01f3b2c91 — BusyBox

Subject

trylink: reformat link flags for readability trylink: add --sort-section alignment: text data bss dec hex filename - 6557 428 3260 10245 2805 busybox + 6555 428 3260 10243 2803 busybox - 909621 1076 12108 922805 e14b5

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Architecture & Compiler Flags

Architecture: x86_64-linux-gnu Compiler: gcc (Ubuntu 11.4.0-1ubuntu1~22.04.3) 11.4.0

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scripts/trylink +89 -25

scripts/trylink+89 -25

@@ -2,6 +2,42 @@

	debug=false

+	# Linker flags used:
+	#
+	# Informational:
+	# --warn-common
+	# -Map $EXE.map
+	# --verbose
+	#
+	# Optimizations:
+	# --sort-common reduces padding
+	# --sort-section alignment reduces padding
+	# --gc-sections throws out unused sections,
+	# does not work for shared libs
+	# -O Not used, maybe useful?
+	#
+	# List of files to link:
+	# $l_list == --start-group -llib1 -llib2 --end-group
+	# --start-group $O_FILES $A_FILES --end-group
+	# or for shlib:
+	# --start-group --whole-archive $A_FILES --no-whole-archive --end-group
+	# otherwise we don't pull in all parts of *.a files. Now we pull in too much.
+	# FIXME: make it work without --whole-archive, or better, with --gc-sections.
+	#
+	# Shared library link:
+	# -shared self-explanatory
+	# -fPIC position-independent code
+	# -Wl,--enable-new-dtags ?
+	# -Wl,-z,combreloc ?
+	# -Wl,-soname="libbusybox.so.$BB_VER"
+	# -static Not used, but may be useful! manpage:
+	# "... This option can be used with -shared.
+	# Doing so means that a shared library
+	# is being created but that all of the library's
+	# external references must be resolved by pulling
+	# in entries from static libraries."
+
+
	try() {
	printf "%s\n" "Output of:" >$EXE.out
	printf "%s\n" "$*" >>$EXE.out
@@ -28,8 +64,10 @@ echo "Trying libraries: $LDLIBS"
	l_list=`echo "$LDLIBS" \| sed -e 's/ / -l/g' -e 's/^/-l/' -e 's/^-l$//'`
	test "x$l_list" != "x" && l_list="-Wl,--start-group $l_list -Wl,--end-group"
	try $CC $LDFLAGS \
-	-o $EXE -Wl,-Map -Wl,$EXE.map \
-	-Wl,--warn-common -Wl,--sort-common -Wl,--gc-sections \
+	-o $EXE \
+	-Wl,--sort-common \
+	-Wl,--sort-section -Wl,alignment \
+	-Wl,--gc-sections \
	-Wl,--start-group $O_FILES $A_FILES -Wl,--end-group \
	$l_list \
	\|\| {
@@ -50,8 +88,10 @@ while test "$LDLIBS"; do
	test "x$l_list" != "x" && l_list="-Wl,--start-group $l_list -Wl,--end-group"
	$debug && echo "Trying -l options: '$l_list'"
	try $CC $LDFLAGS \
-	-o $EXE -Wl,-Map -Wl,$EXE.map \
-	-Wl,--warn-common -Wl,--sort-common -Wl,--gc-sections \
+	-o $EXE \
+	-Wl,--sort-common \
+	-Wl,--sort-section -Wl,alignment \
+	-Wl,--gc-sections \
	-Wl,--start-group $O_FILES $A_FILES -Wl,--end-group \
	$l_list
	if test $? = 0; then
@@ -77,10 +117,15 @@ test "x$l_list" != "x" && l_list="-Wl,--start-group $l_list -Wl,--end-group"
	# --verbose gives us gobs of info to stdout (e.g. linker script used)
	if ! test -f busybox_ldscript; then
	try $CC $LDFLAGS \
-	-o $EXE -Wl,-Map -Wl,$EXE.map \
-	-Wl,--warn-common -Wl,--sort-common -Wl,--gc-sections \
+	-o $EXE \
+	-Wl,--sort-common \
+	-Wl,--sort-section -Wl,alignment \
+	-Wl,--gc-sections \
	-Wl,--start-group $O_FILES $A_FILES -Wl,--end-group \
-	$l_list -Wl,--verbose \
+	$l_list \
+	-Wl,--warn-common \
+	-Wl,-Map -Wl,$EXE.map \
+	-Wl,--verbose \
	\|\| {
	cat $EXE.out
	exit 1
@@ -92,12 +137,18 @@ else
	# (.data SORT_BY_ALIGNMENT(.data.) .gnu.linkonce.d.*)
	# (.bss SORT_BY_ALIGNMENT(.bss.) .gnu.linkonce.b.*)
	# This will eliminate most of the padding (~3kb).
+	# Hmm, "ld --sort-section alignment" should do it too.
	try $CC $LDFLAGS \
-	-o $EXE -Wl,-Map -Wl,$EXE.map \
-	-Wl,--warn-common -Wl,--sort-common -Wl,--gc-sections \
-	-Wl,--start-group $O_FILES $A_FILES -Wl,--end-group \
-	$l_list -Wl,--verbose \
+	-o $EXE \
+	-Wl,--sort-common \
+	-Wl,--sort-section -Wl,alignment \
+	-Wl,--gc-sections \
	-Wl,-T -Wl,busybox_ldscript \
+	-Wl,--start-group $O_FILES $A_FILES -Wl,--end-group \
+	$l_list \
+	-Wl,--warn-common \
+	-Wl,-Map -Wl,$EXE.map \
+	-Wl,--verbose \
	\|\| {
	cat $EXE.out
	exit 1
@@ -118,12 +169,18 @@ if test "$CONFIG_BUILD_LIBBUSYBOX" = y; then

	EXE="$sharedlib_dir/libbusybox.so.${BB_VER}_unstripped"
	try $CC $LDFLAGS \
-	-o $EXE -Wl,-Map -Wl,$EXE.map \
-	-shared -fPIC -Wl,--enable-new-dtags \
-	-Wl,--start-group -Wl,--whole-archive $A_FILES -Wl,--no-whole-archive -Wl,--end-group \
-	$l_list -Wl,--verbose \
-	-Wl,-soname="libbusybox.so.$BB_VER" \
-	-Wl,-z,combreloc \
+	-o $EXE \
+	-shared -fPIC \
+	-Wl,--enable-new-dtags \
+	-Wl,-z,combreloc \
+	-Wl,-soname="libbusybox.so.$BB_VER" \
+	-Wl,--sort-common \
+	-Wl,--sort-section -Wl,alignment \
+	-Wl,--start-group -Wl,--whole-archive $A_FILES -Wl,--no-whole-archive -Wl,--end-group \
+	$l_list \
+	-Wl,--warn-common \
+	-Wl,-Map -Wl,$EXE.map \
+	-Wl,--verbose \
	\|\| {
	echo "Linking $EXE failed"
	cat $EXE.out
@@ -137,11 +194,15 @@ fi
	if test "$CONFIG_FEATURE_SHARED_BUSYBOX" = y; then
	EXE="$sharedlib_dir/busybox_unstripped"
	try $CC $LDFLAGS \
-	-o $EXE -Wl,-Map -Wl,$EXE.map \
-	-Wl,--warn-common -Wl,--sort-common -Wl,--gc-sections \
-	-Wl,--start-group $O_FILES -Wl,--end-group \
-	-Wl,--verbose \
-	-L"$sharedlib_dir" -lbusybox \
+	-o $EXE \
+	-Wl,--sort-common \
+	-Wl,--sort-section -Wl,alignment \
+	-Wl,--gc-sections \
+	-Wl,--start-group $O_FILES -Wl,--end-group \
+	-L"$sharedlib_dir" -lbusybox \
+	-Wl,--warn-common \
+	-Wl,-Map -Wl,$EXE.map \
+	-Wl,--verbose \
	\|\| {
	echo "Linking $EXE failed"
	cat $EXE.out
@@ -174,9 +235,12 @@ int main(int argc, char **argv)

	EXE="$sharedlib_dir/$name"
	try $CC $LDFLAGS "$sharedlib_dir/applet.c" \
-	-o $EXE \
-	-Wl,--warn-common -Wl,--sort-common -Wl,--gc-sections \
-	-L"$sharedlib_dir" -lbusybox \
+	-o $EXE \
+	-Wl,--sort-common \
+	-Wl,--sort-section -Wl,alignment \
+	-Wl,--gc-sections \
+	-L"$sharedlib_dir" -lbusybox \
+	-Wl,--warn-common \
	\|\| {
	echo "Linking $EXE failed"
	cat $EXE.out