UnwindLevel1.c   [plain text]


/* -*- mode: C++; c-basic-offset: 4; -*- 
 *
 * Copyright (c) 2008-2010 Apple Inc. All rights reserved.
 *
 * @APPLE_LICENSE_HEADER_START@
 * 
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this
 * file.
 * 
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 * 
 * @APPLE_LICENSE_HEADER_END@
 * 
 * 
 *  Implements C++ ABI Exception Handling Level 1 as documented at:
 *			<http://www.codesourcery.com/cxx-abi/abi-eh.html>
 *  using libunwind
 * 
 */

#include <stdint.h>
#include <stdbool.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>

#include "libunwind.h"
#include "unwind.h"
#include "InternalMacros.h"

#if __ppc__ || __i386__ ||  __x86_64__

static _Unwind_Reason_Code unwind_phase1(unw_context_t* uc, struct _Unwind_Exception* exception_object)
{
	unw_cursor_t cursor1; 
	unw_init_local(&cursor1, uc);
	
	// walk each frame looking for a place to stop
	for (bool handlerNotFound = true; handlerNotFound; ) {

		// ask libuwind to get next frame (skip over first which is _Unwind_RaiseException)
		int stepResult = unw_step(&cursor1);
		if ( stepResult == 0 ) {
			DEBUG_PRINT_UNWINDING("unwind_phase1(ex_ojb=%p): unw_step() reached bottom => _URC_END_OF_STACK\n", exception_object); 
			return _URC_END_OF_STACK;
		}
		else if ( stepResult < 0 ) {
			DEBUG_PRINT_UNWINDING("unwind_phase1(ex_ojb=%p): unw_step failed => _URC_FATAL_PHASE1_ERROR\n", exception_object); 
			return _URC_FATAL_PHASE1_ERROR;
		}
		
		// see if frame has code to run (has personality routine)
		unw_proc_info_t frameInfo;
		unw_word_t sp;
		if ( unw_get_proc_info(&cursor1, &frameInfo) != UNW_ESUCCESS ) {
			DEBUG_PRINT_UNWINDING("unwind_phase1(ex_ojb=%p): unw_get_proc_info failed => _URC_FATAL_PHASE1_ERROR\n", exception_object);
			return _URC_FATAL_PHASE1_ERROR;
		}
		
		// debugging
		if ( DEBUG_PRINT_UNWINDING_TEST ) {
			char functionName[512];
			unw_word_t	offset;
			if ( (unw_get_proc_name(&cursor1, functionName, 512, &offset) != UNW_ESUCCESS) || (frameInfo.start_ip+offset > frameInfo.end_ip) )
				strcpy(functionName, ".anonymous.");
			unw_word_t pc;
			unw_get_reg(&cursor1, UNW_REG_IP, &pc);
			DEBUG_PRINT_UNWINDING("unwind_phase1(ex_ojb=%p): pc=0x%llX, start_ip=0x%llX, func=%s, lsda=0x%llX, personality=0x%llX\n", 
							exception_object, pc, frameInfo.start_ip, functionName, frameInfo.lsda, frameInfo.handler);
		}
		
		// if there is a personality routine, ask it if it will want to stop at this frame
		if ( frameInfo.handler != 0 ) {
			__personality_routine p = (__personality_routine)(long)(frameInfo.handler);
			DEBUG_PRINT_UNWINDING("unwind_phase1(ex_ojb=%p): calling personality function %p\n", exception_object, p);
			_Unwind_Reason_Code personalityResult = (*p)(1, _UA_SEARCH_PHASE, 
						exception_object->exception_class, exception_object, 
						(struct _Unwind_Context*)(&cursor1));
			switch ( personalityResult ) {
				case _URC_HANDLER_FOUND:
					// found a catch clause or locals that need destructing in this frame
					// stop search and remember stack pointer at the frame
					handlerNotFound = false;
					unw_get_reg(&cursor1, UNW_REG_SP, &sp);
					exception_object->private_2 = sp;
					DEBUG_PRINT_UNWINDING("unwind_phase1(ex_ojb=%p): _URC_HANDLER_FOUND\n", exception_object);
					return _URC_NO_REASON;
					
				case _URC_CONTINUE_UNWIND:
					DEBUG_PRINT_UNWINDING("unwind_phase1(ex_ojb=%p): _URC_CONTINUE_UNWIND\n", exception_object);
					// continue unwinding
					break;
					
				default:
					// something went wrong
					DEBUG_PRINT_UNWINDING("unwind_phase1(ex_ojb=%p): _URC_FATAL_PHASE1_ERROR\n", exception_object);
					return _URC_FATAL_PHASE1_ERROR;
			}
		}
	}
	return _URC_NO_REASON;
}


static _Unwind_Reason_Code unwind_phase2(unw_context_t* uc, struct _Unwind_Exception* exception_object)
{
	unw_cursor_t cursor2; 
	unw_init_local(&cursor2, uc);
	
	DEBUG_PRINT_UNWINDING("unwind_phase2(ex_ojb=%p)\n", exception_object); 
	
	// walk each frame until we reach where search phase said to stop
	while ( true ) {

		// ask libuwind to get next frame (skip over first which is _Unwind_RaiseException)
		int stepResult = unw_step(&cursor2);
		if ( stepResult == 0 ) {
			DEBUG_PRINT_UNWINDING("unwind_phase2(ex_ojb=%p): unw_step() reached bottom => _URC_END_OF_STACK\n", exception_object); 
			return _URC_END_OF_STACK;
		}
		else if ( stepResult < 0 ) {
			DEBUG_PRINT_UNWINDING("unwind_phase2(ex_ojb=%p): unw_step failed => _URC_FATAL_PHASE1_ERROR\n", exception_object); 
			return _URC_FATAL_PHASE2_ERROR;
		}
		
		// get info about this frame
		unw_word_t sp;
		unw_proc_info_t frameInfo;
		unw_get_reg(&cursor2, UNW_REG_SP, &sp);
		if ( unw_get_proc_info(&cursor2, &frameInfo) != UNW_ESUCCESS ) {
			DEBUG_PRINT_UNWINDING("unwind_phase2(ex_ojb=%p): unw_get_proc_info failed => _URC_FATAL_PHASE1_ERROR\n", exception_object);
			return _URC_FATAL_PHASE2_ERROR;
		}
		
		// debugging
		if ( DEBUG_PRINT_UNWINDING_TEST ) {
			char functionName[512];
			unw_word_t	offset;
			if ( (unw_get_proc_name(&cursor2, functionName, 512, &offset) != UNW_ESUCCESS) || (frameInfo.start_ip+offset > frameInfo.end_ip) )
				strcpy(functionName, ".anonymous.");
			DEBUG_PRINT_UNWINDING("unwind_phase2(ex_ojb=%p): start_ip=0x%llX, func=%s, sp=0x%llX, lsda=0x%llX, personality=0x%llX\n", 
							exception_object, frameInfo.start_ip, functionName, sp, frameInfo.lsda, frameInfo.handler);
		}
		
		// if there is a personality routine, tell it we are unwinding
		if ( frameInfo.handler != 0 ) {
			__personality_routine p = (__personality_routine)(long)(frameInfo.handler);
			_Unwind_Action action = _UA_CLEANUP_PHASE;
			if ( sp == exception_object->private_2 )
				action = (_Unwind_Action)(_UA_CLEANUP_PHASE|_UA_HANDLER_FRAME); // tell personality this was the frame it marked in phase 1
			_Unwind_Reason_Code personalityResult = (*p)(1, action, 
						exception_object->exception_class, exception_object, 
						(struct _Unwind_Context*)(&cursor2));
			switch ( personalityResult ) {
				case _URC_CONTINUE_UNWIND:
					// continue unwinding
					DEBUG_PRINT_UNWINDING("unwind_phase2(ex_ojb=%p): _URC_CONTINUE_UNWIND\n", exception_object);
					if ( sp == exception_object->private_2 ) {
						// phase 1 said we would stop at this frame, but we did not...
						ABORT("during phase1 personality function said it would stop here, but now if phase2 it did not stop here");
					}
					break;
				case _URC_INSTALL_CONTEXT:
					DEBUG_PRINT_UNWINDING("unwind_phase2(ex_ojb=%p): _URC_INSTALL_CONTEXT\n", exception_object);
					// personality routine says to transfer control to landing pad
					// we may get control back if landing pad calls _Unwind_Resume()
					if ( DEBUG_PRINT_UNWINDING_TEST ) {
						unw_word_t pc;
						unw_word_t sp;
						unw_get_reg(&cursor2, UNW_REG_IP, &pc);
						unw_get_reg(&cursor2, UNW_REG_SP, &sp);
						DEBUG_PRINT_UNWINDING("unwind_phase2(ex_ojb=%p): re-entering user code with ip=0x%llX, sp=0x%llX\n", exception_object, pc, sp);
					}
					unw_resume(&cursor2);
					// unw_resume() only returns if there was an error
					return _URC_FATAL_PHASE2_ERROR;
				default:
					// something went wrong
					DEBUG_MESSAGE("personality function returned unknown result %d", personalityResult);
					return _URC_FATAL_PHASE2_ERROR;
			}
		}
	}

	// clean up phase did not resume at the frame that the search phase said it would
	return _URC_FATAL_PHASE2_ERROR;
}


static _Unwind_Reason_Code unwind_phase2_forced(unw_context_t* uc, struct _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 ) {
		
		// get info about this frame
		unw_proc_info_t frameInfo;
		if ( unw_get_proc_info(&cursor2, &frameInfo) != UNW_ESUCCESS ) {
			DEBUG_PRINT_UNWINDING("unwind_phase2_forced(ex_ojb=%p): unw_step failed => _URC_END_OF_STACK\n", exception_object); 
			return _URC_FATAL_PHASE1_ERROR;
		}
		
		// debugging
		if ( DEBUG_PRINT_UNWINDING_TEST ) {
			char functionName[512];
			unw_word_t	offset;
			if ( (unw_get_proc_name(&cursor2, functionName, 512, &offset) != UNW_ESUCCESS) || (frameInfo.start_ip+offset > frameInfo.end_ip) )
				strcpy(functionName, ".anonymous.");
			DEBUG_PRINT_UNWINDING("unwind_phase2_forced(ex_ojb=%p): start_ip=0x%llX, func=%s, lsda=0x%llX, personality=0x%llX\n", 
							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);
		DEBUG_PRINT_UNWINDING("unwind_phase2_forced(ex_ojb=%p): stop function returned %d\n", exception_object, stopResult);
		if ( stopResult != _URC_NO_REASON ) {
			DEBUG_PRINT_UNWINDING("unwind_phase2_forced(ex_ojb=%p): stopped by stop function\n", 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)(long)(frameInfo.handler);
			DEBUG_PRINT_UNWINDING("unwind_phase2_forced(ex_ojb=%p): calling personality function %p\n", exception_object, p);
			_Unwind_Reason_Code personalityResult = (*p)(1, action, 
						exception_object->exception_class, exception_object, 
						(struct _Unwind_Context*)(&cursor2));
			switch ( personalityResult ) {
				case _URC_CONTINUE_UNWIND:
					DEBUG_PRINT_UNWINDING("unwind_phase2_forced(ex_ojb=%p): personality returned _URC_CONTINUE_UNWIND\n", exception_object);
					// destructors called, continue unwinding
					break;
				case _URC_INSTALL_CONTEXT:
					DEBUG_PRINT_UNWINDING("unwind_phase2_forced(ex_ojb=%p): personality returned _URC_INSTALL_CONTEXT\n", exception_object);
					// we may get control back if landing pad calls _Unwind_Resume()
					unw_resume(&cursor2);
					break;
				default:
					// something went wrong
					DEBUG_PRINT_UNWINDING("unwind_phase2_forced(ex_ojb=%p): personality returned %d, _URC_FATAL_PHASE2_ERROR\n", 
						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
	DEBUG_PRINT_UNWINDING("unwind_phase2_forced(ex_ojb=%p): calling stop function with _UA_END_OF_STACK\n", 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 __cxa_throw.  Only returns if there is a fatal error
//
EXPORT _Unwind_Reason_Code _Unwind_RaiseException(struct _Unwind_Exception* exception_object)
{
	DEBUG_PRINT_API("_Unwind_RaiseException(ex_obj=%p)\n", exception_object);
	unw_context_t uc;
	unw_getcontext(&uc);

	// mark that this is a non-forced unwind, so _Unwind_Resume() can do the right thing
	exception_object->private_1	= 0;
	exception_object->private_2	= 0;

	// phase 1: the search phase
	_Unwind_Reason_Code phase1 = unwind_phase1(&uc, exception_object);
	if ( phase1 != _URC_NO_REASON )
		return phase1;
	
	// phase 2: the clean up phase
	return unwind_phase2(&uc, exception_object);  
}


//
// When _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 _Unwind_Resume() to continue with the
// unwinding.  Note: the call to _Unwind_Resume() is from compiler
// geneated user code.  All other _Unwind_* routines are called 
// by the C++ runtime __cxa_* routines. 
//
// Re-throwing an exception is implemented by having the code call
// __cxa_rethrow() which in turn calls _Unwind_Resume_or_Rethrow()
//
EXPORT void _Unwind_Resume(struct _Unwind_Exception* exception_object)
{
	DEBUG_PRINT_API("_Unwind_Resume(ex_obj=%p)\n", exception_object);
	unw_context_t uc;
	unw_getcontext(&uc);
	
	if ( exception_object->private_1 != 0 ) 
		unwind_phase2_forced(&uc, exception_object, (_Unwind_Stop_Fn)exception_object->private_1, (void*)exception_object->private_2);  
	else
		unwind_phase2(&uc, exception_object);  
	
	// clients assume _Unwind_Resume() does not return, so all we can do is abort.
	ABORT("_Unwind_Resume() can't return");
}



//
// Not used by C++.  
// Unwinds stack, calling "stop" function at each frame
// Could be used to implement longjmp().
//
EXPORT _Unwind_Reason_Code _Unwind_ForcedUnwind(struct _Unwind_Exception* exception_object, _Unwind_Stop_Fn stop, void* stop_parameter)
{
	DEBUG_PRINT_API("_Unwind_ForcedUnwind(ex_obj=%p, stop=%p)\n", exception_object, 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_1	= (uintptr_t)stop;
	exception_object->private_2	= (uintptr_t)stop_parameter;
	
	// doit
	return unwind_phase2_forced(&uc, exception_object, stop, stop_parameter);  
}


//
// Called by personality handler during phase 2 to get LSDA for current frame
//
EXPORT uintptr_t _Unwind_GetLanguageSpecificData(struct _Unwind_Context* context)
{
	unw_cursor_t* cursor = (unw_cursor_t*)context;
	unw_proc_info_t frameInfo;
	uintptr_t result = 0;
	if ( unw_get_proc_info(cursor, &frameInfo) == UNW_ESUCCESS ) 
		result = frameInfo.lsda;
	DEBUG_PRINT_API("_Unwind_GetLanguageSpecificData(context=%p) => 0x%lX\n", context, result);
	if ( result != 0 ) {
		if ( *((uint8_t*)result) != 0xFF ) 
			DEBUG_MESSAGE("lsda at 0x%lX does not start with 0xFF\n", result);
	}
	return result;
}


//
// Called by personality handler during phase 2 to get register values
//
EXPORT uintptr_t _Unwind_GetGR(struct _Unwind_Context* context, int index)
{
	unw_cursor_t* cursor = (unw_cursor_t*)context;
	unw_word_t result;
	unw_get_reg(cursor, index, &result);
	DEBUG_PRINT_API("_Unwind_GetGR(context=%p, reg=%d) => 0x%llX\n", context, index, (uint64_t)result);
	return result;
}


//
// Called by personality handler during phase 2 to alter register values
//
EXPORT void _Unwind_SetGR(struct _Unwind_Context* context, int index, uintptr_t new_value)
{
	DEBUG_PRINT_API("_Unwind_SetGR(context=%p, reg=%d, value=0x%0llX)\n", context, index, (uint64_t)new_value);
	unw_cursor_t* cursor = (unw_cursor_t*)context;
	unw_set_reg(cursor, index, new_value);
}


//
// Called by personality handler during phase 2 to get instruction pointer
//
EXPORT uintptr_t _Unwind_GetIP(struct _Unwind_Context* context)
{
	unw_cursor_t* cursor = (unw_cursor_t*)context;
	unw_word_t result;
	unw_get_reg(cursor, UNW_REG_IP, &result);
	DEBUG_PRINT_API("_Unwind_GetIP(context=%p) => 0x%llX\n", context, (uint64_t)result);
	return result;
}


//
// Called by personality handler during phase 2 to alter instruction pointer
//
EXPORT void _Unwind_SetIP(struct _Unwind_Context* context, uintptr_t new_value)
{
	DEBUG_PRINT_API("_Unwind_SetIP(context=%p, value=0x%0llX)\n", context, (uint64_t)new_value);
	unw_cursor_t* cursor = (unw_cursor_t*)context;
	unw_set_reg(cursor, UNW_REG_IP, new_value);
}


//
// Called by personality handler during phase 2 to find the start of the function
//
EXPORT uintptr_t _Unwind_GetRegionStart(struct _Unwind_Context* context)
{
	unw_cursor_t* cursor = (unw_cursor_t*)context;
	unw_proc_info_t frameInfo;
	uintptr_t result = 0;
	if ( unw_get_proc_info(cursor, &frameInfo) == UNW_ESUCCESS ) 
		result = frameInfo.start_ip;
	DEBUG_PRINT_API("_Unwind_GetRegionStart(context=%p) => 0x%lX\n", context, result);
	return result;
}


//
// Called by personality handler during phase 2 if a foreign exception is caught 
//
EXPORT void _Unwind_DeleteException(struct _Unwind_Exception* exception_object)
{
	DEBUG_PRINT_API("_Unwind_DeleteException(ex_obj=%p)\n", exception_object);
	if ( exception_object->exception_cleanup != NULL )
		(*exception_object->exception_cleanup)(_URC_FOREIGN_EXCEPTION_CAUGHT, exception_object);
}




//
// symbols in libSystem.dylib in 10.6 and later, but are in libgcc_s.dylib in earlier versions
//
NOT_HERE_BEFORE_10_6(_Unwind_DeleteException)
NOT_HERE_BEFORE_10_6(_Unwind_Find_FDE)
NOT_HERE_BEFORE_10_6(_Unwind_ForcedUnwind)
NOT_HERE_BEFORE_10_6(_Unwind_GetGR)
NOT_HERE_BEFORE_10_6(_Unwind_GetIP)
NOT_HERE_BEFORE_10_6(_Unwind_GetLanguageSpecificData)
NOT_HERE_BEFORE_10_6(_Unwind_GetRegionStart)
NOT_HERE_BEFORE_10_6(_Unwind_RaiseException)
NOT_HERE_BEFORE_10_6(_Unwind_Resume)
NOT_HERE_BEFORE_10_6(_Unwind_SetGR)
NOT_HERE_BEFORE_10_6(_Unwind_SetIP)

#endif // __ppc__ || __i386__ ||  __x86_64__