syscall lab finished

kernel/kalloc.c

@@ -7,6 +7,7 @@
 #include "memlayout.h"
 #include "spinlock.h"
 #include "riscv.h"
+#include "proc.h"
 #include "defs.h"
 
 void freerange(void *pa_start, void *pa_end);
@@ -80,3 +81,17 @@ kalloc(void)
     memset((char*)r, 5, PGSIZE); // fill with junk
   return (void*)r;
 }
+
+int 
+freemem(void)
+{
+  struct run* p = kmem.freelist;
+  uint64 num = 0;
+  while (p) {
+    num += 1;
+    p = p->next;
+  }
+  return num * PGSIZE;
+}
+
+