user: fix build error

kernel/Cargo.toml

@@ -63,6 +63,7 @@ minimum-image-size = 0      # The minimum output file size (in MiB)
 # (the "{}" will be replaced with the path to the bootable disk image)
 run-command = ["qemu-system-x86_64",
     "-drive", "format=raw,file={}",
+    # TODO: use SFSIMG environment variable
     "-drive", "format=raw,file=../user/img/ucore-i386-pic.img,media=disk,cache=writeback",
     "-serial", "mon:stdio",
     "-device", "isa-debug-exit",

kernel/Makefile

@@ -48,7 +48,7 @@ qemu_opts := \
 ifeq ($(arch), x86_64)
 qemu_opts += \
 	-drive format=raw,file=$(bootimage) \
-	-drive format=raw,file="../user/img/ucore-i386-pic.img",media=disk,cache=writeback \
+	-drive format=raw,file=$(SFSIMG),media=disk,cache=writeback \
 	-serial mon:stdio \
 	-device isa-debug-exit
 

user/ucore-ulib/src/lang_items.rs

@@ -1,5 +1,5 @@
-use syscall::{sys_close, sys_dup, sys_exit, sys_open};
-use syscall::{O_RDONLY, O_WRONLY};
+use crate::syscall::{sys_close, sys_dup, sys_exit, sys_open};
+use crate::syscall::{O_RDONLY, O_WRONLY};
 use core::alloc::Layout;
 use core::panic::PanicInfo;