Fix TFTP boot

Author: jasoncouture

Diff for: uefi/src/main.rs

@@ -44,8 +44,6 @@ use x86_64::{
 mod memory_descriptor;
 
 static SYSTEM_TABLE: RacyCell<Option<SystemTable<Boot>>> = RacyCell::new(None);
-static KERNEL_FILENAME: &str = "kernel-x86_64\0";
-static RAMDISK_FILENAME: &str = "ramdisk-x86_64\0";
 
 struct RacyCell<T>(UnsafeCell<T>);
 
@@ -210,15 +208,15 @@ fn load_ramdisk(
     st: &mut SystemTable<Boot>,
     boot_mode: BootMode,
 ) -> Option<&'static mut [u8]> {
-    load_file_from_boot_method(image, st, RAMDISK_FILENAME, boot_mode)
+    load_file_from_boot_method(image, st, "ramdisk-x86_64\0", boot_mode)
 }
 
 fn load_kernel(
     image: Handle,
     st: &mut SystemTable<Boot>,
     boot_mode: BootMode,
 ) -> Option<Kernel<'static>> {
-    let kernel_slice = load_file_from_boot_method(image, st, KERNEL_FILENAME, boot_mode)?;
+    let kernel_slice = load_file_from_boot_method(image, st, "kernel-x86_64\0", boot_mode)?;
     Some(Kernel::parse(kernel_slice))
 }
 
@@ -377,8 +375,7 @@ fn load_file_from_tftp_boot_server(
 
     // Determine the kernel file size.
     let file_size = base_code
-        .tftp_get_file_size(&server_ip, &filename)
-        .expect("Failed to query the file size");
+        .tftp_get_file_size(&server_ip, &filename).ok()?;
     let kernel_size = usize::try_from(file_size).expect("The file size should fit into usize");
 
     // Allocate some memory for the kernel file.