use 'ucore_*.img' by default

kernel/Makefile

@@ -31,14 +31,15 @@ target := $(arch)-blog_os
 kernel := target/$(target)/$(mode)/ucore
 bin := target/$(target)/$(mode)/kernel.bin
 bootimage := target/$(target)/bootimage.bin
-
 user_dir := ../user
-user_bin_path := $(user_dir)/target/$(arch)-ucore/debug
-user_bins := $(patsubst $(user_bin_path)/%.d, $(user_bin_path)/%, $(wildcard $(user_bin_path)/*.d))
-user_obj := build/$(arch)/user.o
 
 export ARCH = $(arch)
-export SFSIMG = $(user_dir)/build/user-$(arch).img
+#export SFSIMG = $(user_dir)/build/user-$(arch).img
+ifeq ($(arch), x86_64)
+export SFSIMG = $(user_dir)/img/ucore-i386.img
+else
+export SFSIMG = $(user_dir)/img/ucore-$(arch).img
+endif
 
 ### qemu options ###
 qemu_opts := \
@@ -186,11 +187,6 @@ endif
 sfsimg:
 	@cd $(user_dir) && make sfsimg
 
-# make user.o from binary files
-$(user_obj): $(user_bins)
-	@cd $(user_bin_path) && \
-		$(ld) -o $(abspath $@) $(patsubst %, -b binary %, $(notdir $(user_bins)))
-
 
 ### install ###
 ifeq ($(board), raspi3)