//===--------------------------- 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 <unwind.h>
#include <stdint.h>
#include <stdbool.h>
#include <stdlib.h>
#include <windef.h>
#include <excpt.h>
#include <winnt.h>
#include <ntstatus.h>
#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
/// Class of foreign exceptions based on unrecognized SEH exceptions.
static const uint64_t kSEHExceptionClass = 0x434C4E4753454800; // CLNGSEH\0
/// Exception cleanup routine used by \c _GCC_specific_handler to
/// free foreign exceptions.
static void seh_exc_cleanup(_Unwind_Reason_Code urc, _Unwind_Exception *exc) {
(void)urc;
if (exc->exception_class != kSEHExceptionClass)
_LIBUNWIND_ABORT("SEH cleanup called on non-SEH exception");
free(exc);
}
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, __personality_routine 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.
exc = (_Unwind_Exception *)malloc(sizeof(_Unwind_Exception));
exc->exception_class = kSEHExceptionClass;
exc->exception_cleanup = seh_exc_cleanup;
memset(exc->private_, 0, sizeof(exc->private_));
}
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) {
__personality_routine p =
(__personality_routine)(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<UnwindCursor<LocalAddressSpace, Registers_x86_64> *>(cursor))
UnwindCursor<LocalAddressSpace, Registers_x86_64>(
context, LocalAddressSpace::sThisAddressSpace);
auto *co = reinterpret_cast<AbstractUnwindCursor *>(cursor);
co->setInfoBasedOnIPRegister();
return UNW_ESUCCESS;
#elif defined(_LIBUNWIND_TARGET_ARM)
new (reinterpret_cast<UnwindCursor<LocalAddressSpace, Registers_arm> *>(cursor))
UnwindCursor<LocalAddressSpace, Registers_arm>(
context, LocalAddressSpace::sThisAddressSpace);
auto *co = reinterpret_cast<AbstractUnwindCursor *>(cursor);
co->setInfoBasedOnIPRegister();
return UNW_ESUCCESS;
#elif defined(_LIBUNWIND_TARGET_AARCH64)
new (reinterpret_cast<UnwindCursor<LocalAddressSpace, Registers_arm64> *>(cursor))
UnwindCursor<LocalAddressSpace, Registers_arm64>(
context, LocalAddressSpace::sThisAddressSpace);
auto *co = reinterpret_cast<AbstractUnwindCursor *>(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<UnwindCursor<LocalAddressSpace, Registers_x86_64> *>(cursor)->getDispatcherContext();
#elif defined(_LIBUNWIND_TARGET_ARM)
return reinterpret_cast<UnwindCursor<LocalAddressSpace, Registers_arm> *>(cursor)->getDispatcherContext();
#elif defined(_LIBUNWIND_TARGET_AARCH64)
return reinterpret_cast<UnwindCursor<LocalAddressSpace, Registers_arm64> *>(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<UnwindCursor<LocalAddressSpace, Registers_x86_64> *>(cursor)->setDispatcherContext(disp);
#elif defined(_LIBUNWIND_TARGET_ARM)
reinterpret_cast<UnwindCursor<LocalAddressSpace, Registers_arm> *>(cursor)->setDispatcherContext(disp);
#elif defined(_LIBUNWIND_TARGET_AARCH64)
reinterpret_cast<UnwindCursor<LocalAddressSpace, Registers_arm64> *>(cursor)->setDispatcherContext(disp);
#endif
}
#endif // defined(_LIBUNWIND_SUPPORT_SEH_UNWIND)