stages/kernel-cmdline: add max cmdline option

Add an additional option called `kernel_line_size`
to allow setting a maximum cmdline size check
value for custom kernels or other restrictions.

This will override the arch defaults, if not set,
then the size map is checked, and if the current
architecture is not in the map, fallback to
4096, which is the max value allowed for
COMMAND_LINE_SIZE.

Signed-off-by: Albert Esteve <aesteve@redhat.com>

stages/org.osbuild.kernel-cmdline

@@ -29,7 +29,8 @@ MAX_SIZE_MAP = {
 def main(tree, options):
     root_fs_uuid = options.get("root_fs_uuid", "")
     additional = options.get("kernel_opts", "")
-    max_cmdline_size = MAX_SIZE_MAP.get(platform.machine().lower(), 4096)
+    max_cmdline_size = options.get("kernel_cmdline_size",
+                                   MAX_SIZE_MAP.get(platform.machine().lower(), 4096))
 
     params = []
 

stages/org.osbuild.kernel-cmdline.meta.json

@@ -30,6 +30,12 @@
         "description": "Additional kernel boot options",
         "type": "string",
         "default": ""
+      },
+      "kernel_cmdline_size": {
+        "description": "Sets a custom maximum kernel cmdline size",
+        "type": "integer",
+        "minimum": 256,
+        "maximum": 4096
       }
     }
   }

stages/test/test_kernel_cmdline.py

@@ -0,0 +1,63 @@
+#!/usr/bin/python3
+
+from unittest import mock
+
+import pytest  # type: ignore
+
+from osbuild import testutil
+
+STAGE_NAME = "org.osbuild.kernel-cmdline"
+
+
+@pytest.mark.parametrize("options, expected", [
+    ({"kernel_opts": "--custom-opt=some"}, "--custom-opt=some"),
+    ({"root_fs_uuid": "some-uuid"}, "root=UUID=some-uuid"),
+    ({"root_fs_uuid": "other-uuid", "kernel_opts": "--custom-opt=other"},
+     "root=UUID=other-uuid --custom-opt=other"),
+])
+def test_kernel_cmdline(tmp_path, stage_module, options, expected):
+    tree = tmp_path / "tree"
+    tree.mkdir()
+
+    stage_module.main(tree, options)
+    cmdline_file = tree / "etc" / "kernel" / "cmdline"
+    assert cmdline_file.exists()
+    assert cmdline_file.read_text() == expected
+
+
+@pytest.mark.parametrize("options, arch", [
+    ({"kernel_opts": "a" * 2049}, "x86_64"),
+    ({"kernel_opts": "a" * 1025}, "arm"),
+    ({"kernel_opts": "a" * 2049}, "aarch64"),
+    ({"kernel_opts": "a" * 257, "kernel_cmdline_size": 256}, "any"),
+])
+@mock.patch("platform.machine")
+def test_kernel_opts_size_check(mock_machine, tmp_path, stage_module, options, arch):
+    tree = tmp_path / "tree"
+    tree.mkdir()
+    mock_machine.return_value = arch
+
+    with pytest.raises(ValueError) as e:
+        stage_module.main(tree, options)
+    assert str(e.value).startswith("The size of the kernel cmdline options cannot be larger than")
+
+
+@pytest.mark.parametrize("options, expected_error", [
+    ({"kernel_cmdline_size": 256}, ""),
+    ({"kernel_cmdline_size": 4096}, ""),
+    ({"kernel_cmdline_size": "not integer"}, "is not of type 'integer'"),
+    ({"kernel_cmdline_size": 0}, "is less than the minimum of 256"),
+    ({"kernel_cmdline_size": 4097}, "is greater than the maximum of 4096"),
+])
+def test_schema_validation_kernel_cmdline(stage_schema, options, expected_error):
+    test_input = {
+        "type": STAGE_NAME,
+        "options": options
+    }
+    res = stage_schema.validate(test_input)
+
+    if not expected_error:
+        assert res.valid
+    else:
+        assert not res.valid
+        testutil.assert_jsonschema_error_contains(res, expected_error, expected_num_errs=1)