diff --git a/executer/kernel/syscall.c b/executer/kernel/syscall.c
index 946f4827..ddc03f57 100644
--- a/executer/kernel/syscall.c
+++ b/executer/kernel/syscall.c
@@ -405,6 +405,25 @@ static int rus_vm_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
 	pfn = phys >> PAGE_SHIFT;
 #if USE_VM_INSERT_PFN
 	for (pix = 0; pix < (pgsize / PAGE_SIZE); ++pix) {
+		struct page *page;
+
+		if (pfn_valid(pfn+pix)) {
+			page = pfn_to_page(pfn+pix);
+			if (!page_count(page)) {
+				get_page(page);
+				/*
+				 * TODO:
+				 * The pages which get_page() has been called with
+				 * should be recorded.  Because these pages have to
+				 * be passed to put_page() before they are freed.
+				 */
+			}
+			error = vm_insert_page(vma, rva+(pix*PAGE_SIZE), page);
+			if (error) {
+				printk("vm_insert_page: %d\n", error);
+			}
+		}
+		else
 		error = vm_insert_pfn(vma, rva+(pix*PAGE_SIZE), pfn+pix);
 		if (error) {
 			break;
@@ -429,7 +448,7 @@ static struct vm_operations_struct rus_vmops = {
 
 static int rus_mmap(struct file *file, struct vm_area_struct *vma)
 {
-	vma->vm_flags |= VM_IO | VM_RESERVED | VM_DONTEXPAND | VM_PFNMAP;
+	vma->vm_flags |= VM_RESERVED | VM_DONTEXPAND | VM_MIXEDMAP;
 	vma->vm_ops = &rus_vmops;
 	return 0;
 }
@@ -1125,13 +1144,16 @@ out:
 	return (IS_ERR_VALUE(map))? (int)map: 0;
 }
 
-static void clear_pte_range(uintptr_t start, uintptr_t len)
+static int clear_pte_range(uintptr_t start, uintptr_t len)
 {
 	struct mm_struct *mm = current->mm;
 	struct vm_area_struct *vma;
 	uintptr_t addr;
 	uintptr_t end;
+	int error;
+	int ret;
 
+	ret = 0;
 	down_read(&mm->mmap_sem);
 	addr = start;
 	while (addr < (start + len)) {
@@ -1148,14 +1170,15 @@ static void clear_pte_range(uintptr_t start, uintptr_t len)
 			end = vma->vm_end;
 		}
 		if (addr < end) {
-			zap_vma_ptes(vma, addr, end-addr);
-			dprintk("clear_pte_range() 0x%lx - 0x%lx OK\n", 
-					vma->vm_start, vma->vm_end);
+			error = zap_vma_ptes(vma, addr, end-addr);
+			if (ret == 0) {
+				ret = error;
+			}
 		}
 		addr = end;
 	}
 	up_read(&mm->mmap_sem);
-	return;
+	return ret;
 }
 
 /**
@@ -1293,7 +1316,11 @@ int __do_in_kernel_syscall(ihk_os_t os, struct mcctrl_channel *c, struct syscall
 				ppd->pid, ppd->rpgtable);
 		}
 
-		clear_pte_range(sc->args[0], sc->args[1]);
+		error = clear_pte_range(sc->args[0], sc->args[1]);
+		if (error) {
+			error = -ENOSYS;
+			goto out;
+		}
 		ret = 0;
 		break;
 
diff --git a/executer/user/mcexec.c b/executer/user/mcexec.c
index 15c19e96..2bcbd2e3 100644
--- a/executer/user/mcexec.c
+++ b/executer/user/mcexec.c
@@ -1161,12 +1161,17 @@ int main_loop(int fd, int cpu, pthread_mutex_t *lock)
 			return w.sr.args[0];
 
 		case __NR_mmap:
-		case __NR_munmap:
 		case __NR_mprotect:
 			/* reserved for internal use */
 			do_syscall_return(fd, cpu, -ENOSYS, 0, 0, 0, 0);
 			break;
 
+		case __NR_munmap:
+			ret = madvise((void *)w.sr.args[0], w.sr.args[1], MADV_DONTNEED);
+			SET_ERR(ret);
+			do_syscall_return(fd, cpu, ret, 0, 0, 0, 0);
+			break;
+
 #ifdef USE_SYSCALL_MOD_CALL
 		case 303:{
 			__dprintf("mcexec.c,mod_cal,mod=%ld,cmd=%ld\n", w.sr.args[0], w.sr.args[1]);