efi_loader: optional pointer for ConvertPointer

If the EFI_OPTIONAL_PTR is set in DebugDisposition, a NULL pointer does not
constitute an invalid parameter.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
diff --git a/include/efi_api.h b/include/efi_api.h
index 759d911..5744f6a 100644
--- a/include/efi_api.h
+++ b/include/efi_api.h
@@ -251,6 +251,8 @@
 	u32 runtime_services_supported;
 };
 
+#define EFI_OPTIONAL_PTR	0x00000001
+
 struct efi_runtime_services {
 	struct efi_table_hdr hdr;
 	efi_status_t (EFIAPI *get_time)(struct efi_time *time,
diff --git a/lib/efi_loader/efi_runtime.c b/lib/efi_loader/efi_runtime.c
index 45baa2f..a4aa1d8 100644
--- a/lib/efi_loader/efi_runtime.c
+++ b/lib/efi_loader/efi_runtime.c
@@ -512,6 +512,12 @@
 		ret = EFI_INVALID_PARAMETER;
 		goto out;
 	}
+	if (!*address) {
+		if (debug_disposition & EFI_OPTIONAL_PTR)
+			return EFI_SUCCESS;
+		else
+			return EFI_INVALID_PARAMETER;
+	}
 
 	addr = (uintptr_t)*address;
 	for (i = 0; i < efi_descriptor_count; i++) {