Merge tag 'kbuild-fixes-v5.11-2' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild

Pull Kbuild fixes from Masahiro Yamada:

 - Use the 'python3' command to invoke python scripts because some
   distributions do not provide the 'python' command any more.

 - Clean-up and update documents

 - Use pkg-config to search libcrypto

 - Fix duplicated debug flags

 - Ignore some more stubs in scripts/kallsyms.c

* tag 'kbuild-fixes-v5.11-2' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild:
  kallsyms: fix nonconverging kallsyms table with lld
  kbuild: fix duplicated flags in DEBUG_CFLAGS
  scripts/clang-tools: switch explicitly to Python 3
  kbuild: remove PYTHON variable
  Documentation/llvm: Add a section about supported architectures
  Revert "checkpatch: add check for keyword 'boolean' in Kconfig definitions"
  scripts: use pkg-config to locate libcrypto
  kconfig: mconf: fix HOSTCC call
  doc: gcc-plugins: update gcc-plugins.rst
  kbuild: simplify GCC_PLUGINS enablement in dummy-tools/gcc
  Documentation/Kbuild: Remove references to gcc-plugin.sh
  scripts: switch explicitly to Python 3

4 files changed, 67 insertions, 28 deletions

diff --git a/Documentation/Makefile b/Documentation/Makefile
index 61a7310b49e0..9c42dde97671 100644
--- a/Documentation/Makefile
+++ b/Documentation/Makefile
@@ -75,7 +75,7 @@ quiet_cmd_sphinx = SPHINX  $@ --> file://$(abspath $(BUILDDIR)/$3/$4)
       cmd_sphinx = $(MAKE) BUILDDIR=$(abspath $(BUILDDIR)) $(build)=Documentation/userspace-api/media $2 && \
 	PYTHONDONTWRITEBYTECODE=1 \
 	BUILDDIR=$(abspath $(BUILDDIR)) SPHINX_CONF=$(abspath $(srctree)/$(src)/$5/$(SPHINX_CONF)) \
-	$(PYTHON) $(srctree)/scripts/jobserver-exec \
+	$(PYTHON3) $(srctree)/scripts/jobserver-exec \
 	$(SHELL) $(srctree)/Documentation/sphinx/parallel-wrapper.sh \
 	$(SPHINXBUILD) \
 	-b $2 \
diff --git a/Documentation/kbuild/gcc-plugins.rst b/Documentation/kbuild/gcc-plugins.rst
index 4b1c10f88e30..3349966f213d 100644
--- a/Documentation/kbuild/gcc-plugins.rst
+++ b/Documentation/kbuild/gcc-plugins.rst
@@ -11,16 +11,13 @@ compiler [1]_. They are useful for runtime instrumentation and static analysis.
 We can analyse, change and add further code during compilation via
 callbacks [2]_, GIMPLE [3]_, IPA [4]_ and RTL passes [5]_.
 
-The GCC plugin infrastructure of the kernel supports all gcc versions from
-4.5 to 6.0, building out-of-tree modules, cross-compilation and building in a
-separate directory.
-Plugin source files have to be compilable by both a C and a C++ compiler as well
-because gcc versions 4.5 and 4.6 are compiled by a C compiler,
-gcc-4.7 can be compiled by a C or a C++ compiler,
-and versions 4.8+ can only be compiled by a C++ compiler.
+The GCC plugin infrastructure of the kernel supports building out-of-tree
+modules, cross-compilation and building in a separate directory.
+Plugin source files have to be compilable by a C++ compiler.
 
-Currently the GCC plugin infrastructure supports only the x86, arm, arm64 and
-powerpc architectures.
+Currently the GCC plugin infrastructure supports only some architectures.
+Grep "select HAVE_GCC_PLUGINS" to find out which architectures support
+GCC plugins.
 
 This infrastructure was ported from grsecurity [6]_ and PaX [7]_.
 
@@ -47,20 +44,13 @@ Files
 	This is a compatibility header for GCC plugins.
 	It should be always included instead of individual gcc headers.
 
-**$(src)/scripts/gcc-plugin.sh**
-
-	This script checks the availability of the included headers in
-	gcc-common.h and chooses the proper host compiler to build the plugins
-	(gcc-4.7 can be built by either gcc or g++).
-
 **$(src)/scripts/gcc-plugins/gcc-generate-gimple-pass.h,
 $(src)/scripts/gcc-plugins/gcc-generate-ipa-pass.h,
 $(src)/scripts/gcc-plugins/gcc-generate-simple_ipa-pass.h,
 $(src)/scripts/gcc-plugins/gcc-generate-rtl-pass.h**
 
 	These headers automatically generate the registration structures for
-	GIMPLE, SIMPLE_IPA, IPA and RTL passes. They support all gcc versions
-	from 4.5 to 6.0.
+	GIMPLE, SIMPLE_IPA, IPA and RTL passes.
 	They should be preferred to creating the structures by hand.
 
 
@@ -68,21 +58,25 @@ Usage
 =====
 
 You must install the gcc plugin headers for your gcc version,
-e.g., on Ubuntu for gcc-4.9::
+e.g., on Ubuntu for gcc-10::
 
-	apt-get install gcc-4.9-plugin-dev
+	apt-get install gcc-10-plugin-dev
 
 Or on Fedora::
 
 	dnf install gcc-plugin-devel
 
-Enable a GCC plugin based feature in the kernel config::
+Enable the GCC plugin infrastructure and some plugin(s) you want to use
+in the kernel config::
 
-	CONFIG_GCC_PLUGIN_CYC_COMPLEXITY = y
+	CONFIG_GCC_PLUGINS=y
+	CONFIG_GCC_PLUGIN_CYC_COMPLEXITY=y
+	CONFIG_GCC_PLUGIN_LATENT_ENTROPY=y
+	...
 
-To compile only the plugin(s)::
+To compile the minimum tool set including the plugin(s)::
 
-	make gcc-plugins
+	make scripts
 
 or just run the kernel make and compile the whole kernel with
 the cyclomatic complexity GCC plugin.
@@ -91,7 +85,8 @@ the cyclomatic complexity GCC plugin.
 4. How to add a new GCC plugin
 ==============================
 
-The GCC plugins are in $(src)/scripts/gcc-plugins/. You can use a file or a directory
-here. It must be added to $(src)/scripts/gcc-plugins/Makefile,
-$(src)/scripts/Makefile.gcc-plugins and $(src)/arch/Kconfig.
+The GCC plugins are in scripts/gcc-plugins/. You need to put plugin source files
+right under scripts/gcc-plugins/. Creating subdirectories is not supported.
+It must be added to scripts/gcc-plugins/Makefile, scripts/Makefile.gcc-plugins
+and a relevant Kconfig file.
 See the cyc_complexity_plugin.c (CONFIG_GCC_PLUGIN_CYC_COMPLEXITY) GCC plugin.
diff --git a/Documentation/kbuild/llvm.rst b/Documentation/kbuild/llvm.rst
index 21c847890d03..b18401d2ba82 100644
--- a/Documentation/kbuild/llvm.rst
+++ b/Documentation/kbuild/llvm.rst
@@ -63,6 +63,50 @@ They can be enabled individually. The full list of the parameters: ::
 Currently, the integrated assembler is disabled by default. You can pass
 ``LLVM_IAS=1`` to enable it.
 
+Supported Architectures
+-----------------------
+
+LLVM does not target all of the architectures that Linux supports and
+just because a target is supported in LLVM does not mean that the kernel
+will build or work without any issues. Below is a general summary of
+architectures that currently work with ``CC=clang`` or ``LLVM=1``. Level
+of support corresponds to "S" values in the MAINTAINERS files. If an
+architecture is not present, it either means that LLVM does not target
+it or there are known issues. Using the latest stable version of LLVM or
+even the development tree will generally yield the best results.
+An architecture's ``defconfig`` is generally expected to work well,
+certain configurations may have problems that have not been uncovered
+yet. Bug reports are always welcome at the issue tracker below!
+
+.. list-table::
+   :widths: 10 10 10
+   :header-rows: 1
+
+   * - Architecture
+     - Level of support
+     - ``make`` command
+   * - arm
+     - Supported
+     - ``LLVM=1``
+   * - arm64
+     - Supported
+     - ``LLVM=1``
+   * - mips
+     - Maintained
+     - ``CC=clang``
+   * - powerpc
+     - Maintained
+     - ``CC=clang``
+   * - riscv
+     - Maintained
+     - ``CC=clang``
+   * - s390
+     - Maintained
+     - ``CC=clang``
+   * - x86
+     - Supported
+     - ``LLVM=1``
+
 Getting Help
 ------------
 
diff --git a/Documentation/kbuild/makefiles.rst b/Documentation/kbuild/makefiles.rst
index 9f6a11881951..300d8edcb994 100644
--- a/Documentation/kbuild/makefiles.rst
+++ b/Documentation/kbuild/makefiles.rst
@@ -755,7 +755,7 @@ more details, with real examples.
 	bits on the scripts nonetheless.
 
 	Kbuild provides variables $(CONFIG_SHELL), $(AWK), $(PERL),
-	$(PYTHON) and $(PYTHON3) to refer to interpreters for the respective
+	and $(PYTHON3) to refer to interpreters for the respective
 	scripts.
 
 	Example::