Strip libgcc to only keep fallback symbols

We use libgcc as fallback for symbols not present in libclang_rt
builtins, however we didn't know what exact symbols were being used,
some may not be intended to fallback.

Create libgcc_stripped, which only contains unwind symbols from libgcc.

Bug: 29275768
Test: bionic-unit-tests
Change-Id: I5b349fa6138e51663bf3b67109b880b4356da8e8

1 files changed, 39 insertions, 15 deletions

diff --git a/scripts/strip.sh b/scripts/strip.sh
index d5369071..0f77da8a 100755
--- a/scripts/strip.sh
+++ b/scripts/strip.sh
@@ -24,6 +24,7 @@
 #   -i ${file}: input file (required)
 #   -o ${file}: output file (required)
 #   -d ${file}: deps file (required)
+#   -k symbols: Symbols to keep (optional)
 #   --add-gnu-debuglink
 #   --keep-mini-debug-info
 #   --keep-symbols
@@ -32,11 +33,11 @@
 
 set -o pipefail
 
-OPTSTRING=d:i:o:-:
+OPTSTRING=d:i:o:k:-:
 
 usage() {
     cat <<EOF
-Usage: strip.sh [options] -i in-file -o out-file -d deps-file
+Usage: strip.sh [options] -k symbols -i in-file -o out-file -d deps-file
 Options:
         --add-gnu-debuglink     Add a gnu-debuglink section to out-file
         --keep-mini-debug-info  Keep compressed debug info in out-file
@@ -71,6 +72,20 @@ do_strip_keep_symbols() {
     fi
 }
 
+do_strip_keep_symbol_list() {
+    if [ -z "${use_gnu_strip}" ]; then
+        echo "do_strip_keep_symbol_list does not work with llvm-objcopy"
+        echo "http://b/131631155"
+        usage
+    fi
+
+    echo "${symbols_to_keep}" | tr ',' '\n' > "${outfile}.symbolList"
+    KEEP_SYMBOLS="-w --strip-unneeded-symbol=* --keep-symbols="
+    KEEP_SYMBOLS+="${outfile}.symbolList"
+
+    "${CROSS_COMPILE}objcopy" "${infile}" "${outfile}.tmp" ${KEEP_SYMBOLS}
+}
+
 do_strip_keep_mini_debug_info() {
     rm -f "${outfile}.dynsyms" "${outfile}.funcsyms" "${outfile}.keep_symbols" "${outfile}.debug" "${outfile}.mini_debuginfo" "${outfile}.mini_debuginfo.xz"
     local fail=
@@ -124,19 +139,21 @@ do_remove_build_id() {
 
 while getopts $OPTSTRING opt; do
     case "$opt" in
-        d) depsfile="${OPTARG}" ;;
-        i) infile="${OPTARG}" ;;
-        o) outfile="${OPTARG}" ;;
-        -)
-            case "${OPTARG}" in
-                add-gnu-debuglink) add_gnu_debuglink=true ;;
-                keep-mini-debug-info) keep_mini_debug_info=true ;;
-                keep-symbols) keep_symbols=true ;;
-                remove-build-id) remove_build_id=true ;;
-                *) echo "Unknown option --${OPTARG}"; usage ;;
-            esac;;
-        ?) usage ;;
-        *) echo "'${opt}' '${OPTARG}'"
+        d) depsfile="${OPTARG}" ;;
+        i) infile="${OPTARG}" ;;
+        o) outfile="${OPTARG}" ;;
+        k) symbols_to_keep="${OPTARG}" ;;
+        -)
+            case "${OPTARG}" in
+                add-gnu-debuglink) add_gnu_debuglink=true ;;
+                keep-mini-debug-info) keep_mini_debug_info=true ;;
+                keep-symbols) keep_symbols=true ;;
+                remove-build-id) remove_build_id=true ;;
+                use-gnu-strip) use_gnu_strip=true ;;
+                *) echo "Unknown option --${OPTARG}"; usage ;;
+            esac;;
+        ?) usage ;;
+        *) echo "'${opt}' '${OPTARG}'"
     esac
 done
 
@@ -160,6 +177,11 @@ if [ ! -z "${keep_symbols}" -a ! -z "${keep_mini_debug_info}" ]; then
     usage
 fi
 
+if [ ! -z "${symbols_to_keep}" -a ! -z "${keep_symbols}" ]; then
+    echo "--keep-symbols and -k cannot be used together"
+    usage
+fi
+
 if [ ! -z "${add_gnu_debuglink}" -a ! -z "${keep_mini_debug_info}" ]; then
     echo "--add-gnu-debuglink cannot be used with --keep-mini-debug-info"
     usage
@@ -169,6 +191,8 @@ rm -f "${outfile}.tmp"
 
 if [ ! -z "${keep_symbols}" ]; then
     do_strip_keep_symbols
+elif [ ! -z "${symbols_to_keep}" ]; then
+    do_strip_keep_symbol_list
 elif [ ! -z "${keep_mini_debug_info}" ]; then
     do_strip_keep_mini_debug_info
 else