[project] Generate syscalls from new interface DSL

This change adds a new interface DSL for specifying objects (with
methods) and interfaces (that expose objects, and optionally have their
own methods).

Significant changes:

- Add the new scripts/definitions Python module to parse the DSL
- Add the new definitions directory containing DSL definition files
- Use cog to generate syscall-related code in kernel and libj6
- Unify ordering of pointer + length pairs in interfaces

scripts/definitions/transformer.py

@@ -0,0 +1,142 @@
+from .parser import Transformer, v_args
+
+def get_opts(args):
+    from .types import Description, Options, Type, UID
+
+    kinds = {
+        Description: "desc",
+        Options: "opts",
+        UID: "uid",
+        Type: "typename",
+    }
+
+    result = dict()
+    outargs = []
+    for a in args:
+        for kind, name in kinds.items():
+            if isinstance(a, kind):
+                result[name] = a
+                break
+        else:
+            outargs.append(a)
+
+    return result, outargs
+
+class DefTransformer(Transformer):
+    def __init__(self, filename):
+        self.filename = filename
+
+    def start(self, args):
+        from .types import Import, Interface, Object
+
+        imports = set()
+        objects = dict()
+        interfaces = dict()
+
+        for o in args:
+            if isinstance(o, Object):
+                objects[o.name] = o
+
+            elif isinstance(o, Interface):
+                interfaces[o.name] = o
+
+            elif isinstance(o, Import):
+                imports.add(o)
+
+        return imports, objects, interfaces
+
+    @v_args(inline=True)
+    def import_statement(self, path):
+        from .types import Import
+        return Import(path)
+
+    def object(self, args):
+        from .types import Object
+        specials, args = get_opts(args)
+        name, args = args[0], args[1:]
+        return Object(name, children=args, **specials)
+
+    def interface(self, args):
+        from .types import Interface
+        specials, args = get_opts(args)
+        name, args = args[0], args[1:]
+        return Interface(name, children=args, **specials)
+
+    def method(self, args):
+        from .types import Method
+        specials, args = get_opts(args)
+        name, args = args[0], args[1:]
+        return Method(name, children=args, **specials)
+
+    def function(self, args):
+        from .types import Function
+        specials, args = get_opts(args)
+        name, args = args[0], args[1:]
+        return Function(name, children=args, **specials)
+
+    def param(self, args):
+        from .types import Param
+        specials, args = get_opts(args)
+        name = args[0]
+        return Param(name, **specials)
+
+    @v_args(inline=True)
+    def expose(self, s):
+        from .types import Expose
+        return Expose(s)
+
+    @v_args(inline=True)
+    def uid(self, s):
+        return s
+
+    @v_args(inline=True)
+    def name(self, s):
+        return s
+
+    @v_args(inline=True)
+    def type(self, s):
+        return s
+
+    @v_args(inline=True)
+    def super(self, s):
+        from .types import ObjectRef
+        return ObjectRef(s, self.filename)
+
+    def options(self, args):
+        from .types import Options
+        return Options([str(s) for s in args])
+
+    def description(self, s):
+        from .types import Description
+        return Description("\n".join(s))
+
+    @v_args(inline=True)
+    def object_name(self, n):
+        from .types import ObjectRef
+        return ObjectRef(n, self.filename)
+
+    def PRIMITIVE(self, s):
+        from .types import get_primitive
+        return get_primitive(s)
+
+    def UID(self, s):
+        from .types import UID
+        return UID(int(s, base=16))
+
+    def INT_TYPE(self, s):
+        return s
+
+    def NUMBER(self, s):
+        if s.startswith("0x"):
+            return int(s,16)
+        return int(s)
+
+    def COMMENT(self, s):
+        return s[2:].strip()
+
+    def IDENTIFIER(self, s):
+        return str(s)
+
+    def PATH(self, s):
+        return str(s[1:-1])
+