scripts/fwgdb.py

# Copyright 2014 The ChromiumOS Authors
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

"""Connect to a DUT in firmware via remote GDB, install custom GDB commands."""

import errno
import glob
import logging
import os
import re
import socket
import time

from chromite.third_party.pyelftools.elftools.elf.elffile import ELFFile

from chromite.lib import build_target_lib
from chromite.lib import constants
from chromite.lib import cros_build_lib
from chromite.lib import timeout_util


# Need to do this before Servo import
cros_build_lib.AssertInsideChroot()

# pylint: disable=import-error,wrong-import-position
from servo import client
from servo import servo_parsing
from servo import terminal_freezer


# pylint: enable=import-error,wrong-import-position


_SRC_ROOT = os.path.join(constants.CHROOT_SOURCE_ROOT, "src")
_SRC_DC = os.path.join(_SRC_ROOT, "platform/depthcharge")
_SRC_VB = os.path.join(_SRC_ROOT, "platform/vboot_reference")
_SRC_LP = os.path.join(_SRC_ROOT, "third_party/coreboot/payloads/libpayload")

_PTRN_GDB = b"Ready for GDB connection"
_PTRN_BOARD = (
    b"Starting(?: read-only| read/write)? depthcharge on ([A-Za-z_]+)..."
)


def GetGdbForElf(elf):
    """Return the correct C compiler prefix for the target ELF file."""
    with open(elf, "rb") as fp:
        return {
            "EM_386": "x86_64-cros-linux-gnu-gdb",
            "EM_X86_64": "x86_64-cros-linux-gnu-gdb",
            "EM_ARM": "armv7a-cros-linux-gnueabihf-gdb",
            "EM_AARCH64": "aarch64-cros-linux-gnu-gdb",
        }[ELFFile(fp).header.e_machine]


def ParseArgs(argv):
    """Parse and validate command line arguments."""
    description = "Debug depthcharge using GDB"
    parser = servo_parsing.ServodClientParser(description=description)
    parser.add_argument(
        "-b", "--board", help="The board overlay name (auto-detect by default)"
    )
    parser.add_argument(
        "-c",
        "--cgdb",
        action="store_true",
        help="Use cgdb curses interface rather than plain gdb",
    )
    parser.add_argument(
        "-y",
        "--symbols",
        help="Root directory or complete path to symbolized ELF "
        "(defaults to /build/<BOARD>/firmware)",
    )
    parser.add_argument(
        "-r",
        "--reboot",
        choices=["yes", "no", "auto"],
        help="Reboot the DUT before connect (default: reboot if "
        "the remote and is unreachable)",
        default="auto",
    )
    parser.add_argument(
        "-e",
        "--execute",
        action="append",
        default=[],
        help="GDB command to run after connect (can be supplied "
        "multiple times)",
    )
    parser.add_argument(
        "-t", "--tty", help="TTY file to connect to (defaults to cpu_uart_pty)"
    )
    opts = parser.parse_args(argv)

    return opts


def FindSymbols(firmware_dir, board):
    """Find the symbolized depthcharge ELF (may be supplied by -y flag)."""

    # Allow overriding the file directly just in case our detection screws up.
    if firmware_dir and firmware_dir.endswith(".elf"):
        return firmware_dir

    if not firmware_dir:
        # Unified builds have the format
        # /build/<board|family>/firmware/<build_target|model>/. The board in
        # depthcharge corresponds to the build_target in unified builds. For this
        # reason we need to glob all boards to find the correct build_target.
        unified_build_dirs = glob.glob("/build/*/firmware/%s" % board)
        if len(unified_build_dirs) == 1:
            firmware_dir = unified_build_dirs[0]
        elif len(unified_build_dirs) > 1:
            raise ValueError(
                "Multiple boards were found (%s). Use -y to specify manually"
                % (", ".join(unified_build_dirs))
            )

    if not firmware_dir:
        firmware_dir = os.path.join(
            build_target_lib.get_default_sysroot_path(board), "firmware"
        )

    # Very old firmware you might still find on GoldenEye had dev.ro.elf.
    basenames = ["dev.elf", "dev.ro.elf"]
    for basename in basenames:
        path = os.path.join(firmware_dir, "depthcharge", basename)
        if not os.path.exists(path):
            path = os.path.join(firmware_dir, basename)
        if os.path.exists(path):
            logging.warning(
                "Auto-detected symbol file at %s... make sure that this"
                " matches the image on your DUT!",
                path,
            )
            return path

    raise ValueError(
        "Could not find depthcharge symbol file (dev.elf)! "
        "(You can use -s to supply it manually.)"
    )


# TODO(jwerner): Fine tune |wait| delay or maybe even make it configurable if
# this causes problems due to load on the host. The callers where this is
# critical should all have their own timeouts now, though, so it's questionable
# whether the delay here is even needed at all anymore.
def ReadAll(fd, wait=0.03):
    """Read from |fd| until no more data has come for at least |wait| seconds."""
    data = []
    try:
        while True:
            time.sleep(wait)
            new_data = os.read(fd, 4096)
            if not new_data:
                break
            data.append(new_data)
    except OSError as e:
        if e.errno != errno.EAGAIN:
            raise
    data = b"".join(data)
    if data:
        logging.debug(data.decode("ascii", errors="replace"))
    return data


def GdbChecksum(message):
    """Calculate a remote-GDB style checksum."""
    chksum = sum(message)
    return (b"%.2x" % chksum)[-2:]


def TestConnection(fd):
    """Return True iff there is a resposive GDB stub on the other end of 'fd'."""
    cmd = b"vUnknownCommand"
    for _ in range(3):
        os.write(fd, b"$%s#%s\n" % (cmd, GdbChecksum(cmd)))
        reply = ReadAll(fd)
        if b"+$#00" in reply:
            os.write(fd, b"+")
            logging.info(
                "TestConnection: Could successfully connect to remote end."
            )
            return True
    logging.info("TestConnection: Remote end does not respond.")
    return False


def main(argv):
    opts = ParseArgs(argv)
    servo = client.ServoClient(host=opts.host, port=opts.port)

    if not opts.tty:
        try:
            opts.tty = servo.get("cpu_uart_pty")
        except (client.ServoClientError, socket.error):
            logging.error(
                "Cannot auto-detect TTY file without servod. Use the --tty "
                "option."
            )
            raise
    with terminal_freezer.TerminalFreezer(opts.tty):
        fd = os.open(opts.tty, os.O_RDWR | os.O_NONBLOCK)

        data = ReadAll(fd)
        if opts.reboot == "auto":
            if TestConnection(fd):
                opts.reboot = "no"
            else:
                opts.reboot = "yes"

        if opts.reboot == "yes":
            logging.info("Rebooting DUT...")
            try:
                servo.set("warm_reset", "on")
                time.sleep(0.1)
                servo.set("warm_reset", "off")
            except (client.ServoClientError, socket.error):
                logging.error(
                    "Cannot reboot without a Servo board. You have to boot "
                    "into developer mode and press CTRL+G manually before "
                    "running fwgdb."
                )
                raise

            # Throw away old data to avoid confusion from messages before the reboot
            data = b""
            msg = "Could not reboot into depthcharge!"
            with timeout_util.Timeout(10, msg):
                while not re.search(_PTRN_BOARD, data):
                    data += ReadAll(fd)

            msg = (
                "Could not enter GDB mode with CTRL+G! "
                '(Confirm that you flashed an "image.dev.bin" image to this DUT, '
                "and that you have GBB_FLAG_FORCE_DEV_SWITCH_ON (0x8) set.)"
            )
            with timeout_util.Timeout(5, msg):
                while not re.search(_PTRN_GDB, data):
                    # Some delay to avoid spamming the console too hard while not being
                    # long enough to cause a user-visible slowdown.
                    time.sleep(0.5)
                    # Send a CTRL+G to tell depthcharge to trap into GDB.
                    logging.debug("[Ctrl+G]")
                    os.write(fd, b"\x07")
                    data += ReadAll(fd)

        if not opts.board:
            matches = re.findall(_PTRN_BOARD, data)
            if not matches:
                raise ValueError(
                    "Could not auto-detect board! Please use -b option."
                )
            opts.board = matches[-1]
            logging.info(
                "Auto-detected board as %s from DUT console output.", opts.board
            )

        if not TestConnection(fd):
            raise IOError(
                "Could not connect to remote end! Confirm that your DUT is "
                "running in GDB mode on %s." % opts.tty
            )

        # Eat up leftover data or it will spill back to terminal
        ReadAll(fd)
        os.close(fd)

        opts.execute.insert(0, "target remote %s" % opts.tty)
        ex_args = sum([["--ex", cmd] for cmd in opts.execute], [])

        elf = FindSymbols(opts.symbols, opts.board)
        gdb_cmd = GetGdbForElf(elf)

        gdb_args = [
            "--symbols",
            elf,
            "--directory",
            _SRC_DC,
            "--directory",
            _SRC_VB,
            "--directory",
            _SRC_LP,
        ] + ex_args

        if opts.cgdb:
            full_cmd = ["cgdb", "-d", gdb_cmd, "--"] + gdb_args
        else:
            full_cmd = [gdb_cmd] + gdb_args

        logging.info("Launching GDB...")
        cros_build_lib.run(
            full_cmd, ignore_sigint=True, debug_level=logging.WARNING
        )