risc-v:need add crt0 to LDELFFLAG

riscv64-unknown-elf-ld: warning: cannot find entry symbol __start; defaulting to 0000000000000000

Signed-off-by: anjiahao <anjiahao@xiaomi.com>

Author: anjiahao1

arch/risc-v/src/Makefile

@@ -143,14 +143,14 @@ $(AOBJS) $(UAOBJS) $(HEAD_OBJ): %$(OBJEXT): %.S
 $(COBJS) $(UCOBJS): %$(OBJEXT): %.c
 	$(call COMPILE, $<, $@)
 
-crt0$(OBJEXT): %$(OBJEXT): %.c
-	$(call COMPILE, $<, $@)
+$(STARTUP_OBJS): %$(OBJEXT): %.c
+	$(Q) $(CC) $(CELFFLAGS) -c common$(DELIM)crt0.c -o crt0$(OBJEXT)
 
 ifeq ($(CONFIG_BUILD_FLAT),y)
-$(BIN): $(OBJS)
+$(BIN): $(STARTUP_OBJS) $(OBJS)
 	$(call ARCHIVE, $@, $(OBJS))
 else
-$(BIN): $(UOBJS)
+$(BIN): $(STARTUP_OBJS) $(UOBJS)
 	$(call ARCHIVE, $@, $(UOBJS))
 endif
 

arch/risc-v/src/common/Toolchain.defs

@@ -445,7 +445,7 @@ LDMODULEFLAGS = -r -T $(call CONVERT_PATH,$(TOPDIR)/libs/libc/elf/gnu-elf.ld)
 CELFFLAGS = $(CFLAGS) -fvisibility=hidden
 CXXELFFLAGS = $(CXXFLAGS) -fvisibility=hidden
 
-LDELFFLAGS = -e __start
+LDELFFLAGS = -e _start
 
 ifeq ($(CONFIG_BINFMT_ELF_RELOCATABLE),y)
   LDELFFLAGS += -r
@@ -457,6 +457,13 @@ else
   LDELFFLAGS += --oformat elf64-littleriscv
 endif
 
+ifneq ($(CONFIG_BUILD_KERNEL),y)
+  # Flat build and protected elf entry point use crt0,
+  # Kernel build will use apps/import/scripts/crt0
+
+  LDELFFLAGS += $(TOPDIR)$(DELIM)arch$(DELIM)risc-v$(DELIM)src$(DELIM)crt0.o
+endif
+
 LDELFFLAGS += -T $(call CONVERT_PATH,$(TOPDIR)/libs/libc/elf/gnu-elf.ld)
 
 # Zig toolchain