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 <[email protected]>
Signed-off-by: Chuck Lever <[email protected]>

1 files changed, 272 insertions, 0 deletions

diff --git a/tools/net/sunrpc/xdrgen/generators/struct.py b/tools/net/sunrpc/xdrgen/generators/struct.py
new file mode 100644
index 000000000000..b694cd470829
--- /dev/null
+++ b/tools/net/sunrpc/xdrgen/generators/struct.py
@@ -0,0 +1,272 @@
+#!/usr/bin/env python3
+# ex: set filetype=python:
+
+"""Generate code to handle XDR struct types"""
+
+from jinja2 import Environment
+
+from generators import SourceGenerator, kernel_c_type
+from generators import create_jinja2_environment, get_jinja2_template
+
+from xdr_ast import _XdrBasic, _XdrVariableLengthString
+from xdr_ast import _XdrFixedLengthOpaque, _XdrVariableLengthOpaque
+from xdr_ast import _XdrFixedLengthArray, _XdrVariableLengthArray
+from xdr_ast import _XdrOptionalData, _XdrStruct, _XdrDeclaration
+from xdr_ast import public_apis
+
+
+def emit_struct_declaration(environment: Environment, node: _XdrStruct) -> None:
+    """Emit one declaration pair for an XDR struct type"""
+    if node.name in public_apis:
+        template = get_jinja2_template(environment, "declaration", "close")
+        print(template.render(name=node.name))
+
+
+def emit_struct_member_definition(
+    environment: Environment, field: _XdrDeclaration
+) -> None:
+    """Emit a definition for one field in an XDR struct"""
+    if isinstance(field, _XdrBasic):
+        template = get_jinja2_template(environment, "definition", field.template)
+        print(
+            template.render(
+                name=field.name,
+                type=kernel_c_type(field.spec),
+                classifier=field.spec.c_classifier,
+            )
+        )
+    elif isinstance(field, _XdrFixedLengthOpaque):
+        template = get_jinja2_template(environment, "definition", field.template)
+        print(
+            template.render(
+                name=field.name,
+                size=field.size,
+            )
+        )
+    elif isinstance(field, _XdrVariableLengthOpaque):
+        template = get_jinja2_template(environment, "definition", field.template)
+        print(template.render(name=field.name))
+    elif isinstance(field, _XdrVariableLengthString):
+        template = get_jinja2_template(environment, "definition", field.template)
+        print(template.render(name=field.name))
+    elif isinstance(field, _XdrFixedLengthArray):
+        template = get_jinja2_template(environment, "definition", field.template)
+        print(
+            template.render(
+                name=field.name,
+                type=kernel_c_type(field.spec),
+                size=field.size,
+            )
+        )
+    elif isinstance(field, _XdrVariableLengthArray):
+        template = get_jinja2_template(environment, "definition", field.template)
+        print(
+            template.render(
+                name=field.name,
+                type=kernel_c_type(field.spec),
+                classifier=field.spec.c_classifier,
+            )
+        )
+    elif isinstance(field, _XdrOptionalData):
+        template = get_jinja2_template(environment, "definition", field.template)
+        print(
+            template.render(
+                name=field.name,
+                type=kernel_c_type(field.spec),
+                classifier=field.spec.c_classifier,
+            )
+        )
+
+
+def emit_struct_definition(environment: Environment, node: _XdrStruct) -> None:
+    """Emit one definition for an XDR struct type"""
+    template = get_jinja2_template(environment, "definition", "open")
+    print(template.render(name=node.name))
+
+    for field in node.fields:
+        emit_struct_member_definition(environment, field)
+
+    template = get_jinja2_template(environment, "definition", "close")
+    print(template.render(name=node.name))
+
+
+def emit_struct_member_decoder(
+    environment: Environment, field: _XdrDeclaration
+) -> None:
+    """Emit a decoder for one field in an XDR struct"""
+    if isinstance(field, _XdrBasic):
+        template = get_jinja2_template(environment, "decoder", field.template)
+        print(
+            template.render(
+                name=field.name,
+                type=field.spec.type_name,
+                classifier=field.spec.c_classifier,
+            )
+        )
+    elif isinstance(field, _XdrFixedLengthOpaque):
+        template = get_jinja2_template(environment, "decoder", field.template)
+        print(
+            template.render(
+                name=field.name,
+                size=field.size,
+            )
+        )
+    elif isinstance(field, _XdrVariableLengthOpaque):
+        template = get_jinja2_template(environment, "decoder", field.template)
+        print(
+            template.render(
+                name=field.name,
+                maxsize=field.maxsize,
+            )
+        )
+    elif isinstance(field, _XdrVariableLengthString):
+        template = get_jinja2_template(environment, "decoder", field.template)
+        print(
+            template.render(
+                name=field.name,
+                maxsize=field.maxsize,
+            )
+        )
+    elif isinstance(field, _XdrFixedLengthArray):
+        template = get_jinja2_template(environment, "decoder", field.template)
+        print(
+            template.render(
+                name=field.name,
+                type=field.spec.type_name,
+                size=field.size,
+                classifier=field.spec.c_classifier,
+            )
+        )
+    elif isinstance(field, _XdrVariableLengthArray):
+        template = get_jinja2_template(environment, "decoder", field.template)
+        print(
+            template.render(
+                name=field.name,
+                type=field.spec.type_name,
+                maxsize=field.maxsize,
+                classifier=field.spec.c_classifier,
+            )
+        )
+    elif isinstance(field, _XdrOptionalData):
+        template = get_jinja2_template(environment, "decoder", field.template)
+        print(
+            template.render(
+                name=field.name,
+                type=field.spec.type_name,
+                classifier=field.spec.c_classifier,
+            )
+        )
+
+
+def emit_struct_decoder(environment: Environment, node: _XdrStruct) -> None:
+    """Emit one decoder function for an XDR struct type"""
+    template = get_jinja2_template(environment, "decoder", "open")
+    print(template.render(name=node.name))
+
+    for field in node.fields:
+        emit_struct_member_decoder(environment, field)
+
+    template = get_jinja2_template(environment, "decoder", "close")
+    print(template.render())
+
+
+def emit_struct_member_encoder(
+    environment: Environment, field: _XdrDeclaration
+) -> None:
+    """Emit an encoder for one field in an XDR struct"""
+    if isinstance(field, _XdrBasic):
+        template = get_jinja2_template(environment, "encoder", field.template)
+        print(
+            template.render(
+                name=field.name,
+                type=field.spec.type_name,
+            )
+        )
+    elif isinstance(field, _XdrFixedLengthOpaque):
+        template = get_jinja2_template(environment, "encoder", field.template)
+        print(
+            template.render(
+                name=field.name,
+                size=field.size,
+            )
+        )
+    elif isinstance(field, _XdrVariableLengthOpaque):
+        template = get_jinja2_template(environment, "encoder", field.template)
+        print(
+            template.render(
+                name=field.name,
+                maxsize=field.maxsize,
+            )
+        )
+    elif isinstance(field, _XdrVariableLengthString):
+        template = get_jinja2_template(environment, "encoder", field.template)
+        print(
+            template.render(
+                name=field.name,
+                maxsize=field.maxsize,
+            )
+        )
+    elif isinstance(field, _XdrFixedLengthArray):
+        template = get_jinja2_template(environment, "encoder", field.template)
+        print(
+            template.render(
+                name=field.name,
+                type=field.spec.type_name,
+                size=field.size,
+            )
+        )
+    elif isinstance(field, _XdrVariableLengthArray):
+        template = get_jinja2_template(environment, "encoder", field.template)
+        print(
+            template.render(
+                name=field.name,
+                type=field.spec.type_name,
+                maxsize=field.maxsize,
+            )
+        )
+    elif isinstance(field, _XdrOptionalData):
+        template = get_jinja2_template(environment, "encoder", field.template)
+        print(
+            template.render(
+                name=field.name,
+                type=field.spec.type_name,
+                classifier=field.spec.c_classifier,
+            )
+        )
+
+
+def emit_struct_encoder(environment: Environment, node: _XdrStruct) -> None:
+    """Emit one encoder function for an XDR struct type"""
+    template = get_jinja2_template(environment, "encoder", "open")
+    print(template.render(name=node.name))
+
+    for field in node.fields:
+        emit_struct_member_encoder(environment, field)
+
+    template = get_jinja2_template(environment, "encoder", "close")
+    print(template.render())
+
+
+class XdrStructGenerator(SourceGenerator):
+    """Generate source code for XDR structs"""
+
+    def __init__(self, language: str, peer: str):
+        """Initialize an instance of this class"""
+        self.environment = create_jinja2_environment(language, "struct")
+        self.peer = peer
+
+    def emit_declaration(self, node: _XdrStruct) -> None:
+        """Emit one declaration pair for an XDR struct type"""
+        emit_struct_declaration(self.environment, node)
+
+    def emit_definition(self, node: _XdrStruct) -> None:
+        """Emit one definition for an XDR struct type"""
+        emit_struct_definition(self.environment, node)
+
+    def emit_decoder(self, node: _XdrStruct) -> None:
+        """Emit one decoder function for an XDR struct type"""
+        emit_struct_decoder(self.environment, node)
+
+    def emit_encoder(self, node: _XdrStruct) -> None:
+        """Emit one encoder function for an XDR struct type"""
+        emit_struct_encoder(self.environment, node)