Merge pull request #5 from pythonbpf/struct_refactor

Struct refactor

Author: r41k0u

pythonbpf/bpf_helper_handler.py

@@ -113,9 +113,9 @@ def bpf_printk_emitter(call, map_ptr, module, builder, func, local_sym_tab=None,
                             var_type = local_var_metadata[var_name]
                             if var_type in struct_sym_tab:
                                 struct_info = struct_sym_tab[var_type]
-                                if field_name in struct_info["fields"]:
-                                    field_index = struct_info["fields"][field_name]
-                                    field_type = struct_info["field_types"][field_index]
+                                if field_name in struct_info.fields:
+                                    field_type = struct_info.field_type(
+                                        field_name)
                                     if isinstance(field_type, ir.IntType):
                                         fmt_parts.append("%lld")
                                         exprs.append(value.value)
@@ -408,7 +408,7 @@ def bpf_perf_event_output_handler(call, map_ptr, module, builder, func, local_sy
             data_type = local_var_metadata[data_name]
             if data_type in struct_sym_tab:
                 struct_info = struct_sym_tab[data_type]
-                size_val = ir.Constant(ir.IntType(64), struct_info["size"])
+                size_val = ir.Constant(ir.IntType(64), struct_info.size)
             else:
                 raise ValueError(
                     f"Struct type {data_type} for variable {data_name} not found in struct symbol table.")

pythonbpf/codegen.py

@@ -3,7 +3,7 @@
 from .license_pass import license_processing
 from .functions_pass import func_proc
 from .maps_pass import maps_proc
-from .structs_pass import structs_proc
+from .structs.structs_pass import structs_proc
 from .globals_pass import globals_processing
 import os
 import subprocess

pythonbpf/expr_pass.py

@@ -79,12 +79,10 @@ def eval_expr(func, module, builder, expr, local_sym_tab, map_sym_tab, structs_s
                 print(local_var_metadata)
                 if local_var_metadata and var_name in local_var_metadata:
                     metadata = structs_sym_tab[local_var_metadata[var_name]]
-                    if attr_name in metadata["fields"]:
-                        field_idx = metadata["fields"][attr_name]
-                        gep = builder.gep(var_ptr, [ir.Constant(ir.IntType(32), 0),
-                                                    ir.Constant(ir.IntType(32), field_idx)])
+                    if attr_name in metadata.fields:
+                        gep = metadata.gep(builder, var_ptr, attr_name)
                         val = builder.load(gep)
-                        field_type = metadata["field_types"][field_idx]
+                        field_type = metadata.field_type(attr_name)
                         return val, field_type
     print("Unsupported expression evaluation")
     return None

pythonbpf/functions_pass.py

@@ -49,21 +49,17 @@ def handle_assign(func, module, builder, stmt, map_sym_tab, local_sym_tab, struc
             struct_type = local_var_metadata[var_name]
             struct_info = structs_sym_tab[struct_type]
 
-            if field_name in struct_info["fields"]:
-                field_idx = struct_info["fields"][field_name]
-                struct_ptr = local_sym_tab[var_name][0]
-                field_ptr = builder.gep(
-                    struct_ptr, [ir.Constant(ir.IntType(32), 0),
-                                 ir.Constant(ir.IntType(32), field_idx)],
-                    inbounds=True)
+            if field_name in struct_info.fields:
+                field_ptr = struct_info.gep(
+                    builder, local_sym_tab[var_name][0], field_name)
                 val = eval_expr(func, module, builder, rval,
                                 local_sym_tab, map_sym_tab, structs_sym_tab)
-                if isinstance(struct_info["field_types"][field_idx], ir.ArrayType) and val[1] == ir.PointerType(ir.IntType(8)):
+                if isinstance(struct_info.field_type(field_name), ir.ArrayType) and val[1] == ir.PointerType(ir.IntType(8)):
                     # TODO: Figure it out, not a priority rn
                     # Special case for string assignment to char array
-                    #str_len = struct_info["field_types"][field_idx].count
-                    #assign_string_to_array(builder, field_ptr, val[0], str_len)
-                    #print(f"Assigned to struct field {var_name}.{field_name}")
+                    # str_len = struct_info["field_types"][field_idx].count
+                    # assign_string_to_array(builder, field_ptr, val[0], str_len)
+                    # print(f"Assigned to struct field {var_name}.{field_name}")
                     pass
                 if val is None:
                     print("Failed to evaluate struct field assignment")
@@ -138,7 +134,7 @@ def handle_assign(func, module, builder, stmt, map_sym_tab, local_sym_tab, struc
                 print(f"Dereferenced and assigned to {var_name}")
             elif call_type in structs_sym_tab and len(rval.args) == 0:
                 struct_info = structs_sym_tab[call_type]
-                ir_type = struct_info["type"]
+                ir_type = struct_info.ir_type
                 # var = builder.alloca(ir_type, name=var_name)
                 # Null init
                 builder.store(ir.Constant(ir_type, None),
@@ -364,7 +360,7 @@ def allocate_mem(module, builder, body, func, ret_type, map_sym_tab, local_sym_t
                             f"Pre-allocated variable {var_name} for deref")
                     elif call_type in structs_sym_tab:
                         struct_info = structs_sym_tab[call_type]
-                        ir_type = struct_info["type"]
+                        ir_type = struct_info.ir_type
                         var = builder.alloca(ir_type, name=var_name)
                         local_var_metadata[var_name] = call_type
                         print(
@@ -548,6 +544,8 @@ def _expr_type(e):
     return found_type or "None"
 
 # For string assignment to fixed-size arrays
+
+
 def assign_string_to_array(builder, target_array_ptr, source_string_ptr, array_length):
     """
     Copy a string (i8*) to a fixed-size array ([N x i8]*)
@@ -556,36 +554,39 @@ def assign_string_to_array(builder, target_array_ptr, source_string_ptr, array_l
     entry_block = builder.block
     copy_block = builder.append_basic_block("copy_char")
     end_block = builder.append_basic_block("copy_end")
-    
+
     # Create loop counter
     i = builder.alloca(ir.IntType(32))
     builder.store(ir.Constant(ir.IntType(32), 0), i)
-    
+
     # Start the loop
     builder.branch(copy_block)
-    
+
     # Copy loop
     builder.position_at_end(copy_block)
     idx = builder.load(i)
-    in_bounds = builder.icmp_unsigned('<', idx, ir.Constant(ir.IntType(32), array_length))
+    in_bounds = builder.icmp_unsigned(
+        '<', idx, ir.Constant(ir.IntType(32), array_length))
     builder.cbranch(in_bounds, copy_block, end_block)
-    
+
     with builder.if_then(in_bounds):
         # Load character from source
         src_ptr = builder.gep(source_string_ptr, [idx])
         char = builder.load(src_ptr)
-        
+
         # Store character in target
-        dst_ptr = builder.gep(target_array_ptr, [ir.Constant(ir.IntType(32), 0), idx])
+        dst_ptr = builder.gep(
+            target_array_ptr, [ir.Constant(ir.IntType(32), 0), idx])
         builder.store(char, dst_ptr)
-        
+
         # Increment counter
         next_idx = builder.add(idx, ir.Constant(ir.IntType(32), 1))
         builder.store(next_idx, i)
-    
+
     builder.position_at_end(end_block)
-    
+
     # Ensure null termination
     last_idx = ir.Constant(ir.IntType(32), array_length - 1)
-    null_ptr = builder.gep(target_array_ptr, [ir.Constant(ir.IntType(32), 0), last_idx])
+    null_ptr = builder.gep(
+        target_array_ptr, [ir.Constant(ir.IntType(32), 0), last_idx])
     builder.store(ir.Constant(ir.IntType(8), 0), null_ptr)

pythonbpf/structs/struct_type.py

@@ -0,0 +1,31 @@
+from llvmlite import ir
+
+
+class StructType:
+    def __init__(self, ir_type, fields, size):
+        self.ir_type = ir_type
+        self.fields = fields
+        self.size = size
+
+    def field_idx(self, field_name):
+        return list(self.fields.keys()).index(field_name)
+
+    def field_type(self, field_name):
+        return self.fields[field_name]
+
+    def gep(self, builder, ptr, field_name):
+        idx = self.field_idx(field_name)
+        return builder.gep(ptr, [ir.Constant(ir.IntType(32), 0),
+                                 ir.Constant(ir.IntType(32), idx)],
+                           inbounds=True)
+
+    def field_size(self, field_name):
+        fld = self.fields[field_name]
+        if isinstance(fld, ir.ArrayType):
+            return fld.count * (fld.element.width // 8)
+        elif isinstance(fld, ir.IntType):
+            return fld.width // 8
+        elif isinstance(fld, ir.PointerType):
+            return 8
+
+        raise TypeError(f"Unsupported field type: {fld}")

pythonbpf/structs/structs_pass.py

@@ -0,0 +1,97 @@
+import ast
+import logging
+from llvmlite import ir
+from pythonbpf.type_deducer import ctypes_to_ir
+from .struct_type import StructType
+
+logger = logging.getLogger(__name__)
+
+# TODO: Shall we allow the following syntax:
+# struct MyStruct:
+#     field1: int
+#     field2: str(32)
+# Where int is mapped to c_uint64?
+# Shall we just int64, int32 and uint32 similarly?
+
+
+def structs_proc(tree, module, chunks):
+    """ Process all class definitions to find BPF structs """
+    structs_sym_tab = {}
+    for cls_node in chunks:
+        if is_bpf_struct(cls_node):
+            print(f"Found BPF struct: {cls_node.name}")
+            struct_info = process_bpf_struct(cls_node, module)
+            structs_sym_tab[cls_node.name] = struct_info
+    return structs_sym_tab
+
+
+def is_bpf_struct(cls_node):
+    return any(
+        isinstance(decorator, ast.Name) and decorator.id == "struct"
+        for decorator in cls_node.decorator_list
+    )
+
+
+def process_bpf_struct(cls_node, module):
+    """ Process a single BPF struct definition """
+
+    fields = parse_struct_fields(cls_node)
+    field_types = list(fields.values())
+    total_size = calc_struct_size(field_types)
+    struct_type = ir.LiteralStructType(field_types)
+    logger.info(f"Created struct {cls_node.name} with fields {fields.keys()}")
+    return StructType(struct_type, fields, total_size)
+
+
+def parse_struct_fields(cls_node):
+    """ Parse fields of a struct class node """
+    fields = {}
+
+    for item in cls_node.body:
+        if isinstance(item, ast.AnnAssign) and \
+           isinstance(item.target, ast.Name):
+            fields[item.target.id] = get_type_from_ann(item.annotation)
+        else:
+            logger.error(f"Unsupported struct field: {ast.dump(item)}")
+            raise TypeError(f"Unsupported field in {ast.dump(cls_node)}")
+    return fields
+
+
+def get_type_from_ann(annotation):
+    """ Convert an AST annotation node to an LLVM IR type for struct fields"""
+    if isinstance(annotation, ast.Call) and \
+       isinstance(annotation.func, ast.Name):
+        if annotation.func.id == "str":
+            # Char array
+            # Assumes constant integer argument
+            length = annotation.args[0].value
+            return ir.ArrayType(ir.IntType(8), length)
+    elif isinstance(annotation, ast.Name):
+        # Int type, written as c_int64, c_uint32, etc.
+        return ctypes_to_ir(annotation.id)
+
+    raise TypeError(f"Unsupported annotation type: {ast.dump(annotation)}")
+
+
+def calc_struct_size(field_types):
+    """ Calculate total size of the struct with alignment and padding """
+    curr_offset = 0
+    for ftype in field_types:
+        if isinstance(ftype, ir.IntType):
+            fsize = ftype.width // 8
+            alignment = fsize
+        elif isinstance(ftype, ir.ArrayType):
+            fsize = ftype.count * (ftype.element.width // 8)
+            alignment = ftype.element.width // 8
+        elif isinstance(ftype, ir.PointerType):
+            # We won't encounter this rn, but for the future
+            fsize = 8
+            alignment = 8
+        else:
+            raise TypeError(f"Unsupported field type: {ftype}")
+
+        padding = (alignment - (curr_offset % alignment)) % alignment
+        curr_offset += padding + fsize
+
+    final_padding = (8 - (curr_offset % 8)) % 8
+    return curr_offset + final_padding