diff --git a/kernel/Cargo.lock b/kernel/Cargo.lock
index 15929e7..a98db90 100644
--- a/kernel/Cargo.lock
+++ b/kernel/Cargo.lock
@@ -230,7 +230,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 [[package]]
 name = "mips"
 version = "0.1.0"
-source = "git+https://github.com/Harry-Chen/rust-mips#8b8cbacb08aaaef93837d46599ce21759ef481de"
+source = "git+https://github.com/Harry-Chen/rust-mips#ec0c31e18a904536ffa19bbd1f5d0d0fd19b2cd1"
 dependencies = [
  "bit_field 0.9.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "bitflags 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
diff --git a/kernel/Makefile b/kernel/Makefile
index ec23b36..31ff5eb 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -298,7 +298,7 @@ else ifeq ($(arch), riscv64)
 else ifeq ($(arch), aarch64)
 	@$(objcopy) $(bootloader) --strip-all -O binary $@
 else ifeq ($(arch), mipsel)
-	# qemu-system-mipsel accepts ELF file only, so don't use objcopy
+# qemu-system-mipsel accepts ELF file only, so objcopy is not needed
 	@$(strip) $(kernel) -o $@
 endif
 
diff --git a/kernel/src/backtrace.rs b/kernel/src/backtrace.rs
index 337cfc8..4262d53 100644
--- a/kernel/src/backtrace.rs
+++ b/kernel/src/backtrace.rs
@@ -73,6 +73,8 @@ pub fn backtrace() {
             current_fp = ((current_fp as isize) - sp_offset) as usize;
         }
 
+        println!("=== BEGIN rCore stack trace ===");
+
         while current_pc >= stext as usize
             && current_pc <= etext as usize
             && current_fp as usize != 0
@@ -81,7 +83,7 @@ pub fn backtrace() {
             match size_of::<usize>() {
                 4 => {
                     println!(
-                        "Stack #{:02} PC: {:#010X} FP: {:#010X}",
+                        "#{:02} PC: {:#010X} FP: {:#010X}",
                         stack_num,
                         current_pc - size_of::<usize>(),
                         current_fp
@@ -89,7 +91,7 @@ pub fn backtrace() {
                 },
                 _ => {
                     println!(
-                        "Stack #{:02} PC: {:#018X} FP: {:#018X}",
+                        "#{:02} PC: {:#018X} FP: {:#018X}",
                         stack_num,
                         current_pc - size_of::<usize>(),
                         current_fp
@@ -143,6 +145,7 @@ pub fn backtrace() {
                     trace!("New PC {:08X} FP {:08X}", current_pc, current_fp);
                     continue;
                 } else {
+                    trace!("No sw ra found, probably due to optimizations.");
                     break;
                 }
             }
@@ -159,5 +162,6 @@ pub fn backtrace() {
                 current_pc = *(current_fp as *const usize).offset(1);
             }
         }
+        println!("=== END rCore stack trace ===");
     }
 }
diff --git a/kernel/src/fs/mod.rs b/kernel/src/fs/mod.rs
index a045552..51e3298 100644
--- a/kernel/src/fs/mod.rs
+++ b/kernel/src/fs/mod.rs
@@ -54,7 +54,7 @@ lazy_static! {
                 fn _user_img_start();
                 fn _user_img_end();
             }
-            println!("Sfs start {:x}, end {:x}", _user_img_start as usize, _user_img_end as usize);
+            info!("SFS linked to kernel, from {:08x} to {:08x}", _user_img_start as usize, _user_img_end as usize);
             Arc::new(unsafe { device::MemBuf::new(_user_img_start, _user_img_end) })
         };
 
@@ -66,13 +66,7 @@ lazy_static! {
             Arc::new(unsafe { device::MemBuf::new(_user_img_start, _user_img_end) })
         };
 
-        let super_block = SimpleFileSystem::read(device2);
-	println!("Superblock: magic = {:x}, freemap_blocks = {:x}", super_block.magic, super_block.freemap_blocks);
-	println!("blocks = {:}", super_block.blocks);
-	println!("unused_blocks = {:}", super_block.unused_blocks);
-
         let sfs = SimpleFileSystem::open(device).expect("failed to open SFS");
-        // println!("{:}", sfs.free_map.read());
         sfs.root_inode()
     };
 }