Implement bpf_probe_read_kernel_str helper, Allow i8* to i8 ArrayType conversion

pythonbpf/assign_pass.py

@@ -2,6 +2,7 @@ import ast
 import logging
 from llvmlite import ir
 from pythonbpf.expr import eval_expr
+from pythonbpf.helper import emit_probe_read_kernel_str_call
 
 logger = logging.getLogger(__name__)
 
@@ -27,27 +28,82 @@ def handle_struct_field_assignment(
 
     # Get field pointer and evaluate value
     field_ptr = struct_info.gep(builder, local_sym_tab[var_name].var, field_name)
-    val = eval_expr(
+    field_type = struct_info.field_type(field_name)
+    val_result = eval_expr(
         func, module, builder, rval, local_sym_tab, map_sym_tab, structs_sym_tab
     )
 
-    if val is None:
+    if val_result is None:
         logger.error(f"Failed to evaluate value for {var_name}.{field_name}")
         return
 
-    # TODO: Handle string assignment to char array (not a priority)
-    field_type = struct_info.field_type(field_name)
-    if isinstance(field_type, ir.ArrayType) and val[1] == ir.PointerType(ir.IntType(8)):
-        logger.warning(
-            f"String to char array assignment not implemented for {var_name}.{field_name}"
+    val, val_type = val_result
+
+    # Special case: i8* string to [N x i8] char array
+    if _is_char_array(field_type) and _is_i8_ptr(val_type):
+        _copy_string_to_char_array(
+            func,
+            module,
+            builder,
+            val,
+            field_ptr,
+            field_type,
+            local_sym_tab,
+            map_sym_tab,
+            structs_sym_tab,
         )
+        logger.info(f"Copied string to char array {var_name}.{field_name}")
         return
 
-    # Store the value
-    builder.store(val[0], field_ptr)
+    # Regular assignment
+    builder.store(val, field_ptr)
     logger.info(f"Assigned to struct field {var_name}.{field_name}")
 
 
+def _copy_string_to_char_array(
+    func,
+    module,
+    builder,
+    src_ptr,
+    dst_ptr,
+    array_type,
+    local_sym_tab,
+    map_sym_tab,
+    struct_sym_tab,
+):
+    """Copy string (i8*) to char array ([N x i8]) using bpf_probe_read_kernel_str"""
+
+    array_size = array_type.count
+
+    # Get pointer to first element: [N x i8]* -> i8*
+    dst_i8_ptr = builder.gep(
+        dst_ptr,
+        [ir.Constant(ir.IntType(32), 0), ir.Constant(ir.IntType(32), 0)],
+        inbounds=True,
+    )
+
+    # Use the shared emitter function
+    emit_probe_read_kernel_str_call(builder, dst_i8_ptr, array_size, src_ptr)
+
+
+def _is_char_array(ir_type):
+    """Check if type is [N x i8]."""
+    return (
+        isinstance(ir_type, ir.ArrayType)
+        and isinstance(ir_type.element, ir.IntType)
+        and ir_type.element.width == 8
+    )
+
+
+def _is_i8_ptr(ir_type):
+    """Check if type is i8*."""
+    return (
+        isinstance(ir_type, ir.PointerType)
+        and isinstance(ir_type.pointee, ir.IntType)
+        and ir_type.pointee.width == 8
+    )
+
+
 def handle_variable_assignment(
     func, module, builder, var_name, rval, local_sym_tab, map_sym_tab, structs_sym_tab
 ):