Adding upstream version 6.1.76.upstream/6.1.76

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 872 insertions, 0 deletions

diff --git a/scripts/bpf_doc.py b/scripts/bpf_doc.py
new file mode 100755
index 000000000..d5c389df6
--- /dev/null
+++ b/scripts/bpf_doc.py
@@ -0,0 +1,872 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# Copyright (C) 2018-2019 Netronome Systems, Inc.
+# Copyright (C) 2021 Isovalent, Inc.
+
+# In case user attempts to run with Python 2.
+from __future__ import print_function
+
+import argparse
+import re
+import sys, os
+import subprocess
+
+helpersDocStart = 'Start of BPF helper function descriptions:'
+
+class NoHelperFound(BaseException):
+    pass
+
+class NoSyscallCommandFound(BaseException):
+    pass
+
+class ParsingError(BaseException):
+    def __init__(self, line='<line not provided>', reader=None):
+        if reader:
+            BaseException.__init__(self,
+                                   'Error at file offset %d, parsing line: %s' %
+                                   (reader.tell(), line))
+        else:
+            BaseException.__init__(self, 'Error parsing line: %s' % line)
+
+
+class APIElement(object):
+    """
+    An object representing the description of an aspect of the eBPF API.
+    @proto: prototype of the API symbol
+    @desc: textual description of the symbol
+    @ret: (optional) description of any associated return value
+    """
+    def __init__(self, proto='', desc='', ret=''):
+        self.proto = proto
+        self.desc = desc
+        self.ret = ret
+
+
+class Helper(APIElement):
+    """
+    An object representing the description of an eBPF helper function.
+    @proto: function prototype of the helper function
+    @desc: textual description of the helper function
+    @ret: description of the return value of the helper function
+    """
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        self.enum_val = None
+
+    def proto_break_down(self):
+        """
+        Break down helper function protocol into smaller chunks: return type,
+        name, distincts arguments.
+        """
+        arg_re = re.compile('((\w+ )*?(\w+|...))( (\**)(\w+))?$')
+        res = {}
+        proto_re = re.compile('(.+) (\**)(\w+)\(((([^,]+)(, )?){1,5})\)$')
+
+        capture = proto_re.match(self.proto)
+        res['ret_type'] = capture.group(1)
+        res['ret_star'] = capture.group(2)
+        res['name']     = capture.group(3)
+        res['args'] = []
+
+        args    = capture.group(4).split(', ')
+        for a in args:
+            capture = arg_re.match(a)
+            res['args'].append({
+                'type' : capture.group(1),
+                'star' : capture.group(5),
+                'name' : capture.group(6)
+            })
+
+        return res
+
+
+class HeaderParser(object):
+    """
+    An object used to parse a file in order to extract the documentation of a
+    list of eBPF helper functions. All the helpers that can be retrieved are
+    stored as Helper object, in the self.helpers() array.
+    @filename: name of file to parse, usually include/uapi/linux/bpf.h in the
+               kernel tree
+    """
+    def __init__(self, filename):
+        self.reader = open(filename, 'r')
+        self.line = ''
+        self.helpers = []
+        self.commands = []
+        self.desc_unique_helpers = set()
+        self.define_unique_helpers = []
+        self.helper_enum_vals = {}
+        self.desc_syscalls = []
+        self.enum_syscalls = []
+
+    def parse_element(self):
+        proto    = self.parse_symbol()
+        desc     = self.parse_desc(proto)
+        ret      = self.parse_ret(proto)
+        return APIElement(proto=proto, desc=desc, ret=ret)
+
+    def parse_helper(self):
+        proto    = self.parse_proto()
+        desc     = self.parse_desc(proto)
+        ret      = self.parse_ret(proto)
+        return Helper(proto=proto, desc=desc, ret=ret)
+
+    def parse_symbol(self):
+        p = re.compile(' \* ?(BPF\w+)$')
+        capture = p.match(self.line)
+        if not capture:
+            raise NoSyscallCommandFound
+        end_re = re.compile(' \* ?NOTES$')
+        end = end_re.match(self.line)
+        if end:
+            raise NoSyscallCommandFound
+        self.line = self.reader.readline()
+        return capture.group(1)
+
+    def parse_proto(self):
+        # Argument can be of shape:
+        #   - "void"
+        #   - "type  name"
+        #   - "type *name"
+        #   - Same as above, with "const" and/or "struct" in front of type
+        #   - "..." (undefined number of arguments, for bpf_trace_printk())
+        # There is at least one term ("void"), and at most five arguments.
+        p = re.compile(' \* ?((.+) \**\w+\((((const )?(struct )?(\w+|\.\.\.)( \**\w+)?)(, )?){1,5}\))$')
+        capture = p.match(self.line)
+        if not capture:
+            raise NoHelperFound
+        self.line = self.reader.readline()
+        return capture.group(1)
+
+    def parse_desc(self, proto):
+        p = re.compile(' \* ?(?:\t| {5,8})Description$')
+        capture = p.match(self.line)
+        if not capture:
+            raise Exception("No description section found for " + proto)
+        # Description can be several lines, some of them possibly empty, and it
+        # stops when another subsection title is met.
+        desc = ''
+        desc_present = False
+        while True:
+            self.line = self.reader.readline()
+            if self.line == ' *\n':
+                desc += '\n'
+            else:
+                p = re.compile(' \* ?(?:\t| {5,8})(?:\t| {8})(.*)')
+                capture = p.match(self.line)
+                if capture:
+                    desc_present = True
+                    desc += capture.group(1) + '\n'
+                else:
+                    break
+
+        if not desc_present:
+            raise Exception("No description found for " + proto)
+        return desc
+
+    def parse_ret(self, proto):
+        p = re.compile(' \* ?(?:\t| {5,8})Return$')
+        capture = p.match(self.line)
+        if not capture:
+            raise Exception("No return section found for " + proto)
+        # Return value description can be several lines, some of them possibly
+        # empty, and it stops when another subsection title is met.
+        ret = ''
+        ret_present = False
+        while True:
+            self.line = self.reader.readline()
+            if self.line == ' *\n':
+                ret += '\n'
+            else:
+                p = re.compile(' \* ?(?:\t| {5,8})(?:\t| {8})(.*)')
+                capture = p.match(self.line)
+                if capture:
+                    ret_present = True
+                    ret += capture.group(1) + '\n'
+                else:
+                    break
+
+        if not ret_present:
+            raise Exception("No return found for " + proto)
+        return ret
+
+    def seek_to(self, target, help_message, discard_lines = 1):
+        self.reader.seek(0)
+        offset = self.reader.read().find(target)
+        if offset == -1:
+            raise Exception(help_message)
+        self.reader.seek(offset)
+        self.reader.readline()
+        for _ in range(discard_lines):
+            self.reader.readline()
+        self.line = self.reader.readline()
+
+    def parse_desc_syscall(self):
+        self.seek_to('* DOC: eBPF Syscall Commands',
+                     'Could not find start of eBPF syscall descriptions list')
+        while True:
+            try:
+                command = self.parse_element()
+                self.commands.append(command)
+                self.desc_syscalls.append(command.proto)
+
+            except NoSyscallCommandFound:
+                break
+
+    def parse_enum_syscall(self):
+        self.seek_to('enum bpf_cmd {',
+                     'Could not find start of bpf_cmd enum', 0)
+        # Searches for either one or more BPF\w+ enums
+        bpf_p = re.compile('\s*(BPF\w+)+')
+        # Searches for an enum entry assigned to another entry,
+        # for e.g. BPF_PROG_RUN = BPF_PROG_TEST_RUN, which is
+        # not documented hence should be skipped in check to
+        # determine if the right number of syscalls are documented
+        assign_p = re.compile('\s*(BPF\w+)\s*=\s*(BPF\w+)')
+        bpf_cmd_str = ''
+        while True:
+            capture = assign_p.match(self.line)
+            if capture:
+                # Skip line if an enum entry is assigned to another entry
+                self.line = self.reader.readline()
+                continue
+            capture = bpf_p.match(self.line)
+            if capture:
+                bpf_cmd_str += self.line
+            else:
+                break
+            self.line = self.reader.readline()
+        # Find the number of occurences of BPF\w+
+        self.enum_syscalls = re.findall('(BPF\w+)+', bpf_cmd_str)
+
+    def parse_desc_helpers(self):
+        self.seek_to(helpersDocStart,
+                     'Could not find start of eBPF helper descriptions list')
+        while True:
+            try:
+                helper = self.parse_helper()
+                self.helpers.append(helper)
+                proto = helper.proto_break_down()
+                self.desc_unique_helpers.add(proto['name'])
+            except NoHelperFound:
+                break
+
+    def parse_define_helpers(self):
+        # Parse FN(...) in #define __BPF_FUNC_MAPPER to compare later with the
+        # number of unique function names present in description and use the
+        # correct enumeration value.
+        # Note: seek_to(..) discards the first line below the target search text,
+        # resulting in FN(unspec) being skipped and not added to self.define_unique_helpers.
+        self.seek_to('#define __BPF_FUNC_MAPPER(FN)',
+                     'Could not find start of eBPF helper definition list')
+        # Searches for one FN(\w+) define or a backslash for newline
+        p = re.compile('\s*FN\((\w+)\)|\\\\')
+        fn_defines_str = ''
+        i = 1  # 'unspec' is skipped as mentioned above
+        while True:
+            capture = p.match(self.line)
+            if capture:
+                fn_defines_str += self.line
+                self.helper_enum_vals[capture.expand(r'bpf_\1')] = i
+                i += 1
+            else:
+                break
+            self.line = self.reader.readline()
+        # Find the number of occurences of FN(\w+)
+        self.define_unique_helpers = re.findall('FN\(\w+\)', fn_defines_str)
+
+    def assign_helper_values(self):
+        seen_helpers = set()
+        for helper in self.helpers:
+            proto = helper.proto_break_down()
+            name = proto['name']
+            try:
+                enum_val = self.helper_enum_vals[name]
+            except KeyError:
+                raise Exception("Helper %s is missing from enum bpf_func_id" % name)
+
+            # Enforce current practice of having the descriptions ordered
+            # by enum value.
+            seen_helpers.add(name)
+            desc_val = len(seen_helpers)
+            if desc_val != enum_val:
+                raise Exception("Helper %s comment order (#%d) must be aligned with its position (#%d) in enum bpf_func_id" % (name, desc_val, enum_val))
+
+            helper.enum_val = enum_val
+
+    def run(self):
+        self.parse_desc_syscall()
+        self.parse_enum_syscall()
+        self.parse_desc_helpers()
+        self.parse_define_helpers()
+        self.assign_helper_values()
+        self.reader.close()
+
+###############################################################################
+
+class Printer(object):
+    """
+    A generic class for printers. Printers should be created with an array of
+    Helper objects, and implement a way to print them in the desired fashion.
+    @parser: A HeaderParser with objects to print to standard output
+    """
+    def __init__(self, parser):
+        self.parser = parser
+        self.elements = []
+
+    def print_header(self):
+        pass
+
+    def print_footer(self):
+        pass
+
+    def print_one(self, helper):
+        pass
+
+    def print_all(self):
+        self.print_header()
+        for elem in self.elements:
+            self.print_one(elem)
+        self.print_footer()
+
+    def elem_number_check(self, desc_unique_elem, define_unique_elem, type, instance):
+        """
+        Checks the number of helpers/syscalls documented within the header file
+        description with those defined as part of enum/macro and raise an
+        Exception if they don't match.
+        """
+        nr_desc_unique_elem = len(desc_unique_elem)
+        nr_define_unique_elem = len(define_unique_elem)
+        if nr_desc_unique_elem != nr_define_unique_elem:
+            exception_msg = '''
+The number of unique %s in description (%d) doesn\'t match the number of unique %s defined in %s (%d)
+''' % (type, nr_desc_unique_elem, type, instance, nr_define_unique_elem)
+            if nr_desc_unique_elem < nr_define_unique_elem:
+                # Function description is parsed until no helper is found (which can be due to
+                # misformatting). Hence, only print the first missing/misformatted helper/enum.
+                exception_msg += '''
+The description for %s is not present or formatted correctly.
+''' % (define_unique_elem[nr_desc_unique_elem])
+            raise Exception(exception_msg)
+
+class PrinterRST(Printer):
+    """
+    A generic class for printers that print ReStructured Text. Printers should
+    be created with a HeaderParser object, and implement a way to print API
+    elements in the desired fashion.
+    @parser: A HeaderParser with objects to print to standard output
+    """
+    def __init__(self, parser):
+        self.parser = parser
+
+    def print_license(self):
+        license = '''\
+.. Copyright (C) All BPF authors and contributors from 2014 to present.
+.. See git log include/uapi/linux/bpf.h in kernel tree for details.
+.. 
+.. SPDX-License-Identifier:  Linux-man-pages-copyleft
+.. 
+.. Please do not edit this file. It was generated from the documentation
+.. located in file include/uapi/linux/bpf.h of the Linux kernel sources
+.. (helpers description), and from scripts/bpf_doc.py in the same
+.. repository (header and footer).
+'''
+        print(license)
+
+    def print_elem(self, elem):
+        if (elem.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$', '', elem.desc, count=1).split('\n'):
+                print('{}{}'.format('\t\t' if line else '', line))
+
+        if (elem.ret):
+            print('\tReturn')
+            for line in elem.ret.rstrip().split('\n'):
+                print('{}{}'.format('\t\t' if line else '', line))
+
+        print('')
+
+    def get_kernel_version(self):
+        try:
+            version = subprocess.run(['git', 'describe'], cwd=linuxRoot,
+                                     capture_output=True, check=True)
+            version = version.stdout.decode().rstrip()
+        except:
+            try:
+                version = subprocess.run(['make', 'kernelversion'], cwd=linuxRoot,
+                                         capture_output=True, check=True)
+                version = version.stdout.decode().rstrip()
+            except:
+                return 'Linux'
+        return 'Linux {version}'.format(version=version)
+
+    def get_last_doc_update(self, delimiter):
+        try:
+            cmd = ['git', 'log', '-1', '--pretty=format:%cs', '--no-patch',
+                   '-L',
+                   '/{}/,/\*\//:include/uapi/linux/bpf.h'.format(delimiter)]
+            date = subprocess.run(cmd, cwd=linuxRoot,
+                                  capture_output=True, check=True)
+            return date.stdout.decode().rstrip()
+        except:
+            return ''
+
+class PrinterHelpersRST(PrinterRST):
+    """
+    A printer for dumping collected information about helpers as a ReStructured
+    Text page compatible with the rst2man program, which can be used to
+    generate a manual page for the helpers.
+    @parser: A HeaderParser with Helper objects to print to standard output
+    """
+    def __init__(self, parser):
+        self.elements = parser.helpers
+        self.elem_number_check(parser.desc_unique_helpers, parser.define_unique_helpers, 'helper', '__BPF_FUNC_MAPPER')
+
+    def print_header(self):
+        header = '''\
+===========
+BPF-HELPERS
+===========
+-------------------------------------------------------------------------------
+list of eBPF helper functions
+-------------------------------------------------------------------------------
+
+:Manual section: 7
+:Version: {version}
+{date_field}{date}
+
+DESCRIPTION
+===========
+
+The extended Berkeley Packet Filter (eBPF) subsystem consists in programs
+written in a pseudo-assembly language, then attached to one of the several
+kernel hooks and run in reaction of specific events. This framework differs
+from the older, "classic" BPF (or "cBPF") in several aspects, one of them being
+the ability to call special functions (or "helpers") from within a program.
+These functions are restricted to a white-list of helpers defined in the
+kernel.
+
+These helpers are used by eBPF programs to interact with the system, or with
+the context in which they work. For instance, they can be used to print
+debugging messages, to get the time since the system was booted, to interact
+with eBPF maps, or to manipulate network packets. Since there are several eBPF
+program types, and that they do not run in the same context, each program type
+can only call a subset of those helpers.
+
+Due to eBPF conventions, a helper can not have more than five arguments.
+
+Internally, eBPF programs call directly into the compiled helper functions
+without requiring any foreign-function interface. As a result, calling helpers
+introduces no overhead, thus offering excellent performance.
+
+This document is an attempt to list and document the helpers available to eBPF
+developers. They are sorted by chronological order (the oldest helpers in the
+kernel at the top).
+
+HELPERS
+=======
+'''
+        kernelVersion = self.get_kernel_version()
+        lastUpdate = self.get_last_doc_update(helpersDocStart)
+
+        PrinterRST.print_license(self)
+        print(header.format(version=kernelVersion,
+                            date_field = ':Date: ' if lastUpdate else '',
+                            date=lastUpdate))
+
+    def print_footer(self):
+        footer = '''
+EXAMPLES
+========
+
+Example usage for most of the eBPF helpers listed in this manual page are
+available within the Linux kernel sources, at the following locations:
+
+* *samples/bpf/*
+* *tools/testing/selftests/bpf/*
+
+LICENSE
+=======
+
+eBPF programs can have an associated license, passed along with the bytecode
+instructions to the kernel when the programs are loaded. The format for that
+string is identical to the one in use for kernel modules (Dual licenses, such
+as "Dual BSD/GPL", may be used). Some helper functions are only accessible to
+programs that are compatible with the GNU Privacy License (GPL).
+
+In order to use such helpers, the eBPF program must be loaded with the correct
+license string passed (via **attr**) to the **bpf**\ () system call, and this
+generally translates into the C source code of the program containing a line
+similar to the following:
+
+::
+
+	char ____license[] __attribute__((section("license"), used)) = "GPL";
+
+IMPLEMENTATION
+==============
+
+This manual page is an effort to document the existing eBPF helper functions.
+But as of this writing, the BPF sub-system is under heavy development. New eBPF
+program or map types are added, along with new helper functions. Some helpers
+are occasionally made available for additional program types. So in spite of
+the efforts of the community, this page might not be up-to-date. If you want to
+check by yourself what helper functions exist in your kernel, or what types of
+programs they can support, here are some files among the kernel tree that you
+may be interested in:
+
+* *include/uapi/linux/bpf.h* is the main BPF header. It contains the full list
+  of all helper functions, as well as many other BPF definitions including most
+  of the flags, structs or constants used by the helpers.
+* *net/core/filter.c* contains the definition of most network-related helper
+  functions, and the list of program types from which they can be used.
+* *kernel/trace/bpf_trace.c* is the equivalent for most tracing program-related
+  helpers.
+* *kernel/bpf/verifier.c* contains the functions used to check that valid types
+  of eBPF maps are used with a given helper function.
+* *kernel/bpf/* directory contains other files in which additional helpers are
+  defined (for cgroups, sockmaps, etc.).
+* The bpftool utility can be used to probe the availability of helper functions
+  on the system (as well as supported program and map types, and a number of
+  other parameters). To do so, run **bpftool feature probe** (see
+  **bpftool-feature**\ (8) for details). Add the **unprivileged** keyword to
+  list features available to unprivileged users.
+
+Compatibility between helper functions and program types can generally be found
+in the files where helper functions are defined. Look for the **struct
+bpf_func_proto** objects and for functions returning them: these functions
+contain a list of helpers that a given program type can call. Note that the
+**default:** label of the **switch ... case** used to filter helpers can call
+other functions, themselves allowing access to additional helpers. The
+requirement for GPL license is also in those **struct bpf_func_proto**.
+
+Compatibility between helper functions and map types can be found in the
+**check_map_func_compatibility**\ () function in file *kernel/bpf/verifier.c*.
+
+Helper functions that invalidate the checks on **data** and **data_end**
+pointers for network processing are listed in function
+**bpf_helper_changes_pkt_data**\ () in file *net/core/filter.c*.
+
+SEE ALSO
+========
+
+**bpf**\ (2),
+**bpftool**\ (8),
+**cgroups**\ (7),
+**ip**\ (8),
+**perf_event_open**\ (2),
+**sendmsg**\ (2),
+**socket**\ (7),
+**tc-bpf**\ (8)'''
+        print(footer)
+
+    def print_proto(self, helper):
+        """
+        Format function protocol with bold and italics markers. This makes RST
+        file less readable, but gives nice results in the manual page.
+        """
+        proto = helper.proto_break_down()
+
+        print('**%s %s%s(' % (proto['ret_type'],
+                              proto['ret_star'].replace('*', '\\*'),
+                              proto['name']),
+              end='')
+
+        comma = ''
+        for a in proto['args']:
+            one_arg = '{}{}'.format(comma, a['type'])
+            if a['name']:
+                if a['star']:
+                    one_arg += ' {}**\ '.format(a['star'].replace('*', '\\*'))
+                else:
+                    one_arg += '** '
+                one_arg += '*{}*\\ **'.format(a['name'])
+            comma = ', '
+            print(one_arg, end='')
+
+        print(')**')
+
+    def print_one(self, helper):
+        self.print_proto(helper)
+        self.print_elem(helper)
+
+
+class PrinterSyscallRST(PrinterRST):
+    """
+    A printer for dumping collected information about the syscall API as a
+    ReStructured Text page compatible with the rst2man program, which can be
+    used to generate a manual page for the syscall.
+    @parser: A HeaderParser with APIElement objects to print to standard
+             output
+    """
+    def __init__(self, parser):
+        self.elements = parser.commands
+        self.elem_number_check(parser.desc_syscalls, parser.enum_syscalls, 'syscall', 'bpf_cmd')
+
+    def print_header(self):
+        header = '''\
+===
+bpf
+===
+-------------------------------------------------------------------------------
+Perform a command on an extended BPF object
+-------------------------------------------------------------------------------
+
+:Manual section: 2
+
+COMMANDS
+========
+'''
+        PrinterRST.print_license(self)
+        print(header)
+
+    def print_one(self, command):
+        print('**%s**' % (command.proto))
+        self.print_elem(command)
+
+
+class PrinterHelpers(Printer):
+    """
+    A printer for dumping collected information about helpers as C header to
+    be included from BPF program.
+    @parser: A HeaderParser with Helper objects to print to standard output
+    """
+    def __init__(self, parser):
+        self.elements = parser.helpers
+        self.elem_number_check(parser.desc_unique_helpers, parser.define_unique_helpers, 'helper', '__BPF_FUNC_MAPPER')
+
+    type_fwds = [
+            'struct bpf_fib_lookup',
+            'struct bpf_sk_lookup',
+            'struct bpf_perf_event_data',
+            'struct bpf_perf_event_value',
+            'struct bpf_pidns_info',
+            'struct bpf_redir_neigh',
+            'struct bpf_sock',
+            'struct bpf_sock_addr',
+            'struct bpf_sock_ops',
+            'struct bpf_sock_tuple',
+            'struct bpf_spin_lock',
+            'struct bpf_sysctl',
+            'struct bpf_tcp_sock',
+            'struct bpf_tunnel_key',
+            'struct bpf_xfrm_state',
+            'struct linux_binprm',
+            'struct pt_regs',
+            'struct sk_reuseport_md',
+            'struct sockaddr',
+            'struct tcphdr',
+            'struct seq_file',
+            'struct tcp6_sock',
+            'struct tcp_sock',
+            'struct tcp_timewait_sock',
+            'struct tcp_request_sock',
+            'struct udp6_sock',
+            'struct unix_sock',
+            'struct task_struct',
+
+            'struct __sk_buff',
+            'struct sk_msg_md',
+            'struct xdp_md',
+            'struct path',
+            'struct btf_ptr',
+            'struct inode',
+            'struct socket',
+            'struct file',
+            'struct bpf_timer',
+            'struct mptcp_sock',
+            'struct bpf_dynptr',
+            'struct iphdr',
+            'struct ipv6hdr',
+    ]
+    known_types = {
+            '...',
+            'void',
+            'const void',
+            'char',
+            'const char',
+            'int',
+            'long',
+            'unsigned long',
+
+            '__be16',
+            '__be32',
+            '__wsum',
+
+            'struct bpf_fib_lookup',
+            'struct bpf_perf_event_data',
+            'struct bpf_perf_event_value',
+            'struct bpf_pidns_info',
+            'struct bpf_redir_neigh',
+            'struct bpf_sk_lookup',
+            'struct bpf_sock',
+            'struct bpf_sock_addr',
+            'struct bpf_sock_ops',
+            'struct bpf_sock_tuple',
+            'struct bpf_spin_lock',
+            'struct bpf_sysctl',
+            'struct bpf_tcp_sock',
+            'struct bpf_tunnel_key',
+            'struct bpf_xfrm_state',
+            'struct linux_binprm',
+            'struct pt_regs',
+            'struct sk_reuseport_md',
+            'struct sockaddr',
+            'struct tcphdr',
+            'struct seq_file',
+            'struct tcp6_sock',
+            'struct tcp_sock',
+            'struct tcp_timewait_sock',
+            'struct tcp_request_sock',
+            'struct udp6_sock',
+            'struct unix_sock',
+            'struct task_struct',
+            'struct path',
+            'struct btf_ptr',
+            'struct inode',
+            'struct socket',
+            'struct file',
+            'struct bpf_timer',
+            'struct mptcp_sock',
+            'struct bpf_dynptr',
+            'struct iphdr',
+            'struct ipv6hdr',
+    }
+    mapped_types = {
+            'u8': '__u8',
+            'u16': '__u16',
+            'u32': '__u32',
+            'u64': '__u64',
+            's8': '__s8',
+            's16': '__s16',
+            's32': '__s32',
+            's64': '__s64',
+            'size_t': 'unsigned long',
+            'struct bpf_map': 'void',
+            'struct sk_buff': 'struct __sk_buff',
+            'const struct sk_buff': 'const struct __sk_buff',
+            'struct sk_msg_buff': 'struct sk_msg_md',
+            'struct xdp_buff': 'struct xdp_md',
+    }
+    # Helpers overloaded for different context types.
+    overloaded_helpers = [
+        'bpf_get_socket_cookie',
+        'bpf_sk_assign',
+    ]
+
+    def print_header(self):
+        header = '''\
+/* This is auto-generated file. See bpf_doc.py for details. */
+
+/* Forward declarations of BPF structs */'''
+
+        print(header)
+        for fwd in self.type_fwds:
+            print('%s;' % fwd)
+        print('')
+
+    def print_footer(self):
+        footer = ''
+        print(footer)
+
+    def map_type(self, t):
+        if t in self.known_types:
+            return t
+        if t in self.mapped_types:
+            return self.mapped_types[t]
+        print("Unrecognized type '%s', please add it to known types!" % t,
+              file=sys.stderr)
+        sys.exit(1)
+
+    seen_helpers = set()
+
+    def print_one(self, helper):
+        proto = helper.proto_break_down()
+
+        if proto['name'] in self.seen_helpers:
+            return
+        self.seen_helpers.add(proto['name'])
+
+        print('/*')
+        print(" * %s" % proto['name'])
+        print(" *")
+        if (helper.desc):
+            # 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' if line else '', line))
+
+        if (helper.ret):
+            print(' *')
+            print(' * Returns')
+            for line in helper.ret.rstrip().split('\n'):
+                print(' *{}{}'.format(' \t' if line else '', line))
+
+        print(' */')
+        print('static %s %s(*%s)(' % (self.map_type(proto['ret_type']),
+                                      proto['ret_star'], proto['name']), end='')
+        comma = ''
+        for i, a in enumerate(proto['args']):
+            t = a['type']
+            n = a['name']
+            if proto['name'] in self.overloaded_helpers and i == 0:
+                    t = 'void'
+                    n = 'ctx'
+            one_arg = '{}{}'.format(comma, self.map_type(t))
+            if n:
+                if a['star']:
+                    one_arg += ' {}'.format(a['star'])
+                else:
+                    one_arg += ' '
+                one_arg += '{}'.format(n)
+            comma = ', '
+            print(one_arg, end='')
+
+        print(') = (void *) %d;' % helper.enum_val)
+        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')
+
+printers = {
+        'helpers': PrinterHelpersRST,
+        'syscall': PrinterSyscallRST,
+}
+
+argParser = argparse.ArgumentParser(description="""
+Parse eBPF header file and generate documentation for the eBPF API.
+The RST-formatted output produced can be turned into a manual page with the
+rst2man utility.
+""")
+argParser.add_argument('--header', action='store_true',
+                       help='generate C header file')
+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')
+argParser.add_argument('target', nargs='?', default='helpers',
+                       choices=printers.keys(), help='eBPF API target')
+args = argParser.parse_args()
+
+# Parse file.
+headerParser = HeaderParser(args.filename)
+headerParser.run()
+
+# Print formatted output to standard output.
+if args.header:
+    if args.target != 'helpers':
+        raise NotImplementedError('Only helpers header generation is supported')
+    printer = PrinterHelpers(headerParser)
+else:
+    printer = printers[args.target](headerParser)
+printer.print_all()