scripts/gdb: add kernel config dumping command

# SPDX-License-Identifier: GPL-2.0

#

# Copyright 2019 Google LLC.

import gdb

import zlib

from linux import utils

class LxConfigDump(gdb.Command):

    """Output kernel config to the filename specified as the command

       argument. Equivalent to 'zcat /proc/config.gz > config.txt' on

       a running target"""

    def __init__(self):

        super(LxConfigDump, self).__init__("lx-configdump", gdb.COMMAND_DATA,

                                           gdb.COMPLETE_FILENAME)

    def invoke(self, arg, from_tty):

        if len(arg) == 0:

            filename = "config.txt"

        else:

            filename = arg

        try:

            py_config_ptr = gdb.parse_and_eval("kernel_config_data + 8")

            py_config_size = gdb.parse_and_eval(

                    "sizeof(kernel_config_data) - 1 - 8 * 2")

        except gdb.error as e:

            raise gdb.GdbError("Can't find config, enable CONFIG_IKCONFIG?")

        inf = gdb.inferiors()[0]

        zconfig_buf = utils.read_memoryview(inf, py_config_ptr,

                                            py_config_size).tobytes()

        config_buf = zlib.decompress(zconfig_buf, 16)

        with open(filename, 'wb') as f:

            f.write(config_buf)

        gdb.write("Dumped config to " + filename + "\n")

LxConfigDump()

    import linux.modules

    import linux.dmesg

    import linux.tasks

    import linux.config

    import linux.cpus

    import linux.lists

    import linux.proc