[RFC PATCH 0/6] kbuild: build the userspace tools in tools/ with the kernel

[RFC PATCH 0/6] kbuild: build the userspace tools in tools/ with the kernel

[Sasha Levin]

The userspace programs under tools/ are disconnected from the rest of the
kernel's build system. Each has its own makefiles and build framework, and
"make" never builds them: apart from the few host tools the build itself needs,
such as objtool and resolve_btfids, nothing under tools/ is compiled as part of
a kernel build.

That makes them easy to break. Most people, and most of the build bots, check a
change with "make allmodconfig && make", which doesn't cover tools/ at all. A
change that breaks a tool passes every build check and is only noticed when
someone happens to build that tool by hand, often much later.

We keep seeing this in tools/testing/: selftests that stop building after a
change elsewhere in the tree, or after a backport to a stable tree, and stay
broken until someone tries to build them. Others brought up the same concern at
LPC.

This series lets the kernel build also build the tools it is configured for:

- tools/Kconfig adds a "Build userspace tools from tools/" menu
  (CONFIG_TOOLS_BUILD) with one entry per tool and per selftests
  directory, so .config records what gets built, and a tool that breaks
  can be turned off on its own.

- "make tools_build" builds the selected tools for the target, each with
  its own build system as it is built standalone, into tools-build/ in
  the object tree.

- With CONFIG_TOOLS_BUILD=y, "make all" builds them too. allmodconfig
  and allyesconfig enable every entry when the compiler can link
  userspace programs, so the usual build test catches tools breakage.
  Toolchains without a C library are unaffected, as are "make vmlinux",
  "make modules" and external module builds.

This is useful beyond build testing: the tools are built for the same
target, from the same tree, as the kernel they go with.

Sasha Levin (6):
  kbuild: factor the userspace ABI flags out into KBUILD_USERABI
  kbuild: add "make tools_build" to build userspace tools from tools/
  tools: build perf in tools_build
  tools: build kernel selftests in tools_build
  kbuild: build the tools selected in tools/Kconfig as part of "make
    all"
  Documentation: describe building tools with the kernel

 .gitignore                                 |   5 +
 Documentation/dev-tools/kselftest.rst      |   4 +
 Documentation/kbuild/kbuild.rst            |   5 +-
 Documentation/process/submit-checklist.rst |   5 +
 Makefile                                   |  24 +-
 lib/Kconfig.debug                          |   2 +
 tools/Kconfig                              | 326 +++++++++++++++++++++
 tools/Makefile.kbuild                      | 198 +++++++++++++
 8 files changed, 562 insertions(+), 7 deletions(-)
 create mode 100644 tools/Kconfig
 create mode 100644 tools/Makefile.kbuild


base-commit: a5ebb76233b79db01e82e061173cb73c6d2b5c6b
prerequisite-patch-id: 68eb8785244b88ec7e696e716420e2d9b1367dbc
prerequisite-patch-id: 37c57cf4c2a9700788cd1755912753f363cbb3f9
prerequisite-patch-id: 7772557d5d842a42f1bbb3ee18d41f337db9783a
prerequisite-patch-id: 75abf8d47ec8093740c215e9eebe7bbb5846ddd6
prerequisite-patch-id: de33c5273a0f7619a54dc6d1fd9c47383b7dd60e
prerequisite-patch-id: 5243b7b03f2c12a6e66c353b0c083f7f21fd7ba2
prerequisite-patch-id: 7153a847ba7b05e49a670caba5d5b8fa2508eff1
prerequisite-patch-id: 67a995618952454c30eb77960a5bf6f897d22547
prerequisite-patch-id: f0580be789bfbd90c903bfef8cf6099609e63347
prerequisite-patch-id: 975b27a83085ae7532771fbd7bb17b779ea2c254
prerequisite-patch-id: fa973600f98f37417659bbe282f76d7cbdfd84ff
prerequisite-patch-id: 333bf51a132f726bf970b5963017bdc607c0e315
prerequisite-patch-id: 7853ec5197ec9b9322a102a6b02dd62bba4df102
prerequisite-patch-id: 70780a52552f78b640178774bce254616b06f831
prerequisite-patch-id: 7a28872d234cdfa7bd5ec851e9dde01a65e91130
prerequisite-patch-id: f75a478f103e8707f7ce1ebb136e3a605f026cae
prerequisite-patch-id: c6aacf3772c239df0224afb7e4bb661fb9b81c63
prerequisite-patch-id: a71f47de3fd339d680c9f18e80f5bcde7eae0abf
-- 
2.53.0

[RFC PATCH 1/6] kbuild: factor the userspace ABI flags out into KBUILD_USERABI

[Sasha Levin]

KBUILD_USERCFLAGS and KBUILD_USERLDFLAGS pick up the flags that select
the target ABI for userspace programs: --target= under clang, -m32/-m64,
or CONFIG_ARCH_USERFLAGS. Collect those in KBUILD_USERABI and export it,
so programs built outside of kbuild's userprogs can be compiled for the
same ABI without also inheriting kbuild's warning and language flags.

No functional change: KBUILD_USERCFLAGS and KBUILD_USERLDFLAGS keep the
same value.

Assisted-by: LLM
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 Makefile | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/Makefile b/Makefile
index 7c855e6fe5448..8c94aff229b21 100644
--- a/Makefile
+++ b/Makefile
@@ -650,7 +650,7 @@ export CPP AR NM STRIP OBJCOPY OBJDUMP READELF PAHOLE RESOLVE_BTFIDS LEX YACC AW
 export PERL PYTHON3 CHECK CHECKFLAGS MAKE UTS_MACHINE HOSTCXX
 export KGZIP KBZIP2 KLZOP LZMA LZ4 XZ ZSTD TAR
 export KBUILD_HOSTCXXFLAGS KBUILD_HOSTLDFLAGS KBUILD_HOSTLDLIBS KBUILD_PROCMACROLDFLAGS LDFLAGS_MODULE
-export KBUILD_USERCFLAGS KBUILD_USERLDFLAGS
+export KBUILD_USERCFLAGS KBUILD_USERLDFLAGS KBUILD_USERABI
 
 export KBUILD_CPPFLAGS NOSTDINC_FLAGS LINUXINCLUDE OBJCOPYFLAGS KBUILD_LDFLAGS
 export KBUILD_CFLAGS CFLAGS_KERNEL CFLAGS_MODULE
@@ -1270,15 +1270,17 @@ endif
 USERFLAGS_FROM_KERNEL := --target=%
 
 ifdef CONFIG_ARCH_USERFLAGS
-KBUILD_USERCFLAGS += $(CONFIG_ARCH_USERFLAGS)
-KBUILD_USERLDFLAGS += $(CONFIG_ARCH_USERFLAGS)
+KBUILD_USERABI := $(CONFIG_ARCH_USERFLAGS)
 else
+KBUILD_USERABI :=
 # If not overridden also inherit the bit size
 USERFLAGS_FROM_KERNEL += -m32 -m64
 endif
 
-KBUILD_USERCFLAGS  += $(filter $(USERFLAGS_FROM_KERNEL), $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS))
-KBUILD_USERLDFLAGS += $(filter $(USERFLAGS_FROM_KERNEL), $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS))
+KBUILD_USERABI += $(filter $(USERFLAGS_FROM_KERNEL), $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS))
+
+KBUILD_USERCFLAGS  += $(KBUILD_USERABI)
+KBUILD_USERLDFLAGS += $(KBUILD_USERABI)
 
 # userspace programs are linked via the compiler, use the correct linker
 ifdef CONFIG_CC_IS_CLANG
-- 
2.53.0

[RFC PATCH 2/6] kbuild: add "make tools_build" to build userspace tools from tools/

[Sasha Levin]

The programs under tools/ have their own build systems and are not built
by "make", so nothing builds them together with the kernel they belong
to, and breakage in them is only noticed when someone happens to build
them by hand, sometimes many stable releases later.

Add a "Build userspace tools from tools/" menu (CONFIG_TOOLS_BUILD) with
an entry for each tool, and a "tools_build" target that builds the
selected ones for the target:

- Each tool is built by its own build system, as it is built
  standalone, into tools-build/ in the object tree. "make clean" removes
  that directory without running the tools' own clean rules.

- The compiler is the one CONFIG_CC_CAN_LINK was tested with: $(CC),
  USERCFLAGS and KBUILD_USERABI, so cross builds, including LLVM=1
  ARCH=<arch> without CROSS_COMPILE, produce target binaries. USERLDFLAGS
  reach the tools as LDFLAGS.

- kbuild's own state (srctree, objtree, VPATH, sub_make_done, ...) and
  the user's CFLAGS/LDFLAGS/O= from the environment or the command line
  are kept away from the tools.

- A tool is rebuilt from scratch when its make arguments change.
  "make -n" shows the build without removing or recording anything.

- On failure, the message names the option that skips the tool.

The menu depends on CC_CAN_LINK, so toolchains without a C library are
unaffected, and is limited to glibc toolchains for x86_64 and arm64,
which is what it has been tested with.

The first entries are the tools that only need a C library: bootconfig,
counter, dma, gpio, hv, iio, spi and usb.

Assisted-by: LLM
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 .gitignore            |  5 +++
 Makefile              |  8 ++++-
 lib/Kconfig.debug     |  2 ++
 tools/Kconfig         | 72 +++++++++++++++++++++++++++++++++++++++
 tools/Makefile.kbuild | 79 +++++++++++++++++++++++++++++++++++++++++++
 5 files changed, 165 insertions(+), 1 deletion(-)
 create mode 100644 tools/Kconfig
 create mode 100644 tools/Makefile.kbuild

diff --git a/.gitignore b/.gitignore
index 9875120ea7bde..6bf05bbd94245 100644
--- a/.gitignore
+++ b/.gitignore
@@ -101,6 +101,11 @@ modules.order
 #
 /tar-install/
 
+#
+# userspace tools (make tools_build)
+#
+/tools-build/
+
 #
 # pacman files (make pacman-pkg)
 #
diff --git a/Makefile b/Makefile
index 8c94aff229b21..af5d0a9d51df9 100644
--- a/Makefile
+++ b/Makefile
@@ -1633,6 +1633,11 @@ tools/%: FORCE
 	$(Q)mkdir -p $(objtree)/tools
 	$(Q)$(MAKE) O=$(abspath $(objtree)) subdir=tools -C $(srctree)/tools/ $*
 
+# The userspace programs selected in tools/Kconfig, built for the target
+PHONY += tools_build
+tools_build: headers
+	$(Q)$(MAKE) -f $(srctree)/tools/Makefile.kbuild
+
 # ---------------------------------------------------------------------------
 # Kernel selftest
 
@@ -1772,7 +1777,7 @@ CLEAN_FILES += vmlinux.symvers modules-only.symvers \
 	       modules.builtin modules.builtin.modinfo modules.nsdeps \
 	       modules.builtin.ranges vmlinux.o.map vmlinux.unstripped \
 	       vmlinux.thinlto-index builtin.order \
-	       compile_commands.json rust/test \
+	       compile_commands.json rust/test tools-build \
 	       rust-project.json .vmlinux.objs .vmlinux.export.c \
 	       .builtin-dtbs-list .builtin-dtbs.S sbom-*.spdx.json
 
@@ -1894,6 +1899,7 @@ help:
 	@echo  '  clang-tidy        - Check with clang-tidy'
 	@echo  ''
 	@echo  'Tools:'
+	@echo  '  tools_build     - Build the userspace tools selected in tools/Kconfig'
 	@echo  '  nsdeps          - Generate missing symbol namespace dependencies'
 	@echo  '  sbom            - Generate Software Bill of Materials'
 	@echo  ''
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 6b24a2c89b84d..16984158977b3 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1913,6 +1913,8 @@ config PROVIDE_OHCI1394_DMA_INIT
 
 source "samples/Kconfig"
 
+source "tools/Kconfig"
+
 config ARCH_HAS_DEVMEM_IS_ALLOWED
 	bool
 
diff --git a/tools/Kconfig b/tools/Kconfig
new file mode 100644
index 0000000000000..bf0643b39b86e
--- /dev/null
+++ b/tools/Kconfig
@@ -0,0 +1,72 @@
+# SPDX-License-Identifier: GPL-2.0-only
+
+config TOOLS_BUILD_ABI
+	def_bool X86_64 || ARM64
+
+config TOOLS_BUILD_GLIBC
+	def_bool $(success,echo '#include <features.h>' | $(CC) $(CLANG_FLAGS) $(USERCFLAGS) -E -dM -x c - | grep -q __GLIBC__)
+
+menuconfig TOOLS_BUILD
+	bool "Build userspace tools from tools/"
+	depends on CC_CAN_LINK && !UML
+	depends on TOOLS_BUILD_ABI && TOOLS_BUILD_GLIBC
+	help
+	  Build the selected programs under tools/ for the target together
+	  with the kernel, as part of "make all", or alone with
+	  "make tools_build". Each program is built by its own build system
+	  into tools-build/ in the object tree. The tools then always match
+	  the kernel they were built with, and a change that breaks one of
+	  them shows up in the same build that compiles the kernel.
+
+	  This needs a compiler that can link glibc programs for the target,
+	  and is currently limited to x86_64 and arm64.
+
+	  If unsure, say N.
+
+if TOOLS_BUILD
+
+config TOOLS_BUILD_BOOTCONFIG
+	bool "bootconfig"
+	help
+	  Build tools/bootconfig, the boot configuration editor, for the
+	  target. This is independent of the host copy that the kernel
+	  build uses for CONFIG_CMDLINE_FROM_BOOTCONFIG.
+
+config TOOLS_BUILD_COUNTER
+	bool "Counter tools"
+	help
+	  Build tools/counter (counter_example, counter_watch_events).
+
+config TOOLS_BUILD_DMA
+	bool "DMA map benchmark"
+	help
+	  Build tools/dma (dma_map_benchmark).
+
+config TOOLS_BUILD_GPIO
+	bool "GPIO tools"
+	help
+	  Build tools/gpio (lsgpio, gpio-hammer, gpio-event-mon,
+	  gpio-watch).
+
+config TOOLS_BUILD_HV
+	bool "Hyper-V guest daemons"
+	help
+	  Build tools/hv (hv_kvp_daemon, hv_vss_daemon and, on x86,
+	  hv_fcopy_uio_daemon).
+
+config TOOLS_BUILD_IIO
+	bool "IIO tools"
+	help
+	  Build tools/iio (lsiio, iio_event_monitor, iio_generic_buffer).
+
+config TOOLS_BUILD_SPI
+	bool "SPI tools"
+	help
+	  Build tools/spi (spidev_test, spidev_fdx).
+
+config TOOLS_BUILD_USB
+	bool "USB tools"
+	help
+	  Build tools/usb (testusb, ffs-test).
+
+endif # TOOLS_BUILD
diff --git a/tools/Makefile.kbuild b/tools/Makefile.kbuild
new file mode 100644
index 0000000000000..820a2d9a3893b
--- /dev/null
+++ b/tools/Makefile.kbuild
@@ -0,0 +1,79 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# Builds the userspace programs selected in tools/Kconfig for the target.
+# Invoked by "make tools_build", which "make all" runs when CONFIG_TOOLS_BUILD
+# is set. Each program is built by its own build system, the way it is built
+# standalone, into $(objtree)/tools-build/.
+
+PHONY := __tools_build
+__tools_build:
+
+include include/config/auto.conf
+
+abs_srctree := $(realpath $(srctree))
+toolsdir := $(abs_srctree)/tools
+outdir := $(CURDIR)/tools-build
+
+# kbuild's state and the user's compiler flags, from the environment or the
+# command line, would change how these build
+unexport srctree objtree srcroot VPATH building_out_of_srctree sub_make_done
+unexport CLANG_FLAGS INSTALL_HDR_PATH O
+unexport CFLAGS CPPFLAGS LDFLAGS EXTRA_CFLAGS EXTRA_LDFLAGS USERCFLAGS USERLDFLAGS
+space := $(subst ,, )
+overrides := $(subst \$(space),\@space@,$(MAKEOVERRIDES))
+MAKEOVERRIDES := $(subst \@space@,\$(space),$(filter-out O=% CFLAGS=% CPPFLAGS=% \
+	LDFLAGS=% EXTRA_CFLAGS=% EXTRA_LDFLAGS=% USERCFLAGS=% USERLDFLAGS=%,$(overrides)))
+
+# Keep Python's bytecode caches out of the source tree
+export PYTHONDONTWRITEBYTECODE := 1
+
+# The compiler CONFIG_CC_CAN_LINK was tested with. The tools take linker
+# flags from LDFLAGS.
+tools-cc := $(CC) $(USERCFLAGS) $(KBUILD_USERABI)
+ifneq ($(USERLDFLAGS),)
+override LDFLAGS := $(USERLDFLAGS)
+export LDFLAGS
+endif
+
+squote := '
+escsq = $(subst $(squote),'\$(squote)',$1)
+
+# $(call build,<output directory>,<make arguments>,<files to check>,<CONFIG_ symbol>)
+# Builds in an empty directory when the make arguments or LDFLAGS changed, or
+# when one of the files is newer than the last build. "make -n" only shows
+# the build.
+build-key = $(call escsq,$(2) LDFLAGS=$(USERLDFLAGS))
+dry-run := $(findstring n,$(firstword -$(MAKEFLAGS)))
+
+define build
+	+$(Q)$(if $(dry-run),,if [ "$$(cat $(1)/.tools_build 2>/dev/null)" != '$(build-key)' ] $(if $(3),|| \
+	   [ -n "$$(find $(3) -newer $(1)/.tools_build -print -quit 2>/dev/null)" ]); then \
+		rm -rf $(1); \
+	fi;) \
+	mkdir -p $(1) && $(MAKE) $(2) && \
+	$(if $(dry-run),:,printf '%s' '$(build-key)' > $(1)/.tools_build) || \
+	{ echo >&2 "tools_build: $(patsubst $(outdir)/%,%,$(1)) failed to build; set CONFIG_$(4)=n to skip it"; false; }
+endef
+
+# Programs in tools/<name>, which track their own header dependencies
+tools-$(CONFIG_TOOLS_BUILD_BOOTCONFIG)	+= bootconfig
+tools-$(CONFIG_TOOLS_BUILD_COUNTER)	+= counter
+tools-$(CONFIG_TOOLS_BUILD_DMA)		+= dma
+tools-$(CONFIG_TOOLS_BUILD_GPIO)	+= gpio
+tools-$(CONFIG_TOOLS_BUILD_HV)		+= hv
+tools-$(CONFIG_TOOLS_BUILD_IIO)		+= iio
+tools-$(CONFIG_TOOLS_BUILD_SPI)		+= spi
+tools-$(CONFIG_TOOLS_BUILD_USB)		+= usb
+
+tool-targets := $(addprefix tool-,$(tools-y))
+
+__tools_build: $(tool-targets)
+
+PHONY += $(tool-targets)
+$(tool-targets): tool-%: FORCE
+	$(call build,$(outdir)/$*,-C $(toolsdir)/$* O=$(outdir)/$* CC='$(call escsq,$(tools-cc))',,TOOLS_BUILD_$(shell echo $* | tr a-z A-Z))
+
+PHONY += FORCE
+FORCE:
+
+.PHONY: $(PHONY)
-- 
2.53.0

[RFC PATCH 3/6] tools: build perf in tools_build

[Sasha Levin]

Add CONFIG_TOOLS_BUILD_PERF. perf is built as it is built standalone,
with optional features enabled when their libraries are installed, and
with -Werror following CONFIG_WERROR. The feature table is left out of
the kernel build log.

CONFIG_TOOLS_BUILD_PERF_MINIMAL turns every optional feature off
instead, so the result does not depend on the build machine. allmodconfig
and allyesconfig turn it on.

Assisted-by: LLM
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 tools/Kconfig         | 15 +++++++++++++++
 tools/Makefile.kbuild | 19 +++++++++++++++++++
 2 files changed, 34 insertions(+)

diff --git a/tools/Kconfig b/tools/Kconfig
index bf0643b39b86e..488f439592150 100644
--- a/tools/Kconfig
+++ b/tools/Kconfig
@@ -59,6 +59,21 @@ config TOOLS_BUILD_IIO
 	help
 	  Build tools/iio (lsiio, iio_event_monitor, iio_generic_buffer).
 
+config TOOLS_BUILD_PERF
+	bool "perf"
+	help
+	  Build tools/perf. As in a standalone perf build, optional
+	  features are enabled when the libraries they need are installed.
+
+config TOOLS_BUILD_PERF_MINIMAL
+	bool "Build perf with all optional features disabled"
+	depends on TOOLS_BUILD_PERF
+	help
+	  Turn off every optional perf feature, so that the result does
+	  not depend on which libraries the build machine has installed.
+	  allmodconfig and allyesconfig turn this on, which keeps their
+	  builds the same on every machine.
+
 config TOOLS_BUILD_SPI
 	bool "SPI tools"
 	help
diff --git a/tools/Makefile.kbuild b/tools/Makefile.kbuild
index 820a2d9a3893b..62fd494253eca 100644
--- a/tools/Makefile.kbuild
+++ b/tools/Makefile.kbuild
@@ -73,6 +73,25 @@ PHONY += $(tool-targets)
 $(tool-targets): tool-%: FORCE
 	$(call build,$(outdir)/$*,-C $(toolsdir)/$* O=$(outdir)/$* CC='$(call escsq,$(tools-cc))',,TOOLS_BUILD_$(shell echo $* | tr a-z A-Z))
 
+# perf, without the feature table in the kernel build log
+perf-flags := CC='$(call escsq,$(tools-cc))' FEATURE_DISPLAY= WERROR=$(if $(CONFIG_WERROR),1,0)
+
+# Every optional feature off, so the result does not depend on which
+# libraries are installed
+perf-flags-$(CONFIG_TOOLS_BUILD_PERF_MINIMAL) += \
+	NO_LIBELF=1 NO_LIBTRACEEVENT=1 NO_JEVENTS=1 NO_LIBPYTHON=1 NO_LIBDW=1 \
+	NO_LIBBPF=1 BUILD_BPF_SKEL=0 NO_SLANG=1 NO_GTK2=1 NO_AIO=1 \
+	NO_BACKTRACE=1 NO_DEMANGLE=1 NO_LZMA=1 NO_LIBZSTD=1 NO_ZLIB=1 \
+	NO_LIBNUMA=1 NO_LIBUNWIND=1 NO_LIBLLVM=1 NO_CAPSTONE=1 NO_LIBPFM4=1 \
+	NO_SDT=1 NO_JVMTI=1 NO_LIBDEBUGINFOD=1 NO_BABELTRACE2=1 NO_RUST=1 \
+	NO_SHELLCHECK=1 NO_PERF_READ_VDSO32=1 NO_PERF_READ_VDSOX32=1
+
+__tools_build: $(if $(CONFIG_TOOLS_BUILD_PERF),perf)
+
+PHONY += perf
+perf: FORCE
+	$(call build,$(outdir)/perf,-C $(toolsdir)/perf -f Makefile.perf O=$(outdir)/perf $(perf-flags) $(perf-flags-y),,TOOLS_BUILD_PERF)
+
 PHONY += FORCE
 FORCE:
 
-- 
2.53.0

[RFC PATCH 4/6] tools: build kernel selftests in tools_build

[Sasha Levin]

Add a "Kernel selftests" sub-menu with one entry per selftests directory
that builds with only a C library and does not write into the source
tree. Each is built as "make kselftest-all" builds it, with KHDR_INCLUDES
pointing at the UAPI headers installed in the object tree, but by its own
make, so the selected ones build in parallel. Selftests whose Makefile
does not use KHDR_INCLUDES still build against the C library's copy of
the UAPI headers.

The selftests do not track header dependencies, so a selftest is built
again from scratch when its own directory, a header or makefile any
selftest may share, or a kernel source it includes directly (the vDSO
test includes the architecture's vDSO code) is newer than its last
build.

Selftests that need libraries beyond the C library, a vmlinux with BTF,
or a sanitizer runtime are left out for now.

Assisted-by: LLM
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 tools/Kconfig         | 239 ++++++++++++++++++++++++++++++++++++++++++
 tools/Makefile.kbuild | 100 ++++++++++++++++++
 2 files changed, 339 insertions(+)

diff --git a/tools/Kconfig b/tools/Kconfig
index 488f439592150..d713741782e22 100644
--- a/tools/Kconfig
+++ b/tools/Kconfig
@@ -84,4 +84,243 @@ config TOOLS_BUILD_USB
 	help
 	  Build tools/usb (testusb, ffs-test).
 
+menuconfig TOOLS_BUILD_SELFTESTS
+	bool "Kernel selftests"
+	help
+	  Build the selected targets under tools/testing/selftests, as
+	  "make kselftest-all" would, without running them.
+
+if TOOLS_BUILD_SELFTESTS
+
+config TOOLS_BUILD_SELFTESTS_ACCT
+	bool "acct"
+
+config TOOLS_BUILD_SELFTESTS_ALLOC_TAG
+	bool "alloc_tag"
+
+config TOOLS_BUILD_SELFTESTS_BREAKPOINTS
+	bool "breakpoints"
+
+config TOOLS_BUILD_SELFTESTS_CACHESTAT
+	bool "cachestat"
+
+config TOOLS_BUILD_SELFTESTS_CGROUP
+	bool "cgroup"
+
+config TOOLS_BUILD_SELFTESTS_CONNECTOR
+	bool "connector"
+
+config TOOLS_BUILD_SELFTESTS_CORE
+	bool "core"
+
+config TOOLS_BUILD_SELFTESTS_COREDUMP
+	bool "coredump"
+
+config TOOLS_BUILD_SELFTESTS_DAMON
+	bool "damon"
+
+config TOOLS_BUILD_SELFTESTS_DMABUF_HEAPS
+	bool "dmabuf-heaps"
+
+config TOOLS_BUILD_SELFTESTS_DRIVERS_DMA_BUF
+	bool "drivers/dma-buf"
+
+config TOOLS_BUILD_SELFTESTS_DRIVERS_NTSYNC
+	bool "drivers/ntsync"
+
+config TOOLS_BUILD_SELFTESTS_EFIVARFS
+	bool "efivarfs"
+
+config TOOLS_BUILD_SELFTESTS_FILELOCK
+	bool "filelock"
+
+config TOOLS_BUILD_SELFTESTS_FILESYSTEMS_BINDERFS
+	bool "filesystems/binderfs"
+
+config TOOLS_BUILD_SELFTESTS_FILESYSTEMS_EPOLL
+	bool "filesystems/epoll"
+
+config TOOLS_BUILD_SELFTESTS_FILESYSTEMS_EVENTFD
+	bool "filesystems/eventfd"
+
+config TOOLS_BUILD_SELFTESTS_FILESYSTEMS_FAILFS
+	bool "filesystems/failfs"
+
+config TOOLS_BUILD_SELFTESTS_FILESYSTEMS_FAT
+	bool "filesystems/fat"
+
+config TOOLS_BUILD_SELFTESTS_FILESYSTEMS_MNTNS_UNBINDABLE
+	bool "filesystems/mntns_unbindable"
+
+config TOOLS_BUILD_SELFTESTS_FILESYSTEMS_MOUNT_CYCLE
+	bool "filesystems/mount_cycle"
+
+config TOOLS_BUILD_SELFTESTS_FILESYSTEMS_NSFS
+	bool "filesystems/nsfs"
+
+config TOOLS_BUILD_SELFTESTS_FILESYSTEMS_UMOUNT_PROPAGATION
+	bool "filesystems/umount_propagation"
+
+config TOOLS_BUILD_SELFTESTS_FILESYSTEMS_XATTR
+	bool "filesystems/xattr"
+
+config TOOLS_BUILD_SELFTESTS_FIRMWARE
+	bool "firmware"
+
+config TOOLS_BUILD_SELFTESTS_FPU
+	bool "fpu"
+
+config TOOLS_BUILD_SELFTESTS_FTRACE
+	bool "ftrace"
+
+config TOOLS_BUILD_SELFTESTS_GPIO
+	bool "gpio"
+
+config TOOLS_BUILD_SELFTESTS_INTEL_PSTATE
+	bool "intel_pstate"
+	depends on X86
+
+config TOOLS_BUILD_SELFTESTS_IPC
+	bool "ipc"
+
+config TOOLS_BUILD_SELFTESTS_IR
+	bool "ir"
+
+config TOOLS_BUILD_SELFTESTS_KCMP
+	bool "kcmp"
+
+config TOOLS_BUILD_SELFTESTS_KEXEC
+	bool "kexec"
+	depends on X86_64
+
+config TOOLS_BUILD_SELFTESTS_KSELFTEST_HARNESS
+	bool "kselftest_harness"
+
+config TOOLS_BUILD_SELFTESTS_LSM
+	bool "lsm"
+
+config TOOLS_BUILD_SELFTESTS_MEDIA_TESTS
+	bool "media_tests"
+
+config TOOLS_BUILD_SELFTESTS_MEMBARRIER
+	bool "membarrier"
+
+config TOOLS_BUILD_SELFTESTS_MINCORE
+	bool "mincore"
+
+config TOOLS_BUILD_SELFTESTS_MOUNT
+	bool "mount"
+
+config TOOLS_BUILD_SELFTESTS_MOUNT_SETATTR
+	bool "mount_setattr"
+
+config TOOLS_BUILD_SELFTESTS_MOVE_MOUNT_SET_GROUP
+	bool "move_mount_set_group"
+
+config TOOLS_BUILD_SELFTESTS_MSEAL_SYSTEM_MAPPINGS
+	bool "mseal_system_mappings"
+
+config TOOLS_BUILD_SELFTESTS_NCI
+	bool "nci"
+
+config TOOLS_BUILD_SELFTESTS_NET_CAN
+	bool "net/can"
+
+config TOOLS_BUILD_SELFTESTS_NET_FORWARDING
+	bool "net/forwarding"
+
+config TOOLS_BUILD_SELFTESTS_NET_MPTCP
+	bool "net/mptcp"
+
+config TOOLS_BUILD_SELFTESTS_PCI_ENDPOINT
+	bool "pci_endpoint"
+
+config TOOLS_BUILD_SELFTESTS_PERF_EVENTS
+	bool "perf_events"
+
+config TOOLS_BUILD_SELFTESTS_PID_NAMESPACE
+	bool "pid_namespace"
+
+config TOOLS_BUILD_SELFTESTS_PIDFD
+	bool "pidfd"
+
+config TOOLS_BUILD_SELFTESTS_PIPE
+	bool "pipe"
+
+config TOOLS_BUILD_SELFTESTS_PROC
+	bool "proc"
+
+config TOOLS_BUILD_SELFTESTS_PTP
+	bool "ptp"
+
+config TOOLS_BUILD_SELFTESTS_PTRACE
+	bool "ptrace"
+
+config TOOLS_BUILD_SELFTESTS_RESCTRL
+	bool "resctrl"
+	depends on X86
+
+config TOOLS_BUILD_SELFTESTS_RING_BUFFER
+	bool "ring-buffer"
+
+config TOOLS_BUILD_SELFTESTS_RLIMITS
+	bool "rlimits"
+
+config TOOLS_BUILD_SELFTESTS_RSEQ
+	bool "rseq"
+
+config TOOLS_BUILD_SELFTESTS_RTC
+	bool "rtc"
+
+config TOOLS_BUILD_SELFTESTS_SCHED
+	bool "sched"
+
+config TOOLS_BUILD_SELFTESTS_SIGNAL
+	bool "signal"
+
+config TOOLS_BUILD_SELFTESTS_SIZE
+	bool "size"
+
+config TOOLS_BUILD_SELFTESTS_SPLICE
+	bool "splice"
+
+config TOOLS_BUILD_SELFTESTS_SYNC
+	bool "sync"
+
+config TOOLS_BUILD_SELFTESTS_SYSCALL_USER_DISPATCH
+	bool "syscall_user_dispatch"
+
+config TOOLS_BUILD_SELFTESTS_TDX
+	bool "tdx"
+	depends on X86
+
+config TOOLS_BUILD_SELFTESTS_THERMAL_INTEL_POWER_FLOOR
+	bool "thermal/intel/power_floor"
+	depends on X86
+
+config TOOLS_BUILD_SELFTESTS_THERMAL_INTEL_WORKLOAD_HINT
+	bool "thermal/intel/workload_hint"
+	depends on X86
+
+config TOOLS_BUILD_SELFTESTS_TIMENS
+	bool "timens"
+
+config TOOLS_BUILD_SELFTESTS_TMPFS
+	bool "tmpfs"
+
+config TOOLS_BUILD_SELFTESTS_USER_EVENTS
+	bool "user_events"
+
+config TOOLS_BUILD_SELFTESTS_VDSO
+	bool "vDSO"
+
+config TOOLS_BUILD_SELFTESTS_WATCHDOG
+	bool "watchdog"
+
+config TOOLS_BUILD_SELFTESTS_X86
+	bool "x86"
+	depends on X86
+
+endif # TOOLS_BUILD_SELFTESTS
+
 endif # TOOLS_BUILD
diff --git a/tools/Makefile.kbuild b/tools/Makefile.kbuild
index 62fd494253eca..c31347258d0a9 100644
--- a/tools/Makefile.kbuild
+++ b/tools/Makefile.kbuild
@@ -92,6 +92,106 @@ PHONY += perf
 perf: FORCE
 	$(call build,$(outdir)/perf,-C $(toolsdir)/perf -f Makefile.perf O=$(outdir)/perf $(perf-flags) $(perf-flags-y),,TOOLS_BUILD_PERF)
 
+# Selftests in tools/testing/selftests/<name>
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_ACCT)	+= acct
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_ALLOC_TAG)	+= alloc_tag
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_BREAKPOINTS)	+= breakpoints
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_CACHESTAT)	+= cachestat
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_CGROUP)	+= cgroup
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_CONNECTOR)	+= connector
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_CORE)	+= core
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_COREDUMP)	+= coredump
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_DAMON)	+= damon
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_DMABUF_HEAPS)	+= dmabuf-heaps
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_DRIVERS_DMA_BUF)	+= drivers/dma-buf
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_DRIVERS_NTSYNC)	+= drivers/ntsync
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_EFIVARFS)	+= efivarfs
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_FILELOCK)	+= filelock
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_FILESYSTEMS_BINDERFS)	+= filesystems/binderfs
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_FILESYSTEMS_EPOLL)	+= filesystems/epoll
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_FILESYSTEMS_EVENTFD)	+= filesystems/eventfd
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_FILESYSTEMS_FAILFS)	+= filesystems/failfs
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_FILESYSTEMS_FAT)	+= filesystems/fat
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_FILESYSTEMS_MNTNS_UNBINDABLE)	+= filesystems/mntns_unbindable
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_FILESYSTEMS_MOUNT_CYCLE)	+= filesystems/mount_cycle
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_FILESYSTEMS_NSFS)	+= filesystems/nsfs
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_FILESYSTEMS_UMOUNT_PROPAGATION)	+= filesystems/umount_propagation
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_FILESYSTEMS_XATTR)	+= filesystems/xattr
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_FIRMWARE)	+= firmware
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_FPU)	+= fpu
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_FTRACE)	+= ftrace
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_GPIO)	+= gpio
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_INTEL_PSTATE)	+= intel_pstate
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_IPC)	+= ipc
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_IR)	+= ir
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_KCMP)	+= kcmp
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_KEXEC)	+= kexec
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_KSELFTEST_HARNESS)	+= kselftest_harness
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_LSM)	+= lsm
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_MEDIA_TESTS)	+= media_tests
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_MEMBARRIER)	+= membarrier
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_MINCORE)	+= mincore
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_MOUNT)	+= mount
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_MOUNT_SETATTR)	+= mount_setattr
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_MOVE_MOUNT_SET_GROUP)	+= move_mount_set_group
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_MSEAL_SYSTEM_MAPPINGS)	+= mseal_system_mappings
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_NCI)	+= nci
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_NET_CAN)	+= net/can
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_NET_FORWARDING)	+= net/forwarding
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_NET_MPTCP)	+= net/mptcp
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_PCI_ENDPOINT)	+= pci_endpoint
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_PERF_EVENTS)	+= perf_events
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_PID_NAMESPACE)	+= pid_namespace
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_PIDFD)	+= pidfd
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_PIPE)	+= pipe
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_PROC)	+= proc
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_PTP)	+= ptp
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_PTRACE)	+= ptrace
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_RESCTRL)	+= resctrl
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_RING_BUFFER)	+= ring-buffer
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_RLIMITS)	+= rlimits
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_RSEQ)	+= rseq
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_RTC)	+= rtc
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_SCHED)	+= sched
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_SIGNAL)	+= signal
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_SIZE)	+= size
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_SPLICE)	+= splice
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_SYNC)	+= sync
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_SYSCALL_USER_DISPATCH)	+= syscall_user_dispatch
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_TDX)	+= tdx
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_THERMAL_INTEL_POWER_FLOOR)	+= thermal/intel/power_floor
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_THERMAL_INTEL_WORKLOAD_HINT)	+= thermal/intel/workload_hint
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_TIMENS)	+= timens
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_TMPFS)	+= tmpfs
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_USER_EVENTS)	+= user_events
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_VDSO)	+= vDSO
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_WATCHDOG)	+= watchdog
+selftests-$(CONFIG_TOOLS_BUILD_SELFTESTS_X86)	+= x86
+
+selftest-flags := CC='$(call escsq,$(tools-cc))' KHDR_INCLUDES='-isystem $(CURDIR)/usr/include'
+
+# Unlike tools/build, the selftests do not track header dependencies. A
+# selftest is built again from scratch when its own directory, a header or
+# makefile any selftest may share, or a kernel source it includes directly
+# is newer than its last build.
+selftest-shared := $(outdir)/selftests/.shared
+selftest-extra-vDSO := $(abs_srctree)/arch/$(SRCARCH)
+
+$(selftest-shared): FORCE
+	$(Q)mkdir -p $(@D); \
+	newest=$$(find $(CURDIR)/usr/include $(toolsdir)/include $(toolsdir)/testing/selftests \
+		-type f \( -name '*.h' -o -name '*.mk' -o -name Makefile \) -printf '%T@\n' | \
+		sort -n | tail -n 1); \
+	touch -d "@$${newest:-0}" $@
+
+selftest-targets := $(addprefix selftest-,$(selftests-y))
+
+__tools_build: $(selftest-targets)
+
+PHONY += $(selftest-targets)
+$(selftest-targets): selftest-%: $(selftest-shared) FORCE
+	$(call build,$(outdir)/selftests/$*,-C $(toolsdir)/testing/selftests/$* OUTPUT=$(outdir)/selftests/$* $(selftest-flags),$(selftest-shared) $(toolsdir)/testing/selftests/$* $(selftest-extra-$*),TOOLS_BUILD_SELFTESTS_$(shell echo $* | tr a-z/- A-Z__))
+
 PHONY += FORCE
 FORCE:
 
-- 
2.53.0

[RFC PATCH 5/6] kbuild: build the tools selected in tools/Kconfig as part of "make all"

[Sasha Levin]

With CONFIG_TOOLS_BUILD set, make "all" depend on tools_build, so the
selected tools are built with every kernel build, and allmodconfig and
allyesconfig builds catch changes that break them.

"make vmlinux", "make modules", single target and external module
builds are unaffected.

Assisted-by: LLM
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 Makefile | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/Makefile b/Makefile
index af5d0a9d51df9..1c55086ea5c8b 100644
--- a/Makefile
+++ b/Makefile
@@ -1638,6 +1638,10 @@ PHONY += tools_build
 tools_build: headers
 	$(Q)$(MAKE) -f $(srctree)/tools/Makefile.kbuild
 
+ifdef CONFIG_TOOLS_BUILD
+all: tools_build
+endif
+
 # ---------------------------------------------------------------------------
 # Kernel selftest
 
-- 
2.53.0

[RFC PATCH 6/6] Documentation: describe building tools with the kernel

[Sasha Levin]

Mention CONFIG_TOOLS_BUILD and "make tools_build" in the submit
checklist, ask for libc-only selftests to be added to tools/Kconfig,
and note that USERCFLAGS and USERLDFLAGS also apply to the tools.

Assisted-by: LLM
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 Documentation/dev-tools/kselftest.rst      | 4 ++++
 Documentation/kbuild/kbuild.rst            | 5 ++++-
 Documentation/process/submit-checklist.rst | 5 +++++
 3 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/Documentation/dev-tools/kselftest.rst b/Documentation/dev-tools/kselftest.rst
index 64c0ec7428a27..407d539e49b01 100644
--- a/Documentation/dev-tools/kselftest.rst
+++ b/Documentation/dev-tools/kselftest.rst
@@ -315,6 +315,10 @@ Contributing new tests (details)
 
     TARGETS += android
 
+ * If the test builds with only a C library, add an entry for it to the
+   "Kernel selftests" menu in tools/Kconfig and to tools/Makefile.kbuild,
+   so that it is built together with the kernel.
+
  * All changes should pass::
 
     kselftest-{all,install,clean,gen_tar}
diff --git a/Documentation/kbuild/kbuild.rst b/Documentation/kbuild/kbuild.rst
index 5a9013bacfb75..3e8e076a262fa 100644
--- a/Documentation/kbuild/kbuild.rst
+++ b/Documentation/kbuild/kbuild.rst
@@ -114,12 +114,15 @@ Additional libraries to link against when building host programs.
 
 USERCFLAGS
 ----------
-Additional options used for $(CC) when compiling userprogs.
+Additional options used for $(CC) when compiling userprogs and the tools
+selected in tools/Kconfig.
 
 USERLDFLAGS
 -----------
 Additional options used for $(LD) when linking userprogs. userprogs are linked
 with CC, so $(USERLDFLAGS) should include "-Wl," prefix as applicable.
+The tools selected in tools/Kconfig get these options on the compiler
+command line.
 
 KBUILD_KCONFIG
 --------------
diff --git a/Documentation/process/submit-checklist.rst b/Documentation/process/submit-checklist.rst
index beb7f94279fdb..9857b05824c2d 100644
--- a/Documentation/process/submit-checklist.rst
+++ b/Documentation/process/submit-checklist.rst
@@ -91,6 +91,11 @@ Build your code
      Use ``make htmldocs`` or ``make pdfdocs`` to check the build and
      fix any issues.
 
+  e) Changes to tools/ or to UAPI headers do not break the userspace tools
+     selected by ``CONFIG_TOOLS_BUILD``. ``allmodconfig`` turns it on when
+     the compiler can link glibc programs for the target (currently x86_64
+     and arm64), and ``make tools_build`` builds only the tools.
+
 2) Builds on multiple CPU architectures by using local cross-compile tools
    or some other build farm.
    Note that testing against architectures of different word sizes
-- 
2.53.0