//===--------------------------- Unwind-seh.cpp ---------------------------===// // // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. // See https://llvm.org/LICENSE.txt for license information. // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception // //===----------------------------------------------------------------------===// // // Implements SEH-based Itanium C++ exceptions. // //===----------------------------------------------------------------------===// #include "config.h" #if defined(_LIBUNWIND_SUPPORT_SEH_UNWIND) #include #include #include #include #include #include #include #include #include "libunwind_ext.h" #include "UnwindCursor.hpp" using namespace libunwind; #define STATUS_USER_DEFINED (1u << 29) #define STATUS_GCC_MAGIC (('G' << 16) | ('C' << 8) | 'C') #define MAKE_CUSTOM_STATUS(s, c) \ ((NTSTATUS)(((s) << 30) | STATUS_USER_DEFINED | (c))) #define MAKE_GCC_EXCEPTION(c) \ MAKE_CUSTOM_STATUS(STATUS_SEVERITY_SUCCESS, STATUS_GCC_MAGIC | ((c) << 24)) /// SEH exception raised by libunwind when the program calls /// \c _Unwind_RaiseException. #define STATUS_GCC_THROW MAKE_GCC_EXCEPTION(0) // 0x20474343 /// SEH exception raised by libunwind to initiate phase 2 of exception /// handling. #define STATUS_GCC_UNWIND MAKE_GCC_EXCEPTION(1) // 0x21474343 static int __unw_init_seh(unw_cursor_t *cursor, CONTEXT *ctx); static DISPATCHER_CONTEXT *__unw_seh_get_disp_ctx(unw_cursor_t *cursor); static void __unw_seh_set_disp_ctx(unw_cursor_t *cursor, DISPATCHER_CONTEXT *disp); /// Common implementation of SEH-style handler functions used by Itanium- /// style frames. Depending on how and why it was called, it may do one of: /// a) Delegate to the given Itanium-style personality function; or /// b) Initiate a collided unwind to halt unwinding. _LIBUNWIND_EXPORT EXCEPTION_DISPOSITION _GCC_specific_handler(PEXCEPTION_RECORD ms_exc, PVOID frame, PCONTEXT ms_ctx, DISPATCHER_CONTEXT *disp, _Unwind_Personality_Fn pers) { unw_cursor_t cursor; _Unwind_Exception *exc; _Unwind_Action action; struct _Unwind_Context *ctx = nullptr; _Unwind_Reason_Code urc; uintptr_t retval, target; bool ours = false; _LIBUNWIND_TRACE_UNWINDING("_GCC_specific_handler(%#010lx(%lx), %p)", ms_exc->ExceptionCode, ms_exc->ExceptionFlags, (void *)frame); if (ms_exc->ExceptionCode == STATUS_GCC_UNWIND) { if (IS_TARGET_UNWIND(ms_exc->ExceptionFlags)) { // Set up the upper return value (the lower one and the target PC // were set in the call to RtlUnwindEx()) for the landing pad. #ifdef __x86_64__ disp->ContextRecord->Rdx = ms_exc->ExceptionInformation[3]; #elif defined(__arm__) disp->ContextRecord->R1 = ms_exc->ExceptionInformation[3]; #elif defined(__aarch64__) disp->ContextRecord->X1 = ms_exc->ExceptionInformation[3]; #endif } // This is the collided unwind to the landing pad. Nothing to do. return ExceptionContinueSearch; } if (ms_exc->ExceptionCode == STATUS_GCC_THROW) { // This is (probably) a libunwind-controlled exception/unwind. Recover the // parameters which we set below, and pass them to the personality function. ours = true; exc = (_Unwind_Exception *)ms_exc->ExceptionInformation[0]; if (!IS_UNWINDING(ms_exc->ExceptionFlags) && ms_exc->NumberParameters > 1) { ctx = (struct _Unwind_Context *)ms_exc->ExceptionInformation[1]; action = (_Unwind_Action)ms_exc->ExceptionInformation[2]; } } else { // Foreign exception. // We can't interact with them (we don't know the original target frame // that we should pass on to RtlUnwindEx in _Unwind_Resume), so just // pass without calling our destructors here. return ExceptionContinueSearch; } if (!ctx) { __unw_init_seh(&cursor, disp->ContextRecord); __unw_seh_set_disp_ctx(&cursor, disp); __unw_set_reg(&cursor, UNW_REG_IP, disp->ControlPc - 1); ctx = (struct _Unwind_Context *)&cursor; if (!IS_UNWINDING(ms_exc->ExceptionFlags)) { if (ours && ms_exc->NumberParameters > 1) action = (_Unwind_Action)(_UA_CLEANUP_PHASE | _UA_FORCE_UNWIND); else action = _UA_SEARCH_PHASE; } else { if (ours && ms_exc->ExceptionInformation[1] == (ULONG_PTR)frame) action = (_Unwind_Action)(_UA_CLEANUP_PHASE | _UA_HANDLER_FRAME); else action = _UA_CLEANUP_PHASE; } } _LIBUNWIND_TRACE_UNWINDING("_GCC_specific_handler() calling personality " "function %p(1, %d, %llx, %p, %p)", (void *)pers, action, exc->exception_class, (void *)exc, (void *)ctx); urc = pers(1, action, exc->exception_class, exc, ctx); _LIBUNWIND_TRACE_UNWINDING("_GCC_specific_handler() personality returned %d", urc); switch (urc) { case _URC_CONTINUE_UNWIND: // If we're in phase 2, and the personality routine said to continue // at the target frame, we're in real trouble. if (action & _UA_HANDLER_FRAME) _LIBUNWIND_ABORT("Personality continued unwind at the target frame!"); return ExceptionContinueSearch; case _URC_HANDLER_FOUND: // If we were called by __libunwind_seh_personality(), indicate that // a handler was found; otherwise, initiate phase 2 by unwinding. if (ours && ms_exc->NumberParameters > 1) return 4 /* ExecptionExecuteHandler in mingw */; // This should never happen in phase 2. if (IS_UNWINDING(ms_exc->ExceptionFlags)) _LIBUNWIND_ABORT("Personality indicated exception handler in phase 2!"); exc->private_[1] = (ULONG_PTR)frame; if (ours) { ms_exc->NumberParameters = 4; ms_exc->ExceptionInformation[1] = (ULONG_PTR)frame; } // FIXME: Indicate target frame in foreign case! // phase 2: the clean up phase RtlUnwindEx(frame, (PVOID)disp->ControlPc, ms_exc, exc, ms_ctx, disp->HistoryTable); _LIBUNWIND_ABORT("RtlUnwindEx() failed"); case _URC_INSTALL_CONTEXT: { // If we were called by __libunwind_seh_personality(), indicate that // a handler was found; otherwise, it's time to initiate a collided // unwind to the target. if (ours && !IS_UNWINDING(ms_exc->ExceptionFlags) && ms_exc->NumberParameters > 1) return 4 /* ExecptionExecuteHandler in mingw */; // This should never happen in phase 1. if (!IS_UNWINDING(ms_exc->ExceptionFlags)) _LIBUNWIND_ABORT("Personality installed context during phase 1!"); #ifdef __x86_64__ exc->private_[2] = disp->TargetIp; __unw_get_reg(&cursor, UNW_X86_64_RAX, &retval); __unw_get_reg(&cursor, UNW_X86_64_RDX, &exc->private_[3]); #elif defined(__arm__) exc->private_[2] = disp->TargetPc; __unw_get_reg(&cursor, UNW_ARM_R0, &retval); __unw_get_reg(&cursor, UNW_ARM_R1, &exc->private_[3]); #elif defined(__aarch64__) exc->private_[2] = disp->TargetPc; __unw_get_reg(&cursor, UNW_ARM64_X0, &retval); __unw_get_reg(&cursor, UNW_ARM64_X1, &exc->private_[3]); #endif __unw_get_reg(&cursor, UNW_REG_IP, &target); ms_exc->ExceptionCode = STATUS_GCC_UNWIND; #ifdef __x86_64__ ms_exc->ExceptionInformation[2] = disp->TargetIp; #elif defined(__arm__) || defined(__aarch64__) ms_exc->ExceptionInformation[2] = disp->TargetPc; #endif ms_exc->ExceptionInformation[3] = exc->private_[3]; // Give NTRTL some scratch space to keep track of the collided unwind. // Don't use the one that was passed in; we don't want to overwrite the // context in the DISPATCHER_CONTEXT. CONTEXT new_ctx; RtlUnwindEx(frame, (PVOID)target, ms_exc, (PVOID)retval, &new_ctx, disp->HistoryTable); _LIBUNWIND_ABORT("RtlUnwindEx() failed"); } // Anything else indicates a serious problem. default: return ExceptionContinueExecution; } } /// Personality function returned by \c __unw_get_proc_info() in SEH contexts. /// This is a wrapper that calls the real SEH handler function, which in /// turn (at least, for Itanium-style frames) calls the real Itanium /// personality function (see \c _GCC_specific_handler()). extern "C" _Unwind_Reason_Code __libunwind_seh_personality(int version, _Unwind_Action state, uint64_t klass, _Unwind_Exception *exc, struct _Unwind_Context *context) { (void)version; (void)klass; EXCEPTION_RECORD ms_exc; bool phase2 = (state & (_UA_SEARCH_PHASE|_UA_CLEANUP_PHASE)) == _UA_CLEANUP_PHASE; ms_exc.ExceptionCode = STATUS_GCC_THROW; ms_exc.ExceptionFlags = 0; ms_exc.NumberParameters = 3; ms_exc.ExceptionInformation[0] = (ULONG_PTR)exc; ms_exc.ExceptionInformation[1] = (ULONG_PTR)context; ms_exc.ExceptionInformation[2] = state; DISPATCHER_CONTEXT *disp_ctx = __unw_seh_get_disp_ctx((unw_cursor_t *)context); EXCEPTION_DISPOSITION ms_act = disp_ctx->LanguageHandler(&ms_exc, (PVOID)disp_ctx->EstablisherFrame, disp_ctx->ContextRecord, disp_ctx); switch (ms_act) { case ExceptionContinueSearch: return _URC_CONTINUE_UNWIND; case 4 /*ExceptionExecuteHandler*/: return phase2 ? _URC_INSTALL_CONTEXT : _URC_HANDLER_FOUND; default: return phase2 ? _URC_FATAL_PHASE2_ERROR : _URC_FATAL_PHASE1_ERROR; } } static _Unwind_Reason_Code unwind_phase2_forced(unw_context_t *uc, _Unwind_Exception *exception_object, _Unwind_Stop_Fn stop, void *stop_parameter) { unw_cursor_t cursor2; __unw_init_local(&cursor2, uc); // Walk each frame until we reach where search phase said to stop while (__unw_step(&cursor2) > 0) { // Update info about this frame. unw_proc_info_t frameInfo; if (__unw_get_proc_info(&cursor2, &frameInfo) != UNW_ESUCCESS) { _LIBUNWIND_TRACE_UNWINDING("unwind_phase2_forced(ex_ojb=%p): __unw_step " "failed => _URC_END_OF_STACK", (void *)exception_object); return _URC_FATAL_PHASE2_ERROR; } // When tracing, print state information. if (_LIBUNWIND_TRACING_UNWINDING) { char functionBuf[512]; const char *functionName = functionBuf; unw_word_t offset; if ((__unw_get_proc_name(&cursor2, functionBuf, sizeof(functionBuf), &offset) != UNW_ESUCCESS) || (frameInfo.start_ip + offset > frameInfo.end_ip)) functionName = ".anonymous."; _LIBUNWIND_TRACE_UNWINDING( "unwind_phase2_forced(ex_ojb=%p): start_ip=0x%" PRIx64 ", func=%s, lsda=0x%" PRIx64 ", personality=0x%" PRIx64, (void *)exception_object, frameInfo.start_ip, functionName, frameInfo.lsda, frameInfo.handler); } // Call stop function at each frame. _Unwind_Action action = (_Unwind_Action)(_UA_FORCE_UNWIND | _UA_CLEANUP_PHASE); _Unwind_Reason_Code stopResult = (*stop)(1, action, exception_object->exception_class, exception_object, (struct _Unwind_Context *)(&cursor2), stop_parameter); _LIBUNWIND_TRACE_UNWINDING( "unwind_phase2_forced(ex_ojb=%p): stop function returned %d", (void *)exception_object, stopResult); if (stopResult != _URC_NO_REASON) { _LIBUNWIND_TRACE_UNWINDING( "unwind_phase2_forced(ex_ojb=%p): stopped by stop function", (void *)exception_object); return _URC_FATAL_PHASE2_ERROR; } // If there is a personality routine, tell it we are unwinding. if (frameInfo.handler != 0) { _Unwind_Personality_Fn p = (_Unwind_Personality_Fn)(intptr_t)(frameInfo.handler); _LIBUNWIND_TRACE_UNWINDING( "unwind_phase2_forced(ex_ojb=%p): calling personality function %p", (void *)exception_object, (void *)(uintptr_t)p); _Unwind_Reason_Code personalityResult = (*p)(1, action, exception_object->exception_class, exception_object, (struct _Unwind_Context *)(&cursor2)); switch (personalityResult) { case _URC_CONTINUE_UNWIND: _LIBUNWIND_TRACE_UNWINDING("unwind_phase2_forced(ex_ojb=%p): " "personality returned " "_URC_CONTINUE_UNWIND", (void *)exception_object); // Destructors called, continue unwinding break; case _URC_INSTALL_CONTEXT: _LIBUNWIND_TRACE_UNWINDING("unwind_phase2_forced(ex_ojb=%p): " "personality returned " "_URC_INSTALL_CONTEXT", (void *)exception_object); // We may get control back if landing pad calls _Unwind_Resume(). __unw_resume(&cursor2); break; default: // Personality routine returned an unknown result code. _LIBUNWIND_TRACE_UNWINDING("unwind_phase2_forced(ex_ojb=%p): " "personality returned %d, " "_URC_FATAL_PHASE2_ERROR", (void *)exception_object, personalityResult); return _URC_FATAL_PHASE2_ERROR; } } } // Call stop function one last time and tell it we've reached the end // of the stack. _LIBUNWIND_TRACE_UNWINDING("unwind_phase2_forced(ex_ojb=%p): calling stop " "function with _UA_END_OF_STACK", (void *)exception_object); _Unwind_Action lastAction = (_Unwind_Action)(_UA_FORCE_UNWIND | _UA_CLEANUP_PHASE | _UA_END_OF_STACK); (*stop)(1, lastAction, exception_object->exception_class, exception_object, (struct _Unwind_Context *)(&cursor2), stop_parameter); // Clean up phase did not resume at the frame that the search phase said it // would. return _URC_FATAL_PHASE2_ERROR; } /// Called by \c __cxa_throw(). Only returns if there is a fatal error. _LIBUNWIND_EXPORT _Unwind_Reason_Code _Unwind_RaiseException(_Unwind_Exception *exception_object) { _LIBUNWIND_TRACE_API("_Unwind_RaiseException(ex_obj=%p)", (void *)exception_object); // Mark that this is a non-forced unwind, so _Unwind_Resume() // can do the right thing. memset(exception_object->private_, 0, sizeof(exception_object->private_)); // phase 1: the search phase // We'll let the system do that for us. RaiseException(STATUS_GCC_THROW, 0, 1, (ULONG_PTR *)&exception_object); // If we get here, either something went horribly wrong or we reached the // top of the stack. Either way, let libc++abi call std::terminate(). return _URC_END_OF_STACK; } /// When \c _Unwind_RaiseException() is in phase2, it hands control /// to the personality function at each frame. The personality /// may force a jump to a landing pad in that function; the landing /// pad code may then call \c _Unwind_Resume() to continue with the /// unwinding. Note: the call to \c _Unwind_Resume() is from compiler /// geneated user code. All other \c _Unwind_* routines are called /// by the C++ runtime \c __cxa_* routines. /// /// Note: re-throwing an exception (as opposed to continuing the unwind) /// is implemented by having the code call \c __cxa_rethrow() which /// in turn calls \c _Unwind_Resume_or_Rethrow(). _LIBUNWIND_EXPORT void _Unwind_Resume(_Unwind_Exception *exception_object) { _LIBUNWIND_TRACE_API("_Unwind_Resume(ex_obj=%p)", (void *)exception_object); if (exception_object->private_[0] != 0) { unw_context_t uc; __unw_getcontext(&uc); unwind_phase2_forced(&uc, exception_object, (_Unwind_Stop_Fn) exception_object->private_[0], (void *)exception_object->private_[4]); } else { // Recover the parameters for the unwind from the exception object // so we can start unwinding again. EXCEPTION_RECORD ms_exc; CONTEXT ms_ctx; UNWIND_HISTORY_TABLE hist; memset(&ms_exc, 0, sizeof(ms_exc)); memset(&hist, 0, sizeof(hist)); ms_exc.ExceptionCode = STATUS_GCC_THROW; ms_exc.ExceptionFlags = EXCEPTION_NONCONTINUABLE; ms_exc.NumberParameters = 4; ms_exc.ExceptionInformation[0] = (ULONG_PTR)exception_object; ms_exc.ExceptionInformation[1] = exception_object->private_[1]; ms_exc.ExceptionInformation[2] = exception_object->private_[2]; ms_exc.ExceptionInformation[3] = exception_object->private_[3]; RtlUnwindEx((PVOID)exception_object->private_[1], (PVOID)exception_object->private_[2], &ms_exc, exception_object, &ms_ctx, &hist); } // Clients assume _Unwind_Resume() does not return, so all we can do is abort. _LIBUNWIND_ABORT("_Unwind_Resume() can't return"); } /// Not used by C++. /// Unwinds stack, calling "stop" function at each frame. /// Could be used to implement \c longjmp(). _LIBUNWIND_EXPORT _Unwind_Reason_Code _Unwind_ForcedUnwind(_Unwind_Exception *exception_object, _Unwind_Stop_Fn stop, void *stop_parameter) { _LIBUNWIND_TRACE_API("_Unwind_ForcedUnwind(ex_obj=%p, stop=%p)", (void *)exception_object, (void *)(uintptr_t)stop); unw_context_t uc; __unw_getcontext(&uc); // Mark that this is a forced unwind, so _Unwind_Resume() can do // the right thing. exception_object->private_[0] = (uintptr_t) stop; exception_object->private_[4] = (uintptr_t) stop_parameter; // do it return unwind_phase2_forced(&uc, exception_object, stop, stop_parameter); } /// Called by personality handler during phase 2 to get LSDA for current frame. _LIBUNWIND_EXPORT uintptr_t _Unwind_GetLanguageSpecificData(struct _Unwind_Context *context) { uintptr_t result = (uintptr_t)__unw_seh_get_disp_ctx((unw_cursor_t *)context)->HandlerData; _LIBUNWIND_TRACE_API( "_Unwind_GetLanguageSpecificData(context=%p) => 0x%" PRIxPTR, (void *)context, result); return result; } /// Called by personality handler during phase 2 to find the start of the /// function. _LIBUNWIND_EXPORT uintptr_t _Unwind_GetRegionStart(struct _Unwind_Context *context) { DISPATCHER_CONTEXT *disp = __unw_seh_get_disp_ctx((unw_cursor_t *)context); uintptr_t result = (uintptr_t)disp->FunctionEntry->BeginAddress + disp->ImageBase; _LIBUNWIND_TRACE_API("_Unwind_GetRegionStart(context=%p) => 0x%" PRIxPTR, (void *)context, result); return result; } static int __unw_init_seh(unw_cursor_t *cursor, CONTEXT *context) { #ifdef _LIBUNWIND_TARGET_X86_64 new (reinterpret_cast *>(cursor)) UnwindCursor( context, LocalAddressSpace::sThisAddressSpace); auto *co = reinterpret_cast(cursor); co->setInfoBasedOnIPRegister(); return UNW_ESUCCESS; #elif defined(_LIBUNWIND_TARGET_ARM) new (reinterpret_cast *>(cursor)) UnwindCursor( context, LocalAddressSpace::sThisAddressSpace); auto *co = reinterpret_cast(cursor); co->setInfoBasedOnIPRegister(); return UNW_ESUCCESS; #elif defined(_LIBUNWIND_TARGET_AARCH64) new (reinterpret_cast *>(cursor)) UnwindCursor( context, LocalAddressSpace::sThisAddressSpace); auto *co = reinterpret_cast(cursor); co->setInfoBasedOnIPRegister(); return UNW_ESUCCESS; #else return UNW_EINVAL; #endif } static DISPATCHER_CONTEXT *__unw_seh_get_disp_ctx(unw_cursor_t *cursor) { #ifdef _LIBUNWIND_TARGET_X86_64 return reinterpret_cast *>(cursor)->getDispatcherContext(); #elif defined(_LIBUNWIND_TARGET_ARM) return reinterpret_cast *>(cursor)->getDispatcherContext(); #elif defined(_LIBUNWIND_TARGET_AARCH64) return reinterpret_cast *>(cursor)->getDispatcherContext(); #else return nullptr; #endif } static void __unw_seh_set_disp_ctx(unw_cursor_t *cursor, DISPATCHER_CONTEXT *disp) { #ifdef _LIBUNWIND_TARGET_X86_64 reinterpret_cast *>(cursor)->setDispatcherContext(disp); #elif defined(_LIBUNWIND_TARGET_ARM) reinterpret_cast *>(cursor)->setDispatcherContext(disp); #elif defined(_LIBUNWIND_TARGET_AARCH64) reinterpret_cast *>(cursor)->setDispatcherContext(disp); #endif } #endif // defined(_LIBUNWIND_SUPPORT_SEH_UNWIND)