@@ -2661,6 +2661,7 @@ 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
new file mode 100644
@@ -0,0 +1,203 @@
+# Reverse debugging test
+#
+# Copyright (c) 2020 ISP RAS
+#
+# Author:
+# Pavel Dovgalyuk <Pavel.Dovgalyuk@ispras.ru>
+#
+# 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_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
+
+ 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')
+ 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)
+
+ # 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
+
+ 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
+
+ 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, '-cpu', 'cortex-a53'))