boot: Add EFISTUB and refactor boot protocols

boot/meson.build

@@ -1,6 +1,44 @@
-kernel_sources += files(
-    'cmdline.c',
-    'main.c',
+objcopy = find_program('objcopy')
+zinnia_bootdir = zinnia_datadir / 'boot'
+
+loader_sources = files(
+    'loader/elf.c',
+    'loader/lib.c',
+    'loader/loader.c',
 )
 
-subdir('limine')
+loader_c_args = [
+    '-ffreestanding',
+    '-nostdinc',
+    '-fno-stack-protector',
+    '-fno-omit-frame-pointer',
+    '-mgeneral-regs-only',
+]
+
+loader_includes = include_directories('loader', 'loader' / target_machine.cpu_family())
+
+loader_objcopy_format = 'unknown'
+
+subdir('loader' / target_machine.cpu_family())
+
+loader_kernel = custom_target(
+    'loader-kernel.o',
+    input: kernel,
+    output: 'loader-kernel.o',
+    command: [
+        objcopy,
+        '-I', 'binary',
+        '-O', loader_objcopy_format,
+        '--rename-section', '.data=.kernel,alloc,load,readonly,data,contents',
+        '@INPUT@',
+        '@OUTPUT@',
+    ],
+)
+
+if kconfig.get('CONFIG_BOOT_EFISTUB', 'n') == 'y'
+    subdir('efi')
+endif
+
+if kconfig.get('CONFIG_BOOT_LIMINE', 'n') == 'y'
+    subdir('limine')
+endif