python-bpf/pythonbpf/functions_pass.py

from llvmlite import ir
import ast

from .bpf_helper_handler import helper_func_list, handle_helper_call
from .type_deducer import ctypes_to_ir


def get_probe_string(func_node):
    """Extract the probe string from the decorator of the function node."""
    # TODO: right now we have the whole string in the section decorator
    # But later we can implement typed tuples for tracepoints and kprobes
    # For helper functions, we return "helper"

    for decorator in func_node.decorator_list:
        if isinstance(decorator, ast.Name) and decorator.id == "bpfglobal":
            return None
        if isinstance(decorator, ast.Call) and isinstance(decorator.func, ast.Name):
            if decorator.func.id == "section" and len(decorator.args) == 1:
                arg = decorator.args[0]
                if isinstance(arg, ast.Constant) and isinstance(arg.value, str):
                    return arg.value
    return "helper"


def handle_assign(func, module, builder, stmt, map_sym_tab, local_sym_tab):
    """Handle assignment statements in the function body."""
    if len(stmt.targets) != 1:
        print("Unsupported multiassignment")
        return

    num_types = ("c_int32", "c_int64", "c_uint32", "c_uint64")

    target = stmt.targets[0]
    if not isinstance(target, ast.Name):
        print("Unsupported assignment target")
        return
    var_name = target.id
    rval = stmt.value
    if isinstance(rval, ast.Constant):
        if isinstance(rval.value, bool):
            if rval.value:
                builder.store(ir.Constant(ir.IntType(1), 1),
                              local_sym_tab[var_name])
            else:
                builder.store(ir.Constant(ir.IntType(1), 0),
                              local_sym_tab[var_name])
            print(f"Assigned constant {rval.value} to {var_name}")
        elif isinstance(rval.value, int):
            # Assume c_int64 for now
            # var = builder.alloca(ir.IntType(64), name=var_name)
            # var.align = 8
            builder.store(ir.Constant(ir.IntType(64), rval.value),
                          local_sym_tab[var_name])
            # local_sym_tab[var_name] = var
            print(f"Assigned constant {rval.value} to {var_name}")
    elif isinstance(rval, ast.Call):
        if isinstance(rval.func, ast.Name):
            call_type = rval.func.id
            print(f"Assignment call type: {call_type}")
            if call_type in num_types and len(rval.args) == 1 and isinstance(rval.args[0], ast.Constant) and isinstance(rval.args[0].value, int):
                ir_type = ctypes_to_ir(call_type)
                # var = builder.alloca(ir_type, name=var_name)
                # var.align = ir_type.width // 8
                builder.store(ir.Constant(
                    ir_type, rval.args[0].value), local_sym_tab[var_name])
                print(f"Assigned {call_type} constant "
                      f"{rval.args[0].value} to {var_name}")
                # local_sym_tab[var_name] = var
            elif call_type in helper_func_list:
                # var = builder.alloca(ir.IntType(64), name=var_name)
                # var.align = 8
                val = handle_helper_call(
                    rval, module, builder, None, local_sym_tab, map_sym_tab)
                builder.store(val, local_sym_tab[var_name])
                # local_sym_tab[var_name] = var
                print(f"Assigned constant {rval.func.id} to {var_name}")
            else:
                print(f"Unsupported assignment call type: {call_type}")
        elif isinstance(rval.func, ast.Attribute):
            if isinstance(rval.func.value, ast.Call) and isinstance(rval.func.value.func, ast.Name):
                map_name = rval.func.value.func.id
                method_name = rval.func.attr
                if map_name in map_sym_tab:
                    map_ptr = map_sym_tab[map_name]
                    if method_name in helper_func_list:
                        val = handle_helper_call(
                            rval, module, builder, func, local_sym_tab, map_sym_tab)
                        # var = builder.alloca(ir.IntType(64), name=var_name)
                        # var.align = 8
                        builder.store(val, local_sym_tab[var_name])
                        # local_sym_tab[var_name] = var
            else:
                print("Unsupported assignment call structure")
        else:
            print("Unsupported assignment call function type")
    else:
        print("Unsupported assignment value type")


def handle_expr(func, module, builder, expr, local_sym_tab, map_sym_tab):
    """Handle expression statements in the function body."""
    call = expr.value
    print(f"Handling expression: {ast.dump(call)}")
    if isinstance(call, ast.Call):
        if isinstance(call.func, ast.Name):
            # check for helpers first
            if call.func.id in helper_func_list:
                handle_helper_call(
                    call, module, builder, func, local_sym_tab, map_sym_tab)
                return
        elif isinstance(call.func, ast.Attribute):
            if isinstance(call.func.value, ast.Call) and isinstance(call.func.value.func, ast.Name):
                method_name = call.func.attr
                if method_name in helper_func_list:
                    handle_helper_call(
                        call, module, builder, func, local_sym_tab, map_sym_tab)
                    return
    elif isinstance(call, ast.Name):
        if call.id in local_sym_tab:
            var = local_sym_tab[call.id]
            val = builder.load(var)
            return val
        else:
            print(f"Undefined variable {call.id}")
            return None
    elif isinstance(call, ast.Constant):
        if isinstance(call.value, int):
            return ir.Constant(ir.IntType(64), call.value)
        elif isinstance(call.value, bool):
            return ir.Constant(ir.IntType(1), int(call.value))
        else:
            print("Unsupported constant type")
            return None
    else:
        print("Unsupported expression statement")


def handle_cond(func, module, builder, cond, local_sym_tab, map_sym_tab):
    if isinstance(cond, ast.Constant):
        if isinstance(cond.value, bool):
            return ir.Constant(ir.IntType(1), int(cond.value))
        elif isinstance(cond.value, int):
            return ir.Constant(ir.IntType(1), int(bool(cond.value)))
        else:
            print("Unsupported constant type in condition")
            return None
    elif isinstance(cond, ast.Name):
        if cond.id in local_sym_tab:
            var = local_sym_tab[cond.id]
            val = builder.load(var)
            return val
        else:
            print(f"Undefined variable {cond.id} in condition")
            return None
    else:
        print("Unsupported condition expression")
        return None


def handle_if(func, module, builder, stmt, map_sym_tab, local_sym_tab):
    """Handle if statements in the function body."""
    print("Handling if statement")
    start = builder.block.parent
    then_block = func.append_basic_block(name="if.then")
    merge_block = func.append_basic_block(name="if.end")
    if stmt.orelse:
        else_block = func.append_basic_block(name="if.else")
    else:
        else_block = None

    cond = handle_cond(func, module, builder, stmt.test,
                       local_sym_tab, map_sym_tab)
    if else_block:
        builder.cbranch(cond, then_block, else_block)
    else:
        builder.cbranch(cond, then_block, merge_block)

    builder.position_at_end(then_block)
    for s in stmt.body:
        process_stmt(func, module, builder, s,
                     local_sym_tab, map_sym_tab, False)
    if not builder.block.is_terminated:
        builder.branch(merge_block)

    if else_block:
        builder.position_at_end(else_block)
        for s in stmt.orelse:
            process_stmt(func, module, builder, s,
                         local_sym_tab, map_sym_tab, False)
        if not builder.block.is_terminated:
            builder.branch(merge_block)

    builder.position_at_end(merge_block)


def process_stmt(func, module, builder, stmt, local_sym_tab, map_sym_tab, did_return, ret_type=ir.IntType(64)):
    # print(f"Processing statement: {ast.dump(stmt)}")
    if isinstance(stmt, ast.Expr):
        handle_expr(func, module, builder, stmt, local_sym_tab, map_sym_tab)
    elif isinstance(stmt, ast.Assign):
        handle_assign(func, module, builder, stmt, map_sym_tab, local_sym_tab)
    elif isinstance(stmt, ast.If):
        handle_if(func, module, builder, stmt, map_sym_tab, local_sym_tab)
    elif isinstance(stmt, ast.Return):
        if stmt.value is None:
            builder.ret(ir.Constant(ir.IntType(32), 0))
            did_return = True
        elif isinstance(stmt.value, ast.Call) and isinstance(stmt.value.func, ast.Name) and len(stmt.value.args) == 1 and isinstance(stmt.value.args[0], ast.Constant) and isinstance(stmt.value.args[0].value, int):
            call_type = stmt.value.func.id
            if ctypes_to_ir(call_type) != ret_type:
                raise ValueError("Return type mismatch: expected"
                                 f"{ctypes_to_ir(call_type)}, got {call_type}")
            else:
                builder.ret(ir.Constant(
                    ret_type, stmt.value.args[0].value))
                did_return = True
        else:
            print("Unsupported return value")
    return did_return


def process_func_body(module, builder, func_node, func, ret_type, map_sym_tab):
    """Process the body of a bpf function"""
    # TODO: A lot.  We just have print -> bpf_trace_printk for now
    did_return = False

    local_sym_tab = {}

    # pre-allocate dynamic variables
    for stmt in func_node.body:
        if isinstance(stmt, ast.Assign):
            if len(stmt.targets) != 1:
                print("Unsupported multiassignment")
                continue
            target = stmt.targets[0]
            if not isinstance(target, ast.Name):
                print("Unsupported assignment target")
                continue
            var_name = target.id
            rval = stmt.value
            if isinstance(rval, ast.Call):
                if isinstance(rval.func, ast.Name):
                    call_type = rval.func.id
                    if call_type in ("c_int32", "c_int64", "c_uint32", "c_uint64"):
                        ir_type = ctypes_to_ir(call_type)
                        var = builder.alloca(ir_type, name=var_name)
                        var.align = ir_type.width // 8
                        print(
                            f"Pre-allocated variable {var_name} of type {call_type}")
                    elif call_type in helper_func_list:
                        # Assume return type is int64 for now
                        ir_type = ir.IntType(64)
                        var = builder.alloca(ir_type, name=var_name)
                        var.align = ir_type.width // 8
                        print(
                            f"Pre-allocated variable {var_name} for helper")
                elif isinstance(rval.func, ast.Attribute):
                    ir_type = ir.PointerType(ir.IntType(64))
                    var = builder.alloca(ir_type, name=var_name)
                    # var.align = ir_type.width // 8
                    print(
                        f"Pre-allocated variable {var_name} for map")
                else:
                    print("Unsupported assignment call function type")
                    continue
            elif isinstance(rval, ast.Constant):
                if isinstance(rval.value, bool):
                    ir_type = ir.IntType(1)
                    var = builder.alloca(ir_type, name=var_name)
                    var.align = 1
                    print(
                        f"Pre-allocated variable {var_name} of type c_bool")
                elif isinstance(rval.value, int):
                    # Assume c_int64 for now
                    ir_type = ir.IntType(64)
                    var = builder.alloca(ir_type, name=var_name)
                    var.align = ir_type.width // 8
                    print(
                        f"Pre-allocated variable {var_name} of type c_int64")
                else:
                    print("Unsupported constant type")
                    continue
            else:
                print("Unsupported assignment value type")
                continue
            local_sym_tab[var_name] = var

    print(f"Local symbol table: {local_sym_tab.keys()}")

    for stmt in func_node.body:
        did_return = process_stmt(func, module, builder, stmt, local_sym_tab,
                                  map_sym_tab, did_return, ret_type)

    if not did_return:
        builder.ret(ir.Constant(ir.IntType(32), 0))


def process_bpf_chunk(func_node, module, return_type, map_sym_tab):
    """Process a single BPF chunk (function) and emit corresponding LLVM IR."""

    func_name = func_node.name

    ret_type = return_type

    # TODO: parse parameters
    param_types = []
    if func_node.args.args:
        # Assume first arg to be ctx
        param_types.append(ir.PointerType())

    func_ty = ir.FunctionType(ret_type, param_types)
    func = ir.Function(module, func_ty, func_name)

    func.linkage = "dso_local"
    func.attributes.add("nounwind")
    func.attributes.add("noinline")
    func.attributes.add("optnone")

    if func_node.args.args:
        # Only look at the first argument for now
        param = func.args[0]
        param.add_attribute("nocapture")

    probe_string = get_probe_string(func_node)
    if probe_string is not None:
        func.section = probe_string

    block = func.append_basic_block(name="entry")
    builder = ir.IRBuilder(block)

    process_func_body(module, builder, func_node, func, ret_type, map_sym_tab)

    return func


def func_proc(tree, module, chunks, map_sym_tab):
    for func_node in chunks:
        is_global = False
        for decorator in func_node.decorator_list:
            if isinstance(decorator, ast.Name) and decorator.id == "map":
                is_global = True
                break
            elif isinstance(decorator, ast.Name) and decorator.id == "bpfglobal":
                is_global = True
                break
        if is_global:
            continue
        func_type = get_probe_string(func_node)
        print(f"Found probe_string of {func_node.name}: {func_type}")

        process_bpf_chunk(func_node, module, ctypes_to_ir(
            infer_return_type(func_node)), map_sym_tab)


def infer_return_type(func_node: ast.FunctionDef):
    if not isinstance(func_node, (ast.FunctionDef, ast.AsyncFunctionDef)):
        raise TypeError("Expected ast.FunctionDef")
    if func_node.returns is not None:
        try:
            return ast.unparse(func_node.returns)
        except Exception:
            node = func_node.returns
            if isinstance(node, ast.Name):
                return node.id
            if isinstance(node, ast.Attribute):
                return getattr(node, "attr", type(node).__name__)
            try:
                return str(node)
            except Exception:
                return type(node).__name__
    found_type = None

    def _expr_type(e):
        if e is None:
            return "None"
        if isinstance(e, ast.Constant):
            return type(e.value).__name__
        if isinstance(e, ast.Name):
            return e.id
        if isinstance(e, ast.Call):
            f = e.func
            if isinstance(f, ast.Name):
                return f.id
            if isinstance(f, ast.Attribute):
                try:
                    return ast.unparse(f)
                except Exception:
                    return getattr(f, "attr", type(f).__name__)
            try:
                return ast.unparse(f)
            except Exception:
                return type(f).__name__
        if isinstance(e, ast.Attribute):
            try:
                return ast.unparse(e)
            except Exception:
                return getattr(e, "attr", type(e).__name__)
        try:
            return ast.unparse(e)
        except Exception:
            return type(e).__name__
    for node in ast.walk(func_node):
        if isinstance(node, ast.Return):
            t = _expr_type(node.value)
            if found_type is None:
                found_type = t
            elif found_type != t:
                raise ValueError("Conflicting return types:"
                                 f"{found_type} vs {t}")
    return found_type or "None"