#!/usr/bin/python3
# Regenerate <arch-syscall.h> and update syscall-names.list.
# Copyright (C) 2020-2022 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 argparse
import io
import os
import sys

import glibcextract
import glibcsyscalls

def atomic_replace(path, contents):
    """Atomically replace PATH with CONTENTS, via a temporary file.

    The name of the temporary file is predictable, so locking is
    required to avoid corruption.

    """
    path_tmp = path + 'T'
    with open(path_tmp, 'w') as tmp:
        tmp.write(contents)
    ok = False
    try:
        os.rename(path_tmp, path)
        ok = True
    finally:
        # On error, try to delete the temporary file.
        if not ok:
            try:
                os.unlink(path_tmp)
            except:
                pass

def main():
    """The main entry point."""
    parser = argparse.ArgumentParser(
        description='System call list consistency checks')
    parser.add_argument('--cc', metavar='CC', required=True,
                        help='C compiler (including options) to use')
    parser.add_argument('--lock', metavar='PATH', required=True,
                        help='file to lock during the updates')
    parser.add_argument('arch_syscall', metavar='ARCH-SYSCALL-H',
                        help='The <arch-syscall.h> file to update')
    parser.add_argument('names_list', metavar='SYSCALL-NAMES-LIST',
                        help='The syscall name list to update ')

    args = parser.parse_args()

    kernel_constants = glibcsyscalls.kernel_constants(args.cc)

    with open(args.lock, 'r+') as lockfile:
        os.lockf(lockfile.fileno(), os.F_LOCK, 0)

        # Replace <arch-syscall.h> with data derived from kernel headers.
        # No merging is necessary here.  Arch-specific changes should go
        # into <fixup-unistd-asm.h>.
        out = io.StringIO()
        out.write('/* AUTOGENERATED by update-syscall-lists.py.  */\n')
        for name, value in sorted(kernel_constants.items()):
            out.write('#define __NR_{} {}\n'.format(name, value))
        atomic_replace(args.arch_syscall, out.getvalue())

        # Merge the architecture-specific system call names into the
        # global names list, syscall-names.list.  This file contains names
        # from other architectures (and comments), so it is necessary to
        # merge the existing files with the names obtained from the
        # kernel.
        with open(args.names_list, 'r') as list_file:
            names_list = glibcsyscalls.SyscallNamesList(list_file)
        merged = names_list.merge(kernel_constants.keys())
        out = io.StringIO()
        for line in merged:
            out.write(line)
        atomic_replace(args.names_list, out.getvalue())

if __name__ == '__main__':
    main()
