tests/avocado/reverse_debugging.py

   1 # Reverse debugging test
   2 #
   3 # Copyright (c) 2020 ISP RAS
   4 #
   5 # Author:
   6 #  Pavel Dovgalyuk <Pavel.Dovgalyuk@ispras.ru>
   7 #
   8 # This work is licensed under the terms of the GNU GPL, version 2 or
   9 # later.  See the COPYING file in the top-level directory.
  10 import os
  11 import logging
  12
  13 from avocado import skipUnless
  14 from avocado_qemu import BUILD_DIR
  15 from avocado.utils import datadrainer
  16 from avocado.utils import gdb
  17 from avocado.utils import process
  18 from avocado.utils.network.ports import find_free_port
  19 from avocado.utils.path import find_command
  20 from boot_linux_console import LinuxKernelTest
  21
  22 class ReverseDebugging(LinuxKernelTest):
  23     """
  24     Test GDB reverse debugging commands: reverse step and reverse continue.
  25     Recording saves the execution of some instructions and makes an initial
  26     VM snapshot to allow reverse execution.
  27     Replay saves the order of the first instructions and then checks that they
  28     are executed backwards in the correct order.
  29     After that the execution is replayed to the end, and reverse continue
  30     command is checked by setting several breakpoints, and asserting
  31     that the execution is stopped at the last of them.
  32     """
  33
  34     timeout = 10
  35     STEPS = 10
  36     endian_is_le = True
  37
  38     def run_vm(self, record, shift, args, replay_path, image_path, port):
  39         logger = logging.getLogger('replay')
  40         vm = self.get_vm()
  41         vm.set_console()
  42         if record:
  43             logger.info('recording the execution...')
  44             mode = 'record'
  45         else:
  46             logger.info('replaying the execution...')
  47             mode = 'replay'
  48             vm.add_args('-gdb', 'tcp::%d' % port, '-S')
  49         vm.add_args('-icount', 'shift=%s,rr=%s,rrfile=%s,rrsnapshot=init' %
  50                     (shift, mode, replay_path),
  51                     '-net', 'none')
  52         vm.add_args('-drive', 'file=%s,if=none' % image_path)
  53         if args:
  54             vm.add_args(*args)
  55         vm.launch()
  56         console_drainer = datadrainer.LineLogger(vm.console_socket.fileno(),
  57                                     logger=self.log.getChild('console'),
  58                                     stop_check=(lambda : not vm.is_running()))
  59         console_drainer.start()
  60         return vm
  61
  62     @staticmethod
  63     def get_reg_le(g, reg):
  64         res = g.cmd(b'p%x' % reg)
  65         num = 0
  66         for i in range(len(res))[-2::-2]:
  67             num = 0x100 * num + int(res[i:i + 2], 16)
  68         return num
  69
  70     @staticmethod
  71     def get_reg_be(g, reg):
  72         res = g.cmd(b'p%x' % reg)
  73         return int(res, 16)
  74
  75     def get_reg(self, g, reg):
  76         # value may be encoded in BE or LE order
  77         if self.endian_is_le:
  78             return self.get_reg_le(g, reg)
  79         else:
  80             return self.get_reg_be(g, reg)
  81
  82     def get_pc(self, g):
  83         return self.get_reg(g, self.REG_PC)
  84
  85     def check_pc(self, g, addr):
  86         pc = self.get_pc(g)
  87         if pc != addr:
  88             self.fail('Invalid PC (read %x instead of %x)' % (pc, addr))
  89
  90     @staticmethod
  91     def gdb_step(g):
  92         g.cmd(b's', b'T05thread:01;')
  93
  94     @staticmethod
  95     def gdb_bstep(g):
  96         g.cmd(b'bs', b'T05thread:01;')
  97
  98     @staticmethod
  99     def vm_get_icount(vm):
 100         return vm.qmp('query-replay')['return']['icount']
 101
 102     def reverse_debugging(self, shift=7, args=None):
 103         logger = logging.getLogger('replay')
 104
 105         # create qcow2 for snapshots
 106         logger.info('creating qcow2 image for VM snapshots')
 107         image_path = os.path.join(self.workdir, 'disk.qcow2')
 108         qemu_img = os.path.join(BUILD_DIR, 'qemu-img')
 109         if not os.path.exists(qemu_img):
 110             qemu_img = find_command('qemu-img', False)
 111         if qemu_img is False:
 112             self.cancel('Could not find "qemu-img", which is required to '
 113                         'create the temporary qcow2 image')
 114         cmd = '%s create -f qcow2 %s 128M' % (qemu_img, image_path)
 115         process.run(cmd)
 116
 117         replay_path = os.path.join(self.workdir, 'replay.bin')
 118         port = find_free_port()
 119
 120         # record the log
 121         vm = self.run_vm(True, shift, args, replay_path, image_path, port)
 122         while self.vm_get_icount(vm) <= self.STEPS:
 123             pass
 124         last_icount = self.vm_get_icount(vm)
 125         vm.shutdown()
 126
 127         logger.info("recorded log with %s+ steps" % last_icount)
 128
 129         # replay and run debug commands
 130         vm = self.run_vm(False, shift, args, replay_path, image_path, port)
 131         logger.info('connecting to gdbstub')
 132         g = gdb.GDBRemote('127.0.0.1', port, False, False)
 133         g.connect()
 134         r = g.cmd(b'qSupported')
 135         if b'qXfer:features:read+' in r:
 136             g.cmd(b'qXfer:features:read:target.xml:0,ffb')
 137         if b'ReverseStep+' not in r:
 138             self.fail('Reverse step is not supported by QEMU')
 139         if b'ReverseContinue+' not in r:
 140             self.fail('Reverse continue is not supported by QEMU')
 141
 142         logger.info('stepping forward')
 143         steps = []
 144         # record first instruction addresses
 145         for _ in range(self.STEPS):
 146             pc = self.get_pc(g)
 147             logger.info('saving position %x' % pc)
 148             steps.append(pc)
 149             self.gdb_step(g)
 150
 151         # visit the recorded instruction in reverse order
 152         logger.info('stepping backward')
 153         for addr in steps[::-1]:
 154             self.gdb_bstep(g)
 155             self.check_pc(g, addr)
 156             logger.info('found position %x' % addr)
 157
 158         # visit the recorded instruction in forward order
 159         logger.info('stepping forward')
 160         for addr in steps:
 161             self.check_pc(g, addr)
 162             self.gdb_step(g)
 163             logger.info('found position %x' % addr)
 164
 165         # set breakpoints for the instructions just stepped over
 166         logger.info('setting breakpoints')
 167         for addr in steps:
 168             # hardware breakpoint at addr with len=1
 169             g.cmd(b'Z1,%x,1' % addr, b'OK')
 170
 171         # this may hit a breakpoint if first instructions are executed
 172         # again
 173         logger.info('continuing execution')
 174         vm.qmp('replay-break', icount=last_icount - 1)
 175         # continue - will return after pausing
 176         # This could stop at the end and get a T02 return, or by
 177         # re-executing one of the breakpoints and get a T05 return.
 178         g.cmd(b'c')
 179         if self.vm_get_icount(vm) == last_icount - 1:
 180             logger.info('reached the end (icount %s)' % (last_icount - 1))
 181         else:
 182             logger.info('hit a breakpoint again at %x (icount %s)' %
 183                         (self.get_pc(g), self.vm_get_icount(vm)))
 184
 185         logger.info('running reverse continue to reach %x' % steps[-1])
 186         # reverse continue - will return after stopping at the breakpoint
 187         g.cmd(b'bc', b'T05thread:01;')
 188
 189         # assume that none of the first instructions is executed again
 190         # breaking the order of the breakpoints
 191         self.check_pc(g, steps[-1])
 192         logger.info('successfully reached %x' % steps[-1])
 193
 194         logger.info('exiting gdb and qemu')
 195         vm.shutdown()
 196
 197 class ReverseDebugging_X86_64(ReverseDebugging):
 198     """
 199     :avocado: tags=accel:tcg
 200     """
 201
 202     REG_PC = 0x10
 203     REG_CS = 0x12
 204     def get_pc(self, g):
 205         return self.get_reg_le(g, self.REG_PC) \
 206             + self.get_reg_le(g, self.REG_CS) * 0x10
 207
 208     # unidentified gitlab timeout problem
 209     @skipUnless(os.getenv('QEMU_TEST_FLAKY_TESTS'), 'Test is unstable on GitLab')
 210
 211     def test_x86_64_pc(self):
 212         """
 213         :avocado: tags=arch:x86_64
 214         :avocado: tags=machine:pc
 215         """
 216         # start with BIOS only
 217         self.reverse_debugging()
 218
 219 class ReverseDebugging_AArch64(ReverseDebugging):
 220     """
 221     :avocado: tags=accel:tcg
 222     """
 223
 224     REG_PC = 32
 225
 226     # unidentified gitlab timeout problem
 227     @skipUnless(os.getenv('QEMU_TEST_FLAKY_TESTS'), 'Test is unstable on GitLab')
 228
 229     def test_aarch64_virt(self):
 230         """
 231         :avocado: tags=arch:aarch64
 232         :avocado: tags=machine:virt
 233         :avocado: tags=cpu:cortex-a53
 234         """
 235         kernel_url = ('https://archives.fedoraproject.org/pub/archive/fedora'
 236                       '/linux/releases/29/Everything/aarch64/os/images/pxeboot'
 237                       '/vmlinuz')
 238         kernel_hash = '8c73e469fc6ea06a58dc83a628fc695b693b8493'
 239         kernel_path = self.fetch_asset(kernel_url, asset_hash=kernel_hash)
 240
 241         self.reverse_debugging(
 242             args=('-kernel', kernel_path))
 243
 244 class ReverseDebugging_ppc64(ReverseDebugging):
 245     """
 246     :avocado: tags=accel:tcg
 247     """
 248
 249     REG_PC = 0x40
 250
 251     # unidentified gitlab timeout problem
 252     @skipUnless(os.getenv('QEMU_TEST_FLAKY_TESTS'), 'Test is unstable on GitLab')
 253
 254     def test_ppc64_pseries(self):
 255         """
 256         :avocado: tags=arch:ppc64
 257         :avocado: tags=machine:pseries
 258         :avocado: tags=flaky
 259         """
 260         # SLOF branches back to its entry point, which causes this test
 261         # to take the 'hit a breakpoint again' path. That's not a problem,
 262         # just slightly different than the other machines.
 263         self.endian_is_le = False
 264         self.reverse_debugging()
 265
 266     # See https://gitlab.com/qemu-project/qemu/-/issues/1992
 267     @skipUnless(os.getenv('QEMU_TEST_FLAKY_TESTS'), 'Test is unstable on GitLab')
 268
 269     def test_ppc64_powernv(self):
 270         """
 271         :avocado: tags=arch:ppc64
 272         :avocado: tags=machine:powernv
 273         :avocado: tags=flaky
 274         """
 275         self.endian_is_le = False
 276         self.reverse_debugging()