# Reverse debugging test # # Copyright (c) 2020 ISP RAS # # Author: # Pavel Dovgalyuk # # This work is licensed under the terms of the GNU GPL, version 2 or # later. See the COPYING file in the top-level directory. import os import logging from avocado import skipIf from avocado_qemu import BUILD_DIR from avocado.utils import gdb from avocado.utils import process from avocado.utils.network.ports import find_free_port from avocado.utils.path import find_command from boot_linux_console import LinuxKernelTest class ReverseDebugging(LinuxKernelTest): """ Test GDB reverse debugging commands: reverse step and reverse continue. Recording saves the execution of some instructions and makes an initial VM snapshot to allow reverse execution. Replay saves the order of the first instructions and then checks that they are executed backwards in the correct order. After that the execution is replayed to the end, and reverse continue command is checked by setting several breakpoints, and asserting that the execution is stopped at the last of them. """ timeout = 10 STEPS = 10 endian_is_le = True def run_vm(self, record, shift, args, replay_path, image_path, port): logger = logging.getLogger('replay') vm = self.get_vm() vm.set_console() if record: logger.info('recording the execution...') mode = 'record' else: logger.info('replaying the execution...') mode = 'replay' vm.add_args('-gdb', 'tcp::%d' % port, '-S') vm.add_args('-icount', 'shift=%s,rr=%s,rrfile=%s,rrsnapshot=init' % (shift, mode, replay_path), '-net', 'none') vm.add_args('-drive', 'file=%s,if=none' % image_path) if args: vm.add_args(*args) vm.launch() return vm @staticmethod def get_reg_le(g, reg): res = g.cmd(b'p%x' % reg) num = 0 for i in range(len(res))[-2::-2]: num = 0x100 * num + int(res[i:i + 2], 16) return num @staticmethod def get_reg_be(g, reg): res = g.cmd(b'p%x' % reg) return int(res, 16) def get_reg(self, g, reg): # value may be encoded in BE or LE order if self.endian_is_le: return self.get_reg_le(g, reg) else: return self.get_reg_be(g, reg) def get_pc(self, g): return self.get_reg(g, self.REG_PC) def check_pc(self, g, addr): pc = self.get_pc(g) if pc != addr: self.fail('Invalid PC (read %x instead of %x)' % (pc, addr)) @staticmethod def gdb_step(g): g.cmd(b's', b'T05thread:01;') @staticmethod def gdb_bstep(g): g.cmd(b'bs', b'T05thread:01;') @staticmethod def vm_get_icount(vm): return vm.qmp('query-replay')['return']['icount'] def reverse_debugging(self, shift=7, args=None): logger = logging.getLogger('replay') # create qcow2 for snapshots logger.info('creating qcow2 image for VM snapshots') image_path = os.path.join(self.workdir, 'disk.qcow2') qemu_img = os.path.join(BUILD_DIR, 'qemu-img') if not os.path.exists(qemu_img): qemu_img = find_command('qemu-img', False) if qemu_img is False: self.cancel('Could not find "qemu-img", which is required to ' 'create the temporary qcow2 image') cmd = '%s create -f qcow2 %s 128M' % (qemu_img, image_path) process.run(cmd) replay_path = os.path.join(self.workdir, 'replay.bin') port = find_free_port() # record the log vm = self.run_vm(True, shift, args, replay_path, image_path, port) while self.vm_get_icount(vm) <= self.STEPS: pass last_icount = self.vm_get_icount(vm) vm.shutdown() logger.info("recorded log with %s+ steps" % last_icount) # replay and run debug commands vm = self.run_vm(False, shift, args, replay_path, image_path, port) logger.info('connecting to gdbstub') g = gdb.GDBRemote('127.0.0.1', port, False, False) g.connect() r = g.cmd(b'qSupported') if b'qXfer:features:read+' in r: g.cmd(b'qXfer:features:read:target.xml:0,ffb') if b'ReverseStep+' not in r: self.fail('Reverse step is not supported by QEMU') if b'ReverseContinue+' not in r: self.fail('Reverse continue is not supported by QEMU') logger.info('stepping forward') steps = [] # record first instruction addresses for _ in range(self.STEPS): pc = self.get_pc(g) logger.info('saving position %x' % pc) steps.append(pc) self.gdb_step(g) # visit the recorded instruction in reverse order logger.info('stepping backward') for addr in steps[::-1]: self.gdb_bstep(g) self.check_pc(g, addr) logger.info('found position %x' % addr) logger.info('seeking to the end (icount %s)' % (last_icount - 1)) vm.qmp('replay-break', icount=last_icount - 1) # continue - will return after pausing g.cmd(b'c', b'T02thread:01;') logger.info('setting breakpoints') for addr in steps: # hardware breakpoint at addr with len=1 g.cmd(b'Z1,%x,1' % addr, b'OK') logger.info('running reverse continue to reach %x' % steps[-1]) # reverse continue - will return after stopping at the breakpoint g.cmd(b'bc', b'T05thread:01;') # assume that none of the first instructions is executed again # breaking the order of the breakpoints self.check_pc(g, steps[-1]) logger.info('successfully reached %x' % steps[-1]) logger.info('exitting gdb and qemu') vm.shutdown() class ReverseDebugging_X86_64(ReverseDebugging): REG_PC = 0x10 REG_CS = 0x12 def get_pc(self, g): return self.get_reg_le(g, self.REG_PC) \ + self.get_reg_le(g, self.REG_CS) * 0x10 # unidentified gitlab timeout problem @skipIf(os.getenv('GITLAB_CI'), 'Running on GitLab') def test_x86_64_pc(self): """ :avocado: tags=arch:x86_64 :avocado: tags=machine:pc """ # start with BIOS only self.reverse_debugging() class ReverseDebugging_AArch64(ReverseDebugging): REG_PC = 32 # unidentified gitlab timeout problem @skipIf(os.getenv('GITLAB_CI'), 'Running on GitLab') def test_aarch64_virt(self): """ :avocado: tags=arch:aarch64 :avocado: tags=machine:virt :avocado: tags=cpu:cortex-a53 """ kernel_url = ('https://archives.fedoraproject.org/pub/archive/fedora' '/linux/releases/29/Everything/aarch64/os/images/pxeboot' '/vmlinuz') kernel_hash = '8c73e469fc6ea06a58dc83a628fc695b693b8493' kernel_path = self.fetch_asset(kernel_url, asset_hash=kernel_hash) self.reverse_debugging( args=('-kernel', kernel_path))