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Disable single stepping once we've stepped over the breakpoint (fix #223) #224

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merged 4 commits into from
Jan 23, 2025
Merged

Disable single stepping once we've stepped over the breakpoint (fix #223) #224

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29f99aa
make sure to properly disable single stepping once we've stepped over…
0vercl0k Jan 23, 2025
688c284
ln
0vercl0k Jan 23, 2025
d868243
ln
0vercl0k Jan 23, 2025
4fe4419
beter error msgs
0vercl0k Jan 23, 2025
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16 changes: 15 additions & 1 deletion src/wtf/fuzzer_hevd.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -61,10 +61,24 @@ bool InsertTestcase(const uint8_t *Buffer, const size_t BufferSize) {
bool Init(const Options_t &Opts, const CpuState_t &) {

//
// Stop the test-case once we return back from the call [DeviceIoControl]
// Set a breakpoint on the first instruction just for fun. Also, that type of
// breakpoint would have caught this bug:
// `https://github.com/0vercl0k/wtf/issues/223`
//

const Gva_t Rip = Gva_t(g_Backend->Rip());
if (!g_Backend->SetBreakpoint(Rip, [](Backend_t *Backend) {
DebugPrint(
"This is a breakpoint executed before the first instruction :)\n");
})) {
DebugPrint("Failed to SetBreakpoint on first instruction\n");
return false;
}

//
// Stop the test-case once we return back from the call [DeviceIoControl]
//

const Gva_t AfterCall = Rip + Gva_t(6);
if (!g_Backend->SetBreakpoint(AfterCall, [](Backend_t *Backend) {
DebugPrint("Back from kernel!\n");
Expand Down
19 changes: 8 additions & 11 deletions src/wtf/kvm_backend.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -1532,7 +1532,8 @@ bool KvmBackend_t::OnExitDebug(struct kvm_debug_exit_arch &Debug) {
// fault.
//

KvmDebugPrint("Disarming bp and turning on RFLAGS.TF (rip={:#x})\n", Rip);
KvmDebugPrint("Disarming bp and will turn on single step (rip={:#x})\n",
Rip);
LastBreakpointGpa_ = Breakpoint.Gpa;

Ram_.RemoveBreakpoint(Breakpoint.Gpa);
Expand All @@ -1558,7 +1559,7 @@ bool KvmBackend_t::OnExitDebug(struct kvm_debug_exit_arch &Debug) {
//

if (TraceType_ != TraceType_t::Rip && !LastBreakpointGpa_) {
fmt::print("Got into OnDebugTrap with LastBreakpointGpa_ = none");
fmt::print("Got into OnDebugTrap with LastBreakpointGpa_ = none\n");
return false;
}

Expand All @@ -1568,7 +1569,7 @@ bool KvmBackend_t::OnExitDebug(struct kvm_debug_exit_arch &Debug) {
//

if (LastBreakpointGpa_) {
KvmDebugPrint("Resetting breakpoint @ {:#x}", *LastBreakpointGpa_);
KvmDebugPrint("Resetting breakpoint @ {:#x}\n", *LastBreakpointGpa_);

//
// Remember if we get there, it is because we hit a breakpoint, turned on
Expand All @@ -1580,12 +1581,7 @@ bool KvmBackend_t::OnExitDebug(struct kvm_debug_exit_arch &Debug) {
LastBreakpointGpa_.reset();
}

if (TraceType_ == TraceType_t::Rip) {
TrapFlag(true);
} else {
KvmDebugPrint("Turning off RFLAGS.TF\n");
}

TrapFlag(TraceType_ == TraceType_t::Rip ? true : false);
return true;
} else {
std::abort();
Expand Down Expand Up @@ -2651,13 +2647,14 @@ void KvmBackend_t::StaticSignalAlarm(int, siginfo_t *, void *) {
}

void KvmBackend_t::TrapFlag(const bool Arm) {
KvmDebugPrint("Turning on RFLAGS.TF\n");

struct kvm_guest_debug Dreg = {0};
Dreg.control = KVM_GUESTDBG_USE_SW_BP | KVM_GUESTDBG_ENABLE;

if (Arm) {
KvmDebugPrint("Turning on SINGLESTEP\n");
Dreg.control |= KVM_GUESTDBG_SINGLESTEP;
} else {
KvmDebugPrint("Turning off SINGLESTEP\n");
}

if (!SetDreg(Dreg)) {
Expand Down
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