From 9664ad11f0b0183b2ebb9b445e0cd332551381f8 Mon Sep 17 00:00:00 2001 From: Song Liu Date: Fri, 3 Feb 2023 10:28:16 -0800 Subject: [PATCH] kpatch-build: support CONFIG_LTO_CLANG_THIN Support CONFIG_LTO_CLANG_THIN with ld.lld --lto-obj-path option. With CONFIG_LTO_CLANG_THIN, .o files are LLVM IR binary, so CDO doesn't work on .o file. To solve this issue, we CDO the thinlto files generated by the --lto-obj-path option. Clang LTO generates the thinlto files after cross file inline, so they are good candidates for CDO. See [1] for more discussions about this. To achieve this, we need: 1. kpatch-build to update kernel Makefile(s) so it generates thinlto files; 2. kpatch-build and kpatch-cc to save the thinlto file properly; 3. kpatch-build to feed these thinlto files to CDO; 4. The user need to supply vmlinux.o, from which we generate the symtab file. We need this because GLOBAL symbols may be marked as LOCAL in LTO vmlinux; [1] https://github.com/dynup/kpatch/issues/1320 Signed-off-by: Song Liu --- kpatch-build/kpatch-build | 59 +++++++++++++++++++++++++++++++++------ kpatch-build/kpatch-cc | 18 ++++++++++++ 2 files changed, 68 insertions(+), 9 deletions(-) diff --git a/kpatch-build/kpatch-build b/kpatch-build/kpatch-build index 45e8b14bf..f71257804 100755 --- a/kpatch-build/kpatch-build +++ b/kpatch-build/kpatch-build @@ -173,11 +173,11 @@ cleanup() { # restore original vmlinux if it was overwritten by sourcedir build [[ -e "$TEMPDIR/vmlinux" ]] && mv -f "$TEMPDIR/vmlinux" "$KERNEL_SRCDIR/" - # restore original link-vmlinux.sh if we updated it for the build + # restore any files that were modified for the build [[ -e "$TEMPDIR/link-vmlinux.sh" ]] && mv -f "$TEMPDIR/link-vmlinux.sh" "$KERNEL_SRCDIR/scripts" - - # restore original Makefile.modfinal if we updated it for the build [[ -e "$TEMPDIR/Makefile.modfinal" ]] && mv -f "$TEMPDIR/Makefile.modfinal" "$KERNEL_SRCDIR/scripts" + [[ -e "$TEMPDIR/Makefile.build" ]] && mv -f "$TEMPDIR/Makefile.build" "$KERNEL_SRCDIR/scripts" + [[ -e "$TEMPDIR/Makefile" ]] && mv -f "$TEMPDIR/Makefile" "$KERNEL_SRCDIR" [[ "$DEBUG" -eq 0 ]] && rm -rf "$TEMPDIR" rm -rf "$RPMTOPDIR" @@ -1054,6 +1054,23 @@ if [[ -n "$CONFIG_DEBUG_INFO_BTF" ]]; then fi fi +if [[ -n "$CONFIG_LTO_CLANG" ]]; then + [[ -n "$CONFIG_LTO_CLANG_THIN" ]] || die "Non-thin LTO is not supported. Please enable CONFIG_LTO_CLANG_THIN" + + # This is a heuristic: use -x to check vmlinux vs. vmlinux.o + [[ -x "$VMLINUX" ]] && die "For kernel with CONFIG_LTO_CLANG, please supply vmlinux.o instead of vmlinux via -v|--vmlinux option." + + # update Makefile so that ld.lld generate vmlinux.o.thinlto.o* files for vmlinux.o + cp -f "$KERNEL_SRCDIR/Makefile" "$TEMPDIR/Makefile" || die + sed -i "s/--thinlto-cache-dir=\$(extmod_prefix).thinlto-cache/--lto-obj-path=vmlinux.o.thinlto.o/g" "$KERNEL_SRCDIR"/Makefile + + # update scripts/Makefile.build so that ld.lld generate XX.o.thinlto.o* files for modules + cp -f "$KERNEL_SRCDIR/scripts/Makefile.build" "$TEMPDIR/Makefile.build" || die + sed -i "s/\$(ld_flags)/\$(ld_flags) --lto-obj-path=\$@.thinlto.o/g" "$KERNEL_SRCDIR"/scripts/Makefile.build + + export KPATCH_CC_LTO=1 +fi + if [[ -n "$CONFIG_CC_IS_CLANG" ]]; then echo "WARNING: Clang support is experimental" fi @@ -1174,9 +1191,14 @@ if [[ -n "$CONFIG_MODVERSIONS" ]]; then trace_on fi +if [[ -n "$CONFIG_LTO_CLANG" ]]; then + DIFF_OBJS="$TEMPDIR/thinlto_objs" +else + DIFF_OBJS="$TEMPDIR/changed_objs" +fi # Read as words, no quotes. # shellcheck disable=SC2013 -for i in $(cat "$TEMPDIR/changed_objs") +for i in $(cat "$DIFF_OBJS") do mkdir -p "$TEMPDIR/patched/$(dirname "$i")" || die cp -f "$BUILDDIR/$i" "$TEMPDIR/patched/$i" || die @@ -1205,7 +1227,8 @@ if [[ -z "$MODNAME" ]] ; then MODNAME="$(module_name_string "$MODNAME")" fi -FILES="$(cat "$TEMPDIR/changed_objs")" +FILES="$(cat "$DIFF_OBJS")" + cd "$TEMPDIR" || die mkdir output declare -a objnames @@ -1229,7 +1252,11 @@ for i in $FILES; do mkdir -p "output/$(dirname "$i")" cd "$BUILDDIR" || die - find_kobj "$i" + if [[ -n "$CONFIG_LTO_CLANG" ]] ; then + KOBJFILE=${i/.o.thinlto.o*/} + else + find_kobj "$i" + fi cd "$TEMPDIR" || die if [[ -e "orig/$i" ]]; then if [[ -n $OOT_MODULE ]]; then @@ -1246,16 +1273,30 @@ for i in $FILES; do else KOBJFILE_NAME=$(basename "${KOBJFILE%.ko}") KOBJFILE_NAME="${KOBJFILE_NAME//-/_}" - KOBJFILE_PATH="${TEMPDIR}/module/$KOBJFILE" + if [[ -n "$CONFIG_LTO_CLANG" ]] ; then + KOBJFILE_PATH="${TEMPDIR}/module/$KOBJFILE.ko" + else + KOBJFILE_PATH="${TEMPDIR}/module/$KOBJFILE" + fi SYMTAB="${KOBJFILE_PATH}.symtab" SYMVERS_FILE="$BUILDDIR/Module.symvers" fi - "$READELF" -s --wide "$KOBJFILE_PATH" > "$SYMTAB" + # With CONFIG_LTO_CLANG, multiple .thinlto files share a + # symtab file. Only generate the symtab file once. + [[ -e "$SYMTAB" ]] || "$READELF" --symbols --wide "$KOBJFILE_PATH" > "$SYMTAB" if [[ "$ARCH" = "ppc64le" ]]; then sed -ri 's/\s+\[: 8\]//' "$SYMTAB" fi + if [[ -n "$CONFIG_LTO_CLANG" ]] ; then + # skip .thinlto file that didn't change at all + diff "orig/$i" "patched/$i" 2> /dev/null && continue + # skip .thinlto file without any functions + num_func=$("$READELF" --symbols "orig/$i" | grep -c FUNC) + [[ $num_func -eq 0 ]] && continue + fi + # create-diff-object orig.o patched.o parent-name parent-symtab # Module.symvers patch-mod-name output.o "$TOOLSDIR"/create-diff-object $CDO_FLAGS "orig/$i" "patched/$i" "$KOBJFILE_NAME" \ @@ -1308,7 +1349,7 @@ fi cd "$TEMPDIR/output" || die # $KPATCH_LDFLAGS and result of find used as list, no quotes. # shellcheck disable=SC2086,SC2046 -"$LD" -r $KPATCH_LDFLAGS -o ../patch/tmp_output.o $(find . -name "*.o") 2>&1 | logger || die +"$LD" -r $KPATCH_LDFLAGS -o ../patch/tmp_output.o $(find . -name "*.o*") 2>&1 | logger || die if [[ "$USE_KLP" -eq 1 ]]; then cp -f "$TEMPDIR"/patch/tmp_output.o "$TEMPDIR"/patch/output.o || die diff --git a/kpatch-build/kpatch-cc b/kpatch-build/kpatch-cc index 2a3d26449..7e9e1bed7 100755 --- a/kpatch-build/kpatch-cc +++ b/kpatch-build/kpatch-cc @@ -79,6 +79,24 @@ elif [[ "$TOOLCHAINCMD" =~ ^(.*-)?ld || "$TOOLCHAINCMD" =~ ^(.*-)?ld.lld ]] ; th args+=(--warn-unresolved-symbols) break ;; + */.tmp_*.o) + # .tmp_*.o is used for single file modules. + # See "cmd_ld_single_m" in scripts/Makefile.build. + if [[ $KPATCH_CC_LTO -eq 1 ]] ; then + mkdir -p "$KPATCH_GCC_TEMPDIR/orig/$(dirname "$relobj")" + cp "${obj/.tmp_/}".thinlto.o* "$KPATCH_GCC_TEMPDIR/orig/$(dirname "$relobj")" + echo "${obj/.tmp_/}".thinlto.o* >> "$KPATCH_GCC_TEMPDIR/thinlto_objs" + fi + break + ;; + *.o) + if [[ $KPATCH_CC_LTO -eq 1 ]] ; then + mkdir -p "$KPATCH_GCC_TEMPDIR/orig/$(dirname "$relobj")" + cp "$obj".thinlto* "$KPATCH_GCC_TEMPDIR/orig/$(dirname "$relobj")" + echo "$obj".thinlto.o* >> "$KPATCH_GCC_TEMPDIR/thinlto_objs" + fi + break + ;; *) break ;;