Create HOS.img with a GPT partition table and EFI partition

Rsconscript

@@ -10,6 +10,7 @@ configure do
   check_c_compiler "x86_64-elf-gcc", use: "x86_64-elf-gcc"
   check_c_compiler
   check_program "mformat", on_fail: "Install the mtools package"
+  check_program "parted"
   check_cfg package: "freetype2", on_fail: "Install libfreetype-dev", use: "freetype"
   sh %w[git submodule update --init]
 end
@@ -17,6 +18,12 @@ end
 # Kernel default font size.
 KFONT_SIZE = 18
 
+# One kilobyte.
+KB = 1024
+
+# One megabyte.
+MB = 1024 * 1024
+
 class HulkBinObj < Builder
   def run(options)
     FileUtils.mkdir_p(File.dirname(@target))
@@ -38,15 +45,24 @@ EOF
   end
 end
 
+# Create a GPT disk image with an EFI partition containing the EFI image.
 class Image < Builder
   def run(options)
     unless @cache.up_to_date?(@target, nil, @sources, @env)
       print_run_message("Creating disk image <target>#{@target}<reset>", nil)
-      File.binwrite(@target, "\0" * (1440 * 1024))
+      efi_image_size = File.stat(@sources.first).size
-      system(*%W[mformat -i #{@target} -f 1440 ::])
+      efi_image_size_mb = (efi_image_size + MB - 1) / MB
+      partition_size_mb = efi_image_size_mb + 1
+      empty_mb = "\0".b * MB
+      File.binwrite(@target, empty_mb * partition_size_mb)
+      system(*%W[mformat -i #{@target} ::])
       system(*%W[mmd -i #{@target} ::/EFI])
       system(*%W[mmd -i #{@target} ::/EFI/BOOT])
       system(*%W[mcopy -i #{@target} #{@sources.first} ::/EFI/BOOT])
+      partition_contents = File.binread(@target)
+      disk_image = empty_mb + partition_contents + empty_mb
+      File.binwrite(@target, disk_image)
+      system(*%W[parted --script #{@target} mklabel gpt mkpart HOS fat32 1MiB #{partition_size_mb + 1}MiB])
       @cache.register_build(@target, nil, @sources, @env)
     end
     true