make: Add MODULE_STATIC_LIB

If a module sets MODULE_STATIC_LIB to true, that module will generate
a .a file instead of a partially linked .o file.

When WITH_LINKER_GC is enables, unreferenced code and data in c files
are dropped from the final elf file. This does not work for most
assembly files, since they put code and data directly into the .text
and .data section. If a .a file is used instead however, files that
have no external references are dropped regardless of which sections
they have.

If MODULE_STATIC_LIB is true, this change also disabled LK_INIT_HOOK*
as files using this as the only entrypoint would also be dropped.

Change-Id: I846ac1bf63018d1d713ca841e03191b1fac35bf4

engine.mk

@@ -193,6 +193,7 @@ endif
 CCACHE ?=
 CC := $(CCACHE) $(TOOLCHAIN_PREFIX)gcc
 LD := $(TOOLCHAIN_PREFIX)ld
+AR := $(TOOLCHAIN_PREFIX)ar
 OBJDUMP := $(TOOLCHAIN_PREFIX)objdump
 OBJCOPY := $(TOOLCHAIN_PREFIX)objcopy
 CPPFILT := $(TOOLCHAIN_PREFIX)c++filt

include/lk/init.h

@@ -76,6 +76,9 @@ struct lk_init_struct {
     const char *name;
 };
 
+#if MODULE_STATIC_LIB
+#define LK_INIT_HOOK_FLAGS(a,b,c,d) _Pragma("GCC error \"init hooks are not fully compatible with static libraries\"")
+#else
 #define LK_INIT_HOOK_FLAGS(_name, _hook, _level, _flags) \
     const struct lk_init_struct _init_struct_##_name __ALIGNED(sizeof(void *)) __SECTION(".lk_init") = { \
         .level = _level, \
@@ -83,6 +86,7 @@ struct lk_init_struct {
         .hook = _hook, \
         .name = #_name, \
     };
+#endif
 
 #define LK_INIT_HOOK(_name, _hook, _level) \
     LK_INIT_HOOK_FLAGS(_name, _hook, _level, LK_INIT_FLAG_PRIMARY_CPU)

make/build.mk

@@ -23,7 +23,7 @@ $(OUTELF): $(ALLMODULE_OBJS) $(EXTRA_OBJS) $(LINKER_SCRIPT) $(EXTRA_LINKER_SCRIP
 	@echo linking $@
 	$(NOECHO)$(SIZE) -t --common $(sort $(ALLMODULE_OBJS)) $(EXTRA_OBJS)
 	$(NOECHO)$(LD) $(GLOBAL_LDFLAGS) -dT $(LINKER_SCRIPT) $(addprefix -T,$(EXTRA_LINKER_SCRIPTS)) \
-		$(ALLMODULE_OBJS) $(EXTRA_OBJS) $(LIBGCC) -Map=$(OUTELF).map -o $@
+		--start-group $(ALLMODULE_OBJS) $(EXTRA_OBJS) --end-group $(LIBGCC) -Map=$(OUTELF).map -o $@
 
 $(OUTELF).sym: $(OUTELF)
 	@echo generating symbols: $@

make/module.mk

@@ -4,6 +4,7 @@
 # args:
 # MODULE : module name (required)
 # MODULE_SRCS : list of source files, local path (required)
+# MODULE_STATIC_LIB : if true generate .a instead of .o
 # MODULE_DEPS : other modules that this one depends on
 # MODULE_DEFINES : #defines local to this module
 # MODULE_OPTFLAGS : OPTFLAGS local to this module
@@ -62,6 +63,10 @@ MODULE_DEFINES += MODULE_SRCDEPS=\"$(subst $(SPACE),_,$(MODULE_SRCDEPS))\"
 MODULE_DEFINES += MODULE_DEPS=\"$(subst $(SPACE),_,$(MODULE_DEPS))\"
 MODULE_DEFINES += MODULE_SRCS=\"$(subst $(SPACE),_,$(MODULE_SRCS))\"
 
+ifeq (true,$(call TOBOOL,$(MODULE_STATIC_LIB)))
+MODULE_DEFINES += MODULE_STATIC_LIB=1
+endif
+
 # generate a per-module config.h file
 MODULE_CONFIG := $(MODULE_BUILDDIR)/module_config.h
 
@@ -84,12 +89,25 @@ include make/compile.mk
 #$(info MODULE_OBJS = $(MODULE_OBJS))
 
 # build a ld -r style combined object
+ifeq (true,$(call TOBOOL,$(MODULE_STATIC_LIB)))
+
+MODULE_OBJECT := $(call TOBUILDDIR,$(MODULE_SRCDIR).mod.a)
+$(MODULE_OBJECT): $(MODULE_OBJS) $(MODULE_EXTRA_OBJS)
+	@$(MKDIR)
+	@echo creating $@
+	$(NOECHO)rm -f $@
+	$(NOECHO)$(AR) rcs $@ $^
+
+else
+
 MODULE_OBJECT := $(call TOBUILDDIR,$(MODULE_SRCDIR).mod.o)
 $(MODULE_OBJECT): $(MODULE_OBJS) $(MODULE_EXTRA_OBJS)
 	@$(MKDIR)
 	@echo linking $@
 	$(NOECHO)$(LD) $(GLOBAL_MODULE_LDFLAGS) -r $^ -o $@
 
+endif
+
 # track all of the source files compiled
 ALLSRCS += $(MODULE_SRCS)
 
@@ -108,6 +126,7 @@ MODULE_SRCDIR :=
 MODULE_BUILDDIR :=
 MODULE_DEPS :=
 MODULE_SRCS :=
+MODULE_STATIC_LIB :=
 MODULE_OBJS :=
 MODULE_DEFINES :=
 MODULE_OPTFLAGS :=