b666ac3b63
lldb today has two rules: When a thread stops at a BreakpointSite, we set the thread's StopReason to be "breakpoint hit" (regardless if we've actually hit the breakpoint, or if we've merely stopped *at* the breakpoint instruction/point and haven't tripped it yet). And second, when resuming a process, any thread sitting at a BreakpointSite is silently stepped over the BreakpointSite -- because we've already flagged the breakpoint hit when we stopped there originally. In this patch, I change lldb to only set a thread's stop reason to breakpoint-hit when we've actually executed the instruction/triggered the breakpoint. When we resume, we only silently step past a BreakpointSite that we've registered as hit. We preserve this state across inferior function calls that the user may do while stopped, etc. Also, when a user adds a new breakpoint at $pc while stopped, or changes $pc to be the address of a BreakpointSite, we will silently step past that breakpoint when the process resumes. This is purely a UX call, I don't think there's any person who wants to set a breakpoint at $pc and then hit it immediately on resuming. One non-intuitive UX from this change, butt is necessary: If you're stopped at a BreakpointSite that has not yet executed, you `stepi`, you will hit the breakpoint and the pc will not yet advance. This thread has not completed its stepi, and the ThreadPlanStepInstruction is still on the stack. If you then `continue` the thread, lldb will now stop and say, "instruction step completed", one instruction past the BreakpointSite. You can continue a second time to resume execution. The bugs driving this change are all from lldb dropping the real stop reason for a thread and setting it to breakpoint-hit when that was not the case. Jim hit one where we have an aarch64 watchpoint that triggers one instruction before a BreakpointSite. On this arch we are notified of the watchpoint hit after the instruction has been unrolled -- we disable the watchpoint, instruction step, re-enable the watchpoint and collect the new value. But now we're on a BreakpointSite so the watchpoint-hit stop reason is lost. Another was reported by ZequanWu in https://discourse.llvm.org/t/lldb-unable-to-break-at-start/78282 we attach to/launch a process with the pc at a BreakpointSite and misbehave. Caroline Tice mentioned it is also a problem they've had with putting a breakpoint on _dl_debug_state. The change to each Process plugin that does execution control is that 1. If we've stopped at a BreakpointSite that has not been executed yet, we will call Thread::SetThreadStoppedAtUnexecutedBP(pc) to record that. When the thread resumes, if the pc is still at the same site, we will continue, hit the breakpoint, and stop again. 2. When we've actually hit a breakpoint (enabled for this thread or not), the Process plugin should call Thread::SetThreadHitBreakpointSite(). When we go to resume the thread, we will push a step-over-breakpoint ThreadPlan before resuming. The biggest set of changes is to StopInfoMachException where we translate a Mach Exception into a stop reason. The Mach exception codes differ in a few places depending on the target (unambiguously), and I didn't want to duplicate the new code for each target so I've tested what mach exceptions we get for each action on each target, and reorganized StopInfoMachException::CreateStopReasonWithMachException to document these possible values, and handle them without specializing based on the target arch. I first landed this patch in July 2024 via https://github.com/llvm/llvm-project/pull/96260 but the CI bots and wider testing found a number of test case failures that needed to be updated, I reverted it. I've fixed all of those issues in separate PRs and this change should run cleanly on all the CI bots now. rdar://123942164
122 lines
4.0 KiB
Python
122 lines
4.0 KiB
Python
"""
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Test that we handle breakpoints on consecutive instructions correctly.
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"""
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import lldb
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from lldbsuite.test.decorators import *
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from lldbsuite.test.lldbtest import *
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from lldbsuite.test import lldbutil
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class ConsecutiveBreakpointsTestCase(TestBase):
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def prepare_test(self):
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self.build()
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(
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self.target,
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self.process,
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self.thread,
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bkpt,
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) = lldbutil.run_to_source_breakpoint(
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self, "Set breakpoint here", lldb.SBFileSpec("main.cpp")
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)
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# Set breakpoint to the next instruction
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frame = self.thread.GetFrameAtIndex(0)
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address = frame.GetPCAddress()
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instructions = self.target.ReadInstructions(address, 2)
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self.assertEqual(len(instructions), 2)
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self.bkpt_address = instructions[1].GetAddress()
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self.breakpoint2 = self.target.BreakpointCreateByAddress(
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self.bkpt_address.GetLoadAddress(self.target)
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)
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self.assertTrue(
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self.breakpoint2 and self.breakpoint2.GetNumLocations() == 1,
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VALID_BREAKPOINT,
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)
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def finish_test(self):
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# Run the process until termination
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self.process.Continue()
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self.assertState(self.process.GetState(), lldb.eStateExited)
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@no_debug_info_test
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def test_continue(self):
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"""Test that continue stops at the second breakpoint."""
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self.prepare_test()
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self.process.Continue()
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self.assertState(self.process.GetState(), lldb.eStateStopped)
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# We should be stopped at the second breakpoint
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self.thread = lldbutil.get_one_thread_stopped_at_breakpoint(
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self.process, self.breakpoint2
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)
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self.assertIsNotNone(
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self.thread, "Expected one thread to be stopped at breakpoint 2"
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)
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self.finish_test()
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@no_debug_info_test
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def test_single_step(self):
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"""Test that single step stops at the second breakpoint."""
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self.prepare_test()
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# Instruction step to the next instruction
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# We haven't executed breakpoint2 yet, we're sitting at it now.
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step_over = False
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self.thread.StepInstruction(step_over)
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step_over = False
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self.thread.StepInstruction(step_over)
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# We've now hit the breakpoint and this StepInstruction has
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# been interrupted, it is still sitting on the thread plan stack.
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self.assertState(self.process.GetState(), lldb.eStateStopped)
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self.assertEqual(
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self.thread.GetFrameAtIndex(0).GetPCAddress().GetLoadAddress(self.target),
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self.bkpt_address.GetLoadAddress(self.target),
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)
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# One more instruction to complete the Step that was interrupted
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# earlier.
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self.thread.StepInstruction(step_over)
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strm = lldb.SBStream()
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self.thread.GetDescription(strm)
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self.assertIn("instruction step into", strm.GetData())
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self.assertIsNotNone(self.thread, "Expected to see that step-in had completed")
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self.finish_test()
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@no_debug_info_test
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def test_single_step_thread_specific(self):
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"""Test that single step stops, even though the second breakpoint is not valid."""
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self.prepare_test()
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# Choose a thread other than the current one. A non-existing thread is
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# fine.
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thread_index = self.process.GetNumThreads() + 1
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self.assertFalse(self.process.GetThreadAtIndex(thread_index).IsValid())
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self.breakpoint2.SetThreadIndex(thread_index)
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step_over = False
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self.thread.StepInstruction(step_over)
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self.assertState(self.process.GetState(), lldb.eStateStopped)
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self.assertEqual(
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self.thread.GetFrameAtIndex(0).GetPCAddress().GetLoadAddress(self.target),
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self.bkpt_address.GetLoadAddress(self.target),
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)
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self.assertEqual(
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self.thread.GetStopReason(),
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lldb.eStopReasonPlanComplete,
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"Stop reason should be 'plan complete'",
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)
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# Hit our second breakpoint
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self.process.Continue()
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self.finish_test()
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