add difftest.sh test

The purpose of this test script is to determine if create-diff-object
can properly recognize object file equivalence when passed the same file
for both the original and patched objects.  This verifies that
create-diff-object is correctly parsing, correlating, and comparing the
different elements of the object file.  In practice, a situation similar
to the test case occurs when a commonly included header file changes,
causing Make to rebuild many objects that have no functional change.

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

test/difftree.sh

@@ -0,0 +1,89 @@
+#!/bin/bash
+
+# The purpose of this test script is to determine if create-diff-object can
+# properly recognize object file equivalence when passed the same file for both
+# the original and patched objects.  This verifies that create-diff-object is
+# correctly parsing, correlating, and comparing the different elements of the
+# object file.  In practice, a situation similar to the test case occurs when a
+# commonly included header file changes, causing Make to rebuild many objects
+# that have no functional change.
+
+# This script requires a built kernel object tree to be in the kpatch cache
+# directory at $HOME/.kpatch/obj
+
+#set -x
+
+OBJDIR="$HOME/.kpatch/obj"
+SCRIPTDIR="$(readlink -f $(dirname $(type -p $0)))"
+TEMPDIR=$(mktemp -d)
+RESULTSDIR="$TEMPDIR/results"
+VMVLINUX="/usr/lib/debug/lib/modules/$(uname -r)/vmlinux" # path for F20
+
+if [[ ! -d $OBJDIR ]]; then
+	echo "please run kpatch-build to populate the object tree in $OBJDIR"
+fi
+
+cd "$OBJDIR" || exit 1
+for i in $(find * -name '*.o')
+do
+	# copied from kpatch-build/kpatch-gcc; keep in sync
+	case $i 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|\
+		kernel/system_certificates.o|\
+		.*.o)
+		continue
+		;;
+	esac
+	# skip objects that are the linked product of more than one object file
+	[[ $(eu-readelf -s $i | grep FILE | wc -l) -ne 1 ]] && continue
+	$SCRIPTDIR/../kpatch-build/create-diff-object $i $i /usr/lib/debug/lib/modules/$(uname -r)/vmlinux "$TEMPDIR/output.o" > "$TEMPDIR/log.txt" 2>&1
+	RETCODE=$?
+	# expect RETCODE to be 3 indicating no change
+	[[ $RETCODE -eq 3 ]] && continue
+	# otherwise record error
+	mkdir -p $RESULTSDIR/$(dirname $i) || exit 1
+	cp "$i" "$RESULTSDIR/$i" || exit 1
+	case $RETCODE in
+		139)
+			echo "$i: segfault" | tee 
+			if [[ ! -e core ]]; then
+				echo "no corefile, run "ulimit -c unlimited" to capture corefile"
+			else
+				mv core "$RESULTSDIR/$i.core" || exit 1
+			fi
+			;;
+		0)
+			echo "$i: incorrectly detected change"
+			mv "$TEMPDIR/log.txt" "$RESULTSDIR/$i.log" || exit 1
+			;;
+		1|2)
+			echo "$i: error code $RETCODE"
+			mv "$TEMPDIR/log.txt" "$RESULTSDIR/$i.log" || exit 1
+			;;
+		*)
+			exit 1 # script error
+			;;
+	esac
+done
+rm -f "$TEMPDIR/log.txt" > /dev/null 2>&1
+
+# try to group the errors together in some meaningful way
+cd "$RESULTSDIR" || exit 1
+echo ""
+echo "Results:"
+for i in $(find * -iname '*.log')
+do
+	echo $(cat $i | head -1 | cut -f2-3 -d':')
+done | sort | uniq -c | sort -n -r | tee "$TEMPDIR/results.log"
+
+echo "results are in $TEMPDIR"