kbuild: rust: keep Rust objects out of Clang LTO with inline helpersgrafted

Under `CONFIG_LTO_CLANG` + `CONFIG_RUST_INLINE_HELPERS`, one may hit
`objtool` errors such as:

    vmlinux.o: error: objtool: _R..._3Gsp4boot+0xd6a:
    can't find jump dest instruction at .text._R..._3Gsp4boot+0x1dfd

The reason is that in such builds, the Clang invocation that compiles
the combined Rust plus helpers bitcode emits LLVM bitcode (again) --
the final code generation happens in the linker's LTO step, which the
`-mllvm` trap options passed to Clang do not reach.

This, in turn, means that unreachable traps are missing, and the
impossible paths do not merely fallthrough to the next symbol, but past
the end of their own section, since LTO builds place each function in
its own section.

Thus filter `CC_FLAGS_LTO` out of the Clang invocation, so that it always
emits machine code directly, with the traps in place.

Assisted-by: LLM
Cc: Gary Guo <gary@garyguo.net>
Cc: Boqun Feng <boqun@kernel.org>
Cc: Alice Ryhl <aliceryhl@google.com>
Cc: Matthew Maurer <mmaurer@google.com>
Cc: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: stable@vger.kernel.org
Fixes: 3a2486cc1da5 ("kbuild: rust: provide an option to inline C helpers into Rust")
Acked-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260816133233.197500-2-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

1 files changed, 335 insertions, 0 deletions

diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile
new file mode 100644
index 000000000..8a4b6ddc6
--- /dev/null
+++ b/tools/testing/selftests/Makefile
@@ -0,0 +1,335 @@
+# SPDX-License-Identifier: GPL-2.0
+TARGETS += acct
+TARGETS += alsa
+TARGETS += amd-pstate
+TARGETS += arm64
+TARGETS += bpf
+TARGETS += breakpoints
+TARGETS += cachestat
+TARGETS += capabilities
+TARGETS += cgroup
+TARGETS += clone3
+TARGETS += connector
+TARGETS += core
+TARGETS += cpufreq
+TARGETS += cpu-hotplug
+TARGETS += damon
+TARGETS += devices/error_logs
+TARGETS += devices/probe
+TARGETS += dmabuf-heaps
+TARGETS += drivers/dma-buf
+TARGETS += drivers/ntsync
+TARGETS += drivers/s390x/uvdevice
+TARGETS += drivers/net
+TARGETS += drivers/net/bonding
+TARGETS += drivers/net/netconsole
+TARGETS += drivers/net/team
+TARGETS += drivers/net/virtio_net
+TARGETS += drivers/platform/x86/intel/ifs
+TARGETS += dt
+TARGETS += efivarfs
+TARGETS += exec
+TARGETS += fchmodat2
+TARGETS += filesystems
+TARGETS += filesystems/binderfs
+TARGETS += filesystems/epoll
+TARGETS += filesystems/failfs
+TARGETS += filesystems/fat
+TARGETS += filesystems/overlayfs
+TARGETS += filesystems/statmount
+TARGETS += filesystems/mount-notify
+TARGETS += filesystems/nsfs
+TARGETS += filesystems/fuse
+TARGETS += filesystems/move_mount
+TARGETS += filesystems/empty_mntns
+TARGETS += filesystems/fsmount_ns
+TARGETS += filesystems/fscontext_ns
+TARGETS += filesystems/mntns_cleanup
+TARGETS += firmware
+TARGETS += fpu
+TARGETS += ftrace
+TARGETS += futex
+TARGETS += gpio
+TARGETS += hid
+TARGETS += intel_pstate
+TARGETS += iommu
+TARGETS += ipc
+TARGETS += ir
+TARGETS += kcmp
+TARGETS += kexec
+TARGETS += kselftest_harness
+TARGETS += kvm
+TARGETS += landlock
+TARGETS += lib
+TARGETS += livepatch
+TARGETS += liveupdate
+TARGETS += lkdtm
+TARGETS += lsm
+TARGETS += membarrier
+TARGETS += memfd
+TARGETS += memory-hotplug
+TARGETS += mincore
+TARGETS += mount
+TARGETS += mount_setattr
+TARGETS += move_mount_set_group
+TARGETS += mqueue
+TARGETS += mseal_system_mappings
+TARGETS += nci
+TARGETS += net
+TARGETS += net/af_unix
+TARGETS += net/can
+TARGETS += net/forwarding
+TARGETS += net/hsr
+TARGETS += net/mptcp
+TARGETS += net/netfilter
+TARGETS += net/openvswitch
+TARGETS += net/ovpn
+TARGETS += net/packetdrill
+TARGETS += net/ppp
+TARGETS += net/rds
+TARGETS += net/tcp_ao
+TARGETS += nolibc
+TARGETS += pci_endpoint
+TARGETS += pcie_bwctrl
+TARGETS += perf_events
+TARGETS += pidfd
+TARGETS += pid_namespace
+TARGETS += pipe
+TARGETS += power_supply
+TARGETS += powerpc
+TARGETS += prctl
+TARGETS += proc
+TARGETS += pstore
+TARGETS += ptrace
+TARGETS += openat2
+TARGETS += rdma
+TARGETS += resctrl
+TARGETS += riscv
+TARGETS += rlimits
+TARGETS += rseq
+TARGETS += rtc
+TARGETS += rust
+TARGETS += sched_ext
+TARGETS += seccomp
+TARGETS += sgx
+TARGETS += signal
+TARGETS += size
+TARGETS += sparc64
+TARGETS += splice
+TARGETS += static_keys
+TARGETS += sync
+TARGETS += syscall_user_dispatch
+TARGETS += sysctl
+TARGETS += tc-testing
+TARGETS += tdx
+TARGETS += thermal/intel/power_floor
+TARGETS += thermal/intel/workload_hint
+TARGETS += timens
+ifneq (1, $(quicktest))
+TARGETS += timers
+endif
+TARGETS += tmpfs
+TARGETS += tpm2
+TARGETS += tty
+TARGETS += ublk
+TARGETS += uevent
+TARGETS += user_events
+TARGETS += vDSO
+TARGETS += mm
+TARGETS += vfio
+TARGETS += x86
+TARGETS += x86/bugs
+TARGETS += zram
+#Please keep the TARGETS list alphabetically sorted
+# Run "make quicktest=1 run_tests" or
+# "make quicktest=1 kselftest" from top level Makefile
+
+TARGETS_HOTPLUG = cpu-hotplug
+TARGETS_HOTPLUG += memory-hotplug
+
+# Networking tests want the net/lib target, include it automatically
+ifneq ($(filter net drivers/net drivers/net/hw,$(TARGETS)),)
+ifeq ($(filter net/lib,$(TARGETS)),)
+	INSTALL_DEP_TARGETS := net/lib
+endif
+endif
+
+# User can optionally provide a TARGETS skiplist. By default we skip
+# targets using BPF since it has cutting edge build time dependencies
+# which require more effort to install.
+SKIP_TARGETS ?= bpf sched_ext
+ifneq ($(SKIP_TARGETS),)
+	TMP := $(filter-out $(SKIP_TARGETS), $(TARGETS))
+	override TARGETS := $(TMP)
+endif
+
+# User can set FORCE_TARGETS to 1 to require all targets to be successfully
+# built; make will fail if any of the targets cannot be built. If
+# FORCE_TARGETS is not set (the default), make will succeed if at least one
+# of the targets gets built.
+FORCE_TARGETS ?=
+
+# Clear LDFLAGS and MAKEFLAGS when implicit rules are missing.  This provides
+# implicit rules to sub-test Makefiles which avoids build failures in test
+# Makefile that don't have explicit build rules.
+ifeq (,$(LINK.c))
+override LDFLAGS =
+override MAKEFLAGS =
+endif
+
+# Append kselftest to KBUILD_OUTPUT and O to avoid cluttering
+# KBUILD_OUTPUT with selftest objects and headers installed
+# by selftests Makefile or lib.mk.
+ifdef building_out_of_srctree
+override LDFLAGS =
+endif
+
+top_srcdir ?= ../../..
+
+ifeq ("$(origin O)", "command line")
+  KBUILD_OUTPUT := $(O)
+endif
+
+ifneq ($(KBUILD_OUTPUT),)
+  # Make's built-in functions such as $(abspath ...), $(realpath ...) cannot
+  # expand a shell special character '~'. We use a somewhat tedious way here.
+  abs_objtree := $(shell cd $(top_srcdir) && mkdir -p $(KBUILD_OUTPUT) && cd $(KBUILD_OUTPUT) && pwd)
+  $(if $(abs_objtree),, \
+    $(error failed to create output directory "$(KBUILD_OUTPUT)"))
+  # $(realpath ...) resolves symlinks
+  abs_objtree := $(realpath $(abs_objtree))
+  BUILD := $(abs_objtree)/kselftest
+  KHDR_INCLUDES := -isystem ${abs_objtree}/usr/include
+else
+  BUILD := $(CURDIR)
+  abs_srctree := $(shell cd $(top_srcdir) && pwd)
+  KHDR_INCLUDES := -isystem ${abs_srctree}/usr/include
+  DEFAULT_INSTALL_HDR_PATH := 1
+endif
+
+# Prepare for headers install
+include $(top_srcdir)/scripts/subarch.include
+ARCH           ?= $(SUBARCH)
+export BUILD
+export KHDR_INCLUDES
+
+# set default goal to all, so make without a target runs all, even when
+# all isn't the first target in the file.
+.DEFAULT_GOAL := all
+
+all:
+	@ret=1;							\
+	for TARGET in $(TARGETS) $(INSTALL_DEP_TARGETS); do	\
+		BUILD_TARGET=$$BUILD/$$TARGET;			\
+		mkdir $$BUILD_TARGET  -p;			\
+		$(MAKE) OUTPUT=$$BUILD_TARGET -C $$TARGET	\
+				O=$(abs_objtree)		\
+				$(if $(FORCE_TARGETS),|| exit);	\
+		ret=$$((ret * $$?));				\
+	done; exit $$ret;
+
+run_tests: all
+	@for TARGET in $(TARGETS); do \
+		BUILD_TARGET=$$BUILD/$$TARGET;	\
+		$(MAKE) OUTPUT=$$BUILD_TARGET -C $$TARGET run_tests \
+				SRC_PATH=$(shell readlink -e $$(pwd)) \
+				OBJ_PATH=$(BUILD)                   \
+				O=$(abs_objtree);		    \
+	done;
+
+hotplug:
+	@for TARGET in $(TARGETS_HOTPLUG); do \
+		BUILD_TARGET=$$BUILD/$$TARGET;	\
+		$(MAKE) OUTPUT=$$BUILD_TARGET -C $$TARGET;\
+	done;
+
+run_hotplug: hotplug
+	@for TARGET in $(TARGETS_HOTPLUG); do \
+		BUILD_TARGET=$$BUILD/$$TARGET;	\
+		$(MAKE) OUTPUT=$$BUILD_TARGET -C $$TARGET run_full_test;\
+	done;
+
+clean_hotplug:
+	@for TARGET in $(TARGETS_HOTPLUG); do \
+		BUILD_TARGET=$$BUILD/$$TARGET;	\
+		$(MAKE) OUTPUT=$$BUILD_TARGET -C $$TARGET clean;\
+	done;
+
+run_pstore_crash:
+	$(MAKE) -C pstore run_crash
+
+# Use $BUILD as the default install root. $BUILD points to the
+# right output location for the following cases:
+# 1. output_dir=kernel_src
+# 2. a separate output directory is specified using O= KBUILD_OUTPUT
+# 3. a separate output directory is specified using KBUILD_OUTPUT
+# Avoid conflict with INSTALL_PATH set by the main Makefile
+#
+KSFT_INSTALL_PATH ?= $(BUILD)/kselftest_install
+KSFT_INSTALL_PATH := $(abspath $(KSFT_INSTALL_PATH))
+# Avoid changing the rest of the logic here and lib.mk.
+INSTALL_PATH := $(KSFT_INSTALL_PATH)
+ALL_SCRIPT := $(INSTALL_PATH)/run_kselftest.sh
+TEST_LIST := $(INSTALL_PATH)/kselftest-list.txt
+
+install: all
+ifdef INSTALL_PATH
+	@# Ask all targets to install their files
+	mkdir -p $(INSTALL_PATH)/kselftest
+	install -m 744 kselftest/module.sh $(INSTALL_PATH)/kselftest/
+	install -m 744 kselftest/runner.sh $(INSTALL_PATH)/kselftest/
+	install -m 744 kselftest/prefix.pl $(INSTALL_PATH)/kselftest/
+	install -m 744 kselftest/ktap_helpers.sh $(INSTALL_PATH)/kselftest/
+	install -m 744 kselftest/ksft.py $(INSTALL_PATH)/kselftest/
+	install -m 744 run_kselftest.sh $(INSTALL_PATH)/
+	rm -f $(TEST_LIST)
+	@ret=1;	\
+	for TARGET in $(TARGETS) $(INSTALL_DEP_TARGETS); do \
+		BUILD_TARGET=$$BUILD/$$TARGET;	\
+		$(MAKE) OUTPUT=$$BUILD_TARGET -C $$TARGET install \
+				INSTALL_PATH=$(INSTALL_PATH)/$$TARGET \
+				SRC_PATH=$(shell readlink -e $$(pwd)) \
+				OBJ_PATH=$(INSTALL_PATH) \
+				O=$(abs_objtree)		\
+				$(if $(FORCE_TARGETS),|| exit);	\
+		ret=$$((ret * $$?));		\
+	done; exit $$ret;
+
+
+	@# Ask all targets to emit their test scripts
+	@# While building kselftest-list.text skip also non-existent TARGET dirs:
+	@# they could be the result of a build failure and should NOT be
+	@# included in the generated runlist.
+	for TARGET in $(TARGETS); do \
+		BUILD_TARGET=$$BUILD/$$TARGET;	\
+		[ ! -d $(INSTALL_PATH)/$$TARGET ] && printf "Skipping non-existent dir: $$TARGET\n" && continue; \
+		printf "Emit Tests for $$TARGET\n"; \
+		$(MAKE) -s --no-print-directory OUTPUT=$$BUILD_TARGET COLLECTION=$$TARGET \
+			-C $$TARGET emit_tests >> $(TEST_LIST); \
+	done;
+	@VERSION=$$(git describe HEAD 2>/dev/null); \
+	if [ -n "$$VERSION" ]; then \
+		echo "$$VERSION" > $(INSTALL_PATH)/VERSION; \
+		printf "Version saved to $(INSTALL_PATH)/VERSION\n"; \
+	else \
+		printf "Unable to get version from git describe\n"; \
+	fi
+	@echo "**Kselftest Installation is complete: $(INSTALL_PATH)**"
+else
+	$(error Error: set INSTALL_PATH to use install)
+endif
+
+FORMAT ?= .gz
+TAR_PATH = $(abspath ${INSTALL_PATH}/kselftest-packages/kselftest.tar${FORMAT})
+gen_tar: install
+	@mkdir -p ${INSTALL_PATH}/kselftest-packages/
+	@tar caf ${TAR_PATH} --exclude=kselftest-packages -C ${INSTALL_PATH} .
+	@echo "Created ${TAR_PATH}"
+
+clean:
+	@for TARGET in $(TARGETS) $(INSTALL_DEP_TARGETS); do \
+		BUILD_TARGET=$$BUILD/$$TARGET;	\
+		$(MAKE) OUTPUT=$$BUILD_TARGET -C $$TARGET clean;\
+	done;
+
+.PHONY: all run_tests hotplug run_hotplug clean_hotplug run_pstore_crash install clean gen_tar