livepatch-build: Strip transient or unneeded symbols

In the process of creating a final hotpatch module file make sure to
strip all transient symbols that have not been caught and removed by
create-diff-object processing. For now these are only the hooks
kpatch load/unload symbols.

For all new object files that are carried along for the final linking
the transient hooks symbols are not stripped and neither are any
unneeded symbols. Strip them explicitly from resulting object file.

Signed-off-by: Pawel Wieczorkiewicz <wipawel@amazon.de>

diff --git a/livepatch-build b/livepatch-build
index 3f0530eb78d9ea456c3adcd6dea6de8f4a3ed4df..cc71640a7425fd520ecdc9d9de62437162c96d76 100755 (executable)
--- a/livepatch-build
+++ b/livepatch-build
@@ -111,6 +111,28 @@ function build_special()
     unset LIVEPATCH_CAPTURE_DIR
 }
 
+strip_extra_symbols ()
+{
+    local -r FILE="$1"
+    local -a STRIP_CMD_OPTS=()
+    local -a SYM_PREFIX=("livepatch_load_data_"
+                         "livepatch_unload_data_"
+                         "livepatch_preapply_data_"
+                         "livepatch_apply_data_"
+                         "livepatch_postapply_data_"
+                         "livepatch_prerevert_data_"
+                         "livepatch_revert_data_"
+                         "livepatch_postrevert_data_")
+
+    STRIP_CMD_OPTS+=("-w")
+    for sym in "${SYM_PREFIX[@]}"; do
+        STRIP_CMD_OPTS+=("-N")
+        STRIP_CMD_OPTS+=("\"${sym}*\"")
+    done
+
+    strip "${STRIP_CMD_OPTS[@]}" "$FILE"
+}
+
 function create_patch()
 {
     echo "Extracting new and modified ELF sections..."
@@ -150,6 +172,7 @@ function create_patch()
     NEW_FILES=$(comm -23 <(cd patched/xen && find . -type f -name '*.o' | sort) <(cd original/xen && find . -type f -name '*.o' | sort))
     for i in $NEW_FILES; do
         cp "patched/$i" "output/$i"
+        strip --strip-unneeded "output/$i"
         CHANGED=1
     done
 
@@ -176,6 +199,8 @@ function create_patch()
         "${TOOLSDIR}"/prelink $debugopt output.o "${PATCHNAME}.livepatch" "$XENSYMS" &>> "${OUTPUT}/prelink.log" || die
     fi
 
+    strip_extra_symbols "${PATCHNAME}.livepatch"
+
     objcopy --add-section .livepatch.depends=depends.bin "${PATCHNAME}.livepatch"
     objcopy --set-section-flags .livepatch.depends=alloc,readonly "${PATCHNAME}.livepatch"