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, 451 insertions, 0 deletions

diff --git a/scripts/bash-completion/make b/scripts/bash-completion/make
new file mode 100644
index 000000000..42e8dcead
--- /dev/null
+++ b/scripts/bash-completion/make
@@ -0,0 +1,451 @@
+# SPDX-License-Identifier: GPL-2.0-only
+# bash completion for GNU make with kbuild extension       -*- shell-script -*-
+
+# Load the default completion script for make. It is typically located at
+# /usr/share/bash-completion/completions/make, but we do not rely on it.
+__kbuild_load_default_make_completion()
+{
+	local -a dirs=("${BASH_COMPLETION_USER_DIR:-${XDG_DATA_HOME:-$HOME/.local/share}/bash-completion}/completions")
+	local ifs=$IFS IFS=: dir compfile this_dir
+
+	for dir in ${XDG_DATA_DIRS:-/usr/local/share:/usr/share}; do
+	        dirs+=("$dir"/bash-completion/completions)
+	done
+	IFS=$ifs
+
+	this_dir="$(realpath "$(dirname "${BASH_SOURCE[0]}")")"
+
+	for dir in "${dirs[@]}"; do
+		if [[ ! -d ${dir} || ${dir} = "${this_dir}" ]]; then
+			continue
+		fi
+
+		for compfile in make make.bash _make; do
+			compfile=$dir/$compfile
+			# Avoid trying to source dirs; https://bugzilla.redhat.com/903540
+			if [[ -f ${compfile} ]] && . "${compfile}" &>/dev/null; then
+
+				__kbuild_default_make_completion=$(
+					# shellcheck disable=SC2046 # word splitting is the point here
+					set -- $(complete -p make)
+
+					while [[ $# -gt 1 && "$1" != -F ]]; do
+						shift
+					done
+
+					if [[ "$1" = -F ]]; then
+						echo "$2"
+					fi
+				)
+
+				return
+			fi
+		done
+	done
+}
+
+__kbuild_load_default_make_completion
+
+__kbuild_handle_variable()
+{
+	local var=${1%%=*}
+	local cur=${cur#"${var}"=}
+	local srctree=$2
+	local keywords=()
+
+	case $var in
+	ARCH)
+		# sub-directories under arch/
+		keywords+=($(find "${srctree}/arch" -mindepth 1 -maxdepth 1 -type d -printf '%P\n'))
+		# architectures hard-coded in the top Makefile
+		keywords+=(i386 x86_64 sparc32 sparc64 parisc64)
+		;;
+	CROSS_COMPILE)
+		# toolchains with a full path
+		local cross_compile=()
+		local c c2
+		_filedir
+
+		for c in "${COMPREPLY[@]}"; do
+			# eval for tilde expansion
+			# suppress error, as this fails when it contains a space
+			eval "c2=${c}" 2>/dev/null || continue
+			if [[ ${c} == *-elfedit && ! -d ${c2} && -x ${c2} ]]; then
+				cross_compile+=("${c%elfedit}")
+			fi
+		done
+
+		# toolchains in the PATH environment
+		while read -r c; do
+			if [[ ${c} == *-elfedit ]]; then
+				keywords+=("${c%elfedit}")
+			fi
+		done < <(compgen -c)
+
+		COMPREPLY=()
+		_filedir -d
+
+		# Add cross_compile directly without passing it to compgen.
+		# Otherwise, toolchain paths with a tilde do not work.
+		# e.g.)
+		#   CROSS_COMPILE=~/0day/gcc-14.2.0-nolibc/aarch64-linux/bin/aarch64-linux-
+		COMPREPLY+=("${cross_compile[@]}")
+		;;
+	LLVM)
+		# LLVM=1 uses the default 'clang' etc.
+		keywords+=(1)
+
+		# suffix for a particular version. LLVM=-18 uses 'clang-18' etc.
+		while read -r c; do
+			if [[ ${c} == clang-[0-9]* ]]; then
+				keywords+=("${c#clang}")
+			fi
+		done < <(compgen -c)
+
+		# directory path to LLVM toolchains
+		_filedir -d
+		;;
+	KCONFIG_ALLCONFIG)
+		# KCONFIG_ALLCONFIG=1 selects the default fragment
+		keywords+=(1)
+		# or the path to a fragment file
+		_filedir
+		;;
+	C | KBUILD_CHECKSRC)
+		keywords+=(1 2)
+		;;
+	V | KBUILD_VERBOSE)
+		keywords+=({,1}{,2})
+		;;
+	W | KBUILD_EXTRA_WARN)
+		keywords+=({,1}{,2}{,3}{,c}{,e})
+		;;
+	KBUILD_ABS_SRCTREE | KBUILD_MODPOST_NOFINAL | KBUILD_MODPOST_WARN | \
+		CLIPPY | KBUILD_CLIPPY | KCONFIG_NOSILENTUPDATE | \
+		KCONFIG_OVERWRITECONFIG | KCONFIG_WARN_UNKNOWN_SYMBOL | \
+		KCONFIG_WERROR )
+		keywords+=(1)
+		;;
+	INSTALL_MOD_STRIP)
+		keywords+=(1 --strip-debug --strip-unneeded)
+		;;
+	O | KBUILD_OUTPUT | M | KBUILD_EXTMOD | MO | KBUILD_EXTMOD_OUTPUT | *_PATH)
+		# variables that take a directory.
+		_filedir -d
+		return
+		;;
+	KBUILD_EXTRA_SYMBOL | KBUILD_KCONFIG | KCONFIG_CONFIG)
+		# variables that take a file.
+		_filedir
+		return
+	esac
+
+	COMPREPLY+=($(compgen -W "${keywords[*]}" -- "${cur}"))
+}
+
+# Check the -C, -f options and 'source' symlink. Return the source tree we are
+# working in.
+__kbuild_get_srctree()
+{
+	local words=("$@")
+	local cwd makef_dir
+
+	# see if a path was specified with -C/--directory
+	for ((i = 1; i < ${#words[@]}; i++)); do
+		if [[ ${words[i]} == -@(C|-directory) ]]; then
+			# eval for tilde expansion.
+			# suppress error, as this fails when it contains a space
+			eval "cwd=${words[i + 1]}" 2>/dev/null
+			break
+		fi
+	done
+
+	if [[ -z ${cwd} ]]; then
+		cwd=.
+	fi
+
+	# see if a Makefile was specified with -f/--file/--makefile
+	for ((i = 1; i < ${#words[@]}; i++)); do
+		if [[ ${words[i]} == -@(f|-?(make)file) ]]; then
+			# eval for tilde expansion
+			# suppress error, as this fails when it contains a space
+			eval "makef_dir=${words[i + 1]%/*}" 2>/dev/null
+			break
+		fi
+	done
+
+	if [ -z "${makef_dir}" ]; then
+		makef_dir=${cwd}
+	elif [[ ${makef_dir} != /* ]]; then
+		makef_dir=${cwd}/${makef_dir}
+	fi
+
+	# If ${makef_dir} is a build directory created by the O= option, there
+	# is a symbolic link 'source', which points to the kernel source tree.
+	if [[ -L ${makef_dir}/source ]]; then
+		makef_dir=$(readlink "${makef_dir}/source")
+	fi
+
+	echo "${makef_dir}"
+}
+
+# Get SRCARCH to do a little more clever things
+__kbuild_get_srcarch()
+{
+	local words=("$@")
+	local arch srcarch uname_m
+
+	# see if ARCH= is explicitly specified
+	for ((i = 1; i < ${#words[@]}; i++)); do
+		if [[ ${words[i]} == ARCH=* ]]; then
+			arch=${words[i]#ARCH=}
+			break
+		fi
+	done
+
+	# If ARCH= is not specified, check the build marchine's architecture
+	if [[ -z ${arch} ]]; then
+		uname_m=$(uname -m)
+
+		# shellcheck disable=SC2209 # 'sh' is SuperH, not a shell command
+		case ${uname_m} in
+		arm64 | aarch64*) arch=arm64 ;;
+		arm* | sa110)     arch=arm ;;
+		i?86 | x86_64)    arch=x86 ;;
+		loongarch*)       arch=loongarch ;;
+		mips*)            arch=mips ;;
+		ppc*)             arch=powerpc ;;
+		riscv*)           arch=riscv ;;
+		s390x)            arch=s390 ;;
+		sh[234]*)         arch=sh ;;
+		sun4u)            arch=sparc64 ;;
+		*)                arch=${uname_m} ;;
+		esac
+	fi
+
+	case ${arch} in
+		parisc64)          srcarch=parisc ;;
+		sparc32 | sparc64) srcarch=sparc ;;
+		i386 | x86_64)     srcarch=x86 ;;
+		*)                 srcarch=${arch} ;;
+	esac
+
+	echo "$srcarch"
+}
+
+# small Makefile to parse obj-* syntax
+__kbuild_tmp_makefile()
+{
+cat <<'EOF'
+.PHONY: __default
+__default:
+	$(foreach m,$(obj-y) $(obj-m) $(obj-),$(foreach s, -objs -y -m -,$($(m:%.o=%$s))) $(m))
+EOF
+echo "include ${1}"
+}
+
+_make_for_kbuild ()
+{
+	# shellcheck disable=SC2034 # these are set by _init_completion
+	local cur prev words cword split
+	_init_completion -s || return
+
+	local srctree
+	srctree=$(__kbuild_get_srctree "${words[@]}")
+
+	# If 'kernel' and 'Documentation' directories are found, we assume this
+	# is a kernel tree. Otherwise, we fall back to the generic rule provided
+	# by the bash-completion project.
+	if [[ ! -d ${srctree}/kernel || ! -d ${srctree}/Documentation ]]; then
+		if [ -n "${__kbuild_default_make_completion}" ]; then
+			"${__kbuild_default_make_completion}" "$@"
+		fi
+		return
+	fi
+
+	# make options with a parameter (copied from the bash-completion project)
+	case ${prev} in
+	--file | --makefile | --old-file | --assume-old | --what-if | --new-file | \
+		--assume-new | -!(-*)[foW])
+		_filedir
+		return
+		;;
+	--include-dir | --directory | -!(-*)[ICm])
+		_filedir -d
+		return
+		;;
+	-!(-*)E)
+		COMPREPLY=($(compgen -v -- "$cur"))
+		return
+		;;
+	--eval | -!(-*)[DVx])
+		return
+		;;
+	--jobs | -!(-*)j)
+		COMPREPLY=($(compgen -W "{1..$(($(_ncpus) * 2))}" -- "$cur"))
+		return
+		;;
+	esac
+
+	local keywords=()
+
+	case ${cur} in
+	-*)
+		# make options (copied from the bash-completion project)
+		local opts
+		opts="$(_parse_help "$1")"
+		COMPREPLY=($(compgen -W "${opts:-$(_parse_usage "$1")}" -- "$cur"))
+		if [[ ${COMPREPLY-} == *= ]]; then
+			compopt -o nospace
+		fi
+		return
+		;;
+	*=*)
+		__kbuild_handle_variable "${cur}" "${srctree}"
+		return
+		;;
+	KBUILD_*)
+		# There are many variables prefixed with 'KBUILD_'.
+		# Display them only when 'KBUILD_' is entered.
+		# shellcheck disable=SC2191 # '=' is appended for variables
+		keywords+=(
+			KBUILD_{CHECKSRC,EXTMOD,EXTMOD_OUTPUT,OUTPUT,VERBOSE,EXTRA_WARN,CLIPPY}=
+			KBUILD_BUILD_{USER,HOST,TIMESTAMP}=
+			KBUILD_MODPOST_{NOFINAL,WARN}=
+			KBUILD_{ABS_SRCTREE,EXTRA_SYMBOLS,KCONFIG}=
+		)
+		;;
+	KCONFIG_*)
+		# There are many variables prefixed with 'KCONFIG_'.
+		# Display them only when 'KCONFIG_' is entered.
+		# shellcheck disable=SC2191 # '=' is appended for variables
+		keywords+=(
+			KCONFIG_{CONFIG,ALLCONFIG,NOSILENTUPDATE,OVERWRITECONFIG}=
+			KCONFIG_{SEED,PROBABILITY}=
+			KCONFIG_WARN_UNKNOWN_SYMBOL=
+			KCONFIG_WERROR=
+		)
+		;;
+	*)
+		# By default, hide KBUILD_* and KCONFIG_* variables.
+		# Instead, display only the prefix parts.
+		keywords+=(KBUILD_ KCONFIG_)
+		;;
+	esac
+
+	if [[ ${cur} != /* && ${cur} != *//* ]]; then
+		local dir srcarch kbuild_file tmp
+		srcarch=$(__kbuild_get_srcarch "${words[@]}")
+
+		# single build
+		dir=${cur}
+		while true; do
+			if [[ ${dir} == */* ]]; then
+				dir=${dir%/*}
+			else
+				dir=.
+			fi
+
+			# Search for 'Kbuild' or 'Makefile' in the parent
+			# directories (may not be a direct parent)
+			if [[ -f ${srctree}/${dir}/Kbuild ]]; then
+				kbuild_file=${srctree}/${dir}/Kbuild
+				break
+			fi
+			if [[ -f ${srctree}/${dir}/Makefile ]]; then
+				kbuild_file=${srctree}/${dir}/Makefile
+				break
+			fi
+
+			if [[ ${dir} == . ]]; then
+				break
+			fi
+		done
+
+		if [[ -n ${kbuild_file} ]]; then
+			tmp=($(__kbuild_tmp_makefile "${kbuild_file}" |
+			       SRCARCH=${srcarch} obj=${dir} src=${srctree}/${dir} \
+			       "${1}" -n -f - 2>/dev/null))
+
+			# Add $(obj)/ prefix
+			if [[ ${dir} != . ]]; then
+				tmp=("${tmp[@]/#/${dir}\/}")
+			fi
+
+			keywords+=("${tmp[@]}")
+		fi
+
+		# *_defconfig and *.config files. These might be grouped into
+		# subdirectories, e.g., arch/powerpc/configs/*/*_defconfig.
+		if [[ ${cur} == */* ]]; then
+			dir=${cur%/*}
+		else
+			dir=.
+		fi
+
+		tmp=($(find "${srctree}/arch/${srcarch}/configs/${dir}" \
+		       "${srctree}/kernel/configs/${dir}" \
+		       -mindepth 1 -maxdepth 1 -type d -printf '%P/\n' \
+		       -o -printf '%P\n' 2>/dev/null))
+
+		if [[ ${dir} != . ]]; then
+			tmp=("${tmp[@]/#/${dir}\/}")
+		fi
+
+		keywords+=("${tmp[@]}")
+	fi
+
+	# shellcheck disable=SC2191 # '=' is appended for variables
+	keywords+=(
+		#
+		# variables (append =)
+		#
+		ARCH=
+		CROSS_COMPILE=
+		LLVM=
+		C= M= MO= O= V= W=
+		INSTALL{,_MOD,_HDR,_DTBS}_PATH=
+		KERNELRELEASE=
+
+		#
+		# targets
+		#
+		all help
+		clean mrproper distclean
+		clang-{tidy,analyzer} compile_commands.json
+		coccicheck
+		dtbs{,_check,_install} dt_binding_{check,schemas}
+		headers{,_install}
+		vmlinux install
+		modules{,_prepare,_install,_sign}
+		vdso_install
+		tags TAGS cscope gtags
+		rust{available,fmt,fmtcheck}
+		kernel{version,release} image_name
+		kselftest{,-all,-install,-clean,-merge}
+
+		# configuration
+		{,old,olddef,sync,def,savedef,rand,listnew,helpnew,test,tiny}config
+		{,build_}{menu,n,g,x}config
+		local{mod,yes}config
+		all{no,yes,mod,def}config
+		{yes2mod,mod2yes,mod2no}config
+
+		# docs
+		{html,textinfo,info,latex,pdf,epub,xml,linkcheck,refcheck,clean}docs
+
+		# package
+		{,bin,src}{rpm,deb}-pkg
+		{pacman,dir,tar}-pkg
+		tar{,gz,bz2,xz,zst}-pkg
+		perf-tar{,gz,bz2,xz,zst}-src-pkg
+	)
+
+	COMPREPLY=($(compgen -W "${keywords[*]}" -- "${cur}"))
+
+	# Do not append a space for variables, subdirs, "KBUILD_", "KCONFIG_".
+	if [[ ${COMPREPLY-} == *[=/] || ${COMPREPLY-} =~ ^(KBUILD|KCONFIG)_$ ]]; then
+		compopt -o nospace
+	fi
+
+} && complete -F _make_for_kbuild make