1#!/usr/bin/env python3 2# SPDX-License-Identifier: GPL-2.0-only 3# 4# Copyright (C) 2018-2019 Netronome Systems, Inc. 5 6# In case user attempts to run with Python 2. 7from __future__ import print_function 8 9import argparse 10import re 11import sys, os 12 13class NoHelperFound(BaseException): 14 pass 15 16class ParsingError(BaseException): 17 def __init__(self, line='<line not provided>', reader=None): 18 if reader: 19 BaseException.__init__(self, 20 'Error at file offset %d, parsing line: %s' % 21 (reader.tell(), line)) 22 else: 23 BaseException.__init__(self, 'Error parsing line: %s' % line) 24 25class Helper(object): 26 """ 27 An object representing the description of an eBPF helper function. 28 @proto: function prototype of the helper function 29 @desc: textual description of the helper function 30 @ret: description of the return value of the helper function 31 """ 32 def __init__(self, proto='', desc='', ret=''): 33 self.proto = proto 34 self.desc = desc 35 self.ret = ret 36 37 def proto_break_down(self): 38 """ 39 Break down helper function protocol into smaller chunks: return type, 40 name, distincts arguments. 41 """ 42 arg_re = re.compile('((\w+ )*?(\w+|...))( (\**)(\w+))?$') 43 res = {} 44 proto_re = re.compile('(.+) (\**)(\w+)\(((([^,]+)(, )?){1,5})\)$') 45 46 capture = proto_re.match(self.proto) 47 res['ret_type'] = capture.group(1) 48 res['ret_star'] = capture.group(2) 49 res['name'] = capture.group(3) 50 res['args'] = [] 51 52 args = capture.group(4).split(', ') 53 for a in args: 54 capture = arg_re.match(a) 55 res['args'].append({ 56 'type' : capture.group(1), 57 'star' : capture.group(5), 58 'name' : capture.group(6) 59 }) 60 61 return res 62 63class HeaderParser(object): 64 """ 65 An object used to parse a file in order to extract the documentation of a 66 list of eBPF helper functions. All the helpers that can be retrieved are 67 stored as Helper object, in the self.helpers() array. 68 @filename: name of file to parse, usually include/uapi/linux/bpf.h in the 69 kernel tree 70 """ 71 def __init__(self, filename): 72 self.reader = open(filename, 'r') 73 self.line = '' 74 self.helpers = [] 75 76 def parse_helper(self): 77 proto = self.parse_proto() 78 desc = self.parse_desc() 79 ret = self.parse_ret() 80 return Helper(proto=proto, desc=desc, ret=ret) 81 82 def parse_proto(self): 83 # Argument can be of shape: 84 # - "void" 85 # - "type name" 86 # - "type *name" 87 # - Same as above, with "const" and/or "struct" in front of type 88 # - "..." (undefined number of arguments, for bpf_trace_printk()) 89 # There is at least one term ("void"), and at most five arguments. 90 p = re.compile(' \* ?((.+) \**\w+\((((const )?(struct )?(\w+|\.\.\.)( \**\w+)?)(, )?){1,5}\))$') 91 capture = p.match(self.line) 92 if not capture: 93 raise NoHelperFound 94 self.line = self.reader.readline() 95 return capture.group(1) 96 97 def parse_desc(self): 98 p = re.compile(' \* ?(?:\t| {5,8})Description$') 99 capture = p.match(self.line) 100 if not capture: 101 # Helper can have empty description and we might be parsing another 102 # attribute: return but do not consume. 103 return '' 104 # Description can be several lines, some of them possibly empty, and it 105 # stops when another subsection title is met. 106 desc = '' 107 while True: 108 self.line = self.reader.readline() 109 if self.line == ' *\n': 110 desc += '\n' 111 else: 112 p = re.compile(' \* ?(?:\t| {5,8})(?:\t| {8})(.*)') 113 capture = p.match(self.line) 114 if capture: 115 desc += capture.group(1) + '\n' 116 else: 117 break 118 return desc 119 120 def parse_ret(self): 121 p = re.compile(' \* ?(?:\t| {5,8})Return$') 122 capture = p.match(self.line) 123 if not capture: 124 # Helper can have empty retval and we might be parsing another 125 # attribute: return but do not consume. 126 return '' 127 # Return value description can be several lines, some of them possibly 128 # empty, and it stops when another subsection title is met. 129 ret = '' 130 while True: 131 self.line = self.reader.readline() 132 if self.line == ' *\n': 133 ret += '\n' 134 else: 135 p = re.compile(' \* ?(?:\t| {5,8})(?:\t| {8})(.*)') 136 capture = p.match(self.line) 137 if capture: 138 ret += capture.group(1) + '\n' 139 else: 140 break 141 return ret 142 143 def run(self): 144 # Advance to start of helper function descriptions. 145 offset = self.reader.read().find('* Start of BPF helper function descriptions:') 146 if offset == -1: 147 raise Exception('Could not find start of eBPF helper descriptions list') 148 self.reader.seek(offset) 149 self.reader.readline() 150 self.reader.readline() 151 self.line = self.reader.readline() 152 153 while True: 154 try: 155 helper = self.parse_helper() 156 self.helpers.append(helper) 157 except NoHelperFound: 158 break 159 160 self.reader.close() 161 162############################################################################### 163 164class Printer(object): 165 """ 166 A generic class for printers. Printers should be created with an array of 167 Helper objects, and implement a way to print them in the desired fashion. 168 @helpers: array of Helper objects to print to standard output 169 """ 170 def __init__(self, helpers): 171 self.helpers = helpers 172 173 def print_header(self): 174 pass 175 176 def print_footer(self): 177 pass 178 179 def print_one(self, helper): 180 pass 181 182 def print_all(self): 183 self.print_header() 184 for helper in self.helpers: 185 self.print_one(helper) 186 self.print_footer() 187 188class PrinterRST(Printer): 189 """ 190 A printer for dumping collected information about helpers as a ReStructured 191 Text page compatible with the rst2man program, which can be used to 192 generate a manual page for the helpers. 193 @helpers: array of Helper objects to print to standard output 194 """ 195 def print_header(self): 196 header = '''\ 197.. Copyright (C) All BPF authors and contributors from 2014 to present. 198.. See git log include/uapi/linux/bpf.h in kernel tree for details. 199.. 200.. %%%LICENSE_START(VERBATIM) 201.. Permission is granted to make and distribute verbatim copies of this 202.. manual provided the copyright notice and this permission notice are 203.. preserved on all copies. 204.. 205.. Permission is granted to copy and distribute modified versions of this 206.. manual under the conditions for verbatim copying, provided that the 207.. entire resulting derived work is distributed under the terms of a 208.. permission notice identical to this one. 209.. 210.. Since the Linux kernel and libraries are constantly changing, this 211.. manual page may be incorrect or out-of-date. The author(s) assume no 212.. responsibility for errors or omissions, or for damages resulting from 213.. the use of the information contained herein. The author(s) may not 214.. have taken the same level of care in the production of this manual, 215.. which is licensed free of charge, as they might when working 216.. professionally. 217.. 218.. Formatted or processed versions of this manual, if unaccompanied by 219.. the source, must acknowledge the copyright and authors of this work. 220.. %%%LICENSE_END 221.. 222.. Please do not edit this file. It was generated from the documentation 223.. located in file include/uapi/linux/bpf.h of the Linux kernel sources 224.. (helpers description), and from scripts/bpf_helpers_doc.py in the same 225.. repository (header and footer). 226 227=========== 228BPF-HELPERS 229=========== 230------------------------------------------------------------------------------- 231list of eBPF helper functions 232------------------------------------------------------------------------------- 233 234:Manual section: 7 235 236DESCRIPTION 237=========== 238 239The extended Berkeley Packet Filter (eBPF) subsystem consists in programs 240written in a pseudo-assembly language, then attached to one of the several 241kernel hooks and run in reaction of specific events. This framework differs 242from the older, "classic" BPF (or "cBPF") in several aspects, one of them being 243the ability to call special functions (or "helpers") from within a program. 244These functions are restricted to a white-list of helpers defined in the 245kernel. 246 247These helpers are used by eBPF programs to interact with the system, or with 248the context in which they work. For instance, they can be used to print 249debugging messages, to get the time since the system was booted, to interact 250with eBPF maps, or to manipulate network packets. Since there are several eBPF 251program types, and that they do not run in the same context, each program type 252can only call a subset of those helpers. 253 254Due to eBPF conventions, a helper can not have more than five arguments. 255 256Internally, eBPF programs call directly into the compiled helper functions 257without requiring any foreign-function interface. As a result, calling helpers 258introduces no overhead, thus offering excellent performance. 259 260This document is an attempt to list and document the helpers available to eBPF 261developers. They are sorted by chronological order (the oldest helpers in the 262kernel at the top). 263 264HELPERS 265======= 266''' 267 print(header) 268 269 def print_footer(self): 270 footer = ''' 271EXAMPLES 272======== 273 274Example usage for most of the eBPF helpers listed in this manual page are 275available within the Linux kernel sources, at the following locations: 276 277* *samples/bpf/* 278* *tools/testing/selftests/bpf/* 279 280LICENSE 281======= 282 283eBPF programs can have an associated license, passed along with the bytecode 284instructions to the kernel when the programs are loaded. The format for that 285string is identical to the one in use for kernel modules (Dual licenses, such 286as "Dual BSD/GPL", may be used). Some helper functions are only accessible to 287programs that are compatible with the GNU Privacy License (GPL). 288 289In order to use such helpers, the eBPF program must be loaded with the correct 290license string passed (via **attr**) to the **bpf**\ () system call, and this 291generally translates into the C source code of the program containing a line 292similar to the following: 293 294:: 295 296 char ____license[] __attribute__((section("license"), used)) = "GPL"; 297 298IMPLEMENTATION 299============== 300 301This manual page is an effort to document the existing eBPF helper functions. 302But as of this writing, the BPF sub-system is under heavy development. New eBPF 303program or map types are added, along with new helper functions. Some helpers 304are occasionally made available for additional program types. So in spite of 305the efforts of the community, this page might not be up-to-date. If you want to 306check by yourself what helper functions exist in your kernel, or what types of 307programs they can support, here are some files among the kernel tree that you 308may be interested in: 309 310* *include/uapi/linux/bpf.h* is the main BPF header. It contains the full list 311 of all helper functions, as well as many other BPF definitions including most 312 of the flags, structs or constants used by the helpers. 313* *net/core/filter.c* contains the definition of most network-related helper 314 functions, and the list of program types from which they can be used. 315* *kernel/trace/bpf_trace.c* is the equivalent for most tracing program-related 316 helpers. 317* *kernel/bpf/verifier.c* contains the functions used to check that valid types 318 of eBPF maps are used with a given helper function. 319* *kernel/bpf/* directory contains other files in which additional helpers are 320 defined (for cgroups, sockmaps, etc.). 321* The bpftool utility can be used to probe the availability of helper functions 322 on the system (as well as supported program and map types, and a number of 323 other parameters). To do so, run **bpftool feature probe** (see 324 **bpftool-feature**\ (8) for details). Add the **unprivileged** keyword to 325 list features available to unprivileged users. 326 327Compatibility between helper functions and program types can generally be found 328in the files where helper functions are defined. Look for the **struct 329bpf_func_proto** objects and for functions returning them: these functions 330contain a list of helpers that a given program type can call. Note that the 331**default:** label of the **switch ... case** used to filter helpers can call 332other functions, themselves allowing access to additional helpers. The 333requirement for GPL license is also in those **struct bpf_func_proto**. 334 335Compatibility between helper functions and map types can be found in the 336**check_map_func_compatibility**\ () function in file *kernel/bpf/verifier.c*. 337 338Helper functions that invalidate the checks on **data** and **data_end** 339pointers for network processing are listed in function 340**bpf_helper_changes_pkt_data**\ () in file *net/core/filter.c*. 341 342SEE ALSO 343======== 344 345**bpf**\ (2), 346**bpftool**\ (8), 347**cgroups**\ (7), 348**ip**\ (8), 349**perf_event_open**\ (2), 350**sendmsg**\ (2), 351**socket**\ (7), 352**tc-bpf**\ (8)''' 353 print(footer) 354 355 def print_proto(self, helper): 356 """ 357 Format function protocol with bold and italics markers. This makes RST 358 file less readable, but gives nice results in the manual page. 359 """ 360 proto = helper.proto_break_down() 361 362 print('**%s %s%s(' % (proto['ret_type'], 363 proto['ret_star'].replace('*', '\\*'), 364 proto['name']), 365 end='') 366 367 comma = '' 368 for a in proto['args']: 369 one_arg = '{}{}'.format(comma, a['type']) 370 if a['name']: 371 if a['star']: 372 one_arg += ' {}**\ '.format(a['star'].replace('*', '\\*')) 373 else: 374 one_arg += '** ' 375 one_arg += '*{}*\\ **'.format(a['name']) 376 comma = ', ' 377 print(one_arg, end='') 378 379 print(')**') 380 381 def print_one(self, helper): 382 self.print_proto(helper) 383 384 if (helper.desc): 385 print('\tDescription') 386 # Do not strip all newline characters: formatted code at the end of 387 # a section must be followed by a blank line. 388 for line in re.sub('\n$', '', helper.desc, count=1).split('\n'): 389 print('{}{}'.format('\t\t' if line else '', line)) 390 391 if (helper.ret): 392 print('\tReturn') 393 for line in helper.ret.rstrip().split('\n'): 394 print('{}{}'.format('\t\t' if line else '', line)) 395 396 print('') 397 398class PrinterHelpers(Printer): 399 """ 400 A printer for dumping collected information about helpers as C header to 401 be included from BPF program. 402 @helpers: array of Helper objects to print to standard output 403 """ 404 405 type_fwds = [ 406 'struct bpf_fib_lookup', 407 'struct bpf_sk_lookup', 408 'struct bpf_perf_event_data', 409 'struct bpf_perf_event_value', 410 'struct bpf_pidns_info', 411 'struct bpf_redir_neigh', 412 'struct bpf_sock', 413 'struct bpf_sock_addr', 414 'struct bpf_sock_ops', 415 'struct bpf_sock_tuple', 416 'struct bpf_spin_lock', 417 'struct bpf_sysctl', 418 'struct bpf_tcp_sock', 419 'struct bpf_tunnel_key', 420 'struct bpf_xfrm_state', 421 'struct pt_regs', 422 'struct sk_reuseport_md', 423 'struct sockaddr', 424 'struct tcphdr', 425 'struct seq_file', 426 'struct tcp6_sock', 427 'struct tcp_sock', 428 'struct tcp_timewait_sock', 429 'struct tcp_request_sock', 430 'struct udp6_sock', 431 'struct task_struct', 432 433 'struct __sk_buff', 434 'struct sk_msg_md', 435 'struct xdp_md', 436 'struct path', 437 'struct btf_ptr', 438 ] 439 known_types = { 440 '...', 441 'void', 442 'const void', 443 'char', 444 'const char', 445 'int', 446 'long', 447 'unsigned long', 448 449 '__be16', 450 '__be32', 451 '__wsum', 452 453 'struct bpf_fib_lookup', 454 'struct bpf_perf_event_data', 455 'struct bpf_perf_event_value', 456 'struct bpf_pidns_info', 457 'struct bpf_redir_neigh', 458 'struct bpf_sk_lookup', 459 'struct bpf_sock', 460 'struct bpf_sock_addr', 461 'struct bpf_sock_ops', 462 'struct bpf_sock_tuple', 463 'struct bpf_spin_lock', 464 'struct bpf_sysctl', 465 'struct bpf_tcp_sock', 466 'struct bpf_tunnel_key', 467 'struct bpf_xfrm_state', 468 'struct pt_regs', 469 'struct sk_reuseport_md', 470 'struct sockaddr', 471 'struct tcphdr', 472 'struct seq_file', 473 'struct tcp6_sock', 474 'struct tcp_sock', 475 'struct tcp_timewait_sock', 476 'struct tcp_request_sock', 477 'struct udp6_sock', 478 'struct task_struct', 479 'struct path', 480 'struct btf_ptr', 481 } 482 mapped_types = { 483 'u8': '__u8', 484 'u16': '__u16', 485 'u32': '__u32', 486 'u64': '__u64', 487 's8': '__s8', 488 's16': '__s16', 489 's32': '__s32', 490 's64': '__s64', 491 'size_t': 'unsigned long', 492 'struct bpf_map': 'void', 493 'struct sk_buff': 'struct __sk_buff', 494 'const struct sk_buff': 'const struct __sk_buff', 495 'struct sk_msg_buff': 'struct sk_msg_md', 496 'struct xdp_buff': 'struct xdp_md', 497 } 498 # Helpers overloaded for different context types. 499 overloaded_helpers = [ 500 'bpf_get_socket_cookie', 501 'bpf_sk_assign', 502 ] 503 504 def print_header(self): 505 header = '''\ 506/* This is auto-generated file. See bpf_helpers_doc.py for details. */ 507 508/* Forward declarations of BPF structs */''' 509 510 print(header) 511 for fwd in self.type_fwds: 512 print('%s;' % fwd) 513 print('') 514 515 def print_footer(self): 516 footer = '' 517 print(footer) 518 519 def map_type(self, t): 520 if t in self.known_types: 521 return t 522 if t in self.mapped_types: 523 return self.mapped_types[t] 524 print("Unrecognized type '%s', please add it to known types!" % t, 525 file=sys.stderr) 526 sys.exit(1) 527 528 seen_helpers = set() 529 530 def print_one(self, helper): 531 proto = helper.proto_break_down() 532 533 if proto['name'] in self.seen_helpers: 534 return 535 self.seen_helpers.add(proto['name']) 536 537 print('/*') 538 print(" * %s" % proto['name']) 539 print(" *") 540 if (helper.desc): 541 # Do not strip all newline characters: formatted code at the end of 542 # a section must be followed by a blank line. 543 for line in re.sub('\n$', '', helper.desc, count=1).split('\n'): 544 print(' *{}{}'.format(' \t' if line else '', line)) 545 546 if (helper.ret): 547 print(' *') 548 print(' * Returns') 549 for line in helper.ret.rstrip().split('\n'): 550 print(' *{}{}'.format(' \t' if line else '', line)) 551 552 print(' */') 553 print('static %s %s(*%s)(' % (self.map_type(proto['ret_type']), 554 proto['ret_star'], proto['name']), end='') 555 comma = '' 556 for i, a in enumerate(proto['args']): 557 t = a['type'] 558 n = a['name'] 559 if proto['name'] in self.overloaded_helpers and i == 0: 560 t = 'void' 561 n = 'ctx' 562 one_arg = '{}{}'.format(comma, self.map_type(t)) 563 if n: 564 if a['star']: 565 one_arg += ' {}'.format(a['star']) 566 else: 567 one_arg += ' ' 568 one_arg += '{}'.format(n) 569 comma = ', ' 570 print(one_arg, end='') 571 572 print(') = (void *) %d;' % len(self.seen_helpers)) 573 print('') 574 575############################################################################### 576 577# If script is launched from scripts/ from kernel tree and can access 578# ../include/uapi/linux/bpf.h, use it as a default name for the file to parse, 579# otherwise the --filename argument will be required from the command line. 580script = os.path.abspath(sys.argv[0]) 581linuxRoot = os.path.dirname(os.path.dirname(script)) 582bpfh = os.path.join(linuxRoot, 'include/uapi/linux/bpf.h') 583 584argParser = argparse.ArgumentParser(description=""" 585Parse eBPF header file and generate documentation for eBPF helper functions. 586The RST-formatted output produced can be turned into a manual page with the 587rst2man utility. 588""") 589argParser.add_argument('--header', action='store_true', 590 help='generate C header file') 591if (os.path.isfile(bpfh)): 592 argParser.add_argument('--filename', help='path to include/uapi/linux/bpf.h', 593 default=bpfh) 594else: 595 argParser.add_argument('--filename', help='path to include/uapi/linux/bpf.h') 596args = argParser.parse_args() 597 598# Parse file. 599headerParser = HeaderParser(args.filename) 600headerParser.run() 601 602# Print formatted output to standard output. 603if args.header: 604 printer = PrinterHelpers(headerParser.helpers) 605else: 606 printer = PrinterRST(headerParser.helpers) 607printer.print_all() 608
