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, 168 insertions, 0 deletions

diff --git a/tools/net/sunrpc/xdrgen/generators/program.py b/tools/net/sunrpc/xdrgen/generators/program.py
new file mode 100644
index 000000000000..83b0ecbae86f
--- /dev/null
+++ b/tools/net/sunrpc/xdrgen/generators/program.py
@@ -0,0 +1,168 @@
+#!/usr/bin/env python3
+# ex: set filetype=python:
+
+"""Generate code for an RPC program's procedures"""
+
+from jinja2 import Environment
+
+from generators import SourceGenerator, create_jinja2_environment
+from xdr_ast import _RpcProgram, _RpcVersion, excluded_apis
+
+
+def emit_version_definitions(
+    environment: Environment, program: str, version: _RpcVersion
+) -> None:
+    """Emit procedure numbers for each RPC version's procedures"""
+    template = environment.get_template("definition/open.j2")
+    print(template.render(program=program.upper()))
+
+    template = environment.get_template("definition/procedure.j2")
+    for procedure in version.procedures:
+        if procedure.name not in excluded_apis:
+            print(
+                template.render(
+                    name=procedure.name,
+                    value=procedure.number,
+                )
+            )
+
+    template = environment.get_template("definition/close.j2")
+    print(template.render())
+
+
+def emit_version_declarations(
+    environment: Environment, program: str, version: _RpcVersion
+) -> None:
+    """Emit declarations for each RPC version's procedures"""
+    arguments = set()
+    for procedure in version.procedures:
+        if procedure.name not in excluded_apis:
+            arguments.add(procedure.argument.type_name)
+    if len(arguments) > 0:
+        print("")
+        template = environment.get_template("declaration/argument.j2")
+        for argument in arguments:
+            print(template.render(program=program, argument=argument))
+
+    results = set()
+    for procedure in version.procedures:
+        if procedure.name not in excluded_apis:
+            results.add(procedure.result.type_name)
+    if len(results) > 0:
+        print("")
+        template = environment.get_template("declaration/result.j2")
+        for result in results:
+            print(template.render(program=program, result=result))
+
+
+def emit_version_argument_decoders(
+    environment: Environment, program: str, version: _RpcVersion
+) -> None:
+    """Emit server argument decoders for each RPC version's procedures"""
+    arguments = set()
+    for procedure in version.procedures:
+        if procedure.name not in excluded_apis:
+            arguments.add(procedure.argument.type_name)
+
+    template = environment.get_template("decoder/argument.j2")
+    for argument in arguments:
+        print(template.render(program=program, argument=argument))
+
+
+def emit_version_result_decoders(
+    environment: Environment, program: str, version: _RpcVersion
+) -> None:
+    """Emit client result decoders for each RPC version's procedures"""
+    results = set()
+    for procedure in version.procedures:
+        if procedure.name not in excluded_apis:
+            results.add(procedure.result.type_name)
+
+    template = environment.get_template("decoder/result.j2")
+    for result in results:
+        print(template.render(program=program, result=result))
+
+
+def emit_version_argument_encoders(
+    environment: Environment, program: str, version: _RpcVersion
+) -> None:
+    """Emit client argument encoders for each RPC version's procedures"""
+    arguments = set()
+    for procedure in version.procedures:
+        if procedure.name not in excluded_apis:
+            arguments.add(procedure.argument.type_name)
+
+    template = environment.get_template("encoder/argument.j2")
+    for argument in arguments:
+        print(template.render(program=program, argument=argument))
+
+
+def emit_version_result_encoders(
+    environment: Environment, program: str, version: _RpcVersion
+) -> None:
+    """Emit server result encoders for each RPC version's procedures"""
+    results = set()
+    for procedure in version.procedures:
+        if procedure.name not in excluded_apis:
+            results.add(procedure.result.type_name)
+
+    template = environment.get_template("encoder/result.j2")
+    for result in results:
+        print(template.render(program=program, result=result))
+
+
+class XdrProgramGenerator(SourceGenerator):
+    """Generate source code for an RPC program's procedures"""
+
+    def __init__(self, language: str, peer: str):
+        """Initialize an instance of this class"""
+        self.environment = create_jinja2_environment(language, "program")
+        self.peer = peer
+
+    def emit_definition(self, node: _RpcProgram) -> None:
+        """Emit procedure numbers for each of an RPC programs's procedures"""
+        raw_name = node.name
+        program = raw_name.lower().removesuffix("_program").removesuffix("_prog")
+
+        for version in node.versions:
+            emit_version_definitions(self.environment, program, version)
+
+    def emit_declaration(self, node: _RpcProgram) -> None:
+        """Emit a declaration pair for each of an RPC programs's procedures"""
+        raw_name = node.name
+        program = raw_name.lower().removesuffix("_program").removesuffix("_prog")
+
+        for version in node.versions:
+            emit_version_declarations(self.environment, program, version)
+
+    def emit_decoder(self, node: _RpcProgram) -> None:
+        """Emit all decoder functions for an RPC program's procedures"""
+        raw_name = node.name
+        program = raw_name.lower().removesuffix("_program").removesuffix("_prog")
+        match self.peer:
+            case "server":
+                for version in node.versions:
+                    emit_version_argument_decoders(
+                        self.environment, program, version,
+                    )
+            case "client":
+                for version in node.versions:
+                    emit_version_result_decoders(
+                        self.environment, program, version,
+                    )
+
+    def emit_encoder(self, node: _RpcProgram) -> None:
+        """Emit all encoder functions for an RPC program's procedures"""
+        raw_name = node.name
+        program = raw_name.lower().removesuffix("_program").removesuffix("_prog")
+        match self.peer:
+            case "server":
+                for version in node.versions:
+                    emit_version_result_encoders(
+                        self.environment, program, version,
+                    )
+            case "client":
+                for version in node.versions:
+                    emit_version_argument_encoders(
+                        self.environment, program, version,
+                    )