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llvm-project/libcxxabi/src/cxa_personality.cpp

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//===------------------------- cxa_exception.cpp --------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is dual licensed under the MIT and the University of Illinois Open
// Source Licenses. See LICENSE.TXT for details.
//
//
// This file implements the "Exception Handling APIs"
// http://mentorembedded.github.io/cxx-abi/abi-eh.html
// http://www.intel.com/design/itanium/downloads/245358.htm
//
//===----------------------------------------------------------------------===//
#include <assert.h>
#include <stdlib.h>
#include <string.h>
#include <typeinfo>
#include "config.h"
#include "cxa_exception.hpp"
#include "cxa_handlers.hpp"
#include "private_typeinfo.h"
#include "unwind.h"
/*
Exception Header Layout:
+---------------------------+-----------------------------+---------------+
| __cxa_exception | _Unwind_Exception CLNGC++\0 | thrown object |
+---------------------------+-----------------------------+---------------+
^
|
+-------------------------------------------------------+
|
+---------------------------+-----------------------------+
| __cxa_dependent_exception | _Unwind_Exception CLNGC++\1 |
+---------------------------+-----------------------------+
Exception Handling Table Layout:
+-----------------+--------+
| lpStartEncoding | (char) |
+---------+-------+--------+---------------+-----------------------+
| lpStart | (encoded with lpStartEncoding) | defaults to funcStart |
+---------+-----+--------+-----------------+---------------+-------+
| ttypeEncoding | (char) | Encoding of the type_info table |
+---------------+-+------+----+----------------------------+----------------+
| classInfoOffset | (ULEB128) | Offset to type_info table, defaults to null |
+-----------------++--------+-+----------------------------+----------------+
| callSiteEncoding | (char) | Encoding for Call Site Table |
+------------------+--+-----+-----+------------------------+--------------------------+
| callSiteTableLength | (ULEB128) | Call Site Table length, used to find Action table |
+---------------------+-----------+---------------------------------------------------+
#ifndef __USING_SJLJ_EXCEPTIONS__
+---------------------+-----------+------------------------------------------------+
| Beginning of Call Site Table The current ip lies within the |
| ... (start, length) range of one of these |
| call sites. There may be action needed. |
| +-------------+---------------------------------+------------------------------+ |
| | start | (encoded with callSiteEncoding) | offset relative to funcStart | |
| | length | (encoded with callSiteEncoding) | length of code fragment | |
| | landingPad | (encoded with callSiteEncoding) | offset relative to lpStart | |
| | actionEntry | (ULEB128) | Action Table Index 1-based | |
| | | | actionEntry == 0 -> cleanup | |
| +-------------+---------------------------------+------------------------------+ |
| ... |
+----------------------------------------------------------------------------------+
#else // __USING_SJLJ_EXCEPTIONS__
+---------------------+-----------+------------------------------------------------+
| Beginning of Call Site Table The current ip is a 1-based index into |
| ... this table. Or it is -1 meaning no |
| action is needed. Or it is 0 meaning |
| terminate. |
| +-------------+---------------------------------+------------------------------+ |
| | landingPad | (ULEB128) | offset relative to lpStart | |
| | actionEntry | (ULEB128) | Action Table Index 1-based | |
| | | | actionEntry == 0 -> cleanup | |
| +-------------+---------------------------------+------------------------------+ |
| ... |
+----------------------------------------------------------------------------------+
#endif // __USING_SJLJ_EXCEPTIONS__
+---------------------------------------------------------------------+
| Beginning of Action Table ttypeIndex == 0 : cleanup |
| ... ttypeIndex > 0 : catch |
| ttypeIndex < 0 : exception spec |
| +--------------+-----------+--------------------------------------+ |
| | ttypeIndex | (SLEB128) | Index into type_info Table (1-based) | |
| | actionOffset | (SLEB128) | Offset into next Action Table entry | |
| +--------------+-----------+--------------------------------------+ |
| ... |
+---------------------------------------------------------------------+-----------------+
| type_info Table, but classInfoOffset does *not* point here! |
| +----------------+------------------------------------------------+-----------------+ |
| | Nth type_info* | Encoded with ttypeEncoding, 0 means catch(...) | ttypeIndex == N | |
| +----------------+------------------------------------------------+-----------------+ |
| ... |
| +----------------+------------------------------------------------+-----------------+ |
| | 1st type_info* | Encoded with ttypeEncoding, 0 means catch(...) | ttypeIndex == 1 | |
| +----------------+------------------------------------------------+-----------------+ |
| +---------------------------------------+-----------+------------------------------+ |
| | 1st ttypeIndex for 1st exception spec | (ULEB128) | classInfoOffset points here! | |
| | ... | (ULEB128) | | |
| | Mth ttypeIndex for 1st exception spec | (ULEB128) | | |
| | 0 | (ULEB128) | | |
| +---------------------------------------+------------------------------------------+ |
| ... |
| +---------------------------------------+------------------------------------------+ |
| | 0 | (ULEB128) | throw() | |
| +---------------------------------------+------------------------------------------+ |
| ... |
| +---------------------------------------+------------------------------------------+ |
| | 1st ttypeIndex for Nth exception spec | (ULEB128) | | |
| | ... | (ULEB128) | | |
| | Mth ttypeIndex for Nth exception spec | (ULEB128) | | |
| | 0 | (ULEB128) | | |
| +---------------------------------------+------------------------------------------+ |
+---------------------------------------------------------------------------------------+
Notes:
* ttypeIndex in the Action Table, and in the exception spec table, is an index,
not a byte count, if positive. It is a negative index offset of
classInfoOffset and the sizeof entry depends on ttypeEncoding.
But if ttypeIndex is negative, it is a positive 1-based byte offset into the
type_info Table.
And if ttypeIndex is zero, it refers to a catch (...).
* landingPad can be 0, this implies there is nothing to be done.
* landingPad != 0 and actionEntry == 0 implies a cleanup needs to be done
@landingPad.
* A cleanup can also be found under landingPad != 0 and actionEntry != 0 in
the Action Table with ttypeIndex == 0.
*/
namespace __cxxabiv1
{
namespace
{
template <class AsType>
uintptr_t readPointerHelper(const uint8_t*& p) {
AsType value;
memcpy(&value, p, sizeof(AsType));
p += sizeof(AsType);
return static_cast<uintptr_t>(value);
}
} // end namespace
extern "C"
{
// private API
// Heavily borrowed from llvm/examples/ExceptionDemo/ExceptionDemo.cpp
// DWARF Constants
enum
{
DW_EH_PE_absptr = 0x00,
DW_EH_PE_uleb128 = 0x01,
DW_EH_PE_udata2 = 0x02,
DW_EH_PE_udata4 = 0x03,
DW_EH_PE_udata8 = 0x04,
DW_EH_PE_sleb128 = 0x09,
DW_EH_PE_sdata2 = 0x0A,
DW_EH_PE_sdata4 = 0x0B,
DW_EH_PE_sdata8 = 0x0C,
DW_EH_PE_pcrel = 0x10,
DW_EH_PE_textrel = 0x20,
DW_EH_PE_datarel = 0x30,
DW_EH_PE_funcrel = 0x40,
DW_EH_PE_aligned = 0x50,
DW_EH_PE_indirect = 0x80,
DW_EH_PE_omit = 0xFF
};
/// Read a uleb128 encoded value and advance pointer
/// See Variable Length Data Appendix C in:
/// @link http://dwarfstd.org/Dwarf4.pdf @unlink
/// @param data reference variable holding memory pointer to decode from
/// @returns decoded value
static
uintptr_t
readULEB128(const uint8_t** data)
{
uintptr_t result = 0;
uintptr_t shift = 0;
unsigned char byte;
const uint8_t *p = *data;
do
{
byte = *p++;
result |= static_cast<uintptr_t>(byte & 0x7F) << shift;
shift += 7;
} while (byte & 0x80);
*data = p;
return result;
}
/// Read a sleb128 encoded value and advance pointer
/// See Variable Length Data Appendix C in:
/// @link http://dwarfstd.org/Dwarf4.pdf @unlink
/// @param data reference variable holding memory pointer to decode from
/// @returns decoded value
static
intptr_t
readSLEB128(const uint8_t** data)
{
uintptr_t result = 0;
uintptr_t shift = 0;
unsigned char byte;
const uint8_t *p = *data;
do
{
byte = *p++;
result |= static_cast<uintptr_t>(byte & 0x7F) << shift;
shift += 7;
} while (byte & 0x80);
*data = p;
if ((byte & 0x40) && (shift < (sizeof(result) << 3)))
result |= static_cast<uintptr_t>(~0) << shift;
return static_cast<intptr_t>(result);
}
/// Read a pointer encoded value and advance pointer
/// See Variable Length Data in:
/// @link http://dwarfstd.org/Dwarf3.pdf @unlink
/// @param data reference variable holding memory pointer to decode from
/// @param encoding dwarf encoding type
/// @returns decoded value
static
uintptr_t
readEncodedPointer(const uint8_t** data, uint8_t encoding)
{
uintptr_t result = 0;
if (encoding == DW_EH_PE_omit)
return result;
const uint8_t* p = *data;
// first get value
switch (encoding & 0x0F)
{
case DW_EH_PE_absptr:
result = readPointerHelper<uintptr_t>(p);
break;
case DW_EH_PE_uleb128:
result = readULEB128(&p);
break;
case DW_EH_PE_sleb128:
result = static_cast<uintptr_t>(readSLEB128(&p));
break;
case DW_EH_PE_udata2:
result = readPointerHelper<uint16_t>(p);
break;
case DW_EH_PE_udata4:
result = readPointerHelper<uint32_t>(p);
break;
case DW_EH_PE_udata8:
result = readPointerHelper<uint64_t>(p);
break;
case DW_EH_PE_sdata2:
result = readPointerHelper<int16_t>(p);
break;
case DW_EH_PE_sdata4:
result = readPointerHelper<int32_t>(p);
break;
case DW_EH_PE_sdata8:
result = readPointerHelper<int64_t>(p);
break;
default:
// not supported
abort();
break;
}
// then add relative offset
switch (encoding & 0x70)
{
case DW_EH_PE_absptr:
// do nothing
break;
case DW_EH_PE_pcrel:
if (result)
result += (uintptr_t)(*data);
break;
case DW_EH_PE_textrel:
case DW_EH_PE_datarel:
case DW_EH_PE_funcrel:
case DW_EH_PE_aligned:
default:
// not supported
abort();
break;
}
// then apply indirection
if (result && (encoding & DW_EH_PE_indirect))
result = *((uintptr_t*)result);
*data = p;
return result;
}
static
void
call_terminate(bool native_exception, _Unwind_Exception* unwind_exception)
{
__cxa_begin_catch(unwind_exception);
if (native_exception)
{
// Use the stored terminate_handler if possible
__cxa_exception* exception_header = (__cxa_exception*)(unwind_exception+1) - 1;
std::__terminate(exception_header->terminateHandler);
}
std::terminate();
}
#if LIBCXXABI_ARM_EHABI
static const void* read_target2_value(const void* ptr)
{
uintptr_t offset = *reinterpret_cast<const uintptr_t*>(ptr);
if (!offset)
return 0;
// "ARM EABI provides a TARGET2 relocation to describe these typeinfo
// pointers. The reason being it allows their precise semantics to be
// deferred to the linker. For bare-metal they turn into absolute
// relocations. For linux they turn into GOT-REL relocations."
// https://gcc.gnu.org/ml/gcc-patches/2009-08/msg00264.html
#if LIBCXXABI_BAREMETAL
return reinterpret_cast<const void*>(reinterpret_cast<uintptr_t>(ptr) +
offset);
#else
return *reinterpret_cast<const void **>(reinterpret_cast<uintptr_t>(ptr) +
offset);
#endif
}
static const __shim_type_info*
get_shim_type_info(uint64_t ttypeIndex, const uint8_t* classInfo,
uint8_t ttypeEncoding, bool native_exception,
_Unwind_Exception* unwind_exception)
{
if (classInfo == 0)
{
// this should not happen. Indicates corrupted eh_table.
call_terminate(native_exception, unwind_exception);
}
assert(ttypeEncoding == DW_EH_PE_absptr && "Unexpected TTypeEncoding");
(void)ttypeEncoding;
const uint8_t* ttypePtr = classInfo - ttypeIndex * sizeof(uintptr_t);
return reinterpret_cast<const __shim_type_info *>(
read_target2_value(ttypePtr));
}
#else // !LIBCXXABI_ARM_EHABI
static
const __shim_type_info*
get_shim_type_info(uint64_t ttypeIndex, const uint8_t* classInfo,
uint8_t ttypeEncoding, bool native_exception,
_Unwind_Exception* unwind_exception)
{
if (classInfo == 0)
{
// this should not happen. Indicates corrupted eh_table.
call_terminate(native_exception, unwind_exception);
}
switch (ttypeEncoding & 0x0F)
{
case DW_EH_PE_absptr:
ttypeIndex *= sizeof(void*);
break;
case DW_EH_PE_udata2:
case DW_EH_PE_sdata2:
ttypeIndex *= 2;
break;
case DW_EH_PE_udata4:
case DW_EH_PE_sdata4:
ttypeIndex *= 4;
break;
case DW_EH_PE_udata8:
case DW_EH_PE_sdata8:
ttypeIndex *= 8;
break;
default:
// this should not happen. Indicates corrupted eh_table.
call_terminate(native_exception, unwind_exception);
}
classInfo -= ttypeIndex;
return (const __shim_type_info*)readEncodedPointer(&classInfo, ttypeEncoding);
}
#endif // !LIBCXXABI_ARM_EHABI
/*
This is checking a thrown exception type, excpType, against a possibly empty
list of catchType's which make up an exception spec.
An exception spec acts like a catch handler, but in reverse. This "catch
handler" will catch an excpType if and only if none of the catchType's in
the list will catch a excpType. If any catchType in the list can catch an
excpType, then this exception spec does not catch the excpType.
*/
#if LIBCXXABI_ARM_EHABI
static
bool
exception_spec_can_catch(int64_t specIndex, const uint8_t* classInfo,
uint8_t ttypeEncoding, const __shim_type_info* excpType,
void* adjustedPtr, _Unwind_Exception* unwind_exception)
{
if (classInfo == 0)
{
// this should not happen. Indicates corrupted eh_table.
call_terminate(false, unwind_exception);
}
assert(ttypeEncoding == DW_EH_PE_absptr && "Unexpected TTypeEncoding");
(void)ttypeEncoding;
// specIndex is negative of 1-based byte offset into classInfo;
specIndex = -specIndex;
--specIndex;
const void** temp = reinterpret_cast<const void**>(
reinterpret_cast<uintptr_t>(classInfo) +
static_cast<uintptr_t>(specIndex) * sizeof(uintptr_t));
// If any type in the spec list can catch excpType, return false, else return true
// adjustments to adjustedPtr are ignored.
while (true)
{
// ARM EHABI exception specification table (filter table) consists of
// several pointers which will directly point to the type info object
// (instead of ttypeIndex). The table will be terminated with 0.
const void** ttypePtr = temp++;
if (*ttypePtr == 0)
break;
// We can get the __shim_type_info simply by performing a
// R_ARM_TARGET2 relocation, and cast the result to __shim_type_info.
const __shim_type_info* catchType =
static_cast<const __shim_type_info*>(read_target2_value(ttypePtr));
void* tempPtr = adjustedPtr;
if (catchType->can_catch(excpType, tempPtr))
return false;
}
return true;
}
#else
static
bool
exception_spec_can_catch(int64_t specIndex, const uint8_t* classInfo,
uint8_t ttypeEncoding, const __shim_type_info* excpType,
void* adjustedPtr, _Unwind_Exception* unwind_exception)
{
if (classInfo == 0)
{
// this should not happen. Indicates corrupted eh_table.
call_terminate(false, unwind_exception);
}
// specIndex is negative of 1-based byte offset into classInfo;
specIndex = -specIndex;
--specIndex;
const uint8_t* temp = classInfo + specIndex;
// If any type in the spec list can catch excpType, return false, else return true
// adjustments to adjustedPtr are ignored.
while (true)
{
uint64_t ttypeIndex = readULEB128(&temp);
if (ttypeIndex == 0)
break;
const __shim_type_info* catchType = get_shim_type_info(ttypeIndex,
classInfo,
ttypeEncoding,
true,
unwind_exception);
void* tempPtr = adjustedPtr;
if (catchType->can_catch(excpType, tempPtr))
return false;
}
return true;
}
#endif
static
void*
get_thrown_object_ptr(_Unwind_Exception* unwind_exception)
{
// Even for foreign exceptions, the exception object is *probably* at unwind_exception + 1
// Regardless, this library is prohibited from touching a foreign exception
void* adjustedPtr = unwind_exception + 1;
if (unwind_exception->exception_class == kOurDependentExceptionClass)
adjustedPtr = ((__cxa_dependent_exception*)adjustedPtr - 1)->primaryException;
return adjustedPtr;
}
namespace
{
struct scan_results
{
int64_t ttypeIndex; // > 0 catch handler, < 0 exception spec handler, == 0 a cleanup
const uint8_t* actionRecord; // Currently unused. Retained to ease future maintenance.
const uint8_t* languageSpecificData; // Needed only for __cxa_call_unexpected
uintptr_t landingPad; // null -> nothing found, else something found
void* adjustedPtr; // Used in cxa_exception.cpp
_Unwind_Reason_Code reason; // One of _URC_FATAL_PHASE1_ERROR,
// _URC_FATAL_PHASE2_ERROR,
// _URC_CONTINUE_UNWIND,
// _URC_HANDLER_FOUND
};
} // unnamed namespace
static
void
set_registers(_Unwind_Exception* unwind_exception, _Unwind_Context* context,
const scan_results& results)
{
#if defined(__USING_SJLJ_EXCEPTIONS__)
#define __builtin_eh_return_data_regno(regno) regno
#endif
_Unwind_SetGR(context, __builtin_eh_return_data_regno(0),
reinterpret_cast<uintptr_t>(unwind_exception));
_Unwind_SetGR(context, __builtin_eh_return_data_regno(1),
static_cast<uintptr_t>(results.ttypeIndex));
_Unwind_SetIP(context, results.landingPad);
}
/*
There are 3 types of scans needed:
1. Scan for handler with native or foreign exception. If handler found,
save state and return _URC_HANDLER_FOUND, else return _URC_CONTINUE_UNWIND.
May also report an error on invalid input.
May terminate for invalid exception table.
_UA_SEARCH_PHASE
2. Scan for handler with foreign exception. Must return _URC_HANDLER_FOUND,
or call terminate.
_UA_CLEANUP_PHASE && _UA_HANDLER_FRAME && !native_exception
3. Scan for cleanups. If a handler is found and this isn't forced unwind,
then terminate, otherwise ignore the handler and keep looking for cleanup.
If a cleanup is found, return _URC_HANDLER_FOUND, else return _URC_CONTINUE_UNWIND.
May also report an error on invalid input.
May terminate for invalid exception table.
_UA_CLEANUP_PHASE && !_UA_HANDLER_FRAME
*/
static void scan_eh_tab(scan_results &results, _Unwind_Action actions,
bool native_exception,
_Unwind_Exception *unwind_exception,
_Unwind_Context *context) {
// Initialize results to found nothing but an error
results.ttypeIndex = 0;
results.actionRecord = 0;
results.languageSpecificData = 0;
results.landingPad = 0;
results.adjustedPtr = 0;
results.reason = _URC_FATAL_PHASE1_ERROR;
// Check for consistent actions
if (actions & _UA_SEARCH_PHASE)
{
// Do Phase 1
if (actions & (_UA_CLEANUP_PHASE | _UA_HANDLER_FRAME | _UA_FORCE_UNWIND))
{
// None of these flags should be set during Phase 1
// Client error
results.reason = _URC_FATAL_PHASE1_ERROR;
return;
}
}
else if (actions & _UA_CLEANUP_PHASE)
{
if ((actions & _UA_HANDLER_FRAME) && (actions & _UA_FORCE_UNWIND))
{
// _UA_HANDLER_FRAME should only be set if phase 1 found a handler.
// If _UA_FORCE_UNWIND is set, phase 1 shouldn't have happened.
// Client error
results.reason = _URC_FATAL_PHASE2_ERROR;
return;
}
}
else // Neither _UA_SEARCH_PHASE nor _UA_CLEANUP_PHASE is set
{
// One of these should be set.
// Client error
results.reason = _URC_FATAL_PHASE1_ERROR;
return;
}
// Start scan by getting exception table address
const uint8_t *lsda = (const uint8_t *)_Unwind_GetLanguageSpecificData(context);
if (lsda == 0)
{
// There is no exception table
results.reason = _URC_CONTINUE_UNWIND;
return;
}
results.languageSpecificData = lsda;
// Get the current instruction pointer and offset it before next
// instruction in the current frame which threw the exception.
uintptr_t ip = _Unwind_GetIP(context) - 1;
// Get beginning current frame's code (as defined by the
// emitted dwarf code)
uintptr_t funcStart = _Unwind_GetRegionStart(context);
#ifdef __USING_SJLJ_EXCEPTIONS__
if (ip == uintptr_t(-1))
{
// no action
results.reason = _URC_CONTINUE_UNWIND;
return;
}
else if (ip == 0)
call_terminate(native_exception, unwind_exception);
// ip is 1-based index into call site table
#else // !__USING_SJLJ_EXCEPTIONS__
uintptr_t ipOffset = ip - funcStart;
#endif // !defined(_USING_SLJL_EXCEPTIONS__)
const uint8_t* classInfo = NULL;
// Note: See JITDwarfEmitter::EmitExceptionTable(...) for corresponding
// dwarf emission
// Parse LSDA header.
uint8_t lpStartEncoding = *lsda++;
const uint8_t* lpStart = (const uint8_t*)readEncodedPointer(&lsda, lpStartEncoding);
if (lpStart == 0)
lpStart = (const uint8_t*)funcStart;
uint8_t ttypeEncoding = *lsda++;
if (ttypeEncoding != DW_EH_PE_omit)
{
// Calculate type info locations in emitted dwarf code which
// were flagged by type info arguments to llvm.eh.selector
// intrinsic
uintptr_t classInfoOffset = readULEB128(&lsda);
classInfo = lsda + classInfoOffset;
}
// Walk call-site table looking for range that
// includes current PC.
uint8_t callSiteEncoding = *lsda++;
#ifdef __USING_SJLJ_EXCEPTIONS__
(void)callSiteEncoding; // When using SjLj exceptions, callSiteEncoding is never used
#endif
uint32_t callSiteTableLength = static_cast<uint32_t>(readULEB128(&lsda));
const uint8_t* callSiteTableStart = lsda;
const uint8_t* callSiteTableEnd = callSiteTableStart + callSiteTableLength;
const uint8_t* actionTableStart = callSiteTableEnd;
const uint8_t* callSitePtr = callSiteTableStart;
while (callSitePtr < callSiteTableEnd)
{
// There is one entry per call site.
#ifndef __USING_SJLJ_EXCEPTIONS__
// The call sites are non-overlapping in [start, start+length)
// The call sites are ordered in increasing value of start
uintptr_t start = readEncodedPointer(&callSitePtr, callSiteEncoding);
uintptr_t length = readEncodedPointer(&callSitePtr, callSiteEncoding);
uintptr_t landingPad = readEncodedPointer(&callSitePtr, callSiteEncoding);
uintptr_t actionEntry = readULEB128(&callSitePtr);
if ((start <= ipOffset) && (ipOffset < (start + length)))
#else // __USING_SJLJ_EXCEPTIONS__
// ip is 1-based index into this table
uintptr_t landingPad = readULEB128(&callSitePtr);
uintptr_t actionEntry = readULEB128(&callSitePtr);
if (--ip == 0)
#endif // __USING_SJLJ_EXCEPTIONS__
{
// Found the call site containing ip.
#ifndef __USING_SJLJ_EXCEPTIONS__
if (landingPad == 0)
{
// No handler here
results.reason = _URC_CONTINUE_UNWIND;
return;
}
landingPad = (uintptr_t)lpStart + landingPad;
#else // __USING_SJLJ_EXCEPTIONS__
++landingPad;
#endif // __USING_SJLJ_EXCEPTIONS__
if (actionEntry == 0)
{
// Found a cleanup
// If this is a type 1 or type 2 search, there are no handlers
// If this is a type 3 search, you want to install the cleanup.
if ((actions & _UA_CLEANUP_PHASE) && !(actions & _UA_HANDLER_FRAME))
{
results.ttypeIndex = 0; // Redundant but clarifying
results.landingPad = landingPad;
results.reason = _URC_HANDLER_FOUND;
return;
}
// No handler here
results.reason = _URC_CONTINUE_UNWIND;
return;
}
// Convert 1-based byte offset into
const uint8_t* action = actionTableStart + (actionEntry - 1);
// Scan action entries until you find a matching handler, cleanup, or the end of action list
while (true)
{
const uint8_t* actionRecord = action;
int64_t ttypeIndex = readSLEB128(&action);
if (ttypeIndex > 0)
{
// Found a catch, does it actually catch?
// First check for catch (...)
const __shim_type_info* catchType =
get_shim_type_info(static_cast<uint64_t>(ttypeIndex),
classInfo, ttypeEncoding,
native_exception, unwind_exception);
if (catchType == 0)
{
// Found catch (...) catches everything, including foreign exceptions
// If this is a type 1 search save state and return _URC_HANDLER_FOUND
// If this is a type 2 search save state and return _URC_HANDLER_FOUND
// If this is a type 3 search !_UA_FORCE_UNWIND, we should have found this in phase 1!
// If this is a type 3 search _UA_FORCE_UNWIND, ignore handler and continue scan
if ((actions & _UA_SEARCH_PHASE) || (actions & _UA_HANDLER_FRAME))
{
// Save state and return _URC_HANDLER_FOUND
results.ttypeIndex = ttypeIndex;
results.actionRecord = actionRecord;
results.landingPad = landingPad;
results.adjustedPtr = get_thrown_object_ptr(unwind_exception);
results.reason = _URC_HANDLER_FOUND;
return;
}
else if (!(actions & _UA_FORCE_UNWIND))
{
// It looks like the exception table has changed
// on us. Likely stack corruption!
call_terminate(native_exception, unwind_exception);
}
}
// Else this is a catch (T) clause and will never
// catch a foreign exception
else if (native_exception)
{
__cxa_exception* exception_header = (__cxa_exception*)(unwind_exception+1) - 1;
void* adjustedPtr = get_thrown_object_ptr(unwind_exception);
const __shim_type_info* excpType =
static_cast<const __shim_type_info*>(exception_header->exceptionType);
if (adjustedPtr == 0 || excpType == 0)
{
// Something very bad happened
call_terminate(native_exception, unwind_exception);
}
if (catchType->can_catch(excpType, adjustedPtr))
{
// Found a matching handler
// If this is a type 1 search save state and return _URC_HANDLER_FOUND
// If this is a type 3 search and !_UA_FORCE_UNWIND, we should have found this in phase 1!
// If this is a type 3 search and _UA_FORCE_UNWIND, ignore handler and continue scan
if (actions & _UA_SEARCH_PHASE)
{
// Save state and return _URC_HANDLER_FOUND
results.ttypeIndex = ttypeIndex;
results.actionRecord = actionRecord;
results.landingPad = landingPad;
results.adjustedPtr = adjustedPtr;
results.reason = _URC_HANDLER_FOUND;
return;
}
else if (!(actions & _UA_FORCE_UNWIND))
{
// It looks like the exception table has changed
// on us. Likely stack corruption!
call_terminate(native_exception, unwind_exception);
}
}
}
// Scan next action ...
}
else if (ttypeIndex < 0)
{
// Found an exception spec. If this is a foreign exception,
// it is always caught.
if (native_exception)
{
// Does the exception spec catch this native exception?
__cxa_exception* exception_header = (__cxa_exception*)(unwind_exception+1) - 1;
void* adjustedPtr = get_thrown_object_ptr(unwind_exception);
const __shim_type_info* excpType =
static_cast<const __shim_type_info*>(exception_header->exceptionType);
if (adjustedPtr == 0 || excpType == 0)
{
// Something very bad happened
call_terminate(native_exception, unwind_exception);
}
if (exception_spec_can_catch(ttypeIndex, classInfo,
ttypeEncoding, excpType,
adjustedPtr, unwind_exception))
{
// native exception caught by exception spec
// If this is a type 1 search, save state and return _URC_HANDLER_FOUND
// If this is a type 3 search !_UA_FORCE_UNWIND, we should have found this in phase 1!
// If this is a type 3 search _UA_FORCE_UNWIND, ignore handler and continue scan
if (actions & _UA_SEARCH_PHASE)
{
// Save state and return _URC_HANDLER_FOUND
results.ttypeIndex = ttypeIndex;
results.actionRecord = actionRecord;
results.landingPad = landingPad;
results.adjustedPtr = adjustedPtr;
results.reason = _URC_HANDLER_FOUND;
return;
}
else if (!(actions & _UA_FORCE_UNWIND))
{
// It looks like the exception table has changed
// on us. Likely stack corruption!
call_terminate(native_exception, unwind_exception);
}
}
}
else
{
// foreign exception caught by exception spec
// If this is a type 1 search, save state and return _URC_HANDLER_FOUND
// If this is a type 2 search, save state and return _URC_HANDLER_FOUND
// If this is a type 3 search !_UA_FORCE_UNWIND, we should have found this in phase 1!
// If this is a type 3 search _UA_FORCE_UNWIND, ignore handler and continue scan
if ((actions & _UA_SEARCH_PHASE) || (actions & _UA_HANDLER_FRAME))
{
// Save state and return _URC_HANDLER_FOUND
results.ttypeIndex = ttypeIndex;
results.actionRecord = actionRecord;
results.landingPad = landingPad;
results.adjustedPtr = get_thrown_object_ptr(unwind_exception);
results.reason = _URC_HANDLER_FOUND;
return;
}
else if (!(actions & _UA_FORCE_UNWIND))
{
// It looks like the exception table has changed
// on us. Likely stack corruption!
call_terminate(native_exception, unwind_exception);
}
}
// Scan next action ...
}
else // ttypeIndex == 0
{
// Found a cleanup
// If this is a type 1 search, ignore it and continue scan
// If this is a type 2 search, ignore it and continue scan
// If this is a type 3 search, save state and return _URC_HANDLER_FOUND
if ((actions & _UA_CLEANUP_PHASE) && !(actions & _UA_HANDLER_FRAME))
{
// Save state and return _URC_HANDLER_FOUND
results.ttypeIndex = ttypeIndex;
results.actionRecord = actionRecord;
results.landingPad = landingPad;
results.adjustedPtr = get_thrown_object_ptr(unwind_exception);
results.reason = _URC_HANDLER_FOUND;
return;
}
}
const uint8_t* temp = action;
int64_t actionOffset = readSLEB128(&temp);
if (actionOffset == 0)
{
// End of action list, no matching handler or cleanup found
results.reason = _URC_CONTINUE_UNWIND;
return;
}
// Go to next action
action += actionOffset;
} // there is no break out of this loop, only return
}
#ifndef __USING_SJLJ_EXCEPTIONS__
else if (ipOffset < start)
{
// There is no call site for this ip
// Something bad has happened. We should never get here.
// Possible stack corruption.
call_terminate(native_exception, unwind_exception);
}
#endif // !__USING_SJLJ_EXCEPTIONS__
} // there might be some tricky cases which break out of this loop
// It is possible that no eh table entry specify how to handle
// this exception. By spec, terminate it immediately.
call_terminate(native_exception, unwind_exception);
}
// public API
/*
The personality function branches on actions like so:
_UA_SEARCH_PHASE
If _UA_CLEANUP_PHASE or _UA_HANDLER_FRAME or _UA_FORCE_UNWIND there's
an error from above, return _URC_FATAL_PHASE1_ERROR.
Scan for anything that could stop unwinding:
1. A catch clause that will catch this exception
(will never catch foreign).
2. A catch (...) (will always catch foreign).
3. An exception spec that will catch this exception
(will always catch foreign).
If a handler is found
If not foreign
Save state in header
return _URC_HANDLER_FOUND
Else a handler not found
return _URC_CONTINUE_UNWIND
_UA_CLEANUP_PHASE
If _UA_HANDLER_FRAME
If _UA_FORCE_UNWIND
How did this happen? return _URC_FATAL_PHASE2_ERROR
If foreign
Do _UA_SEARCH_PHASE to recover state
else
Recover state from header
Transfer control to landing pad. return _URC_INSTALL_CONTEXT
Else
This branch handles both normal C++ non-catching handlers (cleanups)
and forced unwinding.
Scan for anything that can not stop unwinding:
1. A cleanup.
If a cleanup is found
transfer control to it. return _URC_INSTALL_CONTEXT
Else a cleanup is not found: return _URC_CONTINUE_UNWIND
*/
#if !LIBCXXABI_ARM_EHABI
_Unwind_Reason_Code
#ifdef __USING_SJLJ_EXCEPTIONS__
__gxx_personality_sj0
#else
__gxx_personality_v0
#endif
(int version, _Unwind_Action actions, uint64_t exceptionClass,
_Unwind_Exception* unwind_exception, _Unwind_Context* context)
{
if (version != 1 || unwind_exception == 0 || context == 0)
return _URC_FATAL_PHASE1_ERROR;
bool native_exception = (exceptionClass & get_vendor_and_language) ==
(kOurExceptionClass & get_vendor_and_language);
scan_results results;
if (actions & _UA_SEARCH_PHASE)
{
// Phase 1 search: All we're looking for in phase 1 is a handler that
// halts unwinding
scan_eh_tab(results, actions, native_exception, unwind_exception, context);
if (results.reason == _URC_HANDLER_FOUND)
{
// Found one. Can we cache the results somewhere to optimize phase 2?
if (native_exception)
{
__cxa_exception* exception_header = (__cxa_exception*)(unwind_exception+1) - 1;
exception_header->handlerSwitchValue = static_cast<int>(results.ttypeIndex);
exception_header->actionRecord = results.actionRecord;
exception_header->languageSpecificData = results.languageSpecificData;
exception_header->catchTemp = reinterpret_cast<void*>(results.landingPad);
exception_header->adjustedPtr = results.adjustedPtr;
}
return _URC_HANDLER_FOUND;
}
// Did not find a catching-handler. Return the results of the scan
// (normally _URC_CONTINUE_UNWIND, but could have been _URC_FATAL_PHASE1_ERROR
// if we were called improperly).
return results.reason;
}
if (actions & _UA_CLEANUP_PHASE)
{
// Phase 2 search:
// Did we find a catching handler in phase 1?
if (actions & _UA_HANDLER_FRAME)
{
// Yes, phase 1 said we have a catching handler here.
// Did we cache the results of the scan?
if (native_exception)
{
// Yes, reload the results from the cache.
__cxa_exception* exception_header = (__cxa_exception*)(unwind_exception+1) - 1;
results.ttypeIndex = exception_header->handlerSwitchValue;
results.actionRecord = exception_header->actionRecord;
results.languageSpecificData = exception_header->languageSpecificData;
results.landingPad = reinterpret_cast<uintptr_t>(exception_header->catchTemp);
results.adjustedPtr = exception_header->adjustedPtr;
}
else
{
// No, do the scan again to reload the results.
scan_eh_tab(results, actions, native_exception, unwind_exception, context);
// Phase 1 told us we would find a handler. Now in Phase 2 we
// didn't find a handler. The eh table should not be changing!
if (results.reason != _URC_HANDLER_FOUND)
call_terminate(native_exception, unwind_exception);
}
// Jump to the handler
set_registers(unwind_exception, context, results);
return _URC_INSTALL_CONTEXT;
}
// Either we didn't do a phase 1 search (due to forced unwinding), or
// phase 1 reported no catching-handlers.
// Search for a (non-catching) cleanup
scan_eh_tab(results, actions, native_exception, unwind_exception, context);
if (results.reason == _URC_HANDLER_FOUND)
{
// Found a non-catching handler. Jump to it:
set_registers(unwind_exception, context, results);
return _URC_INSTALL_CONTEXT;
}
// Did not find a cleanup. Return the results of the scan
// (normally _URC_CONTINUE_UNWIND, but could have been _URC_FATAL_PHASE2_ERROR
// if we were called improperly).
return results.reason;
}
// We were called improperly: neither a phase 1 or phase 2 search
return _URC_FATAL_PHASE1_ERROR;
}
#else
extern "C" _Unwind_Reason_Code __gnu_unwind_frame(_Unwind_Exception*,
_Unwind_Context*);
// Helper function to unwind one frame.
// ARM EHABI 7.3 and 7.4: If the personality function returns _URC_CONTINUE_UNWIND, the
// personality routine should update the virtual register set (VRS) according to the
// corresponding frame unwinding instructions (ARM EHABI 9.3.)
static _Unwind_Reason_Code continue_unwind(_Unwind_Exception* unwind_exception,
_Unwind_Context* context)
{
if (__gnu_unwind_frame(unwind_exception, context) != _URC_OK)
return _URC_FAILURE;
return _URC_CONTINUE_UNWIND;
}
// ARM register names
#if !LIBCXXABI_USE_LLVM_UNWINDER
static const uint32_t REG_UCB = 12; // Register to save _Unwind_Control_Block
#endif
static const uint32_t REG_SP = 13;
static void save_results_to_barrier_cache(_Unwind_Exception* unwind_exception,
const scan_results& results)
{
unwind_exception->barrier_cache.bitpattern[0] = (uint32_t)results.adjustedPtr;
unwind_exception->barrier_cache.bitpattern[1] = (uint32_t)results.actionRecord;
unwind_exception->barrier_cache.bitpattern[2] = (uint32_t)results.languageSpecificData;
unwind_exception->barrier_cache.bitpattern[3] = (uint32_t)results.landingPad;
unwind_exception->barrier_cache.bitpattern[4] = (uint32_t)results.ttypeIndex;
}
static void load_results_from_barrier_cache(scan_results& results,
const _Unwind_Exception* unwind_exception)
{
results.adjustedPtr = (void*)unwind_exception->barrier_cache.bitpattern[0];
results.actionRecord = (const uint8_t*)unwind_exception->barrier_cache.bitpattern[1];
results.languageSpecificData = (const uint8_t*)unwind_exception->barrier_cache.bitpattern[2];
results.landingPad = (uintptr_t)unwind_exception->barrier_cache.bitpattern[3];
results.ttypeIndex = (int64_t)(int32_t)unwind_exception->barrier_cache.bitpattern[4];
}
extern "C" _Unwind_Reason_Code
__gxx_personality_v0(_Unwind_State state,
_Unwind_Exception* unwind_exception,
_Unwind_Context* context)
{
if (unwind_exception == 0 || context == 0)
return _URC_FATAL_PHASE1_ERROR;
bool native_exception = (unwind_exception->exception_class & get_vendor_and_language) ==
(kOurExceptionClass & get_vendor_and_language);
#if !LIBCXXABI_USE_LLVM_UNWINDER
// Copy the address of _Unwind_Control_Block to r12 so that
// _Unwind_GetLanguageSpecificData() and _Unwind_GetRegionStart() can
// return correct address.
_Unwind_SetGR(context, REG_UCB, reinterpret_cast<uint32_t>(unwind_exception));
#endif
// Check the undocumented force unwinding behavior
bool is_force_unwinding = state & _US_FORCE_UNWIND;
state &= ~_US_FORCE_UNWIND;
scan_results results;
switch (state) {
case _US_VIRTUAL_UNWIND_FRAME:
if (is_force_unwinding)
return continue_unwind(unwind_exception, context);
// Phase 1 search: All we're looking for in phase 1 is a handler that halts unwinding
scan_eh_tab(results, _UA_SEARCH_PHASE, native_exception, unwind_exception, context);
if (results.reason == _URC_HANDLER_FOUND)
{
unwind_exception->barrier_cache.sp = _Unwind_GetGR(context, REG_SP);
if (native_exception)
save_results_to_barrier_cache(unwind_exception, results);
return _URC_HANDLER_FOUND;
}
// Did not find the catch handler
if (results.reason == _URC_CONTINUE_UNWIND)
return continue_unwind(unwind_exception, context);
return results.reason;
case _US_UNWIND_FRAME_STARTING:
// TODO: Support force unwinding in the phase 2 search.
// NOTE: In order to call the cleanup functions, _Unwind_ForcedUnwind()
// will call this personality function with (_US_FORCE_UNWIND |
// _US_UNWIND_FRAME_STARTING).
// Phase 2 search
if (unwind_exception->barrier_cache.sp == _Unwind_GetGR(context, REG_SP))
{
// Found a catching handler in phase 1
if (native_exception)
{
// Load the result from the native exception barrier cache.
load_results_from_barrier_cache(results, unwind_exception);
results.reason = _URC_HANDLER_FOUND;
}
else
{
// Search for the catching handler again for the foreign exception.
scan_eh_tab(results, static_cast<_Unwind_Action>(_UA_CLEANUP_PHASE | _UA_HANDLER_FRAME),
native_exception, unwind_exception, context);
if (results.reason != _URC_HANDLER_FOUND) // phase1 search should guarantee to find one
call_terminate(native_exception, unwind_exception);
}
// Install the context for the catching handler
set_registers(unwind_exception, context, results);
return _URC_INSTALL_CONTEXT;
}
// Either we didn't do a phase 1 search (due to forced unwinding), or
// phase 1 reported no catching-handlers.
// Search for a (non-catching) cleanup
scan_eh_tab(results, _UA_CLEANUP_PHASE, native_exception, unwind_exception, context);
if (results.reason == _URC_HANDLER_FOUND)
{
// Found a non-catching handler
// ARM EHABI 8.4.2: Before we can jump to the cleanup handler, we have to setup some
// internal data structures, so that __cxa_end_cleanup() can get unwind_exception from
// __cxa_get_globals().
__cxa_begin_cleanup(unwind_exception);
// Install the context for the cleanup handler
set_registers(unwind_exception, context, results);
return _URC_INSTALL_CONTEXT;
}
// Did not find any handler
if (results.reason == _URC_CONTINUE_UNWIND)
return continue_unwind(unwind_exception, context);
return results.reason;
case _US_UNWIND_FRAME_RESUME:
return continue_unwind(unwind_exception, context);
}
// We were called improperly: neither a phase 1 or phase 2 search
return _URC_FATAL_PHASE1_ERROR;
}
#endif
__attribute__((noreturn))
void
__cxa_call_unexpected(void* arg)
{
_Unwind_Exception* unwind_exception = static_cast<_Unwind_Exception*>(arg);
if (unwind_exception == 0)
call_terminate(false, unwind_exception);
__cxa_begin_catch(unwind_exception);
bool native_old_exception =
(unwind_exception->exception_class & get_vendor_and_language) ==
(kOurExceptionClass & get_vendor_and_language);
std::unexpected_handler u_handler;
std::terminate_handler t_handler;
__cxa_exception* old_exception_header = 0;
int64_t ttypeIndex;
const uint8_t* lsda;
if (native_old_exception)
{
old_exception_header = (__cxa_exception*)(unwind_exception+1) - 1;
t_handler = old_exception_header->terminateHandler;
u_handler = old_exception_header->unexpectedHandler;
// If std::__unexpected(u_handler) rethrows the same exception,
// these values get overwritten by the rethrow. So save them now:
#if LIBCXXABI_ARM_EHABI
ttypeIndex = (int64_t)(int32_t)unwind_exception->barrier_cache.bitpattern[4];
lsda = (const uint8_t*)unwind_exception->barrier_cache.bitpattern[2];
#else
ttypeIndex = old_exception_header->handlerSwitchValue;
lsda = old_exception_header->languageSpecificData;
#endif
}
else
{
t_handler = std::get_terminate();
u_handler = std::get_unexpected();
}
try
{
std::__unexpected(u_handler);
}
catch (...)
{
// If the old exception is foreign, then all we can do is terminate.
// We have no way to recover the needed old exception spec. There's
// no way to pass that information here. And the personality routine
// can't call us directly and do anything but terminate() if we throw
// from here.
if (native_old_exception)
{
// Have:
// old_exception_header->languageSpecificData
// old_exception_header->actionRecord
// Need
// const uint8_t* classInfo
// uint8_t ttypeEncoding
uint8_t lpStartEncoding = *lsda++;
const uint8_t* lpStart = (const uint8_t*)readEncodedPointer(&lsda, lpStartEncoding);
(void)lpStart; // purposefully unused. Just needed to increment lsda.
uint8_t ttypeEncoding = *lsda++;
if (ttypeEncoding == DW_EH_PE_omit)
std::__terminate(t_handler);
uintptr_t classInfoOffset = readULEB128(&lsda);
const uint8_t* classInfo = lsda + classInfoOffset;
// Is this new exception catchable by the exception spec at ttypeIndex?
// The answer is obviously yes if the new and old exceptions are the same exception
// If no
// throw;
__cxa_eh_globals* globals = __cxa_get_globals_fast();
__cxa_exception* new_exception_header = globals->caughtExceptions;
if (new_exception_header == 0)
// This shouldn't be able to happen!
std::__terminate(t_handler);
bool native_new_exception =
(new_exception_header->unwindHeader.exception_class & get_vendor_and_language) ==
(kOurExceptionClass & get_vendor_and_language);
void* adjustedPtr;
if (native_new_exception && (new_exception_header != old_exception_header))
{
const __shim_type_info* excpType =
static_cast<const __shim_type_info*>(new_exception_header->exceptionType);
adjustedPtr =
new_exception_header->unwindHeader.exception_class == kOurDependentExceptionClass ?
((__cxa_dependent_exception*)new_exception_header)->primaryException :
new_exception_header + 1;
if (!exception_spec_can_catch(ttypeIndex, classInfo, ttypeEncoding,
excpType, adjustedPtr, unwind_exception))
{
// We need to __cxa_end_catch, but for the old exception,
// not the new one. This is a little tricky ...
// Disguise new_exception_header as a rethrown exception, but
// don't actually rethrow it. This means you can temporarily
// end the catch clause enclosing new_exception_header without
// __cxa_end_catch destroying new_exception_header.
new_exception_header->handlerCount = -new_exception_header->handlerCount;
globals->uncaughtExceptions += 1;
// Call __cxa_end_catch for new_exception_header
__cxa_end_catch();
// Call __cxa_end_catch for old_exception_header
__cxa_end_catch();
// Renter this catch clause with new_exception_header
__cxa_begin_catch(&new_exception_header->unwindHeader);
// Rethrow new_exception_header
throw;
}
}
// Will a std::bad_exception be catchable by the exception spec at
// ttypeIndex?
// If no
// throw std::bad_exception();
const __shim_type_info* excpType =
static_cast<const __shim_type_info*>(&typeid(std::bad_exception));
std::bad_exception be;
adjustedPtr = &be;
if (!exception_spec_can_catch(ttypeIndex, classInfo, ttypeEncoding,
excpType, adjustedPtr, unwind_exception))
{
// We need to __cxa_end_catch for both the old exception and the
// new exception. Technically we should do it in that order.
// But it is expedient to do it in the opposite order:
// Call __cxa_end_catch for new_exception_header
__cxa_end_catch();
// Throw std::bad_exception will __cxa_end_catch for
// old_exception_header
throw be;
}
}
}
std::__terminate(t_handler);
}
} // extern "C"
} // __cxxabiv1
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