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| //===-- gcc_personality_v0.c - Implement __gcc_personality_v0 -------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
#include "int_lib.h"
#include <unwind.h>
#if defined(__arm__) && !defined(__ARM_DWARF_EH__) && \
!defined(__USING_SJLJ_EXCEPTIONS__)
// When building with older compilers (e.g. clang <3.9), it is possible that we
// have a version of unwind.h which does not provide the EHABI declarations
// which are quired for the C personality to conform to the specification. In
// order to provide forward compatibility for such compilers, we re-declare the
// necessary interfaces in the helper to permit a standalone compilation of the
// builtins (which contains the C unwinding personality for historical reasons).
#include "unwind-ehabi-helpers.h"
#endif
// 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;
}
#if defined(__arm__) && !defined(__USING_SJLJ_EXCEPTIONS__) && \
!defined(__ARM_DWARF_EH__)
#define USING_ARM_EHABI 1
_Unwind_Reason_Code __gnu_unwind_frame(struct _Unwind_Exception *,
struct _Unwind_Context *);
#endif
static inline _Unwind_Reason_Code
continueUnwind(struct _Unwind_Exception *exceptionObject,
struct _Unwind_Context *context) {
#if USING_ARM_EHABI
// On ARM EHABI the personality routine is responsible for actually
// unwinding a single stack frame before returning (ARM EHABI Sec. 6.1).
if (__gnu_unwind_frame(exceptionObject, context) != _URC_OK)
return _URC_FAILURE;
#endif
return _URC_CONTINUE_UNWIND;
}
// 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)
#elif USING_ARM_EHABI
// The ARM EHABI personality routine has a different signature.
COMPILER_RT_ABI _Unwind_Reason_Code __gcc_personality_v0(
_Unwind_State state, 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 USING_ARM_EHABI
// After resuming from a cleanup we should also continue on to the next
// frame straight away.
if ((state & _US_ACTION_MASK) != _US_UNWIND_FRAME_STARTING)
#else
if (actions & _UA_SEARCH_PHASE)
#endif
return continueUnwind(exceptionObject, context);
// 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 continueUnwind(exceptionObject, context);
uintptr_t pc = (uintptr_t)_Unwind_GetIP(context) - 1;
uintptr_t funcStart = (uintptr_t)_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 continueUnwind(exceptionObject, context);
}
|