From d1c7848b58c610bc83f4b05ff0b8244b59f56175 Mon Sep 17 00:00:00 2001 From: Julian Sun Date: Tue, 23 Jul 2024 05:11:54 -0400 Subject: [PATCH] scripts: add macro_checker script to check unused parameters in macros Recently, I saw a patch[1] on the ext4 mailing list regarding the correction of a macro definition error. Jan mentioned that "The bug in the macro is a really nasty trap...". Because existing compilers are unable to detect unused parameters in macro definitions. This inspired me to write a script to check for unused parameters in macro definitions and to run it. Surprisingly, the script uncovered numerous issues across various subsystems, including filesystems, drivers, and sound etc. Some of these issues involved parameters that were accepted but never used, for example: #define XFS_DAENTER_DBS(mp,w) \ (XFS_DA_NODE_MAXDEPTH + (((w) == XFS_DATA_FORK) ? 2 : 0)) where mp was unused. While others are actual bugs. For example: #define HAL_SEQ_WCSS_UMAC_CE0_SRC_REG(x) \ (ab->hw_params.regs->hal_seq_wcss_umac_ce0_src_reg) #define HAL_SEQ_WCSS_UMAC_CE0_DST_REG(x) \ (ab->hw_params.regs->hal_seq_wcss_umac_ce0_dst_reg) #define HAL_SEQ_WCSS_UMAC_CE1_SRC_REG(x) \ (ab->hw_params.regs->hal_seq_wcss_umac_ce1_src_reg) #define HAL_SEQ_WCSS_UMAC_CE1_DST_REG(x) \ (ab->hw_params.regs->hal_seq_wcss_umac_ce1_dst_reg) where x was entirely unused, and instead, a local variable ab was used. I have submitted patches[2-5] to fix some of these issues, but due to the large number, many still remain unaddressed. I believe that the kernel and matainers would benefit from this script to check for unused parameters in macro definitions. It should be noted that it may cause some false positives in conditional compilation scenarios, such as #ifdef DEBUG static int debug(arg) {}; #else #define debug(arg) #endif So the caller needs to manually verify whether it is a true issue. But this should be fine, because Maintainers should only need to review their own subsystems, which typically results in only a few reports. [1]: https://patchwork.ozlabs.org/project/linux-ext4/patch/1717652596-58760-1-git-send-email-carrionbent@linux.alibaba.com/ [2]: https://lore.kernel.org/linux-xfs/20240721112701.212342-1-sunjunchao2870@gmail.com/ [3]: https://lore.kernel.org/linux-bcachefs/20240721123943.246705-1-sunjunchao2870@gmail.com/ [4]: https://sourceforge.net/p/linux-f2fs/mailman/message/58797811/ [5]: https://sourceforge.net/p/linux-f2fs/mailman/message/58797812/ [sunjunchao2870@gmail.com: reduce false positives] Link: https://lkml.kernel.org/r/20240726031310.254742-1-sunjunchao2870@gmail.com Link: https://lkml.kernel.org/r/20240723091154.52458-1-sunjunchao2870@gmail.com Signed-off-by: Julian Sun Cc: Al Viro Cc: Christian Brauner Cc: Darrick J. Wong Cc: Jan Kara Cc: Junchao Sun Cc: Kalle Valo Cc: Masahiro Yamada Cc: Miguel Ojeda Cc: Nicolas Schier Signed-off-by: Andrew Morton --- scripts/macro_checker.py | 131 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 131 insertions(+) create mode 100755 scripts/macro_checker.py diff --git a/scripts/macro_checker.py b/scripts/macro_checker.py new file mode 100755 index 000000000000..ba550982e98f --- /dev/null +++ b/scripts/macro_checker.py @@ -0,0 +1,131 @@ +#!/usr/bin/python3 +# SPDX-License-Identifier: GPL-2.0 +# Author: Julian Sun + +""" Find macro definitions with unused parameters. """ + +import argparse +import os +import re + +parser = argparse.ArgumentParser() + +parser.add_argument("path", type=str, help="The file or dir path that needs check") +parser.add_argument("-v", "--verbose", action="store_true", + help="Check conditional macros, but may lead to more false positives") +args = parser.parse_args() + +macro_pattern = r"#define\s+(\w+)\(([^)]*)\)" +# below vars were used to reduce false positives +fp_patterns = [r"\s*do\s*\{\s*\}\s*while\s*\(\s*0\s*\)", + r"\(?0\)?", r"\(?1\)?"] +correct_macros = [] +cond_compile_mark = "#if" +cond_compile_end = "#endif" + +def check_macro(macro_line, report): + match = re.match(macro_pattern, macro_line) + if match: + macro_def = re.sub(macro_pattern, '', macro_line) + identifier = match.group(1) + content = match.group(2) + arguments = [item.strip() for item in content.split(',') if item.strip()] + + macro_def = macro_def.strip() + if not macro_def: + return + # used to reduce false positives, like #define endfor_nexthops(rt) } + if len(macro_def) == 1: + return + + for fp_pattern in fp_patterns: + if (re.match(fp_pattern, macro_def)): + return + + for arg in arguments: + # used to reduce false positives + if "..." in arg: + return + for arg in arguments: + if not arg in macro_def and report == False: + return + # if there is a correct macro with the same name, do not report it. + if not arg in macro_def and identifier not in correct_macros: + print(f"Argument {arg} is not used in function-line macro {identifier}") + return + + correct_macros.append(identifier) + + +# remove comment and whitespace +def macro_strip(macro): + comment_pattern1 = r"\/\/*" + comment_pattern2 = r"\/\**\*\/" + + macro = macro.strip() + macro = re.sub(comment_pattern1, '', macro) + macro = re.sub(comment_pattern2, '', macro) + + return macro + +def file_check_macro(file_path, report): + # number of conditional compiling + cond_compile = 0 + # only check .c and .h file + if not file_path.endswith(".c") and not file_path.endswith(".h"): + return + + with open(file_path, "r") as f: + while True: + line = f.readline() + if not line: + break + line = line.strip() + if line.startswith(cond_compile_mark): + cond_compile += 1 + continue + if line.startswith(cond_compile_end): + cond_compile -= 1 + continue + + macro = re.match(macro_pattern, line) + if macro: + macro = macro_strip(macro.string) + while macro[-1] == '\\': + macro = macro[0:-1] + macro = macro.strip() + macro += f.readline() + macro = macro_strip(macro) + if not args.verbose: + if file_path.endswith(".c") and cond_compile != 0: + continue + # 1 is for #ifdef xxx at the beginning of the header file + if file_path.endswith(".h") and cond_compile != 1: + continue + check_macro(macro, report) + +def get_correct_macros(path): + file_check_macro(path, False) + +def dir_check_macro(dir_path): + + for dentry in os.listdir(dir_path): + path = os.path.join(dir_path, dentry) + if os.path.isdir(path): + dir_check_macro(path) + elif os.path.isfile(path): + get_correct_macros(path) + file_check_macro(path, True) + + +def main(): + if os.path.isfile(args.path): + get_correct_macros(args.path) + file_check_macro(args.path, True) + elif os.path.isdir(args.path): + dir_check_macro(args.path) + else: + print(f"{args.path} doesn't exit or is neither a file nor a dir") + +if __name__ == "__main__": + main() \ No newline at end of file