GDBStub: Support watchpoints on linux (cemu-project#1030)

* GDBStub: Support watchpoints on linux
* GDBStub: Use `TCP_NODELAY`

src/Cafe/CMakeLists.txt

@@ -40,6 +40,7 @@ add_library(CemuCafe
   HW/Espresso/Debugger/DebugSymbolStorage.h
   HW/Espresso/Debugger/GDBStub.h
   HW/Espresso/Debugger/GDBStub.cpp
+  HW/Espresso/Debugger/GDBBreakpoints.cpp
   HW/Espresso/Debugger/GDBBreakpoints.h
   HW/Espresso/EspressoISA.h
   HW/Espresso/Interpreter/PPCInterpreterALU.hpp

src/Cafe/HW/Espresso/Debugger/GDBBreakpoints.cpp

@@ -0,0 +1,304 @@
+#include "GDBBreakpoints.h"
+#include "Debugger.h"
+#include "Cafe/HW/Espresso/Recompiler/PPCRecompiler.h"
+
+#if defined(ARCH_X86_64) && BOOST_OS_LINUX
+#include <sys/ptrace.h>
+#include <sys/wait.h>
+#include <sys/user.h>
+
+DRType _GetDR(pid_t tid, int drIndex)
+{
+	size_t drOffset = offsetof(struct user, u_debugreg) + drIndex * sizeof(user::u_debugreg[0]);
+
+	long v;
+	v = ptrace(PTRACE_PEEKUSER, tid, drOffset, nullptr);
+	if (v == -1)
+		perror("ptrace(PTRACE_PEEKUSER)");
+
+	return (DRType)v;
+}
+
+void _SetDR(pid_t tid, int drIndex, DRType newValue)
+{
+	size_t drOffset = offsetof(struct user, u_debugreg) + drIndex * sizeof(user::u_debugreg[0]);
+
+	long rc = ptrace(PTRACE_POKEUSER, tid, drOffset, newValue);
+	if (rc == -1)
+		perror("ptrace(PTRACE_POKEUSER)");
+}
+
+DRType _ReadDR6()
+{
+	pid_t tid = gettid();
+
+	// linux doesn't let us attach to the current thread / threads in the current thread group
+	// we have to create a child process which then modifies the debug registers and quits
+	pid_t child = fork();
+	if (child == -1)
+	{
+		perror("fork");
+		return 0;
+	}
+
+	if (child == 0)
+	{
+		if (ptrace(PTRACE_ATTACH, tid, nullptr, nullptr))
+		{
+			perror("attach");
+			_exit(0);
+		}
+
+		waitpid(tid, NULL, 0);
+
+		uint64_t dr6 = _GetDR(tid, 6);
+
+		if (ptrace(PTRACE_DETACH, tid, nullptr, nullptr))
+			perror("detach");
+
+		// since the status code only uses the lower 8 bits, we have to discard the rest of DR6
+		// this should be fine though, since the lower 4 bits of DR6 contain all the bp conditions
+		_exit(dr6 & 0xff);
+	}
+
+	// wait for child process
+	int wstatus;
+	waitpid(child, &wstatus, 0);
+
+	return (DRType)WEXITSTATUS(wstatus);
+}
+#endif
+
+GDBServer::ExecutionBreakpoint::ExecutionBreakpoint(MPTR address, BreakpointType type, bool visible, std::string reason)
+	: m_address(address), m_removedAfterInterrupt(false), m_reason(std::move(reason))
+{
+	if (type == BreakpointType::BP_SINGLE)
+	{
+		this->m_pauseThreads = true;
+		this->m_restoreAfterInterrupt = false;
+		this->m_deleteAfterAnyInterrupt = false;
+		this->m_pauseOnNextInterrupt = false;
+		this->m_visible = visible;
+	}
+	else if (type == BreakpointType::BP_PERSISTENT)
+	{
+		this->m_pauseThreads = true;
+		this->m_restoreAfterInterrupt = true;
+		this->m_deleteAfterAnyInterrupt = false;
+		this->m_pauseOnNextInterrupt = false;
+		this->m_visible = visible;
+	}
+	else if (type == BreakpointType::BP_RESTORE_POINT)
+	{
+		this->m_pauseThreads = false;
+		this->m_restoreAfterInterrupt = false;
+		this->m_deleteAfterAnyInterrupt = false;
+		this->m_pauseOnNextInterrupt = false;
+		this->m_visible = false;
+	}
+	else if (type == BreakpointType::BP_STEP_POINT)
+	{
+		this->m_pauseThreads = false;
+		this->m_restoreAfterInterrupt = false;
+		this->m_deleteAfterAnyInterrupt = true;
+		this->m_pauseOnNextInterrupt = true;
+		this->m_visible = false;
+	}
+
+	this->m_origOpCode = memory_readU32(address);
+	memory_writeU32(address, DEBUGGER_BP_T_GDBSTUB_TW);
+	PPCRecompiler_invalidateRange(address, address + 4);
+}
+
+GDBServer::ExecutionBreakpoint::~ExecutionBreakpoint()
+{
+	memory_writeU32(this->m_address, this->m_origOpCode);
+	PPCRecompiler_invalidateRange(this->m_address, this->m_address + 4);
+}
+
+uint32 GDBServer::ExecutionBreakpoint::GetVisibleOpCode() const
+{
+	if (this->m_visible)
+		return memory_readU32(this->m_address);
+	else
+		return this->m_origOpCode;
+}
+
+void GDBServer::ExecutionBreakpoint::RemoveTemporarily()
+{
+	memory_writeU32(this->m_address, this->m_origOpCode);
+	PPCRecompiler_invalidateRange(this->m_address, this->m_address + 4);
+	this->m_restoreAfterInterrupt = true;
+}
+
+void GDBServer::ExecutionBreakpoint::Restore()
+{
+	memory_writeU32(this->m_address, DEBUGGER_BP_T_GDBSTUB_TW);
+	PPCRecompiler_invalidateRange(this->m_address, this->m_address + 4);
+	this->m_restoreAfterInterrupt = false;
+}
+
+namespace coreinit
+{
+#if BOOST_OS_LINUX
+	std::vector<pid_t>& OSGetSchedulerThreadIds();
+#endif
+
+	std::vector<std::thread::native_handle_type>& OSGetSchedulerThreads();
+}
+
+GDBServer::AccessBreakpoint::AccessBreakpoint(MPTR address, AccessPointType type)
+	: m_address(address), m_type(type)
+{
+#if defined(ARCH_X86_64) && BOOST_OS_WINDOWS
+	for (auto& hThreadNH : coreinit::OSGetSchedulerThreads())
+	{
+		HANDLE hThread = (HANDLE)hThreadNH;
+		CONTEXT ctx{};
+		ctx.ContextFlags = CONTEXT_DEBUG_REGISTERS;
+		SuspendThread(hThread);
+		GetThreadContext(hThread, &ctx);
+
+		// use BP 2/3 for gdb stub since cemu's internal debugger uses BP 0/1 already
+		ctx.Dr2 = (DWORD64)memory_getPointerFromVirtualOffset(address);
+		ctx.Dr3 = (DWORD64)memory_getPointerFromVirtualOffset(address);
+		// breakpoint 2
+		SetBits(ctx.Dr7, 4, 1, 1);	// breakpoint #3 enabled: true
+		SetBits(ctx.Dr7, 24, 2, 1); // breakpoint #3 condition: 1 (write)
+		SetBits(ctx.Dr7, 26, 2, 3); // breakpoint #3 length: 3 (4 bytes)
+		// breakpoint 3
+		SetBits(ctx.Dr7, 6, 1, 1);	// breakpoint #4 enabled: true
+		SetBits(ctx.Dr7, 28, 2, 3); // breakpoint #4 condition: 3 (read & write)
+		SetBits(ctx.Dr7, 30, 2, 3); // breakpoint #4 length: 3 (4 bytes)
+
+		SetThreadContext(hThread, &ctx);
+		ResumeThread(hThread);
+	}
+#elif defined(ARCH_X86_64) && BOOST_OS_LINUX
+	// linux doesn't let us attach to threads which are in the same thread group as our current thread
+	// we have to create a child process which then modifies the debug registers and quits
+	pid_t child = fork();
+	if (child == -1)
+	{
+		perror("fork");
+		return;
+	}
+
+	if (child == 0)
+	{
+		for (pid_t tid : coreinit::OSGetSchedulerThreadIds())
+		{
+			long rc = ptrace(PTRACE_ATTACH, tid, nullptr, nullptr);
+			if (rc == -1)
+				perror("ptrace(PTRACE_ATTACH)");
+
+			waitpid(tid, nullptr, 0);
+
+			DRType dr7 = _GetDR(tid, 7);
+			// use BP 2/3 for gdb stub since cemu's internal debugger uses BP 0/1 already
+			DRType dr2 = (uint64)memory_getPointerFromVirtualOffset(address);
+			DRType dr3 = (uint64)memory_getPointerFromVirtualOffset(address);
+			// breakpoint 2
+			SetBits(dr7, 4, 1, 1);  // breakpoint #3 enabled: true
+			SetBits(dr7, 24, 2, 1); // breakpoint #3 condition: 1 (write)
+			SetBits(dr7, 26, 2, 3); // breakpoint #3 length: 3 (4 bytes)
+			// breakpoint 3
+			SetBits(dr7, 6, 1, 1);  // breakpoint #4 enabled: true
+			SetBits(dr7, 28, 2, 3); // breakpoint #4 condition: 3 (read & write)
+			SetBits(dr7, 30, 2, 3); // breakpoint #4 length: 3 (4 bytes)
+
+			_SetDR(tid, 2, dr2);
+			_SetDR(tid, 3, dr3);
+			_SetDR(tid, 7, dr7);
+
+			rc = ptrace(PTRACE_DETACH, tid, nullptr, nullptr);
+			if (rc == -1)
+				perror("ptrace(PTRACE_DETACH)");
+		}
+
+		// exit child process
+		_exit(0);
+	}
+
+	// wait for child process
+	waitpid(child, nullptr, 0);
+#else
+	cemuLog_log(LogType::Force, "Debugger read/write breakpoints are not supported on non-x86 CPUs yet.");
+#endif
+}
+
+GDBServer::AccessBreakpoint::~AccessBreakpoint()
+{
+#if defined(ARCH_X86_64) && BOOST_OS_WINDOWS
+	for (auto& hThreadNH : coreinit::OSGetSchedulerThreads())
+	{
+		HANDLE hThread = (HANDLE)hThreadNH;
+		CONTEXT ctx{};
+		ctx.ContextFlags = CONTEXT_DEBUG_REGISTERS;
+		SuspendThread(hThread);
+		GetThreadContext(hThread, &ctx);
+
+		// reset BP 2/3 to zero
+		ctx.Dr2 = (DWORD64)0;
+		ctx.Dr3 = (DWORD64)0;
+		// breakpoint 2
+		SetBits(ctx.Dr7, 4, 1, 0);
+		SetBits(ctx.Dr7, 24, 2, 0);
+		SetBits(ctx.Dr7, 26, 2, 0);
+		// breakpoint 3
+		SetBits(ctx.Dr7, 6, 1, 0);
+		SetBits(ctx.Dr7, 28, 2, 0);
+		SetBits(ctx.Dr7, 30, 2, 0);
+		SetThreadContext(hThread, &ctx);
+		ResumeThread(hThread);
+	}
+#elif defined(ARCH_X86_64) && BOOST_OS_LINUX
+	// linux doesn't let us attach to threads which are in the same thread group as our current thread
+	// we have to create a child process which then modifies the debug registers and quits
+	pid_t child = fork();
+	if (child == -1)
+	{
+		perror("fork");
+		return;
+	}
+
+	if (child == 0)
+	{
+		for (pid_t tid : coreinit::OSGetSchedulerThreadIds())
+		{
+			long rc = ptrace(PTRACE_ATTACH, tid, nullptr, nullptr);
+			if (rc == -1)
+				perror("ptrace(PTRACE_ATTACH)");
+
+			waitpid(tid, nullptr, 0);
+
+			DRType dr7 = _GetDR(tid, 7);
+			// reset BP 2/3 to zero
+			DRType dr2 = 0;
+			DRType dr3 = 0;
+			// breakpoint 2
+			SetBits(dr7, 4, 1, 0);
+			SetBits(dr7, 24, 2, 0);
+			SetBits(dr7, 26, 2, 0);
+			// breakpoint 3
+			SetBits(dr7, 6, 1, 0);
+			SetBits(dr7, 28, 2, 0);
+			SetBits(dr7, 30, 2, 0);
+
+			_SetDR(tid, 2, dr2);
+			_SetDR(tid, 3, dr3);
+			_SetDR(tid, 7, dr7);
+
+			rc = ptrace(PTRACE_DETACH, tid, nullptr, nullptr);
+			if (rc == -1)
+				perror("ptrace(PTRACE_DETACH)");
+		}
+
+		// exit child process
+		_exit(0);
+	}
+
+	// wait for child process
+	waitpid(child, nullptr, 0);
+#endif
+}