From 3e6cea2b67c08f6bf6eeca9b20952daeaa5f55bb Mon Sep 17 00:00:00 2001 From: Pragyansh Chaturvedi Date: Wed, 5 Nov 2025 19:10:58 +0530 Subject: [PATCH] Move get_struct_char_array_ptr from helper/printk_formatter to helper/helper_utils, enable array to ptr conversion in skb_store_bytes --- pythonbpf/helper/helper_utils.py | 80 ++++++++++++++++++++++++++++ pythonbpf/helper/printk_formatter.py | 49 +---------------- 2 files changed, 82 insertions(+), 47 deletions(-) diff --git a/pythonbpf/helper/helper_utils.py b/pythonbpf/helper/helper_utils.py index 71665c8..125011b 100644 --- a/pythonbpf/helper/helper_utils.py +++ b/pythonbpf/helper/helper_utils.py @@ -85,6 +85,52 @@ 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, @@ -97,6 +143,7 @@ def get_or_create_ptr_from_arg( ): """Extract or create pointer from the call arguments.""" + logger.info(f"Getting pointer from arg: {ast.dump(arg)}") if isinstance(arg, ast.Name): # Stack space is already allocated ptr = get_var_ptr_from_name(arg.id, local_sym_tab) @@ -104,6 +151,39 @@ def get_or_create_ptr_from_arg( 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) + elif isinstance(arg, ast.Attribute): + # A struct field + struct_name = arg.value.id + field_name = arg.attr + + if not local_sym_tab or struct_name not in local_sym_tab: + raise ValueError(f"Struct '{struct_name}' not found") + + struct_type = local_sym_tab[struct_name].metadata + if not struct_sym_tab or struct_type not in struct_sym_tab: + raise ValueError(f"Struct type '{struct_type}' not found") + + struct_info = struct_sym_tab[struct_type] + if field_name not in struct_info.fields: + raise ValueError( + f"Field '{field_name}' not found in struct '{struct_name}'" + ) + + field_type = struct_info.field_type(field_name) + struct_ptr = local_sym_tab[struct_name].var + + # Special handling for char arrays + if ( + isinstance(field_type, ir.ArrayType) + 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) + if not ptr: + raise ValueError("Failed to get char array pointer from struct field") + else: + ptr = struct_info.gep(builder, struct_ptr, field_name) + else: # NOTE: For any integer expression reaching this branch, it is probably a struct field or a binop # Evaluate the expression and store the result in a temp variable diff --git a/pythonbpf/helper/printk_formatter.py b/pythonbpf/helper/printk_formatter.py index a18f135..221be10 100644 --- a/pythonbpf/helper/printk_formatter.py +++ b/pythonbpf/helper/printk_formatter.py @@ -4,6 +4,7 @@ import logging 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 logger = logging.getLogger(__name__) @@ -219,7 +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_struct_char_array_ptr( expr, builder, local_sym_tab, struct_sym_tab ) if char_array_ptr: @@ -242,52 +243,6 @@ def _prepare_expr_args(expr, func, module, builder, local_sym_tab, struct_sym_ta return ir.Constant(ir.IntType(64), 0) -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 _handle_pointer_arg(val, func, builder): """Convert pointer type for bpf_printk.""" target, depth = get_base_type_and_depth(val.type)