tools: Add xdrgen

Add a Python-based tool for translating XDR specifications into XDR
encoder and decoder functions written in the Linux kernel's C coding
style. The generator attempts to match the usual C coding style of
the Linux kernel's SunRPC consumers.

This approach is similar to the netlink code generator in
tools/net/ynl .

The maintainability benefits of machine-generated XDR code include:

- Stronger type checking
- Reduces the number of bugs introduced by human error
- Makes the XDR code easier to audit and analyze
- Enables rapid prototyping of new RPC-based protocols
- Hardens the layering between protocol logic and marshaling
- Makes it easier to add observability on demand
- Unit tests might be built for both the tool and (automatically)
  for the generated code

In addition, converting the XDR layer to use memory-safe languages
such as Rust will be easier if much of the code can be converted
automatically.

Tested-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

1 files changed, 44 insertions, 0 deletions

diff --git a/tools/net/sunrpc/xdrgen/generators/enum.py b/tools/net/sunrpc/xdrgen/generators/enum.py
new file mode 100644
index 000000000000..855e43f4ae38
--- /dev/null
+++ b/tools/net/sunrpc/xdrgen/generators/enum.py
@@ -0,0 +1,44 @@
+#!/usr/bin/env python3
+# ex: set filetype=python:
+
+"""Generate code to handle XDR enum types"""
+
+from generators import SourceGenerator, create_jinja2_environment
+from xdr_ast import _XdrEnum, public_apis
+
+
+class XdrEnumGenerator(SourceGenerator):
+    """Generate source code for XDR enum types"""
+
+    def __init__(self, language: str, peer: str):
+        """Initialize an instance of this class"""
+        self.environment = create_jinja2_environment(language, "enum")
+        self.peer = peer
+
+    def emit_declaration(self, node: _XdrEnum) -> None:
+        """Emit one declaration pair for an XDR enum type"""
+        if node.name in public_apis:
+            template = self.environment.get_template("declaration/close.j2")
+            print(template.render(name=node.name))
+
+    def emit_definition(self, node: _XdrEnum) -> None:
+        """Emit one definition for an XDR enum type"""
+        template = self.environment.get_template("definition/open.j2")
+        print(template.render(name=node.name))
+
+        template = self.environment.get_template("definition/enumerator.j2")
+        for enumerator in node.enumerators:
+            print(template.render(name=enumerator.name, value=enumerator.value))
+
+        template = self.environment.get_template("definition/close.j2")
+        print(template.render(name=node.name))
+
+    def emit_decoder(self, node: _XdrEnum) -> None:
+        """Emit one decoder function for an XDR enum type"""
+        template = self.environment.get_template("decoder/enum.j2")
+        print(template.render(name=node.name))
+
+    def emit_encoder(self, node: _XdrEnum) -> None:
+        """Emit one encoder function for an XDR enum type"""
+        template = self.environment.get_template("encoder/enum.j2")
+        print(template.render(name=node.name))