Add ctypes in eval_expr

Author: r41k0u

pythonbpf/expr_pass.py

@@ -4,6 +4,8 @@
 import logging
 from typing import Dict
 
+from .type_deducer import ctypes_to_ir, is_ctypes
+
 logger: Logger = logging.getLogger(__name__)
 
 
@@ -88,6 +90,50 @@ def _handle_deref_call(expr: ast.Call, local_sym_tab: Dict, builder: ir.IRBuilde
     return val, local_sym_tab[arg.id].ir_type
 
 
+def _handle_ctypes_call(
+    func,
+    module,
+    builder,
+    expr,
+    local_sym_tab,
+    map_sym_tab,
+    structs_sym_tab=None,
+):
+    """Handle ctypes type constructor calls."""
+    if len(expr.args) != 1:
+        logger.info("ctypes constructor takes exactly one argument")
+        return None
+
+    arg = expr.args[0]
+    val = eval_expr(
+        func,
+        module,
+        builder,
+        arg,
+        local_sym_tab,
+        map_sym_tab,
+        structs_sym_tab,
+    )
+    if val is None:
+        logger.info("Failed to evaluate argument to ctypes constructor")
+        return None
+    call_type = expr.func.id
+    expected_type = ctypes_to_ir(call_type)
+    if expected_type is None:
+        logger.info(f"Unsupported ctypes type: {call_type}")
+        return None
+    if val[1] != expected_type:
+        # NOTE: We are only considering casting to and from int types for now
+        if isinstance(val[1], ir.IntType) and isinstance(expected_type, ir.IntType):
+            if val[1].width < expected_type.width:
+                val = (builder.sext(val[0], expected_type), expected_type)
+            else:
+                val = (builder.trunc(val[0], expected_type), expected_type)
+        else:
+            raise ValueError(f"Type mismatch: expected {expected_type}, got {val[1]}")
+    return val
+
+
 def eval_expr(
     func,
     module,
@@ -106,6 +152,17 @@ def eval_expr(
         if isinstance(expr.func, ast.Name) and expr.func.id == "deref":
             return _handle_deref_call(expr, local_sym_tab, builder)
 
+        if isinstance(expr.func, ast.Name) and is_ctypes(expr.func.id):
+            return _handle_ctypes_call(
+                func,
+                module,
+                builder,
+                expr,
+                local_sym_tab,
+                map_sym_tab,
+                structs_sym_tab,
+            )
+
         # delayed import to avoid circular dependency
         from pythonbpf.helper import HelperHandlerRegistry, handle_helper_call
 

pythonbpf/functions/functions_pass.py

@@ -359,6 +359,11 @@ def handle_return(builder, stmt, local_sym_tab, ret_type):
         return _handle_none_return(builder)
     elif isinstance(stmt.value, ast.Name) and _is_xdp_name(stmt.value.id):
         return _handle_xdp_return(stmt, builder, ret_type)
+    elif True:
+        val = eval_expr(None, None, builder, stmt.value, local_sym_tab, {}, {})
+        logger.info(f"Evaluated return expression to {val}")
+        builder.ret(val[0])
+        return True
     elif (
         isinstance(stmt.value, ast.Call)
         and isinstance(stmt.value.func, ast.Name)

pythonbpf/type_deducer.py

@@ -1,24 +1,28 @@
 from llvmlite import ir
 
 # TODO: THIS IS NOT SUPPOSED TO MATCH STRINGS :skull:
+mapping = {
+    "c_int8": ir.IntType(8),
+    "c_uint8": ir.IntType(8),
+    "c_int16": ir.IntType(16),
+    "c_uint16": ir.IntType(16),
+    "c_int32": ir.IntType(32),
+    "c_uint32": ir.IntType(32),
+    "c_int64": ir.IntType(64),
+    "c_uint64": ir.IntType(64),
+    "c_float": ir.FloatType(),
+    "c_double": ir.DoubleType(),
+    "c_void_p": ir.IntType(64),
+    # Not so sure about this one
+    "str": ir.PointerType(ir.IntType(8)),
+}
 
 
 def ctypes_to_ir(ctype: str):
-    mapping = {
-        "c_int8": ir.IntType(8),
-        "c_uint8": ir.IntType(8),
-        "c_int16": ir.IntType(16),
-        "c_uint16": ir.IntType(16),
-        "c_int32": ir.IntType(32),
-        "c_uint32": ir.IntType(32),
-        "c_int64": ir.IntType(64),
-        "c_uint64": ir.IntType(64),
-        "c_float": ir.FloatType(),
-        "c_double": ir.DoubleType(),
-        "c_void_p": ir.IntType(64),
-        # Not so sure about this one
-        "str": ir.PointerType(ir.IntType(8)),
-    }
     if ctype in mapping:
         return mapping[ctype]
     raise NotImplementedError(f"No mapping for {ctype}")
+
+
+def is_ctypes(ctype: str) -> bool:
+    return ctype in mapping