diff --git a/kernel/mm/mm.cc b/kernel/mm/mm.cc
index 68ce2f3..6dbc14c 100644
--- a/kernel/mm/mm.cc
+++ b/kernel/mm/mm.cc
@@ -8,8 +8,6 @@
 
 static bool mm_use_virtual_offset;
 
-extern "C" {
-
 pagedirectory_t page_directory __attribute__ ((aligned (4096)));
 
 static mm_mem_range_t mm_mmap_entries[MM_MAX_MMAP_ENTRIES];
@@ -129,8 +127,10 @@ void mm_bootstrap()
     mm_use_virtual_offset = false;
 }
 
-} /* extern "C" */
-
+/**************************************************************************
+ * Map virtual_address to physical_address.                               *
+ * Both addresses should be page-aligned.                                 *
+ *************************************************************************/
 int mm_map(u32_t virtual_address, u32_t physical_address,
            u32_t user_mode, u32_t writable)
 {
@@ -142,7 +142,7 @@ int mm_map(u32_t virtual_address, u32_t physical_address,
         u32_t page_table_address = mm_page_alloc();
         if (page_table_address == 0)
         {
-            return 1;
+            return 0;
         }
         page_directory[directory_index] = page_table_address
                                         | 0x1 << 2  /* PTs can be user mode */
@@ -162,7 +162,7 @@ int mm_map(u32_t virtual_address, u32_t physical_address,
                             | (writable & 0x1) << 1
                             | 0x1;      /* present */
 
-    return 0;
+    return 1;
 }
 
 /**************************************************************************
diff --git a/kernel/mm/mm.h b/kernel/mm/mm.h
index 03d08d9..626111e 100644
--- a/kernel/mm/mm.h
+++ b/kernel/mm/mm.h
@@ -6,10 +6,6 @@
 #include "hos_defines.h"
 #include "multiboot.h"
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 typedef u32_t pagedirectory_entry_t;
 
 #define NUM_PAGETABLE_ENTRIES (PAGE_SIZE / sizeof(pagedirectory_entry_t))
@@ -28,10 +24,6 @@ typedef struct
 void mm_record_mmap_entry(mb_mmap_t * mmap);
 void mm_bootstrap();
 
-#ifdef __cplusplus
-}
-#endif
-
 int mm_map(u32_t virtual_address, u32_t physical_address,
            u32_t user_mode, u32_t writable);