sandbox: Unmap old tags

So far unmapping has not been implemented. This means that if one test
maps a pointer to an address with map_sysmem(), then a second test can
use that same pointer, by mapping the address back to a pointer with
map_to_sysmem(). This is not really desirable, even if it doesn't
cause any problems at the moment.

Implement unmapping, to clean this up.

Signed-off-by: Simon Glass <sjg@chromium.org>

arch/sandbox/cpu/cpu.c

@@ -185,12 +185,28 @@ void *map_physmem(phys_addr_t paddr, unsigned long len, unsigned long flags)
 
 void unmap_physmem(const void *ptr, unsigned long flags)
 {
+	struct sandbox_mapmem_entry *mentry;
+
 #ifdef CONFIG_PCI
 	if (map_dev) {
 		pci_unmap_physmem(ptr, map_len, map_dev);
 		map_dev = NULL;
 	}
 #endif
+
+	/* If it is in emulated RAM, we didn't create a tag, so nothing to do */
+	if (is_in_sandbox_mem(ptr))
+		return;
+
+	mentry = find_tag(ptr);
+	if (mentry) {
+		list_del(&mentry->sibling_node);
+		log_debug("Removed map from %p to %lx\n", ptr,
+			  (ulong)mentry->tag);
+		free(mentry);
+	} else {
+		log_warning("Address not mapped: %p\n", ptr);
+	}
 }
 
 phys_addr_t map_to_sysmem(const void *ptr)