On Sat, Oct 03, 2020 at 08:14:06PM +0300, Pavel Dovgalyuk wrote: > From: Pavel Dovgalyuk > > This is a test for GDB reverse debugging commands: reverse step and reverse continue. > Every test in this suite consists of two phases: record and replay. > 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. > > Signed-off-by: Pavel Dovgalyuk > Reviewed-by: Philippe Mathieu-Daudé > Reviewed-by: Willian Rampazzo > > -- > > v5: > - disabled (as some other tests) when running on gitlab > due to the unidentified timeout problem > --- > MAINTAINERS | 1 > tests/acceptance/reverse_debugging.py | 208 +++++++++++++++++++++++++++++++++ > 2 files changed, 209 insertions(+) > create mode 100644 tests/acceptance/reverse_debugging.py > > diff --git a/MAINTAINERS b/MAINTAINERS > index ea4fa3e481..bd3a7efb75 100644 > --- a/MAINTAINERS > +++ b/MAINTAINERS > @@ -2693,6 +2693,7 @@ F: include/sysemu/replay.h > F: docs/replay.txt > F: stubs/replay.c > F: tests/acceptance/replay_kernel.py > +F: tests/acceptance/reverse_debugging.py > F: qapi/replay.json > > IOVA Tree > diff --git a/tests/acceptance/reverse_debugging.py b/tests/acceptance/reverse_debugging.py > new file mode 100644 > index 0000000000..b72fdf6cdc > --- /dev/null > +++ b/tests/acceptance/reverse_debugging.py > @@ -0,0 +1,208 @@ > +# 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.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 Have you attmepted a "be" test too? I'm curious about why this is defined (and used later) but it's never used as `False`. > + > + def run_vm(self, record, shift, args, replay_path, image_path): > + 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('-s', '-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') This snippet is clearly modeled after the snippet in `boot_linux.BootLinuxBase.download_boot()`. I'm adding an action item to create a generic utility: https://gitlab.com/cleber.gnu/qemu/-/issues/1 > + cmd = '%s create -f qcow2 %s 128M' % (qemu_img, image_path) > + process.run(cmd) > + > + replay_path = os.path.join(self.workdir, 'replay.bin') > + > + # record the log > + vm = self.run_vm(True, shift, args, replay_path, image_path) > + 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) > + logger.info('connecting to gdbstub') > + g = gdb.GDBRemote('127.0.0.1', 1234, 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) Do you think it'd make sense to have more utility methods, such as `step()` and `bstep()` in `avocado.utils.gdb.GDBRemote` itself? > + > + # 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 > + Nitpick: avoid backslash as line continuation, and favor parentheses, that is: def get_pc(self, g): return (self.get_reg_le(g, self.REG_PC) + self.get_reg_le(g, self.REG_CS) * 0x10) Despite the comments and questions, this LGTM: Reviewed-by: Cleber Rosa Tested-by: Cleber Rosa