/* ===-- 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 /* * 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; }