 714 if (os.path.isfile(bpfh)):
 715     argParser.add_argument('--filename', help='path to include/uapi/linux/bpf.h',
 716                            default=bpfh)
 717 else:
 718     argParser.add_argument('--filename', help='path to include/uapi/linux/bpf.h')
 719 argParser.add_argument('target', nargs='?', default='helpers',
 720                        choices=printers.keys(), help='eBPF API target')
 721 args = argParser.parse_args()
 722
 723 # Parse file.
 724 headerParser = HeaderParser(args.filename)
 725 headerParser.run()
 726
 727 # Print formatted output to standard output.
 728 if args.header:
 729     if args.target != 'helpers':
 730         raise NotImplementedError('Only helpers header generation is supported')
 731     printer = PrinterHelpers(headerParser)
 732 else:
 733     printer = printers[args.target](headerParser)
 734 printer.print_all()