Re: [PATCH v2] Makefile: Add clang-tidy and static analyzer support to makefile

Nick Desaulniers
2020-07-08T19:11:07Z

On Wed, Jul 8, 2020 at 11:21 AM 'Nathan Huckleberry' via Clang Built
Linux <clang-built-linux@googlegroups.com> wrote:
>
> This patch adds clang-tidy and the clang static-analyzer as make
> targets. The goal of this patch is to make static analysis tools
> usable and extendable by any developer or researcher who is familiar
> with basic c++.
>
> The current static analysis tools require intimate knowledge of the internal
> workings of the static analysis. Clang-tidy and the clang static analyzers
> expose an easy to use api and allow users unfamiliar with clang to
> write new checks with relative ease.
>
> ===Clang-tidy===
>
> Clang-tidy is an easily extendable 'linter' that runs on the AST.
> Clang-tidy checks are easy to write and understand. A check consists of
> two parts, a matcher and a checker. The matcher is created using a
> domain specific language that acts on the AST
> (https://clang.llvm.org/docs/LibASTMatchersReference.html). When AST
> nodes are found by the matcher a callback is made to the checker. The
> checker can then execute additional checks and issue warnings.
>
> Here is an example clang-tidy check to report functions that have calls
> to local_irq_disable without calls to local_irq_enable and vice-versa.
> Functions flagged with __attribute((annotation("ignore_irq_balancing")))
> are ignored for analysis. (https://reviews.llvm.org/D65828)
>
> ===Clang static analyzer===
>
> The clang static analyzer is a more powerful static analysis tool that
> uses symbolic execution to find bugs. Currently there is a check that
> looks for potential security bugs from invalid uses of kmalloc and
> kfree. There are several more general purpose checks that are useful for
> the kernel.
>
> The clang static analyzer is well documented and designed to be
> extensible.
> (https://clang-analyzer.llvm.org/checker_dev_manual.html)
> (https://github.com/haoNoQ/clang-analyzer-guide/releases/download/v0.1/clang-analyzer-guide-v0.1.pdf)
>
> The main draw of the clang tools is how accessible they are. The clang
> documentation is very nice and these tools are built specifically to be
> easily extendable by any developer. They provide an accessible method of
> bug-finding and research to people who are not overly familiar with the
> kernel codebase.
>
> Signed-off-by: Nathan Huckleberry <nhuck@google.com>
> ---
> Changes V1 -> V2:
> * Remove dependencies on GNU Parallel
> * * Clang-tidy/analyzer now invoked directly from python
> Link: https://lkml.org/lkml/2019/8/6/941
>
> Makefile | 3 +
> scripts/clang-tools/Makefile.clang-tools | 23 ++++++
> .../{ => clang-tools}/gen_compile_commands.py | 0

+ Tom for the rename.

I think we should add scripts/clang-tools/ to MAINTAINERS under
CLANG/LLVM SUPPORT:
```
diff --git a/MAINTAINERS b/MAINTAINERS
index c87b94e6b2f6..42602231929c 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -4211,6 +4211,7 @@ W: https://clangbuiltlinux.github.io/
B: https://github.com/ClangBuiltLinux/linux/issues
C: irc://chat.freenode.net/clangbuiltlinux
F: Documentation/kbuild/llvm.rst
+F: scripts/clang-tools/
K: \b(?i:clang|llvm)\b

CLEANCACHE API
```
that way we get cc'ed properly on proposed changes (should folks use
scripts/get_maintainer.pl).

> scripts/clang-tools/run-clang-tools.py | 77 +++++++++++++++++++
> 4 files changed, 103 insertions(+)
> create mode 100644 scripts/clang-tools/Makefile.clang-tools
> rename scripts/{ => clang-tools}/gen_compile_commands.py (100%)
> create mode 100755 scripts/clang-tools/run-clang-tools.py
>
> diff --git a/Makefile b/Makefile
> index fe0164a654c7..3e2df010b342 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -747,6 +747,7 @@ KBUILD_CFLAGS += $(call cc-option,-fno-allow-store-data-races)
>
> include scripts/Makefile.kcov
> include scripts/Makefile.gcc-plugins
> +include scripts/clang-tools/Makefile.clang-tools
>
> ifdef CONFIG_READABLE_ASM
> # Disable optimizations that make assembler listings hard to read.
> @@ -1543,6 +1544,8 @@ help:
> @echo ' export_report - List the usages of all exported symbols'
> @echo ' headerdep - Detect inclusion cycles in headers'
> @echo ' coccicheck - Check with Coccinelle'
> + @echo ' clang-analyzer - Check with clang static analyzer'
> + @echo ' clang-tidy - Check with clang-tidy'
> @echo ''
> @echo 'Tools:'
> @echo ' nsdeps - Generate missing symbol namespace dependencies'
> diff --git a/scripts/clang-tools/Makefile.clang-tools b/scripts/clang-tools/Makefile.clang-tools
> new file mode 100644
> index 000000000000..e09dc1a8efff
> --- /dev/null
> +++ b/scripts/clang-tools/Makefile.clang-tools
> @@ -0,0 +1,23 @@
> +# SPDX-License-Identifier: GPL-2.0
> +#
> +# Copyright (C) Google LLC, 2020
> +#
> +# Author: Nathan Huckleberry <nhuck@google.com>
> +#
> +PHONY += clang-tidy
> +clang-tidy:
> +ifdef CONFIG_CC_IS_CLANG
> + $(PYTHON3) scripts/clang-tools/gen_compile_commands.py
> + $(PYTHON3) scripts/clang-tools/run-clang-tools.py clang-tidy compile_commands.json
> +else
> + $(error Clang-tidy requires CC=clang)

s/Clang/clang/ to match the case of the target.

> +endif
> +
> +PHONY += clang-analyzer
> +clang-analyzer:
> +ifdef CONFIG_CC_IS_CLANG
> + $(PYTHON3) scripts/clang-tools/gen_compile_commands.py
> + $(PYTHON3) scripts/clang-tools/run-clang-tools.py static-analyzer compile_commands.json
> +else
> + $(error Clang-analyzer requires CC=clang)

s/Clang/clang/ to match the case of the target.

> +endif
> diff --git a/scripts/gen_compile_commands.py b/scripts/clang-tools/gen_compile_commands.py
> similarity index 100%
> rename from scripts/gen_compile_commands.py
> rename to scripts/clang-tools/gen_compile_commands.py
> diff --git a/scripts/clang-tools/run-clang-tools.py b/scripts/clang-tools/run-clang-tools.py
> new file mode 100755
> index 000000000000..d429a150e23a
> --- /dev/null
> +++ b/scripts/clang-tools/run-clang-tools.py
> @@ -0,0 +1,77 @@
> +#!/usr/bin/env python
> +# SPDX-License-Identifier: GPL-2.0
> +#
> +# Copyright (C) Google LLC, 2020
> +#
> +# Author: Nathan Huckleberry <nhuck@google.com>
> +#
> +"""A helper routine run clang-tidy and the clang static-analyzer on
> +compile_commands.json."""
> +
> +import argparse
> +import json
> +import logging
> +import multiprocessing
> +import os
> +import re
> +import subprocess
> +
> +def parse_arguments():
> + """Set up and parses command-line arguments.
> + Returns:
> + args: Dict of parsed args
> + Has keys 'file' and 'type'
> + """
> + usage = """Run clang-tidy or the clang static-analyzer on a
> + compilation database."""
> + parser = argparse.ArgumentParser(description=usage)
> +
> + type_help = ('Type of analysis to be performed')
> + parser.add_argument('type', choices=['clang-tidy', 'static-analyzer'],
> + help=type_help)
> + file_path_help = ('Path to the compilation database to parse')
> + parser.add_argument('file', type=str, help=file_path_help)

I don't know if the kernel has a preferred style for Python, but I
think it would be good to be consistent in the use of single vs double
quotes for strings. My preference is for double quotes, but I don't
know enough about the various PEPs for style or if the kernel has a
preferred style for these.

+ Bill who knows a bit about Python style.

> +
> + args = parser.parse_args()
> +
> + return args
> +
> +def init(l,t):
> + global lock
> + global analysis_type
> + lock = l
> + analysis_type = t

Is this canonical Python? Maybe wrap these functions into methods of
an object you construct, that way you can assign these as instance
variables against `self`, rather than using global variables.

> +
> +def run_analysis(entry):
> + filename = entry['file']
> + p = None
> + if(analysis_type == "clang-tidy"):
> + p = subprocess.run(["clang-tidy", "-p", os.getcwd(),
> + "-checks=-*,linuxkernel-*", filename],
> + stdout=subprocess.PIPE, stderr=subprocess.PIPE)
> + if(analysis_type == "static-analyzer"):
> + p = subprocess.run(["clang-tidy", "-p", os.getcwd(),
> + "-checks=-*,clang-analyzer-*", filename],
> + stdout=subprocess.PIPE, stderr=subprocess.PIPE)

When you have a fair amount of duplication between two branches of an
if/else (for instance, same method invocation and number of
parameters, just slight differences in parameter values), consider if
you can use a ternary to simplify or make the code more concise. That
would also help avoid initializing `p` to `None`:

checks = "-checks=-*,linuxkernel-*" if analysis_type == "clang-tidy"
else "-checks=-*,clang-analyzer-*"
p = subprocess.run(["clang-tidy", "-p", os.getcwd(), checks,
stdout=subprocess.PIPE, stderr=subprocess.PIPE]

then maybe do some validation of the analysis_type when validating
command line arguments earlier.

> + lock.acquire()
> + print(entry['file'])
> + os.write(1, p.stdout)
> + os.write(2, p.stderr)

Please use sys.stdout and sys.stderr rather than magic constants for
their file descriptors.

> + lock.release()
> +
> +
> +def main():
> + args = parse_arguments()
> + filename = args.file
> +
> + #Read JSON data into the datastore variable
> + if filename:

Isn't there a way to make command line arguments required with
Argparse? In that case, would you still need the conditional?

> + with open(filename, 'r') as f:
> + datastore = json.load(f)
> +
> + lock = multiprocessing.Lock()
> + pool = multiprocessing.Pool(initializer=init, initargs=(lock,args.type,))
> + pool.map(run_analysis,datastore)

Please use a space to separate parameters in a parameter list.

> +
> +if __name__ == '__main__':
> + main()

So rather than call a function named main, you could simply construct
an object, then call a method on it or have the constructor simply
kick off the analysis (essentially a mix of `main` and `init`).

--
Thanks,
~Nick Desaulniers