d5e1de6da9
This commit only adds support for the `SBProcess::ReverseContinue()` API. A user-accessible command for this will follow in a later commit. This feature depends on a gdbserver implementation (e.g. `rr`) providing support for the `bc` and `bs` packets. `lldb-server` does not support those packets, and there is no plan to change that. So, for testing purposes, `lldbreverse.py` wraps `lldb-server` with a Python implementation of *very limited* record-and-replay functionality for use by *tests only*. The majority of this PR is test infrastructure (about 700 of the 950 lines added).
419 lines
16 KiB
Python
419 lines
16 KiB
Python
import os
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import os.path
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import lldb
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from lldbsuite.test.lldbtest import *
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from lldbsuite.test.gdbclientutils import *
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from lldbsuite.test.lldbgdbproxy import *
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import lldbgdbserverutils
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import re
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class ThreadSnapshot:
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def __init__(self, thread_id, registers):
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self.thread_id = thread_id
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self.registers = registers
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class MemoryBlockSnapshot:
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def __init__(self, address, data):
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self.address = address
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self.data = data
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class StateSnapshot:
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def __init__(self, thread_snapshots, memory):
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self.thread_snapshots = thread_snapshots
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self.memory = memory
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self.thread_id = None
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class RegisterInfo:
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def __init__(self, lldb_index, bitsize, little_endian):
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self.lldb_index = lldb_index
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self.bitsize = bitsize
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self.little_endian = little_endian
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BELOW_STACK_POINTER = 16384
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ABOVE_STACK_POINTER = 4096
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BLOCK_SIZE = 1024
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SOFTWARE_BREAKPOINTS = 0
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HARDWARE_BREAKPOINTS = 1
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WRITE_WATCHPOINTS = 2
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class ReverseTestBase(GDBProxyTestBase):
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"""
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Base class for tests that need reverse execution.
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This class uses a gdbserver proxy to add very limited reverse-
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execution capability to lldb-server/debugserver for testing
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purposes only.
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To use this class, run the inferior forward until some stopping point.
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Then call `start_recording()` and execute forward again until reaching
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a software breakpoint; this class records the state before each execution executes.
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At that point, the server will accept "bc" and "bs" packets to step
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backwards through the state.
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When executing during recording, we only allow single-step and continue without
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delivering a signal, and only software breakpoint stops are allowed.
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We assume that while recording is enabled, the only effects of instructions
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are on general-purpose registers (read/written by the 'g' and 'G' packets)
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and on memory bytes between [SP - BELOW_STACK_POINTER, SP + ABOVE_STACK_POINTER).
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"""
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"""
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A list of StateSnapshots in time order.
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There is one snapshot per single-stepped instruction,
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representing the state before that instruction was
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executed. The last snapshot in the list is the
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snapshot before the last instruction was executed.
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This is an undo log; we snapshot a superset of the state that may have
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been changed by the instruction's execution.
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"""
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snapshots = None
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recording_enabled = False
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breakpoints = None
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pid = None
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pc_register_info = None
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sp_register_info = None
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general_purpose_register_info = None
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def __init__(self, *args, **kwargs):
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GDBProxyTestBase.__init__(self, *args, **kwargs)
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self.breakpoints = [set(), set(), set(), set(), set()]
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def respond(self, packet):
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if not packet:
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raise ValueError("Invalid empty packet")
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if packet == self.server.PACKET_INTERRUPT:
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# Don't send a response. We'll just run to completion.
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return []
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if self.is_command(packet, "qSupported", ":"):
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reply = self.pass_through(packet)
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return reply + ";ReverseStep+;ReverseContinue+"
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if self.is_command(packet, "vCont", ";"):
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if self.recording_enabled:
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return self.continue_with_recording(packet)
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snapshots = []
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if packet[0] == "c" or packet[0] == "s" or packet[0] == "C" or packet[0] == "S":
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raise ValueError("LLDB should not be sending old-style continuation packets")
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if packet == "bc":
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return self.reverse_continue()
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if packet == "bs":
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return self.reverse_step()
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if packet == 'jThreadsInfo':
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# Suppress this because it contains thread stop reasons which we might
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# need to modify, and we don't want to have to implement that.
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return ""
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if packet[0] == "z" or packet[0] == "Z":
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reply = self.pass_through(packet)
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if reply == "OK":
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self.update_breakpoints(packet)
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return reply
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return GDBProxyTestBase.respond(self, packet)
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def start_recording(self):
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self.recording_enabled = True
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self.snapshots = []
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def stop_recording(self):
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"""
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Don't record when executing foward.
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Reverse execution is still supported until the next forward continue.
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"""
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self.recording_enabled = False
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def is_command(self, packet, cmd, follow_token):
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return packet == cmd or packet[0:len(cmd) + 1] == cmd + follow_token
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def update_breakpoints(self, packet):
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m = re.match("([zZ])([01234]),([0-9a-f]+),([0-9a-f]+)", packet)
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if m is None:
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raise ValueError("Invalid breakpoint packet: " + packet)
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t = int(m.group(2))
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addr = int(m.group(3), 16)
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kind = int(m.group(4), 16)
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if m.group(1) == 'Z':
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self.breakpoints[t].add((addr, kind))
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else:
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self.breakpoints[t].discard((addr, kind))
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def breakpoint_triggered_at(self, pc):
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if any(addr == pc for addr, kind in self.breakpoints[SOFTWARE_BREAKPOINTS]):
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return True
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if any(addr == pc for addr, kind in self.breakpoints[HARDWARE_BREAKPOINTS]):
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return True
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return False
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def watchpoint_triggered(self, new_value_block, current_contents):
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"""Returns the address or None."""
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for watch_addr, kind in breakpoints[WRITE_WATCHPOINTS]:
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for offset in range(0, kind):
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addr = watch_addr + offset
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if (addr >= new_value_block.address and
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addr < new_value_block.address + len(new_value_block.data)):
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index = addr - new_value_block.address
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if new_value_block.data[index*2:(index + 1)*2] != current_contents[index*2:(index + 1)*2]:
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return watch_addr
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return None
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def continue_with_recording(self, packet):
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self.logger.debug("Continue with recording enabled")
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step_packet = "vCont;s"
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if packet == "vCont":
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requested_step = False
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else:
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m = re.match("vCont;(c|s)(.*)", packet)
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if m is None:
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raise ValueError("Unsupported vCont packet: " + packet)
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requested_step = m.group(1) == 's'
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step_packet += m.group(2)
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while True:
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snapshot = self.capture_snapshot()
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reply = self.pass_through(step_packet)
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(stop_signal, stop_pairs) = self.parse_stop(reply)
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if stop_signal != 5:
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raise ValueError("Unexpected stop signal: " + reply)
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is_swbreak = False
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thread_id = None
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for key, value in stop_pairs.items():
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if key == "thread":
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thread_id = self.parse_thread_id(value)
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continue
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if re.match('[0-9a-f]+', key):
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continue
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if key == "swbreak" or (key == "reason" and value == "breakpoint"):
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is_swbreak = True
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continue
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if key in ["name", "threads", "thread-pcs", "reason"]:
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continue
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raise ValueError(f"Unknown stop key '{key}' in {reply}")
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if is_swbreak:
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self.logger.debug("Recording stopped")
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return reply
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if thread_id is None:
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return ValueError("Expected thread ID: " + reply)
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snapshot.thread_id = thread_id
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self.snapshots.append(snapshot)
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if requested_step:
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self.logger.debug("Recording stopped for step")
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return reply
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def parse_stop(self, reply):
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result = {}
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if not reply:
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raise ValueError("Invalid empty packet")
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if reply[0] == "T" and len(reply) >= 3:
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result = {k:v for k, v in self.parse_pairs(reply[3:])}
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return (int(reply[1:3], 16), result)
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raise "Unsupported stop reply: " + reply
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def parse_pairs(self, text):
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for pair in text.split(";"):
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if not pair:
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continue
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m = re.match("([^:]+):(.*)", pair)
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if m is None:
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raise ValueError("Invalid pair text: " + text)
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yield (m.group(1), m.group(2))
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def capture_snapshot(self):
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"""Snapshot all threads and their stack memories."""
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self.ensure_register_info()
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current_thread = self.get_current_thread()
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thread_snapshots = []
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memory = []
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for thread_id in self.get_thread_list():
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registers = {}
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for index in sorted(self.general_purpose_register_info.keys()):
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reply = self.pass_through(f"p{index:x};thread:{thread_id:x};")
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if reply == "" or reply[0] == 'E':
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raise ValueError("Can't read register")
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registers[index] = reply
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thread_snapshot = ThreadSnapshot(thread_id, registers)
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thread_sp = self.get_register(self.sp_register_info, thread_snapshot.registers)
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memory += self.read_memory(thread_sp - BELOW_STACK_POINTER, thread_sp + ABOVE_STACK_POINTER)
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thread_snapshots.append(thread_snapshot)
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self.set_current_thread(current_thread)
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return StateSnapshot(thread_snapshots, memory)
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def restore_snapshot(self, snapshot):
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"""
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Restore the snapshot during reverse execution.
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If this triggers a breakpoint or watchpoint, return the stop reply,
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otherwise None.
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"""
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current_thread = self.get_current_thread()
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stop_reasons = []
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for thread_snapshot in snapshot.thread_snapshots:
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thread_id = thread_snapshot.thread_id
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for lldb_index in sorted(thread_snapshot.registers.keys()):
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data = thread_snapshot.registers[lldb_index]
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reply = self.pass_through(f"P{lldb_index:x}={data};thread:{thread_id:x};")
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if reply != "OK":
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raise ValueError("Can't restore thread register")
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if thread_id == snapshot.thread_id:
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new_pc = self.get_register(self.pc_register_info, thread_snapshot.registers)
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if self.breakpoint_triggered_at(new_pc):
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stop_reasons.append([("reason", "breakpoint")])
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self.set_current_thread(current_thread)
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for block in snapshot.memory:
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current_memory = self.pass_through(f"m{block.address:x},{(len(block.data)/2):x}")
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if not current_memory or current_memory[0] == 'E':
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raise ValueError("Can't read back memory")
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reply = self.pass_through(f"M{block.address:x},{len(block.data)/2:x}:" + block.data)
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if reply != "OK":
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raise ValueError("Can't restore memory")
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watch_addr = self.watchpoint_triggered(block, current_memory[1:])
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if watch_addr is not None:
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stop_reasons.append([("reason", "watchpoint"), ("watch", f"{watch_addr:x}")])
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if stop_reasons:
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pairs = ";".join(f"{key}:{value}" for key, value in stop_reasons[0])
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return f"T05thread:{self.pid:x}.{snapshot.thread_id:x};{pairs};"
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return None
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def reverse_step(self):
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if not self.snapshots:
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self.logger.debug("Reverse-step at history boundary")
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return self.history_boundary_reply(self.get_current_thread())
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self.logger.debug("Reverse-step started")
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snapshot = self.snapshots.pop()
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stop_reply = self.restore_snapshot(snapshot)
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self.set_current_thread(snapshot.thread_id)
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self.logger.debug("Reverse-step stopped")
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if stop_reply is None:
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return self.singlestep_stop_reply(snapshot.thread_id)
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return stop_reply
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def reverse_continue(self):
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self.logger.debug("Reverse-continue started")
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thread_id = None
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while self.snapshots:
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snapshot = self.snapshots.pop()
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stop_reply = self.restore_snapshot(snapshot)
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thread_id = snapshot.thread_id
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if stop_reply is not None:
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self.set_current_thread(thread_id)
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self.logger.debug("Reverse-continue stopped")
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return stop_reply
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if thread_id is None:
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thread_id = self.get_current_thread()
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else:
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self.set_current_thread(snapshot.thread_id)
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self.logger.debug("Reverse-continue stopped at history boundary")
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return self.history_boundary_reply(thread_id)
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def get_current_thread(self):
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reply = self.pass_through("qC")
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return self.parse_thread_id(reply[2:])
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def parse_thread_id(self, thread_id):
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m = re.match("(p([0-9a-f]+)[.])?([0-9a-f]+)$", thread_id)
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if m is None:
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raise ValueError("Invalid thread ID: " + thread_id)
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if self.pid is None:
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self.pid = int(m.group(2), 16)
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return int(m.group(3), 16)
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def history_boundary_reply(self, thread_id):
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return f"T00thread:{self.pid:x}.{thread_id:x};replaylog:begin;"
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def singlestep_stop_reply(self, thread_id):
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return f"T05thread:{self.pid:x}.{thread_id:x};"
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def set_current_thread(self, thread_id):
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"""
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Set current thread in inner gdbserver.
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"""
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if thread_id >= 0:
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self.pass_through(f"Hg{self.pid:x}.{thread_id:x}")
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self.pass_through(f"Hc{self.pid:x}.{thread_id:x}")
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else:
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self.pass_through(f"Hc-1.-1")
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self.pass_through(f"Hg-1.-1")
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def get_register(self, register_info, registers):
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if register_info.bitsize % 8 != 0:
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raise ValueError("Register size must be a multiple of 8 bits")
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if register_info.lldb_index not in registers:
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raise ValueError("Register value not captured")
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data = registers[register_info.lldb_index]
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num_bytes = register_info.bitsize//8
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bytes = []
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for i in range(0, num_bytes):
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bytes.append(int(data[i*2:(i + 1)*2], 16))
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if register_info.little_endian:
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bytes.reverse()
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result = 0
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for byte in bytes:
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result = (result << 8) + byte
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return result
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def read_memory(self, start_addr, end_addr):
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"""
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Read a region of memory from the target.
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Some of the addresses may extend into invalid virtual memory;
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skip those areas.
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Return a list of blocks containing the valid area(s) in the
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requested range.
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"""
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regions = []
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start_addr = start_addr & (BLOCK_SIZE - 1)
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end_addr = (end_addr + BLOCK_SIZE - 1) & (BLOCK_SIZE - 1)
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for addr in range(start_addr, end_addr, BLOCK_SIZE):
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reply = self.pass_through(f"m{addr:x},{(BLOCK_SIZE - 1):x}")
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if reply and reply[0] != 'E':
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block = MemoryBlockSnapshot(addr, reply[1:])
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regions.append(block)
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return regions
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def ensure_register_info(self):
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if self.general_purpose_register_info is not None:
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return
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reply = self.pass_through("qHostInfo")
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little_endian = any(kv == ("endian", "little") for kv in self.parse_pairs(reply))
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self.general_purpose_register_info = {}
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lldb_index = 0
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while True:
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reply = self.pass_through(f"qRegisterInfo{lldb_index:x}")
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if not reply or reply[0] == 'E':
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break
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info = {k:v for k, v in self.parse_pairs(reply)}
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reg_info = RegisterInfo(lldb_index, int(info["bitsize"]), little_endian)
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if info["set"] == "General Purpose Registers" and not "container-regs" in info:
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self.general_purpose_register_info[lldb_index] = reg_info
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if "generic" in info:
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if info["generic"] == "pc":
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self.pc_register_info = reg_info
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elif info["generic"] == "sp":
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self.sp_register_info = reg_info
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lldb_index += 1
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if self.pc_register_info is None or self.sp_register_info is None:
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raise ValueError("Can't find generic pc or sp register")
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def get_thread_list(self):
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threads = []
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reply = self.pass_through("qfThreadInfo")
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while True:
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if not reply:
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raise ValueError("Missing reply packet")
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if reply[0] == 'm':
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for id in reply[1:].split(","):
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threads.append(self.parse_thread_id(id))
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elif reply[0] == 'l':
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return threads
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reply = self.pass_through("qsThreadInfo")
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