On Fri, Aug 7, 2020 at 6:42 AM 'Nathan Huckleberry' via Clang Built Linux <clang-built-linux@xxxxxxxxxxxxxxxx> wrote: > > On Thu, Aug 6, 2020 at 3:44 AM Masahiro Yamada <masahiroy@xxxxxxxxxx> wrote: > > > > On Tue, Jul 28, 2020 at 9:47 AM Nathan Huckleberry <nhuck@xxxxxxxxxx> 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@xxxxxxxxxx> > > > --- > > > Changes v6->v7 > > > * Fix issues with relative paths > > > * Additional style fixes > > > MAINTAINERS | 1 + > > > Makefile | 3 + > > > scripts/clang-tools/Makefile.clang-tools | 23 ++++++ > > > .../{ => clang-tools}/gen_compile_commands.py | 0 > > > scripts/clang-tools/run-clang-tools.py | 74 +++++++++++++++++++ > > > 5 files changed, 101 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/MAINTAINERS b/MAINTAINERS > > > index 1d4aa7f942de..a444564e5572 100644 > > > --- a/MAINTAINERS > > > +++ b/MAINTAINERS > > > @@ -4198,6 +4198,7 @@ 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 > > > 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..5c9d76f77595 > > > --- /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@xxxxxxxxxx> > > > +# > > > +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) > > > +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 clang-analyzer compile_commands.json > > > +else > > > + $(error clang-analyzer requires CC=clang) > > > +endif > > > > > > > > You can unify the almost same two rules. > > > > PHONY += clang-tidy clang-analyzer > > clang-tidy clang-analyzer: > > ifdef CONFIG_CC_IS_CLANG > > $(PYTHON3) scripts/clang-tools/gen_compile_commands.py > > $(PYTHON3) scripts/clang-tools/run-clang-tools.py $@ > > compile_commands.json > > else > > $(error $@ requires CC=clang) > > endif > > > > I like this. > > > > > > > > > But, before we proceed, please tell me > > what this check is intended for. > > > > Clang-tidy invokes clang using the command line > options specified in the compile_commands.json file. > Using gcc command line options causes a bunch of > errors for unknown options. > > > > > > > > > > > Case 1) > > Build the kernel with CC=clang, > > and then run clang-tidy without CC=clang. > > > > $ make CC=clang defconfig > > $ make CC=clang -j$(nproc) > > $ make clang-tidy > > > > scripts/clang-tools/Makefile.clang-tools:13: *** clang-tidy requires > > CC=clang. Stop. > > > > I suppose this case could allow clang-tidy to > be run. > > > > > > > > > Case 2) > > Build the kernel using GCC, > > and then run clang-tidy with CC=clang. > > > > $ make defconfig > > $ make -j$(nproc) > > $ make CC=clang clang-tidy > > > > This patch happily runs clang-tidy > > although compile_commands.json > > contains GCC commands. > > > > This is the worst of the two cases. I'm not > sure how to prevent this other than parsing the > compiler invocation in run-clang-tools.py. > > I'm open to better suggestions. > > > > > > > > > > > So, it checks if you have passed CC=clang > > to "make clang-tidy", where I do not see > > any user of the $(CC) variable. > > > > It does not care whether you have built > > the kernel with GCC or Clang. > > > > > > > > What happens if you run clang-tidy against > > compile_commands.json that contains GCC > > commands? > > Clang-tidy itself uses the command line options from > compile_commands.json to invoke clang. If you run > clang-tidy against GCC commands you get lots of > errors similar to this > > Found compiler error(s). > 12 warnings and 8 errors generated. > Error while processing /usr/local/google/home/nhuck/linux/arch/x86/lib/iomem.c. > error: unknown argument: '-fconserve-stack' [clang-diagnostic-error] > error: unknown argument: '-fno-var-tracking-assignments' > [clang-diagnostic-error] > error: unknown argument: '-mindirect-branch-register' [clang-diagnostic-error] > error: unknown argument: '-mindirect-branch=thunk-extern' > [clang-diagnostic-error] > error: unknown argument: '-mno-fp-ret-in-387' [clang-diagnostic-error] > error: unknown argument: '-mpreferred-stack-boundary=3' [clang-diagnostic-error] > error: unknown argument: '-mskip-rax-setup' [clang-diagnostic-error] > > > > > > > I also care about stale commands > > in compile_commands.json. > > > > I agree with this point, but it's more of a bug with > gen_compile_commands.py. Maybe gen_compile_commands.py > could emit a warning when stale commands are detected in the > .*.cmd files. Nathan, thanks for your comments. I can improve this so compile_commands.json contains only commands from the last build. Working on a patch. -- Best Regards Masahiro Yamada
