serenity_gdb.py

# Copyright (c) 2021, Gunnar Beutner <gunnar@beutner.name>
#
# SPDX-License-Identifier: BSD-2-Clause

import gdb
import gdb.types
import re


def handler_class_for_type(type, re=re.compile('^([^<]+)(<.*>)?$')):
    typename = str(type.tag)

    match = re.match(typename)
    if not match:
        return UnhandledType

    klass = match.group(1)

    if klass == 'AK::Array':
        return AKArray
    elif klass == 'AK::Atomic':
        return AKAtomic
    elif klass == 'AK::DistinctNumeric':
        return AKDistinctNumeric
    elif klass == 'AK::FixedArray':
        return AKFixedArrayPrinter
    elif klass == 'AK::HashMap':
        return AKHashMapPrettyPrinter
    elif klass == 'AK::RefCounted':
        return AKRefCounted
    elif klass == 'AK::RefPtr':
        return AKRefPtr
    elif klass == 'AK::OwnPtr':
        return AKOwnPtr
    elif klass == 'AK::NonnullRefPtr':
        return AKRefPtr
    elif klass == 'AK::SinglyLinkedList':
        return AKSinglyLinkedList
    elif klass == 'AK::String':
        return AKString
    elif klass == 'AK::ByteString':
        return AKDeprecatedString
    elif klass == 'AK::StringView':
        return AKStringView
    elif klass == 'AK::StringImpl':
        return AKStringImpl
    elif klass == 'AK::Variant':
        return AKVariant
    elif klass == 'AK::Optional':
        return AKOptional
    elif klass == 'AK::Vector':
        return AKVector
    elif klass == 'VirtualAddress':
        return VirtualAddress
    else:
        return UnhandledType


class UnhandledType:
    @classmethod
    def prettyprint_type(cls, type):
        return type.name


class AKAtomic:
    def __init__(self, val):
        self.val = val

    def to_string(self):
        return self.val["m_value"]

    @classmethod
    def prettyprint_type(cls, type):
        contained_type = type.template_argument(0)
        return f'AK::Atomic<{handler_class_for_type(contained_type).prettyprint_type(contained_type)}>'


class AKDistinctNumeric:
    def __init__(self, val):
        self.val = val

    def to_string(self):
        return self.val["m_value"]

    @classmethod
    def prettyprint_type(cls, type):
        actual_name = type.template_argument(1)
        parts = actual_name.name.split("::")
        unqualified_name = re.sub(r'__(\w+)_tag', r'\1', actual_name.name)
        if unqualified_name != actual_name.name:
            qualified_name = '::'.join(parts[:-2] + [unqualified_name])
            return qualified_name
        # If the tag is malformed, just print DistinctNumeric<T>
        contained_type = type.template_argument(0)
        return f'AK::DistinctNumeric<{handler_class_for_type(contained_type).prettyprint_type(contained_type)}>'


class AKFixedArrayPrinter:
    def __init__(self, val):
        self.val = val

    def get_storage(self):
        storage = self.val["m_storage"]

        return None if int(storage) == 0 else storage

    def to_string(self):
        storage = self.get_storage()
        if storage is not None:
            size = storage["size"]
        else:
            size = 0

        return f'{AKFixedArrayPrinter.prettyprint_type(self.val.type)} of size {size}'

    def children(self):
        storage = self.get_storage()

        if storage is None:
            return []
        else:
            size = storage["size"]
            elements = storage["elements"]

        # Very arbitrary limit, just to catch UAF'd and garbage vector values with a silly number of elements
        if size > 373373:
            return []

        return [(f"[{i}]", elements[i]) for i in range(size)]

    @classmethod
    def prettyprint_type(cls, type):
        template_type = type.template_argument(0)
        return f'AK::FixedArray<{handler_class_for_type(template_type).prettyprint_type(template_type)}>'


class AKRefCounted:
    def __init__(self, val):
        self.val = val

    def to_string(self):
        return self.val["m_ref_count"]

    @classmethod
    def prettyprint_type(cls, type):
        contained_type = type.template_argument(0)
        return f'AK::RefCounted<{handler_class_for_type(contained_type).prettyprint_type(contained_type)}>'


class AKString:
    def __init__(self, val):
        self.val = val

    def to_string(self):
        # Using the internal structure directly is quite convoluted here because of the packing optimizations
        # of AK::String (could be a short string, a substring, or a normal string).
        # This workaround was described in the gdb bugzilla on a discussion of supporting direct method calls
        # on values: https://sourceware.org/bugzilla/show_bug.cgi?id=13326
        gdb.set_convenience_variable('_tmp', self.val.reference_value())
        string_view = gdb.parse_and_eval('$_tmp.bytes_as_string_view()')
        return AKStringView(string_view).to_string()

    @classmethod
    def prettyprint_type(cls, type):
        return 'AK::String'


class AKDeprecatedString:
    def __init__(self, val):
        self.val = val

    def to_string(self):
        if int(self.val["m_impl"]["m_ptr"]) == 0:
            return '""'
        else:
            impl = AKRefPtr(self.val["m_impl"]).get_pointee().dereference()
            return AKStringImpl(impl).to_string()

    @classmethod
    def prettyprint_type(cls, type):
        return 'AK::ByteString'


class AKStringView:
    def __init__(self, val):
        self.val = val

    def to_string(self):
        if int(self.val["m_length"]) == 0:
            return '""'
        else:
            return self.val["m_characters"].string(length=self.val["m_length"])

    @classmethod
    def prettyprint_type(cls, type):
        return 'AK::StringView'


def get_field_unalloced(val, member, type):
    # Trying to access a variable-length field seems to fail with
    # Python Exception <class 'gdb.error'> value requires 4294967296 bytes, which is more than max-value-size
    # This works around that issue.
    return gdb.parse_and_eval(f"*({type}*)(({val.type.name}*){int(val.address)})->{member}")


class AKStringImpl:
    def __init__(self, val):
        self.val = val

    def to_string(self):
        if int(self.val["m_length"]) == 0:
            return '""'
        else:
            return self.val["m_inline_buffer"].string(length=self.val["m_length"])

    @classmethod
    def prettyprint_type(cls, type):
        return 'AK::StringImpl'


class AKOwnPtr:
    def __init__(self, val):
        self.val = val

    def to_string(self):
        return AKOwnPtr.prettyprint_type(self.val.type)

    def children(self):
        return [('*', self.val["m_ptr"])]

    @classmethod
    def prettyprint_type(cls, type):
        contained_type = type.template_argument(0)
        return f'AK::OwnPtr<{handler_class_for_type(contained_type).prettyprint_type(contained_type)}>'


class AKRefPtr:
    def __init__(self, val):
        self.val = val

    def to_string(self):
        return AKRefPtr.prettyprint_type(self.val.type)

    def get_pointee(self):
        inner_type = self.val.type.template_argument(0)
        inner_type_ptr = inner_type.pointer()
        return self.val["m_ptr"].cast(inner_type_ptr)

    def children(self):
        return [('*', self.get_pointee())]

    @classmethod
    def prettyprint_type(cls, type):
        contained_type = type.template_argument(0)
        return f'AK::RefPtr<{handler_class_for_type(contained_type).prettyprint_type(contained_type)}>'


class AKVariant:
    def __init__(self, val):
        self.val = val
        self.index = int(self.val["m_index"])
        self.contained_types = self.resolve_types(self.val.type)

    def to_string(self):
        return AKVariant.prettyprint_type(self.val.type)

    def children(self):
        data = self.val["m_data"]
        ty = self.contained_types[self.index]
        return [(ty.name, data.cast(ty.pointer()).referenced_value())]

    @classmethod
    def resolve_types(cls, ty):
        contained_types = []
        type_resolved = ty.strip_typedefs()
        index = 0
        while True:
            try:
                arg = type_resolved.template_argument(index)
                index += 1
                contained_types.append(arg)
            except RuntimeError:
                break
        return contained_types

    @classmethod
    def prettyprint_type(cls, ty):
        names = ", ".join(handler_class_for_type(t).prettyprint_type(t) for t in AKVariant.resolve_types(ty))
        return f'AK::Variant<{names}>'


class AKOptional:
    def __init__(self, val):
        self.val = val
        self.has_value = bool(self.val["m_has_value"])
        self.contained_type = self.val.type.strip_typedefs().template_argument(0)

    def to_string(self):
        return AKOptional.prettyprint_type(self.val.type)

    def children(self):
        if self.has_value:
            data = self.val["m_storage"]
            return [(self.contained_type.name, data.cast(self.contained_type.pointer()).referenced_value())]
        return [("OptionalNone", "{}")]

    @classmethod
    def prettyprint_type(cls, type):
        template_type = type.template_argument(0)
        return f'AK::Optional<{template_type}>'


class AKVector:
    def __init__(self, val):
        self.val = val

    def to_string(self):
        return f'{AKVector.prettyprint_type(self.val.type)} of len {int(self.val["m_size"])}'

    def children(self):
        vec_len = int(self.val["m_size"])

        if vec_len == 0:
            return []

        outline_buf = self.val["m_outline_buffer"]

        inner_type_ptr = self.val.type.template_argument(0).pointer()

        if int(outline_buf) != 0:
            elements = outline_buf.cast(inner_type_ptr)
        else:
            elements = get_field_unalloced(self.val, "m_inline_buffer_storage", inner_type_ptr)

        # Very arbitrary limit, just to catch UAF'd and garbage vector values with a silly number of elements
        if vec_len > 373373:
            return []

        return [(f"[{i}]", elements[i]) for i in range(vec_len)]

    @classmethod
    def prettyprint_type(cls, type):
        template_type = type.template_argument(0)
        return f'AK::Vector<{handler_class_for_type(template_type).prettyprint_type(template_type)}>'


class AKArray:
    def __init__(self, val):
        self.val = val
        self.storage_type = self.val.type.template_argument(0)
        self.array_size = self.val.type.template_argument(1)

    def to_string(self):
        return AKArray.prettyprint_type(self.val.type)

    def children(self):
        data_array = self.val["__data"]
        storage_type_ptr = self.storage_type.pointer()
        elements = data_array.cast(storage_type_ptr)

        return [(f"[{i}]", elements[i]) for i in range(self.array_size)]

    @classmethod
    def prettyprint_type(cls, type):
        template_type = type.template_argument(0)
        template_size = type.template_argument(1)
        return f'AK::Array<{template_type}, {template_size}>'


class AKHashMapPrettyPrinter:
    def __init__(self, val):
        self.val = val

    @staticmethod
    def _iter_hashtable(val, cb):
        entry_type_ptr = val.type.template_argument(0).pointer()
        buckets = val["m_buckets"]
        for i in range(0, val["m_capacity"]):
            bucket = buckets[i]
            # if state == Used
            if bucket["state"] & 0xf0 == 0x10:
                cb(bucket["storage"].cast(entry_type_ptr))

    @staticmethod
    def _iter_hashmap(val, cb):
        table = val["m_table"]
        AKHashMapPrettyPrinter._iter_hashtable(table, lambda entry: cb(entry["key"], entry["value"]))

    def to_string(self):
        return AKHashMapPrettyPrinter.prettyprint_type(self.val.type)

    def children(self):
        elements = []

        def cb(key, value):
            nonlocal elements
            elements.append((f"[{key}]", value))

        AKHashMapPrettyPrinter._iter_hashmap(self.val, cb)
        return elements

    @classmethod
    def prettyprint_type(cls, type):
        template_types = list(type.template_argument(i) for i in (0, 1))
        key, value = list(handler_class_for_type(t).prettyprint_type(t) for t in template_types)
        return f'AK::HashMap<{key}, {value}>'


class AKSinglyLinkedList:
    def __init__(self, val):
        self.val = val

    def to_string(self):
        return AKSinglyLinkedList.prettyprint_type(self.val.type)

    def children(self):
        elements = []

        node = self.val["m_head"]
        while node != 0:
            elements.append(node["value"])
            node = node["next"]

        return [(f"[{i}]", elements[i]) for i in range(len(elements))]

    @classmethod
    def prettyprint_type(cls, type):
        template_type = type.template_argument(0)
        return f'AK::SinglyLinkedList<{handler_class_for_type(template_type).prettyprint_type(template_type)}>'


class VirtualAddress:
    def __init__(self, val):
        self.val = val

    def to_string(self):
        return self.val["m_address"]

    @classmethod
    def prettyprint_type(cls, type):
        return 'VirtualAddress'


class SerenityPrettyPrinterLocator(gdb.printing.PrettyPrinter):
    def __init__(self):
        super(SerenityPrettyPrinterLocator, self).__init__("serenity_pretty_printers", [])

    def __call__(self, val):
        type = gdb.types.get_basic_type(val.type)
        handler = handler_class_for_type(type)
        if handler is UnhandledType:
            return None
        return handler(val)


gdb.printing.register_pretty_printer(None, SerenityPrettyPrinterLocator(), replace=True)


class FindThreadCmd(gdb.Command):
    """
    Find SerenityOS thread for the specified TID.
    find_thread TID
    """

    def __init__(self):
        super(FindThreadCmd, self).__init__(
            "find_thread", gdb.COMMAND_USER
        )

    def _find_thread(self, tid):
        threads = gdb.parse_and_eval("Kernel::Thread::g_tid_map")
        thread = None

        def cb(key, value):
            nonlocal thread
            if int(key["m_value"]) == tid:
                thread = value

        AKHashMapPrettyPrinter._iter_hashmap(threads, cb)
        return thread

    def complete(self, text, word):
        return gdb.COMPLETE_SYMBOL

    def invoke(self, args, from_tty):
        argv = gdb.string_to_argv(args)
        if len(argv) == 0:
            gdb.write("Argument required (TID).\n")
            return
        tid = int(argv[0])
        thread = self._find_thread(tid)
        if not thread:
            gdb.write(f"No thread with TID {tid} found.\n")
        else:
            gdb.write(f"{thread}\n")


FindThreadCmd()