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clang-p2996/libcxxabi/src/cxa_personality.cpp
Kazushi (Jam) Marukawa 9d2740f331 [libc++abi] Apply simplify scan_eh_tab to SjLj 
Previous "simplify scan_eh_tab" patch, https://reviews.llvm.org/D93190,
saves landingpad if and only if the target is not using SjLj exceptions.
However, the landingpad is used by SjLj exception handler also.  This
patch changes to set landingpad for both exception handlers.

Differential Revision: https://reviews.llvm.org/D108082
2021-08-24 16:51:53 -04:00

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//===------------------------- cxa_exception.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
//
//
// This file implements the "Exception Handling APIs"
// https://itanium-cxx-abi.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 "__cxxabi_config.h"
#include "cxa_exception.h"
#include "cxa_handlers.h"
#include "private_typeinfo.h"
#include "unwind.h"
#if defined(__SEH__) && !defined(__USING_SJLJ_EXCEPTIONS__)
#include <windows.h>
#include <winnt.h>
extern "C" EXCEPTION_DISPOSITION _GCC_specific_handler(PEXCEPTION_RECORD,
void *, PCONTEXT,
PDISPATCHER_CONTEXT,
_Unwind_Personality_Fn);
#endif
/*
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
/// @param base for adding relative offset, default to 0
/// @returns decoded value
static
uintptr_t
readEncodedPointer(const uint8_t** data, uint8_t encoding, uintptr_t base = 0)
{
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_datarel:
assert((base != 0) && "DW_EH_PE_datarel is invalid with a base of 0");
if (result)
result += base;
break;
case DW_EH_PE_textrel:
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 defined(_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 defined(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, uintptr_t /*base*/ = 0)
{
if (classInfo == 0)
{
// this should not happen. Indicates corrupted eh_table.
call_terminate(native_exception, unwind_exception);
}
assert(((ttypeEncoding == DW_EH_PE_absptr) || // LLVM or GCC 4.6
(ttypeEncoding == DW_EH_PE_pcrel) || // GCC 4.7 baremetal
(ttypeEncoding == (DW_EH_PE_pcrel | DW_EH_PE_indirect))) && // GCC 4.7 linux
"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 // !defined(_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, uintptr_t base = 0)
{
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, base);
}
#endif // !defined(_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 defined(_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,
uintptr_t /*base*/ = 0)
{
if (classInfo == 0)
{
// this should not happen. Indicates corrupted eh_table.
call_terminate(false, unwind_exception);
}
assert(((ttypeEncoding == DW_EH_PE_absptr) || // LLVM or GCC 4.6
(ttypeEncoding == DW_EH_PE_pcrel) || // GCC 4.7 baremetal
(ttypeEncoding == (DW_EH_PE_pcrel | DW_EH_PE_indirect))) && // GCC 4.7 linux
"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,
uintptr_t base = 0)
{
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,
base);
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 (__getExceptionClass(unwind_exception) == 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
#elif defined(__ibmxl__)
// IBM xlclang++ compiler does not support __builtin_eh_return_data_regno.
#define __builtin_eh_return_data_regno(regno) regno + 3
#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;
#if defined(_AIX)
uintptr_t base = _Unwind_GetDataRelBase(context);
#else
uintptr_t base = 0;
#endif
// 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, base);
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__
results.landingPad = landingPad;
if (actionEntry == 0)
{
// Found a cleanup
results.reason = actions & _UA_SEARCH_PHASE
? _URC_CONTINUE_UNWIND
: _URC_HANDLER_FOUND;
return;
}
// Convert 1-based byte offset into
const uint8_t* action = actionTableStart + (actionEntry - 1);
bool hasCleanup = false;
// 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,
base);
if (catchType == 0)
{
// Found catch (...) catches everything, including
// foreign exceptions. This is search phase, cleanup
// phase with foreign exception, or forced unwinding.
assert(actions & (_UA_SEARCH_PHASE | _UA_HANDLER_FRAME |
_UA_FORCE_UNWIND));
results.ttypeIndex = ttypeIndex;
results.actionRecord = actionRecord;
results.adjustedPtr =
get_thrown_object_ptr(unwind_exception);
results.reason = _URC_HANDLER_FOUND;
return;
}
// 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. This is either search
// phase or forced unwinding.
assert(actions &
(_UA_SEARCH_PHASE | _UA_FORCE_UNWIND));
results.ttypeIndex = ttypeIndex;
results.actionRecord = actionRecord;
results.adjustedPtr = adjustedPtr;
results.reason = _URC_HANDLER_FOUND;
return;
}
}
// Scan next action ...
}
else if (ttypeIndex < 0)
{
// Found an exception specification.
if (actions & _UA_FORCE_UNWIND) {
// Skip if forced unwinding.
} else 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, base))
{
// Native exception caught by exception
// specification.
assert(actions & _UA_SEARCH_PHASE);
results.ttypeIndex = ttypeIndex;
results.actionRecord = actionRecord;
results.adjustedPtr = adjustedPtr;
results.reason = _URC_HANDLER_FOUND;
return;
}
} else {
// foreign exception caught by exception spec
results.ttypeIndex = ttypeIndex;
results.actionRecord = actionRecord;
results.adjustedPtr =
get_thrown_object_ptr(unwind_exception);
results.reason = _URC_HANDLER_FOUND;
return;
}
// Scan next action ...
} else {
hasCleanup = true;
}
const uint8_t* temp = action;
int64_t actionOffset = readSLEB128(&temp);
if (actionOffset == 0)
{
// End of action list. If this is phase 2 and we have found
// a cleanup (ttypeIndex=0), return _URC_HANDLER_FOUND;
// otherwise return _URC_CONTINUE_UNWIND.
results.reason = hasCleanup && actions & _UA_CLEANUP_PHASE
? _URC_HANDLER_FOUND
: _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 !defined(_LIBCXXABI_ARM_EHABI)
#if defined(__SEH__) && !defined(__USING_SJLJ_EXCEPTIONS__)
static _Unwind_Reason_Code __gxx_personality_imp
#else
_LIBCXXABI_FUNC_VIS _Unwind_Reason_Code
#ifdef __USING_SJLJ_EXCEPTIONS__
__gxx_personality_sj0
#else
__gxx_personality_v0
#endif
#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;
// Process a catch handler for a native exception first.
if (actions == (_UA_CLEANUP_PHASE | _UA_HANDLER_FRAME) &&
native_exception) {
// Reload the results from the phase 1 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;
// Jump to the handler.
set_registers(unwind_exception, context, results);
// Cache base for calculating the address of ttype in
// __cxa_call_unexpected.
if (results.ttypeIndex < 0) {
#if defined(_AIX)
exception_header->catchTemp = (void *)_Unwind_GetDataRelBase(context);
#else
exception_header->catchTemp = 0;
#endif
}
return _URC_INSTALL_CONTEXT;
}
// In other cases we need to scan LSDA.
scan_eh_tab(results, actions, native_exception, unwind_exception, context);
if (results.reason == _URC_CONTINUE_UNWIND ||
results.reason == _URC_FATAL_PHASE1_ERROR)
return results.reason;
if (actions & _UA_SEARCH_PHASE)
{
// Phase 1 search: All we're looking for in phase 1 is a handler that
// halts unwinding
assert(results.reason == _URC_HANDLER_FOUND);
if (native_exception) {
// For a native exception, cache the LSDA result.
__cxa_exception* exc = (__cxa_exception*)(unwind_exception + 1) - 1;
exc->handlerSwitchValue = static_cast<int>(results.ttypeIndex);
exc->actionRecord = results.actionRecord;
exc->languageSpecificData = results.languageSpecificData;
exc->catchTemp = reinterpret_cast<void*>(results.landingPad);
exc->adjustedPtr = results.adjustedPtr;
}
return _URC_HANDLER_FOUND;
}
assert(actions & _UA_CLEANUP_PHASE);
assert(results.reason == _URC_HANDLER_FOUND);
set_registers(unwind_exception, context, results);
// Cache base for calculating the address of ttype in __cxa_call_unexpected.
if (results.ttypeIndex < 0) {
__cxa_exception* exception_header =
(__cxa_exception*)(unwind_exception + 1) - 1;
#if defined(_AIX)
exception_header->catchTemp = (void *)_Unwind_GetDataRelBase(context);
#else
exception_header->catchTemp = 0;
#endif
}
return _URC_INSTALL_CONTEXT;
}
#if defined(__SEH__) && !defined(__USING_SJLJ_EXCEPTIONS__)
extern "C" _LIBCXXABI_FUNC_VIS EXCEPTION_DISPOSITION
__gxx_personality_seh0(PEXCEPTION_RECORD ms_exc, void *this_frame,
PCONTEXT ms_orig_context, PDISPATCHER_CONTEXT ms_disp)
{
return _GCC_specific_handler(ms_exc, this_frame, ms_orig_context, ms_disp,
__gxx_personality_imp);
}
#endif
#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 !defined(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" _LIBCXXABI_FUNC_VIS _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 = __isOurExceptionClass(unwind_exception);
#if !defined(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
if (is_force_unwinding)
scan_eh_tab(
results,
static_cast<_Unwind_Action>(_UA_CLEANUP_PHASE | _UA_FORCE_UNWIND),
native_exception, unwind_exception, context);
else
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))
_LIBCXXABI_FUNC_VIS 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 = __isOurExceptionClass(unwind_exception);
std::unexpected_handler u_handler;
std::terminate_handler t_handler;
__cxa_exception* old_exception_header = 0;
int64_t ttypeIndex;
const uint8_t* lsda;
uintptr_t base = 0;
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 defined(_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;
base = (uintptr_t)old_exception_header->catchTemp;
#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
// old_exception_header->catchTemp, base for calculating ttype
// Need
// const uint8_t* classInfo
// uint8_t ttypeEncoding
uint8_t lpStartEncoding = *lsda++;
const uint8_t* lpStart =
(const uint8_t*)readEncodedPointer(&lsda, lpStartEncoding, base);
(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 = __isOurExceptionClass(&new_exception_header->unwindHeader);
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 =
__getExceptionClass(&new_exception_header->unwindHeader) == kOurDependentExceptionClass ?
((__cxa_dependent_exception*)new_exception_header)->primaryException :
new_exception_header + 1;
if (!exception_spec_can_catch(ttypeIndex, classInfo, ttypeEncoding,
excpType, adjustedPtr,
unwind_exception, base))
{
// 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, base))
{
// 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);
}
#if defined(_AIX)
// Personality routine for EH using the range table. Make it an alias of
// __gxx_personality_v0().
_LIBCXXABI_FUNC_VIS _Unwind_Reason_Code __xlcxx_personality_v1(
int version, _Unwind_Action actions, uint64_t exceptionClass,
_Unwind_Exception* unwind_exception, _Unwind_Context* context)
__attribute__((__alias__("__gxx_personality_v0")));
#endif
} // extern "C"
} // __cxxabiv1
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