422 lines
15 KiB
Python
422 lines
15 KiB
Python
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#!/usr/bin/python3
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# SPDX-License-Identifier: GPL-2.0-only
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#
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# Copyright (C) 2018 Netronome Systems, Inc.
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# In case user attempts to run with Python 2.
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from __future__ import print_function
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import argparse
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import re
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import sys, os
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class NoHelperFound(BaseException):
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pass
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class ParsingError(BaseException):
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def __init__(self, line='<line not provided>', reader=None):
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if reader:
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BaseException.__init__(self,
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'Error at file offset %d, parsing line: %s' %
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(reader.tell(), line))
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else:
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BaseException.__init__(self, 'Error parsing line: %s' % line)
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class Helper(object):
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"""
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An object representing the description of an eBPF helper function.
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@proto: function prototype of the helper function
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@desc: textual description of the helper function
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@ret: description of the return value of the helper function
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"""
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def __init__(self, proto='', desc='', ret=''):
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self.proto = proto
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self.desc = desc
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self.ret = ret
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def proto_break_down(self):
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"""
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Break down helper function protocol into smaller chunks: return type,
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name, distincts arguments.
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"""
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arg_re = re.compile('^((const )?(struct )?(\w+|...))( (\**)(\w+))?$')
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res = {}
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proto_re = re.compile('^(.+) (\**)(\w+)\(((([^,]+)(, )?){1,5})\)$')
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capture = proto_re.match(self.proto)
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res['ret_type'] = capture.group(1)
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res['ret_star'] = capture.group(2)
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res['name'] = capture.group(3)
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res['args'] = []
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args = capture.group(4).split(', ')
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for a in args:
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capture = arg_re.match(a)
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res['args'].append({
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'type' : capture.group(1),
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'star' : capture.group(6),
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'name' : capture.group(7)
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})
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return res
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class HeaderParser(object):
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"""
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An object used to parse a file in order to extract the documentation of a
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list of eBPF helper functions. All the helpers that can be retrieved are
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stored as Helper object, in the self.helpers() array.
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@filename: name of file to parse, usually include/uapi/linux/bpf.h in the
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kernel tree
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"""
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def __init__(self, filename):
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self.reader = open(filename, 'r')
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self.line = ''
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self.helpers = []
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def parse_helper(self):
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proto = self.parse_proto()
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desc = self.parse_desc()
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ret = self.parse_ret()
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return Helper(proto=proto, desc=desc, ret=ret)
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def parse_proto(self):
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# Argument can be of shape:
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# - "void"
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# - "type name"
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# - "type *name"
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# - Same as above, with "const" and/or "struct" in front of type
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# - "..." (undefined number of arguments, for bpf_trace_printk())
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# There is at least one term ("void"), and at most five arguments.
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p = re.compile('^ \* ((.+) \**\w+\((((const )?(struct )?(\w+|\.\.\.)( \**\w+)?)(, )?){1,5}\))$')
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capture = p.match(self.line)
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if not capture:
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raise NoHelperFound
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self.line = self.reader.readline()
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return capture.group(1)
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def parse_desc(self):
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p = re.compile('^ \* \tDescription$')
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capture = p.match(self.line)
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if not capture:
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# Helper can have empty description and we might be parsing another
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# attribute: return but do not consume.
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return ''
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# Description can be several lines, some of them possibly empty, and it
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# stops when another subsection title is met.
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desc = ''
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while True:
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self.line = self.reader.readline()
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if self.line == ' *\n':
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desc += '\n'
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else:
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p = re.compile('^ \* \t\t(.*)')
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capture = p.match(self.line)
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if capture:
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desc += capture.group(1) + '\n'
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else:
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break
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return desc
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def parse_ret(self):
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p = re.compile('^ \* \tReturn$')
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capture = p.match(self.line)
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if not capture:
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# Helper can have empty retval and we might be parsing another
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# attribute: return but do not consume.
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return ''
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# Return value description can be several lines, some of them possibly
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# empty, and it stops when another subsection title is met.
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ret = ''
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while True:
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self.line = self.reader.readline()
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if self.line == ' *\n':
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ret += '\n'
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else:
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p = re.compile('^ \* \t\t(.*)')
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capture = p.match(self.line)
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if capture:
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ret += capture.group(1) + '\n'
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else:
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break
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return ret
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def run(self):
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# Advance to start of helper function descriptions.
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offset = self.reader.read().find('* Start of BPF helper function descriptions:')
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if offset == -1:
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raise Exception('Could not find start of eBPF helper descriptions list')
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self.reader.seek(offset)
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self.reader.readline()
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self.reader.readline()
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self.line = self.reader.readline()
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while True:
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try:
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helper = self.parse_helper()
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self.helpers.append(helper)
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except NoHelperFound:
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break
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self.reader.close()
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print('Parsed description of %d helper function(s)' % len(self.helpers),
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file=sys.stderr)
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###############################################################################
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class Printer(object):
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"""
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A generic class for printers. Printers should be created with an array of
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Helper objects, and implement a way to print them in the desired fashion.
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@helpers: array of Helper objects to print to standard output
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"""
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def __init__(self, helpers):
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self.helpers = helpers
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def print_header(self):
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pass
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def print_footer(self):
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pass
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def print_one(self, helper):
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pass
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def print_all(self):
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self.print_header()
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for helper in self.helpers:
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self.print_one(helper)
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self.print_footer()
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class PrinterRST(Printer):
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"""
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A printer for dumping collected information about helpers as a ReStructured
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Text page compatible with the rst2man program, which can be used to
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generate a manual page for the helpers.
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@helpers: array of Helper objects to print to standard output
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"""
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def print_header(self):
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header = '''\
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.. Copyright (C) All BPF authors and contributors from 2014 to present.
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.. See git log include/uapi/linux/bpf.h in kernel tree for details.
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..
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.. %%%LICENSE_START(VERBATIM)
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.. Permission is granted to make and distribute verbatim copies of this
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.. manual provided the copyright notice and this permission notice are
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.. preserved on all copies.
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..
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.. Permission is granted to copy and distribute modified versions of this
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.. manual under the conditions for verbatim copying, provided that the
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.. entire resulting derived work is distributed under the terms of a
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.. permission notice identical to this one.
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..
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.. Since the Linux kernel and libraries are constantly changing, this
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.. manual page may be incorrect or out-of-date. The author(s) assume no
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.. responsibility for errors or omissions, or for damages resulting from
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.. the use of the information contained herein. The author(s) may not
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.. have taken the same level of care in the production of this manual,
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.. which is licensed free of charge, as they might when working
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.. professionally.
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..
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.. Formatted or processed versions of this manual, if unaccompanied by
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.. the source, must acknowledge the copyright and authors of this work.
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.. %%%LICENSE_END
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..
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.. Please do not edit this file. It was generated from the documentation
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.. located in file include/uapi/linux/bpf.h of the Linux kernel sources
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.. (helpers description), and from scripts/bpf_helpers_doc.py in the same
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.. repository (header and footer).
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===========
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BPF-HELPERS
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===========
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-------------------------------------------------------------------------------
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list of eBPF helper functions
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-------------------------------------------------------------------------------
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:Manual section: 7
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DESCRIPTION
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===========
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The extended Berkeley Packet Filter (eBPF) subsystem consists in programs
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written in a pseudo-assembly language, then attached to one of the several
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kernel hooks and run in reaction of specific events. This framework differs
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from the older, "classic" BPF (or "cBPF") in several aspects, one of them being
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the ability to call special functions (or "helpers") from within a program.
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These functions are restricted to a white-list of helpers defined in the
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kernel.
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These helpers are used by eBPF programs to interact with the system, or with
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the context in which they work. For instance, they can be used to print
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debugging messages, to get the time since the system was booted, to interact
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with eBPF maps, or to manipulate network packets. Since there are several eBPF
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program types, and that they do not run in the same context, each program type
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can only call a subset of those helpers.
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Due to eBPF conventions, a helper can not have more than five arguments.
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Internally, eBPF programs call directly into the compiled helper functions
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without requiring any foreign-function interface. As a result, calling helpers
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introduces no overhead, thus offering excellent performance.
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This document is an attempt to list and document the helpers available to eBPF
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developers. They are sorted by chronological order (the oldest helpers in the
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kernel at the top).
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HELPERS
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=======
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'''
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print(header)
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def print_footer(self):
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footer = '''
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EXAMPLES
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========
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Example usage for most of the eBPF helpers listed in this manual page are
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available within the Linux kernel sources, at the following locations:
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* *samples/bpf/*
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* *tools/testing/selftests/bpf/*
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LICENSE
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=======
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eBPF programs can have an associated license, passed along with the bytecode
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instructions to the kernel when the programs are loaded. The format for that
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string is identical to the one in use for kernel modules (Dual licenses, such
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as "Dual BSD/GPL", may be used). Some helper functions are only accessible to
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programs that are compatible with the GNU Privacy License (GPL).
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In order to use such helpers, the eBPF program must be loaded with the correct
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license string passed (via **attr**) to the **bpf**\ () system call, and this
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generally translates into the C source code of the program containing a line
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similar to the following:
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::
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char ____license[] __attribute__((section("license"), used)) = "GPL";
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IMPLEMENTATION
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==============
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This manual page is an effort to document the existing eBPF helper functions.
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But as of this writing, the BPF sub-system is under heavy development. New eBPF
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program or map types are added, along with new helper functions. Some helpers
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are occasionally made available for additional program types. So in spite of
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the efforts of the community, this page might not be up-to-date. If you want to
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check by yourself what helper functions exist in your kernel, or what types of
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programs they can support, here are some files among the kernel tree that you
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may be interested in:
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* *include/uapi/linux/bpf.h* is the main BPF header. It contains the full list
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of all helper functions, as well as many other BPF definitions including most
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of the flags, structs or constants used by the helpers.
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* *net/core/filter.c* contains the definition of most network-related helper
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functions, and the list of program types from which they can be used.
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* *kernel/trace/bpf_trace.c* is the equivalent for most tracing program-related
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helpers.
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* *kernel/bpf/verifier.c* contains the functions used to check that valid types
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of eBPF maps are used with a given helper function.
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* *kernel/bpf/* directory contains other files in which additional helpers are
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defined (for cgroups, sockmaps, etc.).
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Compatibility between helper functions and program types can generally be found
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in the files where helper functions are defined. Look for the **struct
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bpf_func_proto** objects and for functions returning them: these functions
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contain a list of helpers that a given program type can call. Note that the
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**default:** label of the **switch ... case** used to filter helpers can call
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other functions, themselves allowing access to additional helpers. The
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requirement for GPL license is also in those **struct bpf_func_proto**.
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Compatibility between helper functions and map types can be found in the
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**check_map_func_compatibility**\ () function in file *kernel/bpf/verifier.c*.
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Helper functions that invalidate the checks on **data** and **data_end**
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pointers for network processing are listed in function
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**bpf_helper_changes_pkt_data**\ () in file *net/core/filter.c*.
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SEE ALSO
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========
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**bpf**\ (2),
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**cgroups**\ (7),
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**ip**\ (8),
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**perf_event_open**\ (2),
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**sendmsg**\ (2),
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**socket**\ (7),
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**tc-bpf**\ (8)'''
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print(footer)
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def print_proto(self, helper):
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"""
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Format function protocol with bold and italics markers. This makes RST
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file less readable, but gives nice results in the manual page.
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"""
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proto = helper.proto_break_down()
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print('**%s %s%s(' % (proto['ret_type'],
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proto['ret_star'].replace('*', '\\*'),
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proto['name']),
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end='')
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comma = ''
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for a in proto['args']:
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one_arg = '{}{}'.format(comma, a['type'])
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if a['name']:
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if a['star']:
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one_arg += ' {}**\ '.format(a['star'].replace('*', '\\*'))
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else:
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one_arg += '** '
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one_arg += '*{}*\\ **'.format(a['name'])
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comma = ', '
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print(one_arg, end='')
|
||
|
|
|
||
|
|
print(')**')
|
||
|
|
|
||
|
|
def print_one(self, helper):
|
||
|
|
self.print_proto(helper)
|
||
|
|
|
||
|
|
if (helper.desc):
|
||
|
|
print('\tDescription')
|
||
|
|
# Do not strip all newline characters: formatted code at the end of
|
||
|
|
# a section must be followed by a blank line.
|
||
|
|
for line in re.sub('\n$', '', helper.desc, count=1).split('\n'):
|
||
|
|
print('{}{}'.format('\t\t' if line else '', line))
|
||
|
|
|
||
|
|
if (helper.ret):
|
||
|
|
print('\tReturn')
|
||
|
|
for line in helper.ret.rstrip().split('\n'):
|
||
|
|
print('{}{}'.format('\t\t' if line else '', line))
|
||
|
|
|
||
|
|
print('')
|
||
|
|
|
||
|
|
###############################################################################
|
||
|
|
|
||
|
|
# If script is launched from scripts/ from kernel tree and can access
|
||
|
|
# ../include/uapi/linux/bpf.h, use it as a default name for the file to parse,
|
||
|
|
# otherwise the --filename argument will be required from the command line.
|
||
|
|
script = os.path.abspath(sys.argv[0])
|
||
|
|
linuxRoot = os.path.dirname(os.path.dirname(script))
|
||
|
|
bpfh = os.path.join(linuxRoot, 'include/uapi/linux/bpf.h')
|
||
|
|
|
||
|
|
argParser = argparse.ArgumentParser(description="""
|
||
|
|
Parse eBPF header file and generate documentation for eBPF helper functions.
|
||
|
|
The RST-formatted output produced can be turned into a manual page with the
|
||
|
|
rst2man utility.
|
||
|
|
""")
|
||
|
|
if (os.path.isfile(bpfh)):
|
||
|
|
argParser.add_argument('--filename', help='path to include/uapi/linux/bpf.h',
|
||
|
|
default=bpfh)
|
||
|
|
else:
|
||
|
|
argParser.add_argument('--filename', help='path to include/uapi/linux/bpf.h')
|
||
|
|
args = argParser.parse_args()
|
||
|
|
|
||
|
|
# Parse file.
|
||
|
|
headerParser = HeaderParser(args.filename)
|
||
|
|
headerParser.run()
|
||
|
|
|
||
|
|
# Print formatted output to standard output.
|
||
|
|
printer = PrinterRST(headerParser.helpers)
|
||
|
|
printer.print_all()
|