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, 118 insertions, 0 deletions

diff --git a/tools/net/sunrpc/xdrgen/subcmds/source.py b/tools/net/sunrpc/xdrgen/subcmds/source.py
new file mode 100644
index 000000000000..00c04ad15b89
--- /dev/null
+++ b/tools/net/sunrpc/xdrgen/subcmds/source.py
@@ -0,0 +1,118 @@
+#!/usr/bin/env python3
+# ex: set filetype=python:
+
+"""Translate an XDR specification into executable code that
+can be compiled for the Linux kernel."""
+
+import logging
+
+from argparse import Namespace
+from lark import logger
+from lark.exceptions import UnexpectedInput
+
+from generators.source_top import XdrSourceTopGenerator
+from generators.enum import XdrEnumGenerator
+from generators.pointer import XdrPointerGenerator
+from generators.program import XdrProgramGenerator
+from generators.typedef import XdrTypedefGenerator
+from generators.struct import XdrStructGenerator
+from generators.union import XdrUnionGenerator
+
+from xdr_ast import transform_parse_tree, _RpcProgram, Specification
+from xdr_ast import _XdrAst, _XdrEnum, _XdrPointer
+from xdr_ast import _XdrStruct, _XdrTypedef, _XdrUnion
+
+from xdr_parse import xdr_parser, set_xdr_annotate
+
+logger.setLevel(logging.INFO)
+
+
+def emit_source_decoder(node: _XdrAst, language: str, peer: str) -> None:
+    """Emit one XDR decoder function for a source file"""
+    if isinstance(node, _XdrEnum):
+        gen = XdrEnumGenerator(language, peer)
+    elif isinstance(node, _XdrPointer):
+        gen = XdrPointerGenerator(language, peer)
+    elif isinstance(node, _XdrTypedef):
+        gen = XdrTypedefGenerator(language, peer)
+    elif isinstance(node, _XdrStruct):
+        gen = XdrStructGenerator(language, peer)
+    elif isinstance(node, _XdrUnion):
+        gen = XdrUnionGenerator(language, peer)
+    elif isinstance(node, _RpcProgram):
+        gen = XdrProgramGenerator(language, peer)
+    else:
+        return
+    gen.emit_decoder(node)
+
+
+def emit_source_encoder(node: _XdrAst, language: str, peer: str) -> None:
+    """Emit one XDR encoder function for a source file"""
+    if isinstance(node, _XdrEnum):
+        gen = XdrEnumGenerator(language, peer)
+    elif isinstance(node, _XdrPointer):
+        gen = XdrPointerGenerator(language, peer)
+    elif isinstance(node, _XdrTypedef):
+        gen = XdrTypedefGenerator(language, peer)
+    elif isinstance(node, _XdrStruct):
+        gen = XdrStructGenerator(language, peer)
+    elif isinstance(node, _XdrUnion):
+        gen = XdrUnionGenerator(language, peer)
+    elif isinstance(node, _RpcProgram):
+        gen = XdrProgramGenerator(language, peer)
+    else:
+        return
+    gen.emit_encoder(node)
+
+
+def generate_server_source(filename: str, root: Specification, language: str) -> None:
+    """Generate server-side source code"""
+
+    gen = XdrSourceTopGenerator(language, "server")
+    gen.emit_source(filename, root)
+
+    for definition in root.definitions:
+        emit_source_decoder(definition.value, language, "server")
+    for definition in root.definitions:
+        emit_source_encoder(definition.value, language, "server")
+
+
+def generate_client_source(filename: str, root: Specification, language: str) -> None:
+    """Generate server-side source code"""
+
+    gen = XdrSourceTopGenerator(language, "client")
+    gen.emit_source(filename, root)
+
+    # cel: todo: client needs XDR size macros
+
+    for definition in root.definitions:
+        emit_source_encoder(definition.value, language, "client")
+    for definition in root.definitions:
+        emit_source_decoder(definition.value, language, "client")
+
+    # cel: todo: client needs PROC macros
+
+
+def handle_parse_error(e: UnexpectedInput) -> bool:
+    """Simple parse error reporting, no recovery attempted"""
+    print(e)
+    return True
+
+
+def subcmd(args: Namespace) -> int:
+    """Generate encoder and decoder functions"""
+
+    set_xdr_annotate(args.annotate)
+    parser = xdr_parser()
+    with open(args.filename, encoding="utf-8") as f:
+        parse_tree = parser.parse(f.read(), on_error=handle_parse_error)
+        ast = transform_parse_tree(parse_tree)
+        match args.peer:
+            case "server":
+                generate_server_source(args.filename, ast, args.language)
+            case "client":
+                generate_client_source(args.filename, ast, args.language)
+            case _:
+                print("Code generation for", args.peer, "is not yet supported")
+
+    return 0