sandbox: vm: add temporary vm_virt_to_phys() implementation

sandbox/vm/page.c

@@ -2,6 +2,7 @@
 #include <socks/memblock.h>
 #include <socks/vm.h>
 #include <string.h>
+#include <assert.h>
 #include <stdio.h>
 
 /* array of pages, one for each physical page frame present in RAM */
@@ -41,9 +42,18 @@ static size_t page_order_bytes[] = {
 
 /* temporary */
 static void *tmp_vaddr_base = NULL;
-void tmp_set_vaddr_base(void *p)
+static size_t tmp_vaddr_len = 0;
+void tmp_set_vaddr_base(void *p, size_t len)
 {
 	tmp_vaddr_base = p;
+	tmp_vaddr_len = len;
+}
+
+phys_addr_t vm_virt_to_phys(void *p)
+{
+	phys_addr_t x = (phys_addr_t)p - (phys_addr_t)tmp_vaddr_base;
+	assert(x < tmp_vaddr_len);
+	return x;
 }
 
 void vm_page_init_array()