Remove get_struct_char_array_ptr in favour of get_char_array_ptr_and_size, wrap it in get_or_crate_ptr_from_arg to use in bpf_helper_handler

Author: r41k0u

pythonbpf/helper/bpf_helper_handler.py

@@ -8,7 +8,6 @@
     get_flags_val,
     get_data_ptr_and_size,
     get_buffer_ptr_and_size,
-    get_char_array_ptr_and_size,
     get_ptr_from_arg,
     get_int_value_from_arg,
 )
@@ -464,7 +463,7 @@ def bpf_probe_read_kernel_str_emitter(
         )
 
     # Get destination buffer (char array -> i8*)
-    dst_ptr, dst_size = get_char_array_ptr_and_size(
+    dst_ptr, dst_size = get_or_create_ptr_from_arg(
         call.args[0], builder, local_sym_tab, struct_sym_tab
     )
 

pythonbpf/helper/helper_utils.py

@@ -85,52 +85,6 @@ def create_int_constant_ptr(value, builder, local_sym_tab, int_width=64):
     return ptr
 
 
-def get_struct_char_array_ptr(expr, builder, local_sym_tab, struct_sym_tab):
-    """Get pointer to first element of char array in struct field, or None."""
-    if not (isinstance(expr, ast.Attribute) and isinstance(expr.value, ast.Name)):
-        return None
-
-    var_name = expr.value.id
-    field_name = expr.attr
-
-    # Check if it's a valid struct field
-    if not (
-        local_sym_tab
-        and var_name in local_sym_tab
-        and struct_sym_tab
-        and local_sym_tab[var_name].metadata in struct_sym_tab
-    ):
-        return None
-
-    struct_type = local_sym_tab[var_name].metadata
-    struct_info = struct_sym_tab[struct_type]
-
-    if field_name not in struct_info.fields:
-        return None
-
-    field_type = struct_info.field_type(field_name)
-
-    # Check if it's a char array
-    is_char_array = (
-        isinstance(field_type, ir.ArrayType)
-        and isinstance(field_type.element, ir.IntType)
-        and field_type.element.width == 8
-    )
-
-    if not is_char_array:
-        return None
-
-    # Get field pointer and GEP to first element: [N x i8]* -> i8*
-    struct_ptr = local_sym_tab[var_name].var
-    field_ptr = struct_info.gep(builder, struct_ptr, field_name)
-
-    return builder.gep(
-        field_ptr,
-        [ir.Constant(ir.IntType(32), 0), ir.Constant(ir.IntType(32), 0)],
-        inbounds=True,
-    )
-
-
 def get_or_create_ptr_from_arg(
     func,
     module,
@@ -148,6 +102,7 @@ def get_or_create_ptr_from_arg(
         # Stack space is already allocated
         ptr = get_var_ptr_from_name(arg.id, local_sym_tab)
     elif isinstance(arg, ast.Constant) and isinstance(arg.value, int):
+        int_width = 64  # Deafult to i64
         if expected_type and isinstance(expected_type, ir.IntType):
             int_width = expected_type.width
         ptr = create_int_constant_ptr(arg.value, builder, local_sym_tab, int_width)
@@ -178,7 +133,9 @@ def get_or_create_ptr_from_arg(
             and isinstance(field_type.element, ir.IntType)
             and field_type.element.width == 8
         ):
-            ptr = get_struct_char_array_ptr(arg, builder, local_sym_tab, struct_sym_tab)
+            ptr, sz = get_char_array_ptr_and_size(
+                arg, builder, local_sym_tab, struct_sym_tab
+            )
             if not ptr:
                 raise ValueError("Failed to get char array pointer from struct field")
         else:
@@ -203,6 +160,10 @@ def get_or_create_ptr_from_arg(
             val = builder.trunc(val, expected_type)
         builder.store(val, ptr)
 
+    # NOTE: For char arrays, also return size
+    if sz:
+        return ptr, sz
+
     return ptr
 
 

pythonbpf/helper/printk_formatter.py

@@ -4,7 +4,7 @@
 from llvmlite import ir
 from pythonbpf.expr import eval_expr, get_base_type_and_depth, deref_to_depth
 from pythonbpf.expr.vmlinux_registry import VmlinuxHandlerRegistry
-from pythonbpf.helper.helper_utils import get_struct_char_array_ptr
+from pythonbpf.helper.helper_utils import get_char_array_ptr_and_size
 
 logger = logging.getLogger(__name__)
 
@@ -220,7 +220,7 @@ def _prepare_expr_args(expr, func, module, builder, local_sym_tab, struct_sym_ta
     """Evaluate and prepare an expression to use as an arg for bpf_printk."""
 
     # Special case: struct field char array needs pointer to first element
-    char_array_ptr = get_struct_char_array_ptr(
+    char_array_ptr, _ = get_char_array_ptr_and_size(
         expr, builder, local_sym_tab, struct_sym_tab
     )
     if char_array_ptr: