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#!/usr/bin/env python3
# SPDX-License-Identifier: GPL-2.0
# Copyright (C) Google LLC, 2018
# Author: Tom Roeder <>
"""A tool for generating compile_commands.json in the Linux kernel."""
import argparse
import json
import logging
import os
import re
import subprocess
import sys
_DEFAULT_OUTPUT = 'compile_commands.json'
_FILENAME_PATTERN = r'^\..*\.cmd$'
_LINE_PATTERN = r'^cmd_[^ ]*\.o := (.* )([^ ]*\.c) *(;|$)'
# The tools/ directory adopts a different build system, and produces .cmd
# files in a different format. Do not support it.
_EXCLUDE_DIRS = ['.git', 'Documentation', 'include', 'tools']
def parse_arguments():
"""Sets up and parses command-line arguments.
log_level: A logging level to filter log output.
directory: The work directory where the objects were built.
ar: Command used for parsing .a archives.
output: Where to write the compile-commands JSON file.
paths: The list of files/directories to handle to find .cmd files.
usage = 'Creates a compile_commands.json database from kernel .cmd files'
parser = argparse.ArgumentParser(description=usage)
directory_help = ('specify the output directory used for the kernel build '
'(defaults to the working directory)')
parser.add_argument('-d', '--directory', type=str, default='.',
output_help = ('path to the output command database (defaults to ' +
parser.add_argument('-o', '--output', type=str, default=_DEFAULT_OUTPUT,
log_level_help = ('the level of log messages to produce (defaults to ' +
parser.add_argument('--log_level', choices=_VALID_LOG_LEVELS,
default=_DEFAULT_LOG_LEVEL, help=log_level_help)
ar_help = 'command used for parsing .a archives'
parser.add_argument('-a', '--ar', type=str, default='llvm-ar', help=ar_help)
paths_help = ('directories to search or files to parse '
'(files should be *.o, *.a, or modules.order). '
'If nothing is specified, the current directory is searched')
parser.add_argument('paths', type=str, nargs='*', help=paths_help)
args = parser.parse_args()
return (args.log_level,
args.paths if len(args.paths) > 0 else [])
def cmdfiles_in_dir(directory):
"""Generate the iterator of .cmd files found under the directory.
Walk under the given directory, and yield every .cmd file found.
directory: The directory to search for .cmd files.
The path to a .cmd file.
filename_matcher = re.compile(_FILENAME_PATTERN)
exclude_dirs = [ os.path.join(directory, d) for d in _EXCLUDE_DIRS ]
for dirpath, dirnames, filenames in os.walk(directory, topdown=True):
# Prune unwanted directories.
if dirpath in exclude_dirs:
dirnames[:] = []
for filename in filenames:
if filename_matcher.match(filename):
yield os.path.join(dirpath, filename)
def to_cmdfile(path):
"""Return the path of .cmd file used for the given build artifact
Path: file path
The path to .cmd file
dir, base = os.path.split(path)
return os.path.join(dir, '.' + base + '.cmd')
def cmdfiles_for_o(obj):
"""Generate the iterator of .cmd files associated with the object
Yield the .cmd file used to build the given object
obj: The object path
The path to .cmd file
yield to_cmdfile(obj)
def cmdfiles_for_a(archive, ar):
"""Generate the iterator of .cmd files associated with the archive.
Parse the given archive, and yield every .cmd file used to build it.
archive: The archive to parse
The path to every .cmd file found
for obj in subprocess.check_output([ar, '-t', archive]).decode().split():
yield to_cmdfile(obj)
def cmdfiles_for_modorder(modorder):
"""Generate the iterator of .cmd files associated with the modules.order.
Parse the given modules.order, and yield every .cmd file used to build the
contained modules.
modorder: The modules.order file to parse
The path to every .cmd file found
with open(modorder) as f:
for line in f:
ko = line.rstrip()
base, ext = os.path.splitext(ko)
if ext != '.ko':
sys.exit('{}: module path must end with .ko'.format(ko))
mod = base + '.mod'
# The first line of *.mod lists the objects that compose the module.
with open(mod) as m:
for obj in m.readline().split():
yield to_cmdfile(obj)
def process_line(root_directory, command_prefix, file_path):
"""Extracts information from a .cmd line and creates an entry from it.
root_directory: The directory that was searched for .cmd files. Usually
used directly in the "directory" entry in compile_commands.json.
command_prefix: The extracted command line, up to the last element.
file_path: The .c file from the end of the extracted command.
Usually relative to root_directory, but sometimes absolute.
An entry to append to compile_commands.
ValueError: Could not find the extracted file based on file_path and
root_directory or file_directory.
# The .cmd files are intended to be included directly by Make, so they
# escape the pound sign '#', either as '\#' or '$(pound)' (depending on the
# kernel version). The compile_commands.json file is not interepreted
# by Make, so this code replaces the escaped version with '#'.
prefix = command_prefix.replace('\#', '#').replace('$(pound)', '#')
# Use os.path.abspath() to normalize the path resolving '.' and '..' .
abs_path = os.path.abspath(os.path.join(root_directory, file_path))
if not os.path.exists(abs_path):
raise ValueError('File %s not found' % abs_path)
return {
'directory': root_directory,
'file': abs_path,
'command': prefix + file_path,
def main():
"""Walks through the directory and finds and parses .cmd files."""
log_level, directory, output, ar, paths = parse_arguments()
level = getattr(logging, log_level)
logging.basicConfig(format='%(levelname)s: %(message)s', level=level)
line_matcher = re.compile(_LINE_PATTERN)
compile_commands = []
for path in paths:
# If 'path' is a directory, handle all .cmd files under it.
# Otherwise, handle .cmd files associated with the file.
# Most of built-in objects are linked via archives (built-in.a or lib.a)
# but some objects are linked to vmlinux directly.
# Modules are listed in modules.order.
if os.path.isdir(path):
cmdfiles = cmdfiles_in_dir(path)
elif path.endswith('.o'):
cmdfiles = cmdfiles_for_o(path)
elif path.endswith('.a'):
cmdfiles = cmdfiles_for_a(path, ar)
elif path.endswith('modules.order'):
cmdfiles = cmdfiles_for_modorder(path)
sys.exit('{}: unknown file type'.format(path))
for cmdfile in cmdfiles:
with open(cmdfile, 'rt') as f:
result = line_matcher.match(f.readline())
if result:
entry = process_line(directory,,
except ValueError as err:'Could not add line from %s: %s',
cmdfile, err)
with open(output, 'wt') as f:
json.dump(compile_commands, f, indent=2, sort_keys=True)
if __name__ == '__main__':