From 3db1cfb91b9b2b7cf6c5564995c446567baa371a Mon Sep 17 00:00:00 2001
From: Song Liu <song@kernel.org>
Date: Fri, 3 Feb 2023 10:28:16 -0800
Subject: [PATCH 102/107] 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 <song@kernel.org>
---
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 45e8b14..f712578 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+\[<localentry>: 8\]//' "$SYMTAB"
fi
+ if [[ -n "$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 2a3d264..7e9e1be 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
;;
--
2.37.3