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1#!/usr/bin/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 print('Parsed description of %d helper function(s)' % len(self.helpers),
162 file=sys.stderr)
163
164###############################################################################
165
166class Printer(object):
167 """
168 A generic class for printers. Printers should be created with an array of
169 Helper objects, and implement a way to print them in the desired fashion.
170 @helpers: array of Helper objects to print to standard output
171 """
172 def __init__(self, helpers):
173 self.helpers = helpers
174
175 def print_header(self):
176 pass
177
178 def print_footer(self):
179 pass
180
181 def print_one(self, helper):
182 pass
183
184 def print_all(self):
185 self.print_header()
186 for helper in self.helpers:
187 self.print_one(helper)
188 self.print_footer()
189
190class PrinterRST(Printer):
191 """
192 A printer for dumping collected information about helpers as a ReStructured
193 Text page compatible with the rst2man program, which can be used to
194 generate a manual page for the helpers.
195 @helpers: array of Helper objects to print to standard output
196 """
197 def print_header(self):
198 header = '''\
199.. Copyright (C) All BPF authors and contributors from 2014 to present.
200.. See git log include/uapi/linux/bpf.h in kernel tree for details.
201..
202.. %%%LICENSE_START(VERBATIM)
203.. Permission is granted to make and distribute verbatim copies of this
204.. manual provided the copyright notice and this permission notice are
205.. preserved on all copies.
206..
207.. Permission is granted to copy and distribute modified versions of this
208.. manual under the conditions for verbatim copying, provided that the
209.. entire resulting derived work is distributed under the terms of a
210.. permission notice identical to this one.
211..
212.. Since the Linux kernel and libraries are constantly changing, this
213.. manual page may be incorrect or out-of-date. The author(s) assume no
214.. responsibility for errors or omissions, or for damages resulting from
215.. the use of the information contained herein. The author(s) may not
216.. have taken the same level of care in the production of this manual,
217.. which is licensed free of charge, as they might when working
218.. professionally.
219..
220.. Formatted or processed versions of this manual, if unaccompanied by
221.. the source, must acknowledge the copyright and authors of this work.
222.. %%%LICENSE_END
223..
224.. Please do not edit this file. It was generated from the documentation
225.. located in file include/uapi/linux/bpf.h of the Linux kernel sources
226.. (helpers description), and from scripts/bpf_helpers_doc.py in the same
227.. repository (header and footer).
228
229===========
230BPF-HELPERS
231===========
232-------------------------------------------------------------------------------
233list of eBPF helper functions
234-------------------------------------------------------------------------------
235
236:Manual section: 7
237
238DESCRIPTION
239===========
240
241The extended Berkeley Packet Filter (eBPF) subsystem consists in programs
242written in a pseudo-assembly language, then attached to one of the several
243kernel hooks and run in reaction of specific events. This framework differs
244from the older, "classic" BPF (or "cBPF") in several aspects, one of them being
245the ability to call special functions (or "helpers") from within a program.
246These functions are restricted to a white-list of helpers defined in the
247kernel.
248
249These helpers are used by eBPF programs to interact with the system, or with
250the context in which they work. For instance, they can be used to print
251debugging messages, to get the time since the system was booted, to interact
252with eBPF maps, or to manipulate network packets. Since there are several eBPF
253program types, and that they do not run in the same context, each program type
254can only call a subset of those helpers.
255
256Due to eBPF conventions, a helper can not have more than five arguments.
257
258Internally, eBPF programs call directly into the compiled helper functions
259without requiring any foreign-function interface. As a result, calling helpers
260introduces no overhead, thus offering excellent performance.
261
262This document is an attempt to list and document the helpers available to eBPF
263developers. They are sorted by chronological order (the oldest helpers in the
264kernel at the top).
265
266HELPERS
267=======
268'''
269 print(header)
270
271 def print_footer(self):
272 footer = '''
273EXAMPLES
274========
275
276Example usage for most of the eBPF helpers listed in this manual page are
277available within the Linux kernel sources, at the following locations:
278
279* *samples/bpf/*
280* *tools/testing/selftests/bpf/*
281
282LICENSE
283=======
284
285eBPF programs can have an associated license, passed along with the bytecode
286instructions to the kernel when the programs are loaded. The format for that
287string is identical to the one in use for kernel modules (Dual licenses, such
288as "Dual BSD/GPL", may be used). Some helper functions are only accessible to
289programs that are compatible with the GNU Privacy License (GPL).
290
291In order to use such helpers, the eBPF program must be loaded with the correct
292license string passed (via **attr**) to the **bpf**\ () system call, and this
293generally translates into the C source code of the program containing a line
294similar to the following:
295
296::
297
298 char ____license[] __attribute__((section("license"), used)) = "GPL";
299
300IMPLEMENTATION
301==============
302
303This manual page is an effort to document the existing eBPF helper functions.
304But as of this writing, the BPF sub-system is under heavy development. New eBPF
305program or map types are added, along with new helper functions. Some helpers
306are occasionally made available for additional program types. So in spite of
307the efforts of the community, this page might not be up-to-date. If you want to
308check by yourself what helper functions exist in your kernel, or what types of
309programs they can support, here are some files among the kernel tree that you
310may be interested in:
311
312* *include/uapi/linux/bpf.h* is the main BPF header. It contains the full list
313 of all helper functions, as well as many other BPF definitions including most
314 of the flags, structs or constants used by the helpers.
315* *net/core/filter.c* contains the definition of most network-related helper
316 functions, and the list of program types from which they can be used.
317* *kernel/trace/bpf_trace.c* is the equivalent for most tracing program-related
318 helpers.
319* *kernel/bpf/verifier.c* contains the functions used to check that valid types
320 of eBPF maps are used with a given helper function.
321* *kernel/bpf/* directory contains other files in which additional helpers are
322 defined (for cgroups, sockmaps, etc.).
323
324Compatibility between helper functions and program types can generally be found
325in the files where helper functions are defined. Look for the **struct
326bpf_func_proto** objects and for functions returning them: these functions
327contain a list of helpers that a given program type can call. Note that the
328**default:** label of the **switch ... case** used to filter helpers can call
329other functions, themselves allowing access to additional helpers. The
330requirement for GPL license is also in those **struct bpf_func_proto**.
331
332Compatibility between helper functions and map types can be found in the
333**check_map_func_compatibility**\ () function in file *kernel/bpf/verifier.c*.
334
335Helper functions that invalidate the checks on **data** and **data_end**
336pointers for network processing are listed in function
337**bpf_helper_changes_pkt_data**\ () in file *net/core/filter.c*.
338
339SEE ALSO
340========
341
342**bpf**\ (2),
343**cgroups**\ (7),
344**ip**\ (8),
345**perf_event_open**\ (2),
346**sendmsg**\ (2),
347**socket**\ (7),
348**tc-bpf**\ (8)'''
349 print(footer)
350
351 def print_proto(self, helper):
352 """
353 Format function protocol with bold and italics markers. This makes RST
354 file less readable, but gives nice results in the manual page.
355 """
356 proto = helper.proto_break_down()
357
358 print('**%s %s%s(' % (proto['ret_type'],
359 proto['ret_star'].replace('*', '\\*'),
360 proto['name']),
361 end='')
362
363 comma = ''
364 for a in proto['args']:
365 one_arg = '{}{}'.format(comma, a['type'])
366 if a['name']:
367 if a['star']:
368 one_arg += ' {}**\ '.format(a['star'].replace('*', '\\*'))
369 else:
370 one_arg += '** '
371 one_arg += '*{}*\\ **'.format(a['name'])
372 comma = ', '
373 print(one_arg, end='')
374
375 print(')**')
376
377 def print_one(self, helper):
378 self.print_proto(helper)
379
380 if (helper.desc):
381 print('\tDescription')
382 # Do not strip all newline characters: formatted code at the end of
383 # a section must be followed by a blank line.
384 for line in re.sub('\n$', '', helper.desc, count=1).split('\n'):
385 print('{}{}'.format('\t\t' if line else '', line))
386
387 if (helper.ret):
388 print('\tReturn')
389 for line in helper.ret.rstrip().split('\n'):
390 print('{}{}'.format('\t\t' if line else '', line))
391
392 print('')
393
394###############################################################################
395
396# If script is launched from scripts/ from kernel tree and can access
397# ../include/uapi/linux/bpf.h, use it as a default name for the file to parse,
398# otherwise the --filename argument will be required from the command line.
399script = os.path.abspath(sys.argv[0])
400linuxRoot = os.path.dirname(os.path.dirname(script))
401bpfh = os.path.join(linuxRoot, 'include/uapi/linux/bpf.h')
402
403argParser = argparse.ArgumentParser(description="""
404Parse eBPF header file and generate documentation for eBPF helper functions.
405The RST-formatted output produced can be turned into a manual page with the
406rst2man utility.
407""")
408if (os.path.isfile(bpfh)):
409 argParser.add_argument('--filename', help='path to include/uapi/linux/bpf.h',
410 default=bpfh)
411else:
412 argParser.add_argument('--filename', help='path to include/uapi/linux/bpf.h')
413args = argParser.parse_args()
414
415# Parse file.
416headerParser = HeaderParser(args.filename)
417headerParser.run()
418
419# Print formatted output to standard output.
420printer = PrinterRST(headerParser.helpers)
421printer.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
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_sock',
412 'struct bpf_sock_addr',
413 'struct bpf_sock_ops',
414 'struct bpf_sock_tuple',
415 'struct bpf_spin_lock',
416 'struct bpf_sysctl',
417 'struct bpf_tcp_sock',
418 'struct bpf_tunnel_key',
419 'struct bpf_xfrm_state',
420 'struct pt_regs',
421 'struct sk_reuseport_md',
422 'struct sockaddr',
423 'struct tcphdr',
424 'struct seq_file',
425 'struct tcp6_sock',
426 'struct tcp_sock',
427 'struct tcp_timewait_sock',
428 'struct tcp_request_sock',
429 'struct udp6_sock',
430 'struct task_struct',
431
432 'struct __sk_buff',
433 'struct sk_msg_md',
434 'struct xdp_md',
435 ]
436 known_types = {
437 '...',
438 'void',
439 'const void',
440 'char',
441 'const char',
442 'int',
443 'long',
444 'unsigned long',
445
446 '__be16',
447 '__be32',
448 '__wsum',
449
450 'struct bpf_fib_lookup',
451 'struct bpf_perf_event_data',
452 'struct bpf_perf_event_value',
453 'struct bpf_pidns_info',
454 'struct bpf_sk_lookup',
455 'struct bpf_sock',
456 'struct bpf_sock_addr',
457 'struct bpf_sock_ops',
458 'struct bpf_sock_tuple',
459 'struct bpf_spin_lock',
460 'struct bpf_sysctl',
461 'struct bpf_tcp_sock',
462 'struct bpf_tunnel_key',
463 'struct bpf_xfrm_state',
464 'struct pt_regs',
465 'struct sk_reuseport_md',
466 'struct sockaddr',
467 'struct tcphdr',
468 'struct seq_file',
469 'struct tcp6_sock',
470 'struct tcp_sock',
471 'struct tcp_timewait_sock',
472 'struct tcp_request_sock',
473 'struct udp6_sock',
474 'struct task_struct',
475 }
476 mapped_types = {
477 'u8': '__u8',
478 'u16': '__u16',
479 'u32': '__u32',
480 'u64': '__u64',
481 's8': '__s8',
482 's16': '__s16',
483 's32': '__s32',
484 's64': '__s64',
485 'size_t': 'unsigned long',
486 'struct bpf_map': 'void',
487 'struct sk_buff': 'struct __sk_buff',
488 'const struct sk_buff': 'const struct __sk_buff',
489 'struct sk_msg_buff': 'struct sk_msg_md',
490 'struct xdp_buff': 'struct xdp_md',
491 }
492 # Helpers overloaded for different context types.
493 overloaded_helpers = [
494 'bpf_get_socket_cookie',
495 'bpf_sk_assign',
496 ]
497
498 def print_header(self):
499 header = '''\
500/* This is auto-generated file. See bpf_helpers_doc.py for details. */
501
502/* Forward declarations of BPF structs */'''
503
504 print(header)
505 for fwd in self.type_fwds:
506 print('%s;' % fwd)
507 print('')
508
509 def print_footer(self):
510 footer = ''
511 print(footer)
512
513 def map_type(self, t):
514 if t in self.known_types:
515 return t
516 if t in self.mapped_types:
517 return self.mapped_types[t]
518 print("Unrecognized type '%s', please add it to known types!" % t,
519 file=sys.stderr)
520 sys.exit(1)
521
522 seen_helpers = set()
523
524 def print_one(self, helper):
525 proto = helper.proto_break_down()
526
527 if proto['name'] in self.seen_helpers:
528 return
529 self.seen_helpers.add(proto['name'])
530
531 print('/*')
532 print(" * %s" % proto['name'])
533 print(" *")
534 if (helper.desc):
535 # Do not strip all newline characters: formatted code at the end of
536 # a section must be followed by a blank line.
537 for line in re.sub('\n$', '', helper.desc, count=1).split('\n'):
538 print(' *{}{}'.format(' \t' if line else '', line))
539
540 if (helper.ret):
541 print(' *')
542 print(' * Returns')
543 for line in helper.ret.rstrip().split('\n'):
544 print(' *{}{}'.format(' \t' if line else '', line))
545
546 print(' */')
547 print('static %s %s(*%s)(' % (self.map_type(proto['ret_type']),
548 proto['ret_star'], proto['name']), end='')
549 comma = ''
550 for i, a in enumerate(proto['args']):
551 t = a['type']
552 n = a['name']
553 if proto['name'] in self.overloaded_helpers and i == 0:
554 t = 'void'
555 n = 'ctx'
556 one_arg = '{}{}'.format(comma, self.map_type(t))
557 if n:
558 if a['star']:
559 one_arg += ' {}'.format(a['star'])
560 else:
561 one_arg += ' '
562 one_arg += '{}'.format(n)
563 comma = ', '
564 print(one_arg, end='')
565
566 print(') = (void *) %d;' % len(self.seen_helpers))
567 print('')
568
569###############################################################################
570
571# If script is launched from scripts/ from kernel tree and can access
572# ../include/uapi/linux/bpf.h, use it as a default name for the file to parse,
573# otherwise the --filename argument will be required from the command line.
574script = os.path.abspath(sys.argv[0])
575linuxRoot = os.path.dirname(os.path.dirname(script))
576bpfh = os.path.join(linuxRoot, 'include/uapi/linux/bpf.h')
577
578argParser = argparse.ArgumentParser(description="""
579Parse eBPF header file and generate documentation for eBPF helper functions.
580The RST-formatted output produced can be turned into a manual page with the
581rst2man utility.
582""")
583argParser.add_argument('--header', action='store_true',
584 help='generate C header file')
585if (os.path.isfile(bpfh)):
586 argParser.add_argument('--filename', help='path to include/uapi/linux/bpf.h',
587 default=bpfh)
588else:
589 argParser.add_argument('--filename', help='path to include/uapi/linux/bpf.h')
590args = argParser.parse_args()
591
592# Parse file.
593headerParser = HeaderParser(args.filename)
594headerParser.run()
595
596# Print formatted output to standard output.
597if args.header:
598 printer = PrinterHelpers(headerParser.helpers)
599else:
600 printer = PrinterRST(headerParser.helpers)
601printer.print_all()