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/* ===-- gcc_personality_v0.c - Implement __gcc_personality_v0 -------------===
*
* 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.
*
* ===----------------------------------------------------------------------===
*
*/
#include "int_lib.h"
#include <unwind.h>
/*
* Pointer encodings documented at:
* http://refspecs.freestandards.org/LSB_1.3.0/gLSB/gLSB/ehframehdr.html
*/
#define DW_EH_PE_omit 0xff /* no data follows */
#define DW_EH_PE_absptr 0x00
#define DW_EH_PE_uleb128 0x01
#define DW_EH_PE_udata2 0x02
#define DW_EH_PE_udata4 0x03
#define DW_EH_PE_udata8 0x04
#define DW_EH_PE_sleb128 0x09
#define DW_EH_PE_sdata2 0x0A
#define DW_EH_PE_sdata4 0x0B
#define DW_EH_PE_sdata8 0x0C
#define DW_EH_PE_pcrel 0x10
#define DW_EH_PE_textrel 0x20
#define DW_EH_PE_datarel 0x30
#define DW_EH_PE_funcrel 0x40
#define DW_EH_PE_aligned 0x50
#define DW_EH_PE_indirect 0x80 /* gcc extension */
/* read a uleb128 encoded value and advance pointer */
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 |= (byte & 0x7f) << shift;
shift += 7;
} while (byte & 0x80);
*data = p;
return result;
}
/* read a pointer encoded value and advance pointer */
static uintptr_t readEncodedPointer(const uint8_t** data, uint8_t encoding)
{
const uint8_t* p = *data;
uintptr_t result = 0;
if ( encoding == DW_EH_PE_omit )
return 0;
/* first get value */
switch (encoding & 0x0F) {
case DW_EH_PE_absptr:
result = *((const uintptr_t*)p);
p += sizeof(uintptr_t);
break;
case DW_EH_PE_uleb128:
result = readULEB128(&p);
break;
case DW_EH_PE_udata2:
result = *((const uint16_t*)p);
p += sizeof(uint16_t);
break;
case DW_EH_PE_udata4:
result = *((const uint32_t*)p);
p += sizeof(uint32_t);
break;
case DW_EH_PE_udata8:
result = *((const uint64_t*)p);
p += sizeof(uint64_t);
break;
case DW_EH_PE_sdata2:
result = *((const int16_t*)p);
p += sizeof(int16_t);
break;
case DW_EH_PE_sdata4:
result = *((const int32_t*)p);
p += sizeof(int32_t);
break;
case DW_EH_PE_sdata8:
result = *((const int64_t*)p);
p += sizeof(int64_t);
break;
case DW_EH_PE_sleb128:
default:
/* not supported */
compilerrt_abort();
break;
}
/* then add relative offset */
switch ( encoding & 0x70 ) {
case DW_EH_PE_absptr:
/* do nothing */
break;
case DW_EH_PE_pcrel:
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 */
compilerrt_abort();
break;
}
/* then apply indirection */
if (encoding & DW_EH_PE_indirect) {
result = *((const uintptr_t*)result);
}
*data = p;
return result;
}
/*
* The C compiler makes references to __gcc_personality_v0 in
* the dwarf unwind information for translation units that use
* __attribute__((cleanup(xx))) on local variables.
* This personality routine is called by the system unwinder
* on each frame as the stack is unwound during a C++ exception
* throw through a C function compiled with -fexceptions.
*/
#if __USING_SJLJ_EXCEPTIONS__
// the setjump-longjump based exceptions personality routine has a different name
COMPILER_RT_ABI _Unwind_Reason_Code
__gcc_personality_sj0(int version, _Unwind_Action actions,
uint64_t exceptionClass, struct _Unwind_Exception* exceptionObject,
struct _Unwind_Context *context)
#else
COMPILER_RT_ABI _Unwind_Reason_Code
__gcc_personality_v0(int version, _Unwind_Action actions,
uint64_t exceptionClass, struct _Unwind_Exception* exceptionObject,
struct _Unwind_Context *context)
#endif
{
/* Since C does not have catch clauses, there is nothing to do during */
/* phase 1 (the search phase). */
if ( actions & _UA_SEARCH_PHASE )
return _URC_CONTINUE_UNWIND;
/* There is nothing to do if there is no LSDA for this frame. */
const uint8_t* lsda = (uint8_t*)_Unwind_GetLanguageSpecificData(context);
if ( lsda == (uint8_t*) 0 )
return _URC_CONTINUE_UNWIND;
uintptr_t pc = _Unwind_GetIP(context)-1;
uintptr_t funcStart = _Unwind_GetRegionStart(context);
uintptr_t pcOffset = pc - funcStart;
/* Parse LSDA header. */
uint8_t lpStartEncoding = *lsda++;
if (lpStartEncoding != DW_EH_PE_omit) {
readEncodedPointer(&lsda, lpStartEncoding);
}
uint8_t ttypeEncoding = *lsda++;
if (ttypeEncoding != DW_EH_PE_omit) {
readULEB128(&lsda);
}
/* Walk call-site table looking for range that includes current PC. */
uint8_t callSiteEncoding = *lsda++;
uint32_t callSiteTableLength = readULEB128(&lsda);
const uint8_t* callSiteTableStart = lsda;
const uint8_t* callSiteTableEnd = callSiteTableStart + callSiteTableLength;
const uint8_t* p=callSiteTableStart;
while (p < callSiteTableEnd) {
uintptr_t start = readEncodedPointer(&p, callSiteEncoding);
uintptr_t length = readEncodedPointer(&p, callSiteEncoding);
uintptr_t landingPad = readEncodedPointer(&p, callSiteEncoding);
readULEB128(&p); /* action value not used for C code */
if ( landingPad == 0 )
continue; /* no landing pad for this entry */
if ( (start <= pcOffset) && (pcOffset < (start+length)) ) {
/* Found landing pad for the PC.
* Set Instruction Pointer to so we re-enter function
* at landing pad. The landing pad is created by the compiler
* to take two parameters in registers.
*/
_Unwind_SetGR(context, __builtin_eh_return_data_regno(0),
(uintptr_t)exceptionObject);
_Unwind_SetGR(context, __builtin_eh_return_data_regno(1), 0);
_Unwind_SetIP(context, (funcStart + landingPad));
return _URC_INSTALL_CONTEXT;
}
}
/* No landing pad found, continue unwinding. */
return _URC_CONTINUE_UNWIND;
}
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