parse_syscalls.py

#!/usr/bin/env python3
#
# Copyright (c) 2017 Intel Corporation
#
# SPDX-License-Identifier: Apache-2.0

"""
Script to scan Zephyr include directories and emit system call and subsystem metadata

System calls require a great deal of boilerplate code in order to implement
completely. This script is the first step in the build system's process of
auto-generating this code by doing a text scan of directories containing
C or header files, and building up a database of system calls and their
function call prototypes. This information is emitted to a generated
JSON file for further processing.

This script also scans for struct definitions such as __subsystem and
__net_socket, emitting a JSON dictionary mapping tags to all the struct
declarations found that were tagged with them.

If the output JSON file already exists, its contents are checked against
what information this script would have outputted; if the result is that the
file would be unchanged, it is not modified to prevent unnecessary
incremental builds.
"""

import sys
import re
import argparse
import os
import json
from pathlib import PurePath

regex_flags = re.MULTILINE | re.VERBOSE

syscall_regex = re.compile(r'''
(?:__syscall|__syscall_always_inline)\s+   # __syscall attribute, must be first
([^(]+)                                    # type and name of system call (split later)
[(]                                        # Function opening parenthesis
([^)]*)                                    # Arg list (split later)
[)]                                        # Closing parenthesis
''', regex_flags)

struct_tags = ["__subsystem", "__net_socket"]

tagged_struct_decl_template = r'''
%s\s+                           # tag, must be first
struct\s+                       # struct keyword is next
([^{]+)                         # name of subsystem
[{]                             # Open curly bracket
'''

def tagged_struct_update(target_list, tag, contents):
    regex = re.compile(tagged_struct_decl_template % tag, regex_flags)
    items = [mo.groups()[0].strip() for mo in regex.finditer(contents)]
    target_list.extend(items)


def analyze_headers(include_dir, scan_dir, file_list):
    syscall_ret = []
    tagged_ret = {}

    for tag in struct_tags:
        tagged_ret[tag] = []

    syscall_files = dict()

    # Get the list of header files which contains syscalls to be emitted.
    # If file_list does not exist, we emit all syscalls.
    if file_list:
        with open(file_list, "r", encoding="utf-8") as fp:
            contents = fp.read()

            for one_file in contents.split(";"):
                if os.path.isfile(one_file):
                    syscall_files[one_file] = {"emit": True}
                else:
                    sys.stderr.write(f"{one_file} does not exists!\n")
                    sys.exit(1)

    multiple_directories = set()
    if include_dir:
        multiple_directories |= set(include_dir)
    if scan_dir:
        multiple_directories |= set(scan_dir)

    # Convert to a list to keep the output deterministic
    multiple_directories = sorted(multiple_directories)

    # Look for source files under various directories.
    # Due to "syscalls/*.h" being included unconditionally in various
    # other header files. We must generate the associated syscall
    # header files (e.g. for function stubs).
    for base_path in multiple_directories:
        for root, dirs, files in os.walk(base_path, topdown=True):
            dirs.sort()
            files.sort()
            for fn in files:

                # toolchain/common.h has the definitions of these tags which we
                # don't want to trip over
                path = os.path.join(root, fn)
                if (not (path.endswith(".h") or path.endswith(".c")) or
                        path.endswith(os.path.join(os.sep, 'toolchain',
                                                   'common.h'))):
                    continue

                path = PurePath(os.path.normpath(path)).as_posix()

                if path not in syscall_files:
                    if include_dir and base_path in include_dir:
                        syscall_files[path] = {"emit" : True}
                    else:
                        syscall_files[path] = {"emit" : False}

    # Parse files to extract syscall functions
    for one_file in syscall_files:
        with open(one_file, "r", encoding="utf-8") as fp:
            try:
                contents = fp.read()
            except Exception:
                sys.stderr.write("Error decoding %s\n" % path)
                raise

        fn = os.path.basename(one_file)

        try:
            to_emit = syscall_files[one_file]["emit"] | args.emit_all_syscalls

            syscall_result = [(mo.groups(), fn, to_emit)
                              for mo in syscall_regex.finditer(contents)]
            for tag in struct_tags:
                tagged_struct_update(tagged_ret[tag], tag, contents)
        except Exception:
            sys.stderr.write("While parsing %s\n" % fn)
            raise

        syscall_ret.extend(syscall_result)

    return syscall_ret, tagged_ret


def update_file_if_changed(path, new):
    if os.path.exists(path):
        with open(path, 'r') as fp:
            old = fp.read()

        if new != old:
            with open(path, 'w') as fp:
                fp.write(new)
    else:
        with open(path, 'w') as fp:
            fp.write(new)


def parse_args():
    global args
    parser = argparse.ArgumentParser(
        description=__doc__,
        formatter_class=argparse.RawDescriptionHelpFormatter, allow_abbrev=False)

    parser.add_argument(
        "-i", "--include", required=False, action="append",
        help="Include directories recursively scanned for .h files "
             "containing syscalls that must be present in final binary. "
             "Can be specified multiple times: -i topdir1 -i topdir2 ...")
    parser.add_argument(
        "--scan", required=False, action="append",
        help="Scan directories recursively for .h files containing "
             "syscalls that need stubs generated but may not need to "
             "be present in final binary. Can be specified multiple "
             "times.")
    parser.add_argument(
        "-j", "--json-file", required=True,
        help="Write system call prototype information as json to file")
    parser.add_argument(
        "-t", "--tag-struct-file", required=True,
        help="Write tagged struct name information as json to file")
    parser.add_argument(
        "--file-list", required=False,
        help="Text file containing semi-colon separated list of "
             "header file where only syscalls in these files "
             "are emitted.")
    parser.add_argument(
        "--emit-all-syscalls", required=False, action="store_true",
        help="Emit all potential syscalls in the tree")

    args = parser.parse_args()


def main():
    parse_args()

    syscalls, tagged = analyze_headers(args.include, args.scan,
                                       args.file_list)

    # Only write json files if they don't exist or have changes since
    # they will force an incremental rebuild.

    syscalls_in_json = json.dumps(
        syscalls,
        indent=4,
        sort_keys=True
    )
    update_file_if_changed(args.json_file, syscalls_in_json)

    tagged_struct_in_json = json.dumps(
        tagged,
        indent=4,
        sort_keys=True
    )
    update_file_if_changed(args.tag_struct_file, tagged_struct_in_json)


if __name__ == "__main__":
    main()