x86, efi: Pass a minimal map to SetVirtualAddressMap()

Experimentation with various EFI implementations has shown that functions
outside runtime services will still update their pointers if
SetVirtualAddressMap() is called with memory descriptors outside the
runtime area. This is obviously insane, and therefore is unsurprising.
Evidence from instrumenting another EFI implementation suggests that it
only passes the set of descriptors covering runtime regions, so let's
avoid any problems by doing the same. Runtime descriptors are copied to
a separate memory map, and only that map is passed back to the firmware.

Signed-off-by: Matthew Garrett <mjg@redhat.com>
Link: http://lkml.kernel.org/r/1304623186-18261-4-git-send-email-mjg@redhat.com
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

arch/x86/platform/efi/efi.c

@@ -502,7 +502,8 @@ void __init efi_enter_virtual_mode(void)
 	efi_status_t status;
 	unsigned long size;
 	u64 end, systab, addr, npages, end_pfn;
-	void *p, *va;
+	void *p, *va, *new_memmap = NULL;
+	int count = 0;
 
 	efi.systab = NULL;
 
@@ -569,15 +570,21 @@ void __init efi_enter_virtual_mode(void)
 			systab += md->virt_addr - md->phys_addr;
 			efi.systab = (efi_system_table_t *) (unsigned long) systab;
 		}
+		new_memmap = krealloc(new_memmap,
+				      (count + 1) * memmap.desc_size,
+				      GFP_KERNEL);
+		memcpy(new_memmap + (count * memmap.desc_size), md,
+		       memmap.desc_size);
+		count++;
 	}
 
 	BUG_ON(!efi.systab);
 
 	status = phys_efi_set_virtual_address_map(
-		memmap.desc_size * memmap.nr_map,
+		memmap.desc_size * count,
 		memmap.desc_size,
 		memmap.desc_version,
-		memmap.phys_map);
+		(efi_memory_desc_t *)__pa(new_memmap));
 
 	if (status != EFI_SUCCESS) {
 		printk(KERN_ALERT "Unable to switch EFI into virtual mode "
@@ -605,6 +612,7 @@ void __init efi_enter_virtual_mode(void)
 		runtime_code_page_mkexec();
 	early_iounmap(memmap.map, memmap.nr_map * memmap.desc_size);
 	memmap.map = NULL;
+	kfree(new_memmap);
 }
 
 /*