From 5febf432df1cfa5b25d99b54c32103fafbdd0eb9 Mon Sep 17 00:00:00 2001
From: Miguel Ojeda <ojeda@kernel.org>
Date: Sun, 16 Aug 2026 15:32:33 +0200
Subject: kbuild: rust: keep Rust objects out of Clang LTO with inline helpers

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>
---
 lib/Makefile | 336 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 336 insertions(+)
 create mode 100644 lib/Makefile

(limited to 'lib/Makefile')

diff --git a/lib/Makefile b/lib/Makefile
new file mode 100644
index 000000000..7f75cc6ed
--- /dev/null
+++ b/lib/Makefile
@@ -0,0 +1,336 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# Makefile for some libs needed in the kernel.
+#
+
+ccflags-remove-$(CONFIG_FUNCTION_TRACER) += $(CC_FLAGS_FTRACE)
+
+# Branch profiling isn't noinstr-safe
+ifdef CONFIG_TRACE_BRANCH_PROFILING
+CFLAGS_smp_processor_id.o += -DDISABLE_BRANCH_PROFILING
+endif
+
+# These files are disabled because they produce lots of non-interesting and/or
+# flaky coverage that is not a function of syscall inputs. For example,
+# rbtree can be global and individual rotations don't correlate with inputs.
+KCOV_INSTRUMENT_string.o := n
+KCOV_INSTRUMENT_rbtree.o := n
+KCOV_INSTRUMENT_list_debug.o := n
+KCOV_INSTRUMENT_debugobjects.o := n
+KCOV_INSTRUMENT_dynamic_debug.o := n
+KCOV_INSTRUMENT_fault-inject.o := n
+KCOV_INSTRUMENT_find_bit.o := n
+
+# string.o implements standard library functions like memset/memcpy etc.
+# Use -ffreestanding to ensure that the compiler does not try to "optimize"
+# them into calls to themselves.
+CFLAGS_string.o := -ffreestanding
+
+# Early boot use of cmdline, don't instrument it
+ifdef CONFIG_AMD_MEM_ENCRYPT
+KASAN_SANITIZE_string.o := n
+
+CFLAGS_string.o += -fno-stack-protector
+endif
+
+lib-y := ctype.o string.o vsprintf.o cmdline.o \
+	 rbtree.o radix-tree.o timerqueue.o xarray.o \
+	 maple_tree.o idr.o extable.o irq_regs.o argv_split.o \
+	 flex_proportions.o ratelimit.o \
+	 is_single_threaded.o plist.o decompress.o kobject_uevent.o \
+	 earlycpio.o seq_buf.o siphash.o dec_and_lock.o \
+	 nmi_backtrace.o win_minmax.o memcat_p.o \
+	 buildid.o objpool.o iomem_copy.o sys_info.o
+
+lib-$(CONFIG_UNION_FIND) += union_find.o
+lib-$(CONFIG_PRINTK) += dump_stack.o
+lib-$(CONFIG_SMP) += cpumask.o
+lib-$(CONFIG_MIN_HEAP) += min_heap.o
+
+lib-y	+= kobject.o klist.o
+obj-y	+= lockref.o
+
+CONTEXT_ANALYSIS_rhashtable.o := y
+
+obj-y += bcd.o sort.o parser.o debug_locks.o random32.o \
+	 bust_spinlocks.o kasprintf.o bitmap.o scatterlist.o \
+	 list_sort.o uuid.o iov_iter.o clz_ctz.o \
+	 bsearch.o find_bit.o llist.o lwq.o memweight.o kfifo.o \
+	 percpu-refcount.o rhashtable.o base64.o \
+	 once.o refcount.o rcuref.o usercopy.o errseq.o bucket_locks.o \
+	 generic-radix-tree.o bitmap-str.o
+obj-y += string_helpers.o
+obj-y += hexdump.o
+obj-$(CONFIG_TEST_HEXDUMP) += test_hexdump.o
+obj-y += kstrtox.o
+obj-$(CONFIG_FIND_BIT_BENCHMARK) += find_bit_benchmark.o
+obj-$(CONFIG_FIND_BIT_BENCHMARK_RUST) += find_bit_benchmark_rust.o
+obj-$(CONFIG_TEST_BPF) += test_bpf.o
+test_dhry-objs := dhry_1.o dhry_2.o dhry_run.o
+obj-$(CONFIG_TEST_DHRY) += test_dhry.o
+obj-$(CONFIG_TEST_FIRMWARE) += test_firmware.o
+obj-$(CONFIG_TEST_BITOPS) += test_bitops.o
+CFLAGS_test_bitops.o += -Werror
+obj-$(CONFIG_TEST_SYSCTL) += test_sysctl.o
+obj-$(CONFIG_TEST_IDA) += test_ida.o
+obj-$(CONFIG_TEST_UBSAN) += test_ubsan.o
+CFLAGS_test_ubsan.o += $(call cc-disable-warning, unused-but-set-variable)
+UBSAN_SANITIZE_test_ubsan.o := y
+obj-$(CONFIG_TEST_KSTRTOX) += test-kstrtox.o
+obj-$(CONFIG_TEST_LKM) += test_module.o
+obj-$(CONFIG_TEST_VMALLOC) += test_vmalloc.o
+obj-$(CONFIG_TEST_WORKQUEUE) += test_workqueue.o
+obj-$(CONFIG_TEST_RHASHTABLE) += test_rhashtable.o
+obj-$(CONFIG_TEST_STATIC_KEYS) += test_static_keys.o
+obj-$(CONFIG_TEST_STATIC_KEYS) += test_static_key_base.o
+obj-$(CONFIG_TEST_DYNAMIC_DEBUG) += test_dynamic_debug.o
+
+obj-$(CONFIG_TEST_BITMAP) += test_bitmap.o
+ifeq ($(CONFIG_CC_IS_CLANG)$(CONFIG_KASAN),yy)
+# FIXME: Clang breaks test_bitmap_const_eval when KASAN and GCOV are enabled
+GCOV_PROFILE_test_bitmap.o := n
+endif
+
+obj-$(CONFIG_TEST_XARRAY) += test_xarray.o
+obj-$(CONFIG_TEST_MAPLE_TREE) += test_maple_tree.o
+obj-$(CONFIG_TEST_PARMAN) += test_parman.o
+obj-$(CONFIG_TEST_KMOD) += test_kmod.o
+obj-$(CONFIG_TEST_DEBUG_VIRTUAL) += test_debug_virtual.o
+obj-$(CONFIG_TEST_MEMCAT_P) += test_memcat_p.o
+obj-$(CONFIG_TEST_OBJAGG) += test_objagg.o
+obj-$(CONFIG_TEST_MEMINIT) += test_meminit.o
+obj-$(CONFIG_TEST_LOCKUP) += test_lockup.o
+obj-$(CONFIG_TEST_HMM) += test_hmm.o
+obj-$(CONFIG_TEST_FREE_PAGES) += test_free_pages.o
+obj-$(CONFIG_TEST_REF_TRACKER) += test_ref_tracker.o
+obj-$(CONFIG_TEST_OBJPOOL) += test_objpool.o
+obj-$(CONFIG_TEST_KEXEC_HANDOVER) += test_kho.o
+
+obj-$(CONFIG_TEST_FPU) += test_fpu.o
+test_fpu-y := test_fpu_glue.o test_fpu_impl.o
+CFLAGS_test_fpu_impl.o += $(CC_FLAGS_FPU)
+CFLAGS_REMOVE_test_fpu_impl.o += $(CC_FLAGS_NO_FPU)
+
+obj-y += kunit/
+
+ifeq ($(CONFIG_DEBUG_KOBJECT),y)
+CFLAGS_kobject.o += -DDEBUG
+CFLAGS_kobject_uevent.o += -DDEBUG
+endif
+
+obj-$(CONFIG_DEBUG_INFO_REDUCED) += debug_info.o
+CFLAGS_debug_info.o += $(call cc-option, -femit-struct-debug-detailed=any)
+
+obj-y += math/ crc/ crypto/ tests/ vdso/ raid/
+
+obj-$(CONFIG_GENERIC_IOMAP) += iomap.o
+obj-$(CONFIG_HAS_IOMEM) += iomap_copy.o devres.o
+obj-$(CONFIG_CHECK_SIGNATURE) += check_signature.o
+obj-$(CONFIG_DEBUG_LOCKING_API_SELFTESTS) += locking-selftest.o
+
+obj-$(CONFIG_GENERIC_CPU_CACHE_MAINTENANCE) += cache_maint.o
+
+lib-y += logic_pio.o
+
+lib-$(CONFIG_INDIRECT_IOMEM) += logic_iomem.o
+
+obj-$(CONFIG_TRACE_MMIO_ACCESS) += trace_readwrite.o
+
+obj-$(CONFIG_GENERIC_HWEIGHT) += hweight.o
+
+obj-$(CONFIG_BTREE) += btree.o
+obj-$(CONFIG_INTERVAL_TREE) += interval_tree.o
+obj-$(CONFIG_ASSOCIATIVE_ARRAY) += assoc_array.o
+obj-$(CONFIG_DEBUG_PREEMPT) += smp_processor_id.o
+obj-$(CONFIG_LIST_HARDENED) += list_debug.o
+obj-$(CONFIG_DEBUG_OBJECTS) += debugobjects.o
+
+obj-$(CONFIG_GENERIC_BITREVERSE) += bitrev.o
+obj-$(CONFIG_LINEAR_RANGES) += linear_ranges.o
+obj-$(CONFIG_PACKING)	+= packing.o
+obj-$(CONFIG_PACKING_KUNIT_TEST) += packing_test.o
+obj-$(CONFIG_XXHASH)	+= xxhash.o
+obj-$(CONFIG_GENERIC_ALLOCATOR) += genalloc.o
+
+obj-$(CONFIG_842_COMPRESS) += 842/
+obj-$(CONFIG_842_DECOMPRESS) += 842/
+obj-$(CONFIG_ZLIB_INFLATE) += zlib_inflate/
+obj-$(CONFIG_ZLIB_DEFLATE) += zlib_deflate/
+obj-$(CONFIG_ZLIB_DFLTCC) += zlib_dfltcc/
+obj-$(CONFIG_REED_SOLOMON) += reed_solomon/
+obj-$(CONFIG_BCH) += bch.o
+obj-$(CONFIG_LZO_COMPRESS) += lzo/
+obj-$(CONFIG_LZO_DECOMPRESS) += lzo/
+obj-$(CONFIG_LZ4_COMPRESS) += lz4/
+obj-$(CONFIG_LZ4HC_COMPRESS) += lz4/
+obj-$(CONFIG_LZ4_DECOMPRESS) += lz4/
+obj-$(CONFIG_ZSTD_COMPRESS) += zstd/
+obj-$(CONFIG_ZSTD_DECOMPRESS) += zstd/
+obj-$(CONFIG_XZ_DEC) += xz/
+
+lib-$(CONFIG_DECOMPRESS_GZIP) += decompress_inflate.o
+lib-$(CONFIG_DECOMPRESS_BZIP2) += decompress_bunzip2.o
+lib-$(CONFIG_DECOMPRESS_LZMA) += decompress_unlzma.o
+lib-$(CONFIG_DECOMPRESS_XZ) += decompress_unxz.o
+lib-$(CONFIG_DECOMPRESS_LZO) += decompress_unlzo.o
+lib-$(CONFIG_DECOMPRESS_LZ4) += decompress_unlz4.o
+lib-$(CONFIG_DECOMPRESS_ZSTD) += decompress_unzstd.o
+
+obj-$(CONFIG_TEXTSEARCH) += textsearch.o
+obj-$(CONFIG_TEXTSEARCH_KMP) += ts_kmp.o
+obj-$(CONFIG_TEXTSEARCH_BM) += ts_bm.o
+obj-$(CONFIG_TEXTSEARCH_FSM) += ts_fsm.o
+obj-$(CONFIG_SMP) += percpu_counter.o
+obj-$(CONFIG_AUDIT_GENERIC) += audit.o
+obj-$(CONFIG_AUDIT_COMPAT_GENERIC) += compat_audit.o
+
+obj-$(CONFIG_IOMMU_HELPER) += iommu-helper.o
+obj-$(CONFIG_FAULT_INJECTION) += fault-inject.o
+obj-$(CONFIG_FAULT_INJECTION_USERCOPY) += fault-inject-usercopy.o
+obj-$(CONFIG_NOTIFIER_ERROR_INJECTION) += notifier-error-inject.o
+obj-$(CONFIG_PM_NOTIFIER_ERROR_INJECT) += pm-notifier-error-inject.o
+obj-$(CONFIG_NETDEV_NOTIFIER_ERROR_INJECT) += netdev-notifier-error-inject.o
+obj-$(CONFIG_MEMORY_NOTIFIER_ERROR_INJECT) += memory-notifier-error-inject.o
+obj-$(CONFIG_OF_RECONFIG_NOTIFIER_ERROR_INJECT) += \
+	of-reconfig-notifier-error-inject.o
+obj-$(CONFIG_FUNCTION_ERROR_INJECTION) += error-inject.o
+
+obj-$(CONFIG_CODE_TAGGING) += codetag.o
+obj-$(CONFIG_MEM_ALLOC_PROFILING) += alloc_tag.o
+
+lib-$(CONFIG_GENERIC_BUG) += bug.o
+
+obj-$(CONFIG_HAVE_ARCH_TRACEHOOK) += syscall.o
+obj-$(CONFIG_ARCH_NEED_CMPXCHG_1_EMU) += cmpxchg-emu.o
+
+obj-$(CONFIG_DYNAMIC_DEBUG_CORE) += dynamic_debug.o
+#ensure exported functions have prototypes
+CFLAGS_dynamic_debug.o := -DDYNAMIC_DEBUG_MODULE
+
+obj-$(CONFIG_SYMBOLIC_ERRNAME) += errname.o
+
+obj-$(CONFIG_NLATTR) += nlattr.o
+
+obj-$(CONFIG_LRU_CACHE) += lru_cache.o
+
+obj-$(CONFIG_GENERIC_CSUM) += checksum.o
+
+obj-$(CONFIG_GENERIC_ATOMIC64) += atomic64.o
+
+obj-$(CONFIG_ATOMIC64_SELFTEST) += atomic64_test.o
+
+obj-$(CONFIG_CPU_RMAP) += cpu_rmap.o
+
+obj-$(CONFIG_CLOSURES) += closure.o
+
+obj-$(CONFIG_DQL) += dynamic_queue_limits.o
+
+obj-$(CONFIG_GLOB) += glob.o
+
+obj-$(CONFIG_DIMLIB) += dim/
+obj-$(CONFIG_SIGNATURE) += digsig.o
+
+lib-$(CONFIG_CLZ_TAB) += clz_tab.o
+
+obj-$(CONFIG_GENERIC_STRNCPY_FROM_USER) += strncpy_from_user.o
+obj-$(CONFIG_GENERIC_STRNLEN_USER) += strnlen_user.o
+
+obj-$(CONFIG_GENERIC_NET_UTILS) += net_utils.o
+
+obj-$(CONFIG_SG_SPLIT) += sg_split.o
+obj-$(CONFIG_SG_POOL) += sg_pool.o
+obj-$(CONFIG_MEMREGION) += memregion.o
+obj-$(CONFIG_STMP_DEVICE) += stmp_device.o
+obj-$(CONFIG_IRQ_POLL) += irq_poll.o
+
+# stackdepot.c should not be instrumented or call instrumented functions.
+# Prevent the compiler from calling builtins like memcmp() or bcmp() from this
+# file.
+CFLAGS_stackdepot.o += -fno-builtin
+CONTEXT_ANALYSIS_stackdepot.o := y
+obj-$(CONFIG_STACKDEPOT) += stackdepot.o
+KASAN_SANITIZE_stackdepot.o := n
+# In particular, instrumenting stackdepot.c with KMSAN will result in infinite
+# recursion.
+KMSAN_SANITIZE_stackdepot.o := n
+KCOV_INSTRUMENT_stackdepot.o := n
+
+obj-$(CONFIG_REF_TRACKER) += ref_tracker.o
+
+libfdt_files = fdt.o fdt_ro.o fdt_wip.o fdt_rw.o fdt_sw.o fdt_strerror.o \
+	       fdt_empty_tree.o fdt_addresses.o
+$(foreach file, $(libfdt_files), \
+	$(eval CFLAGS_$(file) = -I $(srctree)/scripts/dtc/libfdt))
+lib-$(CONFIG_LIBFDT) += $(libfdt_files)
+
+obj-$(CONFIG_BOOT_CONFIG) += bootconfig.o
+obj-$(CONFIG_BOOT_CONFIG_EMBED) += bootconfig-data.o
+
+$(obj)/bootconfig-data.o: $(obj)/default.bconf
+
+targets += default.bconf
+filechk_defbconf = cat $(or $(real-prereqs), /dev/null)
+$(obj)/default.bconf: $(CONFIG_BOOT_CONFIG_EMBED_FILE) FORCE
+	$(call filechk,defbconf)
+
+obj-$(CONFIG_RBTREE_TEST) += rbtree_test.o
+obj-$(CONFIG_INTERVAL_TREE_TEST) += interval_tree_test.o
+
+obj-$(CONFIG_PERCPU_TEST) += percpu_test.o
+
+obj-$(CONFIG_ASN1) += asn1_decoder.o
+obj-$(CONFIG_ASN1_ENCODER) += asn1_encoder.o
+
+obj-$(CONFIG_FONT_SUPPORT) += fonts/
+
+#
+# Build a fast OID lookip registry from include/linux/oid_registry.h
+#
+obj-$(CONFIG_OID_REGISTRY) += oid_registry.o
+
+$(obj)/oid_registry.o: $(obj)/oid_registry_data.c
+
+$(obj)/oid_registry_data.c: $(srctree)/include/linux/oid_registry.h \
+			    $(src)/build_OID_registry
+	$(call cmd,build_OID_registry)
+
+quiet_cmd_build_OID_registry = GEN     $@
+      cmd_build_OID_registry = perl $(src)/build_OID_registry $< $@
+
+clean-files	+= oid_registry_data.c
+
+obj-$(CONFIG_UCS2_STRING) += ucs2_string.o
+obj-$(CONFIG_UBSAN) += ubsan.o
+
+UBSAN_SANITIZE_ubsan.o := n
+KASAN_SANITIZE_ubsan.o := n
+KCSAN_SANITIZE_ubsan.o := n
+KMSAN_SANITIZE_ubsan.o := n
+CFLAGS_ubsan.o := -fno-stack-protector $(DISABLE_KSTACK_ERASE)
+
+obj-$(CONFIG_SBITMAP) += sbitmap.o
+
+obj-$(CONFIG_PARMAN) += parman.o
+
+obj-y += group_cpus.o
+
+# GCC library routines
+obj-$(CONFIG_GENERIC_LIB_ASHLDI3) += ashldi3.o
+obj-$(CONFIG_GENERIC_LIB_ASHRDI3) += ashrdi3.o
+obj-$(CONFIG_GENERIC_LIB_LSHRDI3) += lshrdi3.o
+obj-$(CONFIG_GENERIC_LIB_MULDI3) += muldi3.o
+obj-$(CONFIG_GENERIC_LIB_CMPDI2) += cmpdi2.o
+obj-$(CONFIG_GENERIC_LIB_UCMPDI2) += ucmpdi2.o
+obj-$(CONFIG_OBJAGG) += objagg.o
+
+# pldmfw library
+obj-$(CONFIG_PLDMFW) += pldmfw/
+
+obj-$(CONFIG_GENERIC_LIB_DEVMEM_IS_ALLOWED) += devmem_is_allowed.o
+
+obj-$(CONFIG_FIRMWARE_TABLE) += fw_table.o
+
+CONTEXT_ANALYSIS_test_context-analysis.o := y
+obj-$(CONFIG_CONTEXT_ANALYSIS_TEST) += test_context-analysis.o
+
+subdir-$(CONFIG_FORTIFY_SOURCE) += test_fortify
-- 
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