[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/templates/syscall/client/private/syscall_trampolines.s

@@ -0,0 +1,23 @@
+%macro SYSCALL 2
+	global __syscall_%1
+	__syscall_%1:
+		push rbp
+		mov rbp, rsp
+
+		; args should already be in rdi, etc, but rcx will
+		; get stomped, so stash it in r10, which isn't a
+		; callee-saved register, but also isn't used in the
+		; function call ABI.
+		mov r10, rcx
+
+		mov rax, %2
+		syscall
+		; result is now already in rax, so just return
+
+		pop rbp
+		ret
+%endmacro
+
+{% for id, scope, method in interface.methods %}
+SYSCALL {% if scope %}{{ scope.name }}_{% endif %}{{ method.name }} {{ id }}
+{% endfor %}

scripts/definitions/templates/syscall/client/public/_object_.hh

@@ -0,0 +1,41 @@
+#pragma once
+/// \file {{filename}}
+{% if object.super %}
+
+#include <j6/{{ object.super.name }}.hh>
+{% endif %}
+
+namespace j6 {
+
+{% if object.desc %}
+{{ object.desc|indent('/// ', first=True) }}
+{% endif %}
+class {{ object.name }}
+{% if object.super %}    : public {{ object.super.name }}
+{% endif %}
+{
+public:
+{% macro argument(type, name, first, options=False) -%}
+    {%- for ctype, suffix in type.c_names(options) -%}
+        {%- if not first or not loop.first %}, {% endif %}{{ ctype }} {{ name }}{{ suffix }}
+    {%- endfor -%}
+{%- endmacro -%}
+
+{% for method in object.methods %}
+{% if method.desc %}    /// {{ method.desc|indent('    /// ') }}{% endif %} 
+{% for param in method.params %}
+{% if param.desc %}    /// \arg {{ "%-10s"|format(param.name) }} {{ param.desc }}
+{% endif %}
+{% endfor %}
+    {%+ if method.static %}static {% endif %}j6_status_t {{ method.name }} (
+{%- for param in method.params %}{{ argument(param.type, param.name, loop.first, options=param.options) }}{% endfor -%});
+
+{% endfor %}
+    ~{{ object.name }}();
+
+private:
+    {{ object.name }}(j6_handle_t handle) : m_handle {handle} {}
+    j6_handle_t m_handle;
+}
+
+} // namespace j6

scripts/definitions/templates/syscall/client/public/syscalls.h

@@ -0,0 +1,25 @@
+#pragma once
+
+#include <j6/types.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+{% macro argument(type, name, first, options=False) -%}
+    {%- for ctype, suffix in type.c_names(options) -%}
+        {%- if not first or not loop.first %}, {% endif %}{{ ctype }} {{ name }}{{ suffix }}
+    {%- endfor -%}
+{%- endmacro %}
+ 
+{% for id, scope, method in interface.methods %}
+j6_status_t __syscall_{% if scope %}{{ scope.name }}_{% endif %}{{ method.name }} (
+    {%- if not method.static -%}{{ argument(scope.reftype, "self", True) }}{% endif -%}
+    {%- set first = method.static -%}
+    {%- for param in method.params %}{{ argument(param.type, param.name, first, options=param.options) }}{% set first = False %}{% endfor -%}
+);
+{% endfor %}
+
+#ifdef __cplusplus
+}
+#endif
+