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LibDebug: Implement ability to set watchpoints
Now we can set hardware watchpoints for our variables! :^) These watchpoints will be automatically removed when they go out of scope.
This commit is contained in:
parent
3123ffb19d
commit
7a1396f509
Notes:
sideshowbarker
2024-07-18 19:26:44 +09:00
Author: https://github.com/FalseHonesty Commit: https://github.com/SerenityOS/serenity/commit/7a1396f5098 Pull-request: https://github.com/SerenityOS/serenity/pull/6353 Reviewed-by: https://github.com/bgianfo ✅
@ -42,6 +42,9 @@ __BEGIN_DECLS
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#define PT_POKEDEBUG 10
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#define PT_PEEKDEBUG 11
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#define DEBUG_STATUS_REGISTER 6
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#define DEBUG_CONTROL_REGISTER 7
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// FIXME: PID/TID ISSUE
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// Affects the entirety of LibDebug and Userland/strace.cpp.
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// See also Kernel/Ptrace.cpp
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@ -32,6 +32,7 @@
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#include <LibCore/File.h>
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#include <LibRegex/Regex.h>
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#include <stdlib.h>
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#include <sys/mman.h>
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namespace Debug {
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@ -52,6 +53,11 @@ DebugSession::~DebugSession()
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}
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m_breakpoints.clear();
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for (const auto& wp : m_watchpoints) {
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disable_watchpoint(wp.key);
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}
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m_watchpoints.clear();
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if (ptrace(PT_DETACH, m_debuggee_pid, 0, 0) < 0) {
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perror("PT_DETACH");
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}
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@ -141,6 +147,24 @@ Optional<u32> DebugSession::peek(u32* address) const
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return result;
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}
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bool DebugSession::poke_debug(u32 register_index, u32 data)
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{
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if (ptrace(PT_POKEDEBUG, m_debuggee_pid, reinterpret_cast<u32*>(register_index), data) < 0) {
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perror("PT_POKEDEBUG");
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return false;
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}
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return true;
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}
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Optional<u32> DebugSession::peek_debug(u32 register_index) const
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{
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Optional<u32> result;
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int rc = ptrace(PT_PEEKDEBUG, m_debuggee_pid, reinterpret_cast<u32*>(register_index), 0);
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if (errno == 0)
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result = static_cast<u32>(rc);
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return result;
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}
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bool DebugSession::insert_breakpoint(void* address)
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{
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// We insert a software breakpoint by
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@ -209,6 +233,68 @@ bool DebugSession::breakpoint_exists(void* address) const
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return m_breakpoints.contains(address);
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}
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bool DebugSession::insert_watchpoint(void* address, u32 ebp)
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{
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auto current_register_status = peek_debug(DEBUG_CONTROL_REGISTER);
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if (!current_register_status.has_value())
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return false;
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u32 dr7_value = current_register_status.value();
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u32 next_available_index;
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for (next_available_index = 0; next_available_index < 4; next_available_index++) {
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auto bitmask = 1 << (next_available_index * 2);
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if ((dr7_value & bitmask) == 0)
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break;
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}
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if (next_available_index > 3)
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return false;
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WatchPoint watchpoint { address, next_available_index, ebp };
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if (!poke_debug(next_available_index, reinterpret_cast<uintptr_t>(address)))
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return false;
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dr7_value |= (1u << (next_available_index * 2)); // Enable local breakpoint for our index
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auto condition_shift = 16 + (next_available_index * 4);
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dr7_value &= ~(0b11u << condition_shift);
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dr7_value |= 1u << condition_shift; // Trigger on writes
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auto length_shift = 18 + (next_available_index * 4);
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dr7_value &= ~(0b11u << length_shift);
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// FIXME: take variable size into account?
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dr7_value |= 0b11u << length_shift; // 4 bytes wide
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if (!poke_debug(DEBUG_CONTROL_REGISTER, dr7_value))
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return false;
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m_watchpoints.set(address, watchpoint);
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return true;
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}
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bool DebugSession::remove_watchpoint(void* address)
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{
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if (!disable_watchpoint(address))
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return false;
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return m_watchpoints.remove(address);
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}
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bool DebugSession::disable_watchpoint(void* address)
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{
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VERIFY(watchpoint_exists(address));
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auto watchpoint = m_watchpoints.get(address).value();
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if (!poke_debug(watchpoint.debug_register_index, 0))
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return false;
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auto current_register_status = peek_debug(DEBUG_CONTROL_REGISTER);
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if (!current_register_status.has_value())
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return false;
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u32 dr7_value = current_register_status.value();
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dr7_value &= ~(1u << watchpoint.debug_register_index * 2);
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if (!poke_debug(watchpoint.debug_register_index, dr7_value))
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return false;
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return true;
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}
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bool DebugSession::watchpoint_exists(void* address) const
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{
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return m_watchpoints.contains(address);
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}
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PtraceRegisters DebugSession::get_registers() const
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{
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PtraceRegisters regs;
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@ -278,6 +364,8 @@ void DebugSession::detach()
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for (auto& breakpoint : m_breakpoints.keys()) {
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remove_breakpoint(breakpoint);
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}
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for (auto& watchpoint : m_watchpoints.keys())
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remove_watchpoint(watchpoint);
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continue_debuggee();
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}
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@ -54,6 +54,9 @@ public:
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bool poke(u32* address, u32 data);
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Optional<u32> peek(u32* address) const;
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bool poke_debug(u32 register_index, u32 data);
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Optional<u32> peek_debug(u32 register_index) const;
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enum class BreakPointState {
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Enabled,
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Disabled,
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@ -87,6 +90,17 @@ public:
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bool remove_breakpoint(void* address);
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bool breakpoint_exists(void* address) const;
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struct WatchPoint {
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void* address { nullptr };
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u32 debug_register_index { 0 };
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u32 ebp { 0 };
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};
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bool insert_watchpoint(void* address, u32 ebp);
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bool remove_watchpoint(void* address);
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bool disable_watchpoint(void* address);
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bool watchpoint_exists(void* address) const;
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void dump_breakpoints()
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{
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for (auto addr : m_breakpoints.keys()) {
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@ -182,6 +196,7 @@ private:
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bool m_is_debuggee_dead { false };
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HashMap<void*, BreakPoint> m_breakpoints;
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HashMap<void*, WatchPoint> m_watchpoints;
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// Maps from base address to loaded library
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HashMap<String, NonnullOwnPtr<LoadedLibrary>> m_loaded_libraries;
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@ -223,6 +238,45 @@ void DebugSession::run(DesiredInitialDebugeeState initial_debugee_state, Callbac
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state = State::FreeRun;
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auto regs = get_registers();
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auto debug_status = peek_debug(DEBUG_STATUS_REGISTER);
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if (debug_status.has_value() && (debug_status.value() & 0b1111) > 0) {
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// Tripped a watchpoint
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auto watchpoint_index = debug_status.value() & 0b1111;
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Optional<WatchPoint> watchpoint {};
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for (auto wp : m_watchpoints) {
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if ((watchpoint_index & (1 << wp.value.debug_register_index)) == 0)
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continue;
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watchpoint = wp.value;
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break;
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}
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if (watchpoint.has_value()) {
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auto required_ebp = watchpoint.value().ebp;
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auto found_ebp = false;
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u32 current_ebp = regs.ebp;
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u32 current_instruction = regs.eip;
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do {
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if (current_ebp == required_ebp) {
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found_ebp = true;
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break;
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}
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auto return_address = peek(reinterpret_cast<u32*>(current_ebp + sizeof(FlatPtr)));
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auto next_ebp = peek(reinterpret_cast<u32*>(current_ebp));
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VERIFY(return_address.has_value());
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VERIFY(next_ebp.has_value());
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current_instruction = return_address.value();
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current_ebp = next_ebp.value();
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} while (current_ebp && current_instruction);
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if (!found_ebp) {
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dbgln("Removing watchpoint at {:p} because it went out of scope!", watchpoint.value().address);
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remove_watchpoint(watchpoint.value().address);
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continue;
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}
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}
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}
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Optional<BreakPoint> current_breakpoint;
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if (state == State::FreeRun || state == State::Syscall) {
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