feat: Add ARM64 (arm64) stemcell build support

Rakefile

@@ -3,15 +3,17 @@ require "standard/rake"
 
 namespace :stemcell do
   desc "Build a base OS image for use in stemcells"
-  task :build_os_image, [:operating_system_name, :operating_system_version, :os_image_path] do |_, args|
+  task :build_os_image, [:operating_system_name, :operating_system_version, :os_image_path, :architecture] do |_, args|
     require "bosh/stemcell/archive_handler"
     require "bosh/stemcell/build_environment"
     require "bosh/stemcell/definition"
     require "bosh/stemcell/os_image_builder"
     require "bosh/stemcell/stage_collection"
     require "bosh/stemcell/stage_runner"
 
-    definition = Bosh::Stemcell::Definition.for("null", "null", args.operating_system_name, args.operating_system_version)
+    args.with_defaults(architecture: Bosh::Stemcell::Definition::DEFAULT_ARCHITECTURE)
+
+    definition = Bosh::Stemcell::Definition.for("null", "null", args.operating_system_name, args.operating_system_version, args.architecture)
     environment = Bosh::Stemcell::BuildEnvironment.new(
       ENV.to_hash,
       definition,
@@ -42,17 +44,17 @@ namespace :stemcell do
   end
 
   desc "Build a stemcell, requires `os_image_path` pointing at an image created via `stemcell:build_os_image`"
-  task :build, [:infrastructure_name, :hypervisor_name, :operating_system_name, :operating_system_version, :os_image_path, :build_number] do |_, args|
+  task :build, [:infrastructure_name, :hypervisor_name, :operating_system_name, :operating_system_version, :os_image_path, :build_number, :architecture] do |_, args|
     require "bosh/stemcell/build_environment"
     require "bosh/stemcell/definition"
     require "bosh/stemcell/stage_collection"
     require "bosh/stemcell/stage_runner"
     require "bosh/stemcell/stemcell_packager"
     require "bosh/stemcell/stemcell_builder"
 
-    args.with_defaults(build_number: "0000")
+    args.with_defaults(build_number: "0000", architecture: Bosh::Stemcell::Definition::DEFAULT_ARCHITECTURE)
 
-    definition = Bosh::Stemcell::Definition.for(args.infrastructure_name, args.hypervisor_name, args.operating_system_name, args.operating_system_version)
+    definition = Bosh::Stemcell::Definition.for(args.infrastructure_name, args.hypervisor_name, args.operating_system_name, args.operating_system_version, args.architecture)
     environment = Bosh::Stemcell::BuildEnvironment.new(
       ENV.to_hash,
       definition,

bosh-stemcell/lib/bosh/stemcell/arch.rb

@@ -7,5 +7,10 @@ def self.arch
     def self.x86_64?
       arch == "x86_64"
     end
+
+    # GNU triplet prefix used for multiarch library paths, e.g. x86_64-linux-gnu
+    def self.gnu_arch
+      x86_64? ? "x86_64" : "aarch64"
+    end
   end
 end

bosh-stemcell/lib/bosh/stemcell/build_environment.rb

@@ -193,10 +193,11 @@ def exclude_exclusions
         when Infrastructure::Gdch::NAME
           " --tag ~exclude_on_gdch"
         end,
+        " --tag ~exclude_on_#{definition.architecture}",
         if operating_system.variant?
           " --tag ~exclude_on_#{operating_system.variant}"
         end
-      ].compact.join(" ").rstrip
+      ].compact.join(" ").squeeze(" ").rstrip
     end
 
     def image_file_path

bosh-stemcell/lib/bosh/stemcell/builder_options.rb

@@ -24,6 +24,7 @@ def default
         "stemcell_operating_system" => operating_system.name,
         "stemcell_operating_system_version" => operating_system.version,
         "stemcell_operating_system_variant" => operating_system.variant,
+        "stemcell_arch" => definition.architecture,
         "ruby_bin" => ruby_bin,
         "image_create_disk_size" => image_create_disk_size,
         "os_image_tgz" => os_image_tgz_path

bosh-stemcell/lib/bosh/stemcell/definition.rb

@@ -3,20 +3,24 @@
 
 module Bosh::Stemcell
   class Definition
-    attr_reader :infrastructure, :hypervisor_name, :operating_system
+    DEFAULT_ARCHITECTURE = "amd64".freeze
 
-    def self.for(infrastructure_name, hypervisor_name, operating_system_name, operating_system_version)
+    attr_reader :infrastructure, :hypervisor_name, :operating_system, :architecture
+
+    def self.for(infrastructure_name, hypervisor_name, operating_system_name, operating_system_version, architecture = DEFAULT_ARCHITECTURE)
       new(
         Bosh::Stemcell::Infrastructure.for(infrastructure_name),
         hypervisor_name,
-        Bosh::Stemcell::OperatingSystem.for(operating_system_name, operating_system_version)
+        Bosh::Stemcell::OperatingSystem.for(operating_system_name, operating_system_version),
+        architecture
       )
     end
 
-    def initialize(infrastructure, hypervisor_name, operating_system)
+    def initialize(infrastructure, hypervisor_name, operating_system, architecture = DEFAULT_ARCHITECTURE)
       @infrastructure = infrastructure
       @hypervisor_name = hypervisor_name
       @operating_system = operating_system
+      @architecture = architecture || DEFAULT_ARCHITECTURE
     end
 
     def stemcell_name(disk_format)
@@ -28,6 +32,8 @@ def stemcell_name(disk_format)
       stemcell_name_parts << operating_system.version if operating_system.version
       stemcell_name_parts << operating_system.variant if operating_system.variant
       stemcell_name_parts << disk_format unless disk_format == infrastructure.default_disk_format
+      # amd64 stemcell names carry no architecture suffix; other architectures do.
+      stemcell_name_parts << architecture unless architecture == DEFAULT_ARCHITECTURE
 
       stemcell_name_parts.join("-")
     end
@@ -38,7 +44,8 @@ def disk_formats
 
     def ==(other)
       infrastructure == other.infrastructure &&
-        operating_system == other.operating_system
+        operating_system == other.operating_system &&
+        architecture == other.architecture
     end
   end
 end

bosh-stemcell/lib/bosh/stemcell/infrastructure.rb

@@ -46,6 +46,15 @@ def additional_cloud_properties
         {}
       end
 
+      # Maps the BOSH/Debian architecture to the value recorded as
+      # cloud_properties.architecture in stemcell.MF, which CPIs consume unchanged.
+      # Raises for an unmapped architecture; override where a CPI expects another spelling.
+      def architecture_name(architecture)
+        {"amd64" => "x86_64", "arm64" => "aarch64"}.fetch(architecture) do
+          raise ArgumentError, "Unsupported stemcell architecture: #{architecture}"
+        end
+      end
+
       def ==(other)
         name == other.name &&
           hypervisor == other.hypervisor &&
@@ -129,6 +138,12 @@ def additional_cloud_properties
           "boot_mode" => "uefi-preferred"
         }
       end
+
+      # The AWS CPI passes the architecture to EC2 RegisterImage unchanged, which
+      # accepts "arm64" but not "aarch64".
+      def architecture_name(architecture)
+        (architecture == "arm64") ? "arm64" : super
+      end
     end
 
     class Alicloud < Base

bosh-stemcell/lib/bosh/stemcell/stemcell_packager.rb

@@ -50,7 +50,7 @@ def manifest(disk_format)
       end
 
       def manifest_cloud_properties(disk_format, infrastructure, stemcell_name)
-        architecture = "x86_64"
+        architecture = infrastructure.architecture_name(definition.architecture)
 
         {
           "name" => stemcell_name,