From 2ac206b3bae51e0843e858bb0332aff8786ba3d0 Mon Sep 17 00:00:00 2001
From: Artem Savkov <asavkov@redhat.com>
Date: Wed, 14 Mar 2018 10:37:10 +0100
Subject: [PATCH] Undefined reference failure logic rework

Don't die outright when encountering an 'undefined reference' error,
instead write those down and check if needed symbols are provided by the
resulting module or core kpatch module.

Fixes #783.

v2:
  - make undefined_references and new_symbols unique before comparing
  - remove leftover $KMOD_PATH from new_symbols readelf

Signed-off-by: Artem Savkov <asavkov@redhat.com>
---
 kpatch-build/kpatch-build | 30 ++++++++++++++++++++++++++++--
 1 file changed, 28 insertions(+), 2 deletions(-)

diff --git a/kpatch-build/kpatch-build b/kpatch-build/kpatch-build
index 61009f0..24647b4 100755
--- a/kpatch-build/kpatch-build
+++ b/kpatch-build/kpatch-build
@@ -713,8 +713,13 @@ export KPATCH_GCC_TEMPDIR
 CROSS_COMPILE="$TOOLSDIR/kpatch-gcc " \
 	KBUILD_MODPOST_WARN=1 \
 	make "-j$CPUS" $TARGETS 2>&1 | logger || die
-grep "undefined reference" "$LOGFILE" | grep -qv kpatch_shadow && die
-grep "undefined!" "$LOGFILE" | grep -qv kpatch_shadow && die
+
+# source.c:(.section+0xFF): undefined reference to `symbol'
+grep "undefined reference" "$LOGFILE" | sed -r "s/^.*\`(.*)'$/\1/" \
+	>${TEMPDIR}/undefined_references
+
+# WARNING: "symbol" [path/to/module.ko] undefined!
+grep "undefined!" "$LOGFILE" | cut -d\" -f2 >>${TEMPDIR}/undefined_references
 
 if [[ ! -e "$TEMPDIR/changed_objs" ]]; then
 	die "no changed objects found"
@@ -854,6 +859,27 @@ if ! "$KPATCH_MODULE"; then
 	check_pipe_status create-klp-module
 fi
 
+readelf --wide --symbols "$TEMPDIR/patch/$MODNAME.ko" 2>/dev/null | \
+	awk '($4=="FUNC" || $4=="OBJECT") && ($5=="GLOBAL" || $5=="WEAK") && $7!="UND" {print $NF}' \
+	>${TEMPDIR}/new_symbols
+
+if "$KPATCH_MODULE"; then
+	cat >>${TEMPDIR}/new_symbols <<-EOF
+		kpatch_shadow_free
+		kpatch_shadow_alloc
+		kpatch_register
+		kpatch_shadow_get
+		kpatch_unregister
+		kpatch_root_kobj
+	EOF
+fi
+
+# Compare undefined_references and new_symbols files and print only the first
+# column containing lines unique to first file.
+UNDEFINED=$(comm -23 <(sort -u ${TEMPDIR}/undefined_references) \
+	<(sort -u ${TEMPDIR}/new_symbols) | tr '\n' ' ')
+[[ ! -z "$UNDEFINED" ]] && die "Undefined symbols: $UNDEFINED"
+
 cp -f "$TEMPDIR/patch/$MODNAME.ko" "$BASE" || die
 
 [[ "$DEBUG" -eq 0 ]] && rm -f "$LOGFILE"