glibcsyscalls.py

#!/usr/bin/python3
# Helpers for glibc system call list processing.
# Copyright (C) 2018-2024 Free Software Foundation, Inc.
# This file is part of the GNU C Library.
#
# The GNU C Library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2.1 of the License, or (at your option) any later version.
#
# The GNU C Library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with the GNU C Library; if not, see
# <http://www.gnu.org/licenses/>.

import os
import re

if __name__ != '__main__':
    # When called as a main program, this is not needed.
    import glibcextract

def extract_system_call_name(macro):
    """Convert the macro name (with __NR_) to a system call name."""
    prefix = '__NR_'
    if macro.startswith(prefix):
        return macro[len(prefix):]
    else:
        raise ValueError('invalid system call name: {!r}'.format(macro))

# Matches macros for system call names.
RE_SYSCALL = re.compile('__NR_.*')

# Some __NR_ constants are not real
RE_PSEUDO_SYSCALL = re.compile(r"""__NR_(
    # Reserved system call.
    (unused|reserved)[0-9]+

    # Pseudo-system call which describes a range.
    |(syscalls|arch_specific_syscall|(OABI_)?SYSCALL_BASE|SYSCALL_MASK)
    |(|64_|[NO]32_)Linux(_syscalls)?
   )""", re.X)

def kernel_constants(cc):
    """Return a dictionary with the kernel-defined system call numbers.

    This comes from <asm/unistd.h>.

    """
    return {extract_system_call_name(name) : int(value)
            for name, value in glibcextract.compute_macro_consts(
                    '#include <asm/unistd.h>\n'
                    # Regularize the kernel definitions if necessary.
                    '#include <fixup-asm-unistd.h>',
                    cc, macro_re=RE_SYSCALL, exclude_re=RE_PSEUDO_SYSCALL)
            .items()}

class SyscallNamesList:
    """The list of known system call names.

    glibc keeps a list of system call names.  The <sys/syscall.h>
    header needs to provide a SYS_ name for each __NR_ macro,
    and the generated <bits/syscall.h> header uses an
    architecture-independent list, so that there is a chance that
    system calls arriving late on certain architectures will automatically
    get the expected SYS_ macro.

    syscalls: list of strings with system call names
    kernel_version: tuple of integers; the kernel version given in the file

    """
    def __init__(self, lines):
        self.syscalls = []
        old_name = None
        self.kernel_version = None
        self.__lines = tuple(lines)
        for line in self.__lines:
            line = line.strip()
            if (not line) or line[0] == '#':
                continue
            comps = line.split()
            if len(comps) == 1:
                self.syscalls.append(comps[0])
                if old_name is not None:
                    if comps[0] < old_name:
                        raise ValueError(
                            'name list is not sorted: {!r} < {!r}'.format(
                                comps[0], old_name))
                old_name = comps[0]
                continue
            if len(comps) == 2 and comps[0] == "kernel":
                if self.kernel_version is not None:
                    raise ValueError(
                        "multiple kernel versions: {!r} and !{r}".format(
                            kernel_version, comps[1]))
                self.kernel_version = tuple(map(int, comps[1].split(".")))
                continue
            raise ValueError("invalid line: !r".format(line))
        if self.kernel_version is None:
            raise ValueError("missing kernel version")

    def merge(self, names):
        """Merge sequence NAMES and return the lines of the new file."""
        names = list(set(names) - set(self.syscalls))
        names.sort()
        names.reverse()
        result = []
        def emit_name():
            result.append(names[-1] + "\n")
            del names[-1]

        for line in self.__lines:
            comps = line.strip().split()
            if len(comps) == 1 and not comps[0].startswith("#"):
                # File has a system call at this position.  Insert all
                # the names that come before the name in the file
                # lexicographically.
                while names and names[-1] < comps[0]:
                    emit_name()
            result.append(line)
        while names:
            emit_name()

        return result

def load_arch_syscall_header(path):
    """"Load the system call header form the file PATH.

    The file must consist of lines of this form:

    #define __NR_exit 1

    The file is parsed verbatim, without running it through a C
    preprocessor or parser.  The intent is that the file can be
    readily processed by tools.

    """
    with open(path) as inp:
        result = {}
        old_name = None
        for line in inp:
            line = line.strip()

            # Ignore the initial comment line.
            if line.startswith("/*") and line.endswith("*/"):
                continue

            define, name, number = line.split(' ', 2)
            if define != '#define':
                raise ValueError("invalid syscall header line: {!r}".format(
                    line))
            result[extract_system_call_name(name)] = int(number)

            # Check list order.
            if old_name is not None:
                if name < old_name:
                    raise ValueError(
                        'system call list is not sorted: {!r} < {!r}'.format(
                            name, old_name))
            old_name = name
        return result

def linux_kernel_version(cc):
    """Return the (major, minor) version of the Linux kernel headers."""
    sym_data = ['#include <linux/version.h>', 'START',
                ('LINUX_VERSION_CODE', 'LINUX_VERSION_CODE')]
    val = glibcextract.compute_c_consts(sym_data, cc)['LINUX_VERSION_CODE']
    val = int(val)
    return ((val & 0xff0000) >> 16, (val & 0xff00) >> 8)

class ArchSyscall:
    """Canonical name and location of a syscall header."""

    def __init__(self, name, path):
        self.name = name
        self.path = path

    def __repr__(self):
        return 'ArchSyscall(name={!r}, patch={!r})'.format(
            self.name, self.path)

def list_arch_syscall_headers(topdir):
    """A generator which returns all the ArchSyscall objects in a tree."""

    sysdeps = os.path.join(topdir, 'sysdeps', 'unix', 'sysv', 'linux')
    for root, dirs, files in os.walk(sysdeps):
        if root != sysdeps:
            for filename in files:
                if filename == 'arch-syscall.h':
                    yield ArchSyscall(
                        name=os.path.relpath(root, sysdeps),
                        path=os.path.join(root, filename))

def __main():
    """Entry point when called as the main program."""

    import argparse
    import sys

    # Top-level directory of the source tree.
    topdir = os.path.realpath(os.path.join(
        os.path.dirname(os.path.realpath(__file__)), *('..',) * 4))

    def get_parser():
        parser = argparse.ArgumentParser(description=__doc__)
        subparsers = parser.add_subparsers(dest='command', required=True)
        subparsers.add_parser('list-headers',
            help='Print the absolute paths of all arch-syscall.h header files')
        subparser = subparsers.add_parser('query-syscall',
            help='Summarize the implementation status of system calls')
        subparser.add_argument('syscalls', help='Which syscalls to check',
                               nargs='+')
        return parser
    parser = get_parser()
    args = parser.parse_args()

    if args.command == 'list-headers':
        for header in sorted([syscall.path for syscall
                              in list_arch_syscall_headers(topdir)]):
            print(header)

    elif args.command == 'query-syscall':
        # List of system call tables.
        tables = sorted(list_arch_syscall_headers(topdir),
                          key=lambda syscall: syscall.name)
        for table in tables:
            table.numbers = load_arch_syscall_header(table.path)

        for nr in args.syscalls:
            defined = [table.name for table in tables
                           if nr in table.numbers]
            undefined = [table.name for table in tables
                             if nr not in table.numbers]
            if not defined:
                print('{}: not defined on any architecture'.format(nr))
            elif not undefined:
                print('{}: defined on all architectures'.format(nr))
            else:
                print('{}:'.format(nr))
                print('  defined: {}'.format(' '.join(defined)))
                print('  undefined: {}'.format(' '.join(undefined)))

    else:
        # Unrecognized command.
        usage(1)

if __name__ == '__main__':
    __main()