Make map val struct type allocation work by fixing pointer deref and debuginfogen: WIP

Author: r41k0u

pythonbpf/allocation_pass.py

@@ -178,7 +178,7 @@ def _allocate_for_map_method(
     # Main variable (pointer to pointer)
     ir_type = ir.PointerType(ir.IntType(64))
     var = builder.alloca(ir_type, name=var_name)
-    local_sym_tab[var_name] = LocalSymbol(var, ir_type)
+    local_sym_tab[var_name] = LocalSymbol(var, ir_type, value_type)
     # Temporary variable for computed values
     tmp_ir_type = value_ir_type
     var_tmp = builder.alloca(tmp_ir_type, name=f"{var_name}_tmp")

pythonbpf/expr/expr_pass.py

@@ -61,6 +61,7 @@ def _handle_constant_expr(module, builder, expr: ast.Constant):
 
 
 def _handle_attribute_expr(
+    func,
     expr: ast.Attribute,
     local_sym_tab: Dict,
     structs_sym_tab: Dict,
@@ -76,6 +77,89 @@ def _handle_attribute_expr(
             logger.info(
                 f"Variable type: {var_type}, Variable ptr: {var_ptr}, Variable Metadata: {var_metadata}"
             )
+            # Check if this is a pointer to a struct (from map lookup)
+            if (
+                isinstance(var_type, ir.PointerType)
+                and var_metadata
+                and isinstance(var_metadata, str)
+            ):
+                if var_metadata in structs_sym_tab:
+                    logger.info(
+                        f"Handling pointer to struct {var_metadata} from map lookup"
+                    )
+
+                    if func is None:
+                        raise ValueError(
+                            f"func parameter required for null-safe pointer access to {var_name}.{attr_name}"
+                        )
+
+                    # Load the pointer value (ptr<struct>)
+                    struct_ptr = builder.load(var_ptr)
+
+                    # Create blocks for null check
+                    null_check_block = builder.block
+                    not_null_block = func.append_basic_block(
+                        name=f"{var_name}_not_null"
+                    )
+                    merge_block = func.append_basic_block(name=f"{var_name}_merge")
+
+                    # Check if pointer is null
+                    null_ptr = ir.Constant(struct_ptr.type, None)
+                    is_not_null = builder.icmp_signed("!=", struct_ptr, null_ptr)
+                    logger.info(f"Inserted null check for pointer {var_name}")
+
+                    builder.cbranch(is_not_null, not_null_block, merge_block)
+
+                    # Not-null block: Access the field
+                    builder.position_at_end(not_null_block)
+
+                    # Get struct metadata
+                    metadata = structs_sym_tab[var_metadata]
+                    struct_ptr = builder.bitcast(
+                        struct_ptr, metadata.ir_type.as_pointer()
+                    )
+
+                    if attr_name not in metadata.fields:
+                        raise ValueError(
+                            f"Field '{attr_name}' not found in struct '{var_metadata}'"
+                        )
+
+                    # GEP to field
+                    field_gep = metadata.gep(builder, struct_ptr, attr_name)
+
+                    # Load field value
+                    field_val = builder.load(field_gep)
+                    field_type = metadata.field_type(attr_name)
+
+                    logger.info(
+                        f"Loaded field {attr_name} from struct pointer, type: {field_type}"
+                    )
+
+                    # Branch to merge
+                    not_null_after_load = builder.block
+                    builder.branch(merge_block)
+
+                    # Merge block: PHI node for the result
+                    builder.position_at_end(merge_block)
+                    phi = builder.phi(field_type, name=f"{var_name}_{attr_name}")
+
+                    # If null, return zero/default value
+                    if isinstance(field_type, ir.IntType):
+                        zero_value = ir.Constant(field_type, 0)
+                    elif isinstance(field_type, ir.PointerType):
+                        zero_value = ir.Constant(field_type, None)
+                    elif isinstance(field_type, ir.ArrayType):
+                        # For arrays, we can't easily create a zero constant
+                        # This case is tricky - for now, just use undef
+                        zero_value = ir.Constant(field_type, ir.Undefined)
+                    else:
+                        zero_value = ir.Constant(field_type, ir.Undefined)
+
+                    phi.add_incoming(zero_value, null_check_block)
+                    phi.add_incoming(field_val, not_null_after_load)
+
+                    logger.info(f"Created PHI node for {var_name}.{attr_name}")
+                    return phi, field_type
             if (
                 hasattr(var_metadata, "__module__")
                 and var_metadata.__module__ == "vmlinux"
@@ -568,7 +652,9 @@ def eval_expr(
         logger.warning(f"Unknown call: {ast.dump(expr)}")
         return None
     elif isinstance(expr, ast.Attribute):
-        return _handle_attribute_expr(expr, local_sym_tab, structs_sym_tab, builder)
+        return _handle_attribute_expr(
+            func, expr, local_sym_tab, structs_sym_tab, builder
+        )
     elif isinstance(expr, ast.BinOp):
         return _handle_binary_op(
             func,

pythonbpf/expr/ir_ops.py

@@ -48,3 +48,10 @@ def deref_to_depth(func, builder, val, target_depth):
         cur_val = phi
         cur_type = pointee_type
     return cur_val
+
+
+def deref_struct_ptr(
+    func, builder, struct_ptr, struct_metadata, field_name, structs_sym_tab
+):
+    """Dereference a pointer to a struct type."""
+    return deref_to_depth(func, builder, struct_ptr, 1)

pythonbpf/maps/map_debug_info.py

@@ -117,6 +117,7 @@ def _get_key_val_dbg_type(name, generator, structs_sym_tab):
 
     type_obj = structs_sym_tab.get(name)
     if type_obj:
+        logger.info(f"Found struct named {name}, generating debug type")
         return _get_struct_debug_type(type_obj, generator, structs_sym_tab)
 
     # Fallback to basic types
@@ -165,6 +166,6 @@ def _get_struct_debug_type(struct_obj, generator, structs_sym_tab):
         )
         elements_arr.append(member)
     struct_type = generator.create_struct_type(
-        elements_arr, struct_obj.size, is_distinct=True
+        elements_arr, struct_obj.size * 8, is_distinct=True
     )
     return struct_type