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artiq/artiq/runtime/artiq_personality.c

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C
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#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <unwind.h>
#include "artiq_personality.h"
/* Logging */
#ifndef NDEBUG
#define EH_LOG0(fmt) fprintf(stderr, "%s: " fmt "\n", __func__)
#define EH_LOG(fmt, ...) fprintf(stderr, "%s: " fmt "\n", __func__, __VA_ARGS__)
#else
#define EH_LOG0(fmt)
#define EH_LOG(fmt, ...)
#endif
#define EH_FAIL(err) \
do { \
fprintf(stderr, "%s fatal: %s\n", __func__, err); \
abort(); \
} while(0)
#define EH_ASSERT(expr) \
if(!(expr)) EH_FAIL(#expr)
/* DWARF format handling */
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 in: http://dwarfstd.org/Dwarf3.pdf
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 sleb128 encoded value and advance pointer
// See Variable Length Data in: http://dwarfstd.org/Dwarf3.pdf
static uintptr_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 |= (byte & 0x7f) << shift;
shift += 7;
}
while (byte & 0x80);
*data = p;
if ((byte & 0x40) && (shift < (sizeof(result) << 3))) {
result |= (~0 << shift);
}
return result;
}
static unsigned getEncodingSize(uint8_t Encoding) {
if (Encoding == DW_EH_PE_omit)
return 0;
switch (Encoding & 0x0F) {
case DW_EH_PE_absptr:
return sizeof(uintptr_t);
case DW_EH_PE_udata2:
return sizeof(uint16_t);
case DW_EH_PE_udata4:
return sizeof(uint32_t);
case DW_EH_PE_udata8:
return sizeof(uint64_t);
case DW_EH_PE_sdata2:
return sizeof(int16_t);
case DW_EH_PE_sdata4:
return sizeof(int32_t);
case DW_EH_PE_sdata8:
return sizeof(int64_t);
default:
// not supported
abort();
}
}
// Read a pointer encoded value and advance pointer
// See Variable Length Data in: http://dwarfstd.org/Dwarf3.pdf
static uintptr_t readEncodedPointer(const uint8_t **data, uint8_t encoding) {
uintptr_t result = 0;
const uint8_t *p = *data;
if (encoding == DW_EH_PE_omit)
return(result);
// first get value
switch (encoding & 0x0F) {
case DW_EH_PE_absptr:
memcpy(&result, p, sizeof(uintptr_t));
p += sizeof(uintptr_t);
break;
case DW_EH_PE_uleb128:
result = readULEB128(&p);
break;
// Note: This case has not been tested
case DW_EH_PE_sleb128:
result = readSLEB128(&p);
break;
case DW_EH_PE_udata2:
{
uint16_t valu16;
memcpy(&valu16, p, sizeof(uint16_t));
result = valu16;
}
p += sizeof(uint16_t);
break;
case DW_EH_PE_udata4:
{
uint32_t valu32;
memcpy(&valu32, p, sizeof(uint32_t));
result = valu32;
}
p += sizeof(uint32_t);
break;
case DW_EH_PE_udata8:
{
uint64_t valu64;
memcpy(&valu64, p, sizeof(uint64_t));
result = valu64;
}
p += sizeof(uint64_t);
break;
case DW_EH_PE_sdata2:
{
int16_t val16;
memcpy(&val16, p, sizeof(int16_t));
result = val16;
}
p += sizeof(int16_t);
break;
case DW_EH_PE_sdata4:
{
int32_t val32;
memcpy(&val32, p, sizeof(int32_t));
result = val32;
}
p += sizeof(int32_t);
break;
case DW_EH_PE_sdata8:
{
int64_t val64;
memcpy(&val64, p, sizeof(int64_t));
result = val64;
}
p += sizeof(int64_t);
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:
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 (encoding & DW_EH_PE_indirect) {
result = *((uintptr_t*)result);
}
*data = p;
return result;
}
/* Raising */
#define ARTIQ_EXCEPTION_CLASS 0x4152545141525451LL // 'ARTQARTQ'
static void __artiq_cleanup(_Unwind_Reason_Code reason, struct _Unwind_Exception *exc);
static _Unwind_Reason_Code __artiq_uncaught_exception(
int version, _Unwind_Action actions, uint64_t exceptionClass,
struct _Unwind_Exception *exceptionObject, struct _Unwind_Context *context,
void *stop_parameter);
struct artiq_raised_exception {
struct _Unwind_Exception unwind;
struct artiq_exception artiq;
int handled;
struct artiq_backtrace_item backtrace[1024];
size_t backtrace_size;
};
static struct artiq_raised_exception inflight;
void __artiq_raise(struct artiq_exception *artiq_exn) {
EH_LOG("===> raise (name=%s, msg=%s, params=[%lld,%lld,%lld])",
artiq_exn->name, artiq_exn->message,
(long long int)artiq_exn->param[0],
(long long int)artiq_exn->param[1],
(long long int)artiq_exn->param[2]);
memmove(&inflight.artiq, artiq_exn, sizeof(struct artiq_exception));
inflight.unwind.exception_class = ARTIQ_EXCEPTION_CLASS;
inflight.unwind.exception_cleanup = &__artiq_cleanup;
inflight.handled = 0;
inflight.backtrace_size = 0;
_Unwind_Reason_Code result = _Unwind_RaiseException(&inflight.unwind);
EH_ASSERT((result == _URC_END_OF_STACK) &&
"Unexpected error during unwinding");
// If we're here, there are no handlers, only cleanups.
// Force unwinding anyway; we shall stop at nothing except the end of stack.
result = _Unwind_ForcedUnwind(&inflight.unwind, &__artiq_uncaught_exception,
NULL);
EH_FAIL("_Unwind_ForcedUnwind should not return");
}
void __artiq_reraise() {
if(inflight.handled) {
EH_LOG0("===> reraise");
__artiq_raise(&inflight.artiq);
} else {
EH_LOG0("===> resume");
EH_ASSERT((inflight.artiq.typeinfo != 0) &&
"Need an exception to reraise");
_Unwind_Resume(&inflight.unwind);
abort();
}
}
/* Unwinding */
// The code below does not refer to the `inflight` global.
static void __artiq_cleanup(_Unwind_Reason_Code reason, struct _Unwind_Exception *exc) {
EH_LOG0("===> cleanup");
struct artiq_raised_exception *inflight = (struct artiq_raised_exception*) exc;
// The in-flight exception is statically allocated, so we don't need to free it.
// But, we clear it to mark it as processed.
memset(&inflight->artiq, 0, sizeof(struct artiq_exception));
}
static _Unwind_Reason_Code __artiq_uncaught_exception(
int version, _Unwind_Action actions, uint64_t exceptionClass,
struct _Unwind_Exception *exceptionObject, struct _Unwind_Context *context,
void *stop_parameter) {
struct artiq_raised_exception *inflight =
(struct artiq_raised_exception*)exceptionObject;
EH_ASSERT(inflight->backtrace_size <
sizeof(inflight->backtrace) / sizeof(inflight->backtrace[0]) &&
"Out of space for backtrace");
uintptr_t pc = _Unwind_GetIP(context);
uintptr_t funcStart = _Unwind_GetRegionStart(context);
uintptr_t pcOffset = pc - funcStart;
EH_LOG("===> uncaught (pc=%p+%p)", (void*)funcStart, (void*)pcOffset);
inflight->backtrace[inflight->backtrace_size].function = funcStart;
inflight->backtrace[inflight->backtrace_size].offset = pcOffset;
++inflight->backtrace_size;
if(actions & _UA_END_OF_STACK) {
EH_LOG0("end of stack");
__artiq_terminate(&inflight->artiq, inflight->backtrace, inflight->backtrace_size);
} else {
EH_LOG0("continue");
return _URC_NO_REASON;
}
}
_Unwind_Reason_Code __artiq_personality(
int version, _Unwind_Action actions, uint64_t exceptionClass,
struct _Unwind_Exception *exceptionObject, struct _Unwind_Context *context);
_Unwind_Reason_Code __artiq_personality(
int version, _Unwind_Action actions, uint64_t exceptionClass,
struct _Unwind_Exception *exceptionObject, struct _Unwind_Context *context) {
EH_LOG("===> entry (actions =%s%s%s%s; class=%08lx; object=%p, context=%p)",
(actions & _UA_SEARCH_PHASE ? " search" : ""),
(actions & _UA_CLEANUP_PHASE ? " cleanup" : ""),
(actions & _UA_HANDLER_FRAME ? " handler" : ""),
(actions & _UA_FORCE_UNWIND ? " force-unwind" : ""),
exceptionClass, exceptionObject, context);
EH_ASSERT((exceptionClass == ARTIQ_EXCEPTION_CLASS) &&
"Foreign exceptions are not supported");
struct artiq_raised_exception *inflight =
(struct artiq_raised_exception*)exceptionObject;
EH_LOG("=> exception name=%s",
inflight->artiq.name);
// Get a pointer to LSDA. If there's no LSDA, this function doesn't
// actually handle any exceptions.
const uint8_t *lsda = (const uint8_t*) _Unwind_GetLanguageSpecificData(context);
if(lsda == NULL)
return _URC_CONTINUE_UNWIND;
EH_LOG("lsda=%p", lsda);
// Get the current instruction pointer and offset it before next
// instruction in the current frame which threw the exception.
uintptr_t pc = _Unwind_GetIP(context) - 1;
// Get beginning of the current frame's code.
uintptr_t funcStart = _Unwind_GetRegionStart(context);
uintptr_t pcOffset = pc - funcStart;
EH_LOG("=> pc=%p (%p+%p)", (void*)pc, (void*)funcStart, (void*)pcOffset);
// Parse LSDA header.
uint8_t lpStartEncoding = *lsda++;
if (lpStartEncoding != DW_EH_PE_omit) {
readEncodedPointer(&lsda, lpStartEncoding);
}
uint8_t ttypeEncoding = *lsda++;
const uint8_t *classInfo = NULL;
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;
EH_LOG("classInfo=%p", classInfo);
}
// 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 *actionTableStart = callSiteTableEnd;
const uint8_t *callSitePtr = callSiteTableStart;
while(callSitePtr < callSiteTableEnd) {
uintptr_t start = readEncodedPointer(&callSitePtr,
callSiteEncoding);
uintptr_t length = readEncodedPointer(&callSitePtr,
callSiteEncoding);
uintptr_t landingPad = readEncodedPointer(&callSitePtr,
callSiteEncoding);
uintptr_t actionValue = readULEB128(&callSitePtr);
EH_LOG("call site (start=+%p, len=%d, landingPad=+%p, actionValue=%d)",
(void*)start, (int)length, (void*)landingPad, (int)actionValue);
if(landingPad == 0) {
EH_LOG0("no landing pad, skipping");
continue;
}
if((start <= pcOffset) && (pcOffset < (start + length))) {
EH_LOG0("=> call site matches pc");
int exceptionMatched = 0;
if(actionValue) {
const uint8_t *actionEntry = actionTableStart + (actionValue - 1);
EH_LOG("actionEntry=%p", actionEntry);
for(;;) {
// Each emitted DWARF action corresponds to a 2 tuple of
// type info address offset, and action offset to the next
// emitted action.
intptr_t typeInfoOffset = readSLEB128(&actionEntry);
const uint8_t *tempActionEntry = actionEntry;
intptr_t actionOffset = readSLEB128(&tempActionEntry);
EH_LOG("typeInfoOffset=%p actionOffset=%p",
(void*)typeInfoOffset, (void*)actionOffset);
EH_ASSERT((typeInfoOffset >= 0) && "Filter clauses are not supported");
unsigned encodingSize = getEncodingSize(ttypeEncoding);
const uint8_t *typeInfoPtrPtr = classInfo - typeInfoOffset * encodingSize;
uintptr_t typeInfoPtr = readEncodedPointer(&typeInfoPtrPtr, ttypeEncoding);
EH_LOG("encodingSize=%u typeInfoPtrPtr=%p typeInfoPtr=%p",
encodingSize, typeInfoPtrPtr, (void*)typeInfoPtr);
EH_LOG("typeInfo=%s", (char*)typeInfoPtr);
if(typeInfoPtr == 0 || inflight->artiq.typeinfo == typeInfoPtr) {
EH_LOG0("matching action found");
exceptionMatched = 1;
break;
}
if (!actionOffset)
break;
actionEntry += actionOffset;
}
}
if(!(actions & _UA_SEARCH_PHASE)) {
EH_LOG0("=> jumping to landing pad");
if(actions & _UA_HANDLER_FRAME)
inflight->handled = 1;
_Unwind_SetGR(context, __builtin_eh_return_data_regno(0),
(uintptr_t)exceptionObject);
_Unwind_SetGR(context, __builtin_eh_return_data_regno(1),
(uintptr_t)&inflight->artiq);
_Unwind_SetIP(context, funcStart + landingPad);
return _URC_INSTALL_CONTEXT;
} else if(exceptionMatched) {
EH_LOG0("=> handler found");
return _URC_HANDLER_FOUND;
} else {
EH_LOG0("=> handler not found");
return _URC_CONTINUE_UNWIND;
}
}
}
return _URC_CONTINUE_UNWIND;
}
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