Re: [PATCH 08/10] kbuild: do not include include/config/auto.conf from shell scripts

[Nicolas Schier <n.schier@avm.de>]

On Mon, Dec 13, 2021 at 04:29:39AM +0900, Masahiro Yamada wrote:
> Richard Weinberger pointed out the risk of sourcing the kernel config
> from shell scripts [1], and proposed some patches [2], [3]. It is a good
> point, but it took a long time because I was wondering how to fix this.
> 
> This commit goes with simple grep approach because there are only a few
> scripts including the kernel configuration.
> 
> scripts/link_vmlinux.sh has references to a bunch of CONFIG options,
> all of which are boolean. I added is_enabled() helper as
> scripts/package/{mkdebian,builddeb} do.
> 
> scripts/gen_autoksyms.sh uses 'eval', stating "to expand the whitelist
> path". I removed it since it is the issue we are trying to fix.
> 
> I was a bit worried about the cost of invoking the grep command over
> again. I extracted the grep parts from it, and measured the cost. It
> was approximately 0.03 sec, which I hope is acceptable.
> 
> [test code]
> 
>   $ cat test-grep.sh
>   #!/bin/sh
> 
>   is_enabled() {
>           grep -q "^$1=y" include/config/auto.conf
>   }
> 
>   is_enabled CONFIG_LTO_CLANG
>   is_enabled CONFIG_LTO_CLANG
>   is_enabled CONFIG_STACK_VALIDATION
>   is_enabled CONFIG_UNWINDER_ORC
>   is_enabled CONFIG_FTRACE_MCOUNT_USE_OBJTOOL
>   is_enabled CONFIG_VMLINUX_VALIDATION
>   is_enabled CONFIG_FRAME_POINTER
>   is_enabled CONFIG_GCOV_KERNEL
>   is_enabled CONFIG_LTO_CLANG
>   is_enabled CONFIG_RETPOLINE
>   is_enabled CONFIG_X86_SMAP
>   is_enabled CONFIG_LTO_CLANG
>   is_enabled CONFIG_VMLINUX_MAP
>   is_enabled CONFIG_KALLSYMS_ALL
>   is_enabled CONFIG_KALLSYMS_ABSOLUTE_PERCPU
>   is_enabled CONFIG_KALLSYMS_BASE_RELATIVE
>   is_enabled CONFIG_DEBUG_INFO_BTF
>   is_enabled CONFIG_KALLSYMS
>   is_enabled CONFIG_DEBUG_INFO_BTF
>   is_enabled CONFIG_BPF
>   is_enabled CONFIG_BUILDTIME_TABLE_SORT
>   is_enabled CONFIG_KALLSYMS
> 
>   $ time ./test-grep.sh
>   real    0m0.036s
>   user    0m0.027s
>   sys     m0.009s
> 
> [1]: https://lore.kernel.org/all/1919455.eZKeABUfgV@blindfold/
> [2]: https://lore.kernel.org/all/20180219092245.26404-1-richard@nod.at/
> [3]: https://lore.kernel.org/all/20210920213957.1064-2-richard@nod.at/
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> ---
> 
>  scripts/gen_autoksyms.sh |  6 ++---
>  scripts/link-vmlinux.sh  | 47 ++++++++++++++++++++--------------------
>  scripts/setlocalversion  |  9 ++++----
>  3 files changed, 30 insertions(+), 32 deletions(-)
> 
> diff --git a/scripts/gen_autoksyms.sh b/scripts/gen_autoksyms.sh
> index 6ed0d225c8b1..12ffb01f13cb 100755
> --- a/scripts/gen_autoksyms.sh
> +++ b/scripts/gen_autoksyms.sh
> @@ -26,10 +26,8 @@ if [ -n "$CONFIG_MODVERSIONS" ]; then
>  	needed_symbols="$needed_symbols module_layout"
>  fi

As kernel test robot pointed out, gen_autoksyms.sh still sources
include/config/auto.conf.  What about this:


diff --git a/scripts/gen_autoksyms.sh b/scripts/gen_autoksyms.sh
index 31872d95468b..be9ee250200e 100755
--- a/scripts/gen_autoksyms.sh
+++ b/scripts/gen_autoksyms.sh
@@ -16,13 +16,11 @@ case "$KBUILD_VERBOSE" in
        ;;
 esac
 
-# We need access to CONFIG_ symbols
-. include/config/auto.conf
 
 needed_symbols=
 
 # Special case for modversions (see modpost.c)
-if [ -n "$CONFIG_MODVERSIONS" ]; then
+if grep -qe "^CONFIG_MODVERSIONS=y" include/config/auto.conf; then
        needed_symbols="$needed_symbols module_layout"
 fi
 

For the other hunks:

Reviewed-by: Nicolas Schier <n.schier@avm.de>


>  
> -ksym_wl=
> -if [ -n "$CONFIG_UNUSED_KSYMS_WHITELIST" ]; then
> -	# Use 'eval' to expand the whitelist path and check if it is relative
> -	eval ksym_wl="$CONFIG_UNUSED_KSYMS_WHITELIST"
> +ksym_wl=$(sed -n 's/^CONFIG_UNUSED_KSYMS_WHITELIST="\(.*\)"$/\1/p' include/config/auto.conf)
> +if [ -n "$ksym_wl" ]; then
>  	[ "${ksym_wl}" != "${ksym_wl#/}" ] || ksym_wl="$abs_srctree/$ksym_wl"
>  	if [ ! -f "$ksym_wl" ] || [ ! -r "$ksym_wl" ]; then
>  		echo "ERROR: '$ksym_wl' whitelist file not found" >&2
> diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
> index 5cdd9bc5c385..a4b61a2f65db 100755
> --- a/scripts/link-vmlinux.sh
> +++ b/scripts/link-vmlinux.sh
> @@ -34,6 +34,10 @@ LD="$1"
>  KBUILD_LDFLAGS="$2"
>  LDFLAGS_vmlinux="$3"
>  
> +is_enabled() {
> +	grep -q "^$1=y" include/config/auto.conf
> +}
> +
>  # Nice output in kbuild format
>  # Will be supressed by "make -s"
>  info()
> @@ -80,11 +84,11 @@ modpost_link()
>  		${KBUILD_VMLINUX_LIBS}				\
>  		--end-group"
>  
> -	if [ -n "${CONFIG_LTO_CLANG}" ]; then
> +	if is_enabled CONFIG_LTO_CLANG; then
>  		gen_initcalls
>  		lds="-T .tmp_initcalls.lds"
>  
> -		if [ -n "${CONFIG_MODVERSIONS}" ]; then
> +		if is_enabled CONFIG_MODVERSIONS; then
>  			gen_symversions
>  			lds="${lds} -T .tmp_symversions.lds"
>  		fi
> @@ -104,21 +108,21 @@ objtool_link()
>  	local objtoolcmd;
>  	local objtoolopt;
>  
> -	if [ "${CONFIG_LTO_CLANG} ${CONFIG_STACK_VALIDATION}" = "y y" ]; then
> +	if is_enabled CONFIG_LTO_CLANG && is_enabled CONFIG_STACK_VALIDATION; then
>  		# Don't perform vmlinux validation unless explicitly requested,
>  		# but run objtool on vmlinux.o now that we have an object file.
> -		if [ -n "${CONFIG_UNWINDER_ORC}" ]; then
> +		if is_enabled CONFIG_UNWINDER_ORC; then
>  			objtoolcmd="orc generate"
>  		fi
>  
>  		objtoolopt="${objtoolopt} --duplicate"
>  
> -		if [ -n "${CONFIG_FTRACE_MCOUNT_USE_OBJTOOL}" ]; then
> +		if is_enabled CONFIG_FTRACE_MCOUNT_USE_OBJTOOL; then
>  			objtoolopt="${objtoolopt} --mcount"
>  		fi
>  	fi
>  
> -	if [ -n "${CONFIG_VMLINUX_VALIDATION}" ]; then
> +	if is_enabled CONFIG_VMLINUX_VALIDATION; then
>  		objtoolopt="${objtoolopt} --noinstr"
>  	fi
>  
> @@ -127,16 +131,16 @@ objtool_link()
>  			objtoolcmd="check"
>  		fi
>  		objtoolopt="${objtoolopt} --vmlinux"
> -		if [ -z "${CONFIG_FRAME_POINTER}" ]; then
> +		if ! is_enabled CONFIG_FRAME_POINTER; then
>  			objtoolopt="${objtoolopt} --no-fp"
>  		fi
> -		if [ -n "${CONFIG_GCOV_KERNEL}" ] || [ -n "${CONFIG_LTO_CLANG}" ]; then
> +		if is_enabled CONFIG_GCOV_KERNEL || is_enabled CONFIG_LTO_CLANG; then
>  			objtoolopt="${objtoolopt} --no-unreachable"
>  		fi
> -		if [ -n "${CONFIG_RETPOLINE}" ]; then
> +		if is_enabled CONFIG_RETPOLINE; then
>  			objtoolopt="${objtoolopt} --retpoline"
>  		fi
> -		if [ -n "${CONFIG_X86_SMAP}" ]; then
> +		if is_enabled CONFIG_X86_SMAP; then
>  			objtoolopt="${objtoolopt} --uaccess"
>  		fi
>  		info OBJTOOL ${1}
> @@ -161,7 +165,7 @@ vmlinux_link()
>  	# skip output file argument
>  	shift
>  
> -	if [ -n "${CONFIG_LTO_CLANG}" ]; then
> +	if is_enabled CONFIG_LTO_CLANG; then
>  		# Use vmlinux.o instead of performing the slow LTO link again.
>  		objs=vmlinux.o
>  		libs=
> @@ -189,7 +193,7 @@ vmlinux_link()
>  		ldflags="${ldflags} ${wl}--strip-debug"
>  	fi
>  
> -	if [ -n "${CONFIG_VMLINUX_MAP}" ]; then
> +	if is_enabled CONFIG_VMLINUX_MAP; then
>  		ldflags="${ldflags} ${wl}-Map=${output}.map"
>  	fi
>  
> @@ -239,15 +243,15 @@ kallsyms()
>  {
>  	local kallsymopt;
>  
> -	if [ -n "${CONFIG_KALLSYMS_ALL}" ]; then
> +	if is_enabled CONFIG_KALLSYMS_ALL; then
>  		kallsymopt="${kallsymopt} --all-symbols"
>  	fi
>  
> -	if [ -n "${CONFIG_KALLSYMS_ABSOLUTE_PERCPU}" ]; then
> +	if is_enabled CONFIG_KALLSYMS_ABSOLUTE_PERCPU; then
>  		kallsymopt="${kallsymopt} --absolute-percpu"
>  	fi
>  
> -	if [ -n "${CONFIG_KALLSYMS_BASE_RELATIVE}" ]; then
> +	if is_enabled CONFIG_KALLSYMS_BASE_RELATIVE; then
>  		kallsymopt="${kallsymopt} --base-relative"
>  	fi
>  
> @@ -312,9 +316,6 @@ if [ "$1" = "clean" ]; then
>  	exit 0
>  fi
>  
> -# We need access to CONFIG_ symbols
> -. include/config/auto.conf
> -
>  # Update version
>  info GEN .version
>  if [ -r .version ]; then
> @@ -343,7 +344,7 @@ tr '\0' '\n' < modules.builtin.modinfo | sed -n 's/^[[:alnum:]:_]*\.file=//p' |
>  	tr ' ' '\n' | uniq | sed -e 's:^:kernel/:' -e 's/$/.ko/' > modules.builtin
>  
>  btf_vmlinux_bin_o=""
> -if [ -n "${CONFIG_DEBUG_INFO_BTF}" ]; then
> +if is_enabled CONFIG_DEBUG_INFO_BTF; then
>  	btf_vmlinux_bin_o=.btf.vmlinux.bin.o
>  	if ! gen_btf .tmp_vmlinux.btf $btf_vmlinux_bin_o ; then
>  		echo >&2 "Failed to generate BTF for vmlinux"
> @@ -355,7 +356,7 @@ fi
>  kallsymso=""
>  kallsymso_prev=""
>  kallsyms_vmlinux=""
> -if [ -n "${CONFIG_KALLSYMS}" ]; then
> +if is_enabled CONFIG_KALLSYMS; then
>  
>  	# kallsyms support
>  	# Generate section listing all symbols and add it into vmlinux
> @@ -395,12 +396,12 @@ fi
>  vmlinux_link vmlinux "${kallsymso}" ${btf_vmlinux_bin_o}
>  
>  # fill in BTF IDs
> -if [ -n "${CONFIG_DEBUG_INFO_BTF}" -a -n "${CONFIG_BPF}" ]; then
> +if is_enabled CONFIG_DEBUG_INFO_BTF && is_enabled CONFIG_BPF; then
>  	info BTFIDS vmlinux
>  	${RESOLVE_BTFIDS} vmlinux
>  fi
>  
> -if [ -n "${CONFIG_BUILDTIME_TABLE_SORT}" ]; then
> +if is_enabled CONFIG_BUILDTIME_TABLE_SORT; then
>  	info SORTTAB vmlinux
>  	if ! sorttable vmlinux; then
>  		echo >&2 Failed to sort kernel tables
> @@ -412,7 +413,7 @@ info SYSMAP System.map
>  mksysmap vmlinux System.map
>  
>  # step a (see comment above)
> -if [ -n "${CONFIG_KALLSYMS}" ]; then
> +if is_enabled CONFIG_KALLSYMS; then
>  	mksysmap ${kallsyms_vmlinux} .tmp_System.map
>  
>  	if ! cmp -s System.map .tmp_System.map; then
> diff --git a/scripts/setlocalversion b/scripts/setlocalversion
> index 6b54e46a0f12..d06137405190 100755
> --- a/scripts/setlocalversion
> +++ b/scripts/setlocalversion
> @@ -111,9 +111,7 @@ if $scm_only; then
>  	exit
>  fi
>  
> -if test -e include/config/auto.conf; then
> -	. include/config/auto.conf
> -else
> +if ! test -e include/config/auto.conf; then
>  	echo "Error: kernelrelease not valid - run 'make prepare' to update it" >&2
>  	exit 1
>  fi
> @@ -125,10 +123,11 @@ if test ! "$srctree" -ef .; then
>  fi
>  
>  # CONFIG_LOCALVERSION and LOCALVERSION (if set)
> -res="${res}${CONFIG_LOCALVERSION}${LOCALVERSION}"
> +config_localversion=$(sed -n 's/^CONFIG_LOCALVERSION="\(.*\)"$/\1/p' include/config/auto.conf)
> +res="${res}${config_localversion}${LOCALVERSION}"
>  
>  # scm version string if not at a tagged commit
> -if test "$CONFIG_LOCALVERSION_AUTO" = "y"; then
> +if grep -q "^CONFIG_LOCALVERSION_AUTO=y$" include/config/auto.conf; then
>  	# full scm version string
>  	res="$res$(scm_version)"
>  elif [ "${LOCALVERSION+set}" != "set" ]; then
> -- 
> 2.32.0
>