restructure building process

Right now, we do three build passes: one to build the original tree
(full) build, one to build the patch tree (diff build), then one to
rebuild original objects that where changed by the patch (diff build).

This is going to be a problem when we try to support (near) full tree
rebuilds due to changes in commonly included header files.

This commit changes the build process to intercept calls to gcc by make
using the CROSS_COMPILE environment variable and, during the patched
build phase, copies the original object for any object that is about to
rebuilt due to a change.

This reduces the number of build passes to the minimum possible (two).

Signed-off-by: Seth Jennings <sjenning@redhat.com>

kpatch-build/Makefile

@@ -14,7 +14,7 @@ create-diff-object: create-diff-object.c list.h lookup.c lookup.h insn/insn.c \
 
 install: all
 	$(INSTALL) -d $(LIBEXECDIR)
-	$(INSTALL) $(TARGETS) $(LIBEXECDIR)
+	$(INSTALL) $(TARGETS) kpatch-gcc $(LIBEXECDIR)
 	$(INSTALL) -d $(BINDIR)
 	$(INSTALL) kpatch-build $(BINDIR)
 

kpatch-build/kpatch-build

@@ -392,48 +392,25 @@ export KCFLAGS="-I$DATADIR/patch -ffunction-sections -fdata-sections"
 
 echo "Building original kernel"
 make mrproper >> "$LOGFILE" 2>&1 || die
-make "-j$CPUS" $TARGETS "O=$OBJDIR" >> "$LOGFILE" 2>&1 || die
+CROSS_COMPILE="$TOOLSDIR/kpatch-gcc " make "-j$CPUS" $TARGETS "O=$OBJDIR" >> "$LOGFILE" 2>&1 || die
 
 echo "Building patched kernel"
 patch -N -p1 < "$APPLIEDPATCHFILE" >> "$LOGFILE" 2>&1 || die
-make "-j$CPUS" $TARGETS "O=$OBJDIR" 2>&1 | tee -a "$TEMPDIR/patched_build.log" >> "$LOGFILE"
+mkdir -p "$TEMPDIR/orig" "$TEMPDIR/patched"
+export TEMPDIR
+CROSS_COMPILE="$TOOLSDIR/kpatch-gcc " make "-j$CPUS" $TARGETS "O=$OBJDIR"  >> "$LOGFILE" 2>&1 || die
 [[ "${PIPESTATUS[0]}" -eq 0 ]] || die
 
-echo "Detecting changed objects"
-while read line; do
-	[[ "$line" =~ CC ]] || continue
-	eval set -- "$line"
-	case $2 in
-		init/version.o) continue ;;
-		scripts/mod/devicetable-offsets.s) continue ;;
-		scripts/mod/file2alias.o) continue ;;
-		*.mod.o) continue ;;
-		arch/x86/kernel/asm-offsets.s) die "a struct definition change was detected" ;;
-		\[M\]) obj=$3 ;;
-		*) obj=$2 ;;
-	esac
+if [[ ! -e "$TEMPDIR/changed_objs" ]]; then
+	die "no changed objects found"
+fi
 
-	echo $obj >> $TEMPDIR/changed_objs
-done < "$TEMPDIR/patched_build.log"
-
-[[ ! -s "$TEMPDIR/changed_objs" ]] && die "no changed objects were detected"
-
-mkdir "$TEMPDIR/patched"
-for i in $(cat $TEMPDIR/changed_objs); do
-	mkdir -p "$TEMPDIR/patched/$(dirname $i)"
+for i in $(cat "$TEMPDIR/changed_objs")
+do
+	mkdir -p "$TEMPDIR/patched/$(dirname $i)" || die
 	cp -f "$OBJDIR/$i" "$TEMPDIR/patched/$i" || die
 done
 
-echo "Rebuilding original objects"
-patch -R -p1 < "$APPLIEDPATCHFILE" >> "$LOGFILE" 2>&1
-rm -f "$APPLIEDPATCHFILE"
-make "-j$CPUS" $TARGETS "O=$OBJDIR" >> "$LOGFILE" 2>&1 || die
-mkdir "$TEMPDIR/orig"
-for i in $(cat $TEMPDIR/changed_objs); do
-	mkdir -p "$TEMPDIR/orig/$(dirname $i)"
-	cp -f "$OBJDIR/$i" "$TEMPDIR/orig/$i" || die
-done
-
 echo "Extracting new and modified ELF sections"
 cd "$TEMPDIR/orig"
 FILES="$(find * -type f)"

kpatch-build/kpatch-gcc

@@ -0,0 +1,33 @@
+#!/bin/bash
+
+set -x
+
+TOOLCHAINCMD="$1"
+shift
+
+if [[ "$TOOLCHAINCMD" != "gcc" ]] || [[ -z "$TEMPDIR" ]]; then
+    exec "$TOOLCHAINCMD" "$@"
+fi
+
+declare -a args=($@)
+
+while [ "$#" -gt 0 ]; do
+	if [ "$1" = "-o" ]; then
+		case "$2" in
+			*.mod.o|*built-in.o|vmlinux.o|.tmp_kallsyms1.o|.tmp_kallsyms2.o|init/version.o|arch/x86/boot/version.o|arch/x86/boot/compressed/eboot.o|arch/x86/boot/header.o|arch/x86/boot/compressed/efi_stub_64.o|arch/x86/boot/compressed/piggy.o|.*.o)
+			break;
+			;;
+		*.o)
+			mkdir -p "$TEMPDIR/orig/$(dirname $2)"
+			cp -f "$2" "$TEMPDIR/orig/$2"
+			echo "$2" >> "$TEMPDIR/changed_objs"
+			;;
+		*)
+			break
+			;;
+		esac
+	fi
+	shift
+done
+
+exec "$TOOLCHAINCMD" "${args[@]}"