From: Masahiro Yamada masahiroy@kernel.org

[ Upstream commit 87c7ee67deb7fce9951a5f9d80641138694aad17 ]

In the follow-up of commit fb3041d61f68 ("kbuild: fix SIGPIPE error message for AR=gcc-ar and AR=llvm-ar"), Kees Cook pointed out that tools should _not_ catch their own SIGPIPEs [1] [2].

Based on his feedback, LLVM was fixed [3].

However, Python's default behavior is to show noisy bracktrace when SIGPIPE is sent. So, scripts written in Python are basically in the same situation as the buggy llvm tools.

Example:

$ make -s allnoconfig $ make -s allmodconfig $ scripts/diffconfig .config.old .config | head -n1 -ALIX n Traceback (most recent call last): File "/home/masahiro/linux/scripts/diffconfig", line 132, in <module> main() File "/home/masahiro/linux/scripts/diffconfig", line 130, in main print_config("+", config, None, b[config]) File "/home/masahiro/linux/scripts/diffconfig", line 64, in print_config print("+%s %s" % (config, new_value)) BrokenPipeError: [Errno 32] Broken pipe

Python documentation [4] notes how to make scripts die immediately and silently:

""" Piping output of your program to tools like head(1) will cause a SIGPIPE signal to be sent to your process when the receiver of its standard output closes early. This results in an exception like BrokenPipeError: [Errno 32] Broken pipe. To handle this case, wrap your entry point to catch this exception as follows:

import os import sys

def main(): try: # simulate large output (your code replaces this loop) for x in range(10000): print("y") # flush output here to force SIGPIPE to be triggered # while inside this try block. sys.stdout.flush() except BrokenPipeError: # Python flushes standard streams on exit; redirect remaining output # to devnull to avoid another BrokenPipeError at shutdown devnull = os.open(os.devnull, os.O_WRONLY) os.dup2(devnull, sys.stdout.fileno()) sys.exit(1) # Python exits with error code 1 on EPIPE

if __name__ == '__main__': main()

Do not set SIGPIPE’s disposition to SIG_DFL in order to avoid BrokenPipeError. Doing that would cause your program to exit unexpectedly whenever any socket connection is interrupted while your program is still writing to it. """

Currently, tools/perf/scripts/python/intel-pt-events.py seems to be the only script that fixes the issue that way.

tools/perf/scripts/python/compaction-times.py uses another approach signal.signal(signal.SIGPIPE, signal.SIG_DFL) but the Python documentation clearly says "Don't do it".

I cannot fix all Python scripts since there are so many. I fixed some in the scripts/ directory.

[1]: https://lore.kernel.org/all/202211161056.1B9611A@keescook/ [2]: https://github.com/llvm/llvm-project/issues/59037 [3]: https://github.com/llvm/llvm-project/commit/4787efa38066adb51e2c049499d25b36... [4]: https://docs.python.org/3/library/signal.html#note-on-sigpipe

Signed-off-by: Masahiro Yamada masahiroy@kernel.org Reviewed-by: Nick Desaulniers ndesaulniers@google.com Reviewed-by: Nicolas Schier nicolas@fjasle.eu Signed-off-by: Sasha Levin sashal@kernel.org --- scripts/checkkconfigsymbols.py | 13 ++++++++++++- scripts/clang-tools/run-clang-tools.py | 21 ++++++++++++++------- scripts/diffconfig | 16 ++++++++++++++-- 3 files changed, 40 insertions(+), 10 deletions(-)

diff --git a/scripts/checkkconfigsymbols.py b/scripts/checkkconfigsymbols.py index 217d21abc86e8..36c920e713137 100755 --- a/scripts/checkkconfigsymbols.py +++ b/scripts/checkkconfigsymbols.py @@ -115,7 +115,7 @@ def parse_options(): return args

-def main(): +def print_undefined_symbols(): """Main function of this module.""" args = parse_options()

@@ -467,5 +467,16 @@ def parse_kconfig_file(kfile): return defined, references

+def main(): + try: + print_undefined_symbols() + except BrokenPipeError: + # Python flushes standard streams on exit; redirect remaining output + # to devnull to avoid another BrokenPipeError at shutdown + devnull = os.open(os.devnull, os.O_WRONLY) + os.dup2(devnull, sys.stdout.fileno()) + sys.exit(1) # Python exits with error code 1 on EPIPE + + if __name__ == "__main__": main() diff --git a/scripts/clang-tools/run-clang-tools.py b/scripts/clang-tools/run-clang-tools.py index 56f2ec8f0f40a..3266708a86586 100755 --- a/scripts/clang-tools/run-clang-tools.py +++ b/scripts/clang-tools/run-clang-tools.py @@ -61,14 +61,21 @@ def run_analysis(entry):

def main(): - args = parse_arguments() + try: + args = parse_arguments()

- lock = multiprocessing.Lock() - pool = multiprocessing.Pool(initializer=init, initargs=(lock, args)) - # Read JSON data into the datastore variable - with open(args.path, "r") as f: - datastore = json.load(f) - pool.map(run_analysis, datastore) + lock = multiprocessing.Lock() + pool = multiprocessing.Pool(initializer=init, initargs=(lock, args)) + # Read JSON data into the datastore variable + with open(args.path, "r") as f: + datastore = json.load(f) + pool.map(run_analysis, datastore) + except BrokenPipeError: + # Python flushes standard streams on exit; redirect remaining output + # to devnull to avoid another BrokenPipeError at shutdown + devnull = os.open(os.devnull, os.O_WRONLY) + os.dup2(devnull, sys.stdout.fileno()) + sys.exit(1) # Python exits with error code 1 on EPIPE

if __name__ == "__main__": diff --git a/scripts/diffconfig b/scripts/diffconfig index d5da5fa05d1d3..43f0f3d273ae7 100755 --- a/scripts/diffconfig +++ b/scripts/diffconfig @@ -65,7 +65,7 @@ def print_config(op, config, value, new_value): else: print(" %s %s -> %s" % (config, value, new_value))

-def main(): +def show_diff(): global merge_style

# parse command line args @@ -129,4 +129,16 @@ def main(): for config in new: print_config("+", config, None, b[config])

-main() +def main(): + try: + show_diff() + except BrokenPipeError: + # Python flushes standard streams on exit; redirect remaining output + # to devnull to avoid another BrokenPipeError at shutdown + devnull = os.open(os.devnull, os.O_WRONLY) + os.dup2(devnull, sys.stdout.fileno()) + sys.exit(1) # Python exits with error code 1 on EPIPE + + +if __name__ == '__main__': + main()