//===--------------------------- Unwind-sjlj.c ----------------------------===//
//
// 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.
//
//
// Implements setjump-longjump based C++ exceptions
//
//===----------------------------------------------------------------------===//
#include <unwind.h>
#include <stdint.h>
#include <stdbool.h>
#include <stdlib.h>
#include "config.h"
#include "unwind_ext.h"
//
// 32-bit iOS uses setjump/longjump based C++ exceptions.
// Other architectures use "zero cost" exceptions.
//
// With SJLJ based exceptions, any function that has a catch clause or needs to
// do any clean up when an exception propagates through it, needs to call
// _Unwind_SjLj_Register() at the start of the function and
// _Unwind_SjLj_Unregister() at the end. The register function is called with
// the address of a block of memory in the function's stack frame. The runtime
// keeps a linked list (stack) of these blocks - one per thread. The calling
// function also sets the personality and lsda fields of the block.
//
#if _LIBUNWIND_BUILD_SJLJ_APIS
struct _Unwind_FunctionContext {
// next function in stack of handlers
struct _Unwind_FunctionContext *prev;
// set by calling function before registering to be the landing pad
uintptr_t resumeLocation;
// set by personality handler to be parameters passed to landing pad function
uintptr_t resumeParameters[4];
// set by calling function before registering
__personality_routine personality; // arm offset=24
uintptr_t lsda; // arm offset=28
// variable length array, contains registers to restore
// 0 = r7, 1 = pc, 2 = sp
void *jbuf[];
};
/// Called at start of each function that catches exceptions
_LIBUNWIND_EXPORT void
_Unwind_SjLj_Register(struct _Unwind_FunctionContext *fc) {
fc->prev = __Unwind_SjLj_GetTopOfFunctionStack();
__Unwind_SjLj_SetTopOfFunctionStack(fc);
}
/// Called at end of each function that catches exceptions
_LIBUNWIND_EXPORT void
_Unwind_SjLj_Unregister(struct _Unwind_FunctionContext *fc) {
__Unwind_SjLj_SetTopOfFunctionStack(fc->prev);
}
static _Unwind_Reason_Code
unwind_phase1(struct _Unwind_Exception *exception_object) {
_Unwind_FunctionContext_t c = __Unwind_SjLj_GetTopOfFunctionStack();
_LIBUNWIND_TRACE_UNWINDING("unwind_phase1: initial function-context=%p\n", c);
// walk each frame looking for a place to stop
for (bool handlerNotFound = true; handlerNotFound; c = c->prev) {
// check for no more frames
if (c == NULL) {
_LIBUNWIND_TRACE_UNWINDING("unwind_phase1(ex_ojb=%p): reached "
"bottom => _URC_END_OF_STACK\n",
exception_object);
return _URC_END_OF_STACK;
}
_LIBUNWIND_TRACE_UNWINDING("unwind_phase1: function-context=%p\n", c);
// if there is a personality routine, ask it if it will want to stop at this
// frame
if (c->personality != NULL) {
_LIBUNWIND_TRACE_UNWINDING("unwind_phase1(ex_ojb=%p): calling "
"personality function %p\n",
exception_object, c->personality);
_Unwind_Reason_Code personalityResult = (*c->personality)(
1, _UA_SEARCH_PHASE, exception_object->exception_class,
exception_object, (struct _Unwind_Context *)c);
switch (personalityResult) {
case _URC_HANDLER_FOUND:
// found a catch clause or locals that need destructing in this frame
// stop search and remember function context
handlerNotFound = false;
exception_object->private_2 = (uintptr_t) c;
_LIBUNWIND_TRACE_UNWINDING("unwind_phase1(ex_ojb=%p): "
"_URC_HANDLER_FOUND\n", exception_object);
return _URC_NO_REASON;
case _URC_CONTINUE_UNWIND:
_LIBUNWIND_TRACE_UNWINDING("unwind_phase1(ex_ojb=%p): "
"_URC_CONTINUE_UNWIND\n", exception_object);
// continue unwinding
break;
default:
// something went wrong
_LIBUNWIND_TRACE_UNWINDING(
"unwind_phase1(ex_ojb=%p): _URC_FATAL_PHASE1_ERROR\n",
exception_object);
return _URC_FATAL_PHASE1_ERROR;
}
}
}
return _URC_NO_REASON;
}
static _Unwind_Reason_Code
unwind_phase2(struct _Unwind_Exception *exception_object) {
_LIBUNWIND_TRACE_UNWINDING("unwind_phase2(ex_ojb=%p)\n", exception_object);
// walk each frame until we reach where search phase said to stop
_Unwind_FunctionContext_t c = __Unwind_SjLj_GetTopOfFunctionStack();
while (true) {
_LIBUNWIND_TRACE_UNWINDING("unwind_phase2s(ex_ojb=%p): context=%p\n",
exception_object, c);
// check for no more frames
if (c == NULL) {
_LIBUNWIND_TRACE_UNWINDING("unwind_phase2(ex_ojb=%p): unw_step() reached "
"bottom => _URC_END_OF_STACK\n",
exception_object);
return _URC_END_OF_STACK;
}
// if there is a personality routine, tell it we are unwinding
if (c->personality != NULL) {
_Unwind_Action action = _UA_CLEANUP_PHASE;
if ((uintptr_t) c == exception_object->private_2)
action = (_Unwind_Action)(
_UA_CLEANUP_PHASE |
_UA_HANDLER_FRAME); // tell personality this was the frame it marked
// in phase 1
_Unwind_Reason_Code personalityResult =
(*c->personality)(1, action, exception_object->exception_class,
exception_object, (struct _Unwind_Context *)c);
switch (personalityResult) {
case _URC_CONTINUE_UNWIND:
// continue unwinding
_LIBUNWIND_TRACE_UNWINDING(
"unwind_phase2(ex_ojb=%p): _URC_CONTINUE_UNWIND\n",
exception_object);
if ((uintptr_t) c == exception_object->private_2) {
// phase 1 said we would stop at this frame, but we did not...
_LIBUNWIND_ABORT("during phase1 personality function said it would "
"stop here, but now if phase2 it did not stop here");
}
break;
case _URC_INSTALL_CONTEXT:
_LIBUNWIND_TRACE_UNWINDING("unwind_phase2(ex_ojb=%p): "
"_URC_INSTALL_CONTEXT, will resume at "
"landing pad %p\n",
exception_object, c->jbuf[1]);
// personality routine says to transfer control to landing pad
// we may get control back if landing pad calls _Unwind_Resume()
__Unwind_SjLj_SetTopOfFunctionStack(c);
__builtin_longjmp(c->jbuf, 1);
// unw_resume() only returns if there was an error
return _URC_FATAL_PHASE2_ERROR;
default:
// something went wrong
_LIBUNWIND_DEBUG_LOG("personality function returned unknown result %d",
personalityResult);
return _URC_FATAL_PHASE2_ERROR;
}
}
c = c->prev;
}
// clean up phase did not resume at the frame that the search phase said it
// would
return _URC_FATAL_PHASE2_ERROR;
}
static _Unwind_Reason_Code
unwind_phase2_forced(struct _Unwind_Exception *exception_object,
_Unwind_Stop_Fn stop, void *stop_parameter) {
// walk each frame until we reach where search phase said to stop
_Unwind_FunctionContext_t c = __Unwind_SjLj_GetTopOfFunctionStack();
while (true) {
// get next frame (skip over first which is _Unwind_RaiseException)
if (c == NULL) {
_LIBUNWIND_TRACE_UNWINDING("unwind_phase2(ex_ojb=%p): unw_step() reached "
"bottom => _URC_END_OF_STACK\n",
exception_object);
return _URC_END_OF_STACK;
}
// call stop function at each frame
_Unwind_Action action =
(_Unwind_Action)(_UA_FORCE_UNWIND | _UA_CLEANUP_PHASE);
_Unwind_Reason_Code stopResult =
(*stop)(1, action, exception_object->exception_class, exception_object,
(struct _Unwind_Context *)c, stop_parameter);
_LIBUNWIND_TRACE_UNWINDING("unwind_phase2_forced(ex_ojb=%p): "
"stop function returned %d\n",
exception_object, stopResult);
if (stopResult != _URC_NO_REASON) {
_LIBUNWIND_TRACE_UNWINDING("unwind_phase2_forced(ex_ojb=%p): "
"stopped by stop function\n",
exception_object);
return _URC_FATAL_PHASE2_ERROR;
}
// if there is a personality routine, tell it we are unwinding
if (c->personality != NULL) {
__personality_routine p = (__personality_routine) c->personality;
_LIBUNWIND_TRACE_UNWINDING("unwind_phase2_forced(ex_ojb=%p): "
"calling personality function %p\n",
exception_object, p);
_Unwind_Reason_Code personalityResult =
(*p)(1, action, exception_object->exception_class, exception_object,
(struct _Unwind_Context *)c);
switch (personalityResult) {
case _URC_CONTINUE_UNWIND:
_LIBUNWIND_TRACE_UNWINDING("unwind_phase2_forced(ex_ojb=%p): "
"personality returned _URC_CONTINUE_UNWIND\n",
exception_object);
// destructors called, continue unwinding
break;
case _URC_INSTALL_CONTEXT:
_LIBUNWIND_TRACE_UNWINDING("unwind_phase2_forced(ex_ojb=%p): "
"personality returned _URC_INSTALL_CONTEXT\n",
exception_object);
// we may get control back if landing pad calls _Unwind_Resume()
__Unwind_SjLj_SetTopOfFunctionStack(c);
__builtin_longjmp(c->jbuf, 1);
break;
default:
// something went wrong
_LIBUNWIND_TRACE_UNWINDING("unwind_phase2_forced(ex_ojb=%p): "
"personality returned %d, "
"_URC_FATAL_PHASE2_ERROR\n",
exception_object, personalityResult);
return _URC_FATAL_PHASE2_ERROR;
}
}
c = c->prev;
}
// call stop function one last time and tell it we've reached the end of the
// stack
_LIBUNWIND_TRACE_UNWINDING("unwind_phase2_forced(ex_ojb=%p): calling stop "
"function with _UA_END_OF_STACK\n",
exception_object);
_Unwind_Action lastAction =
(_Unwind_Action)(_UA_FORCE_UNWIND | _UA_CLEANUP_PHASE | _UA_END_OF_STACK);
(*stop)(1, lastAction, exception_object->exception_class, exception_object,
(struct _Unwind_Context *)c, stop_parameter);
// clean up phase did not resume at the frame that the search phase said it
// would
return _URC_FATAL_PHASE2_ERROR;
}
/// Called by __cxa_throw. Only returns if there is a fatal error
_LIBUNWIND_EXPORT _Unwind_Reason_Code
_Unwind_SjLj_RaiseException(struct _Unwind_Exception *exception_object) {
_LIBUNWIND_TRACE_API("_Unwind_SjLj_RaiseException(ex_obj=%p)\n", exception_object);
// mark that this is a non-forced unwind, so _Unwind_Resume() can do the right
// thing
exception_object->private_1 = 0;
exception_object->private_2 = 0;
// phase 1: the search phase
_Unwind_Reason_Code phase1 = unwind_phase1(exception_object);
if (phase1 != _URC_NO_REASON)
return phase1;
// phase 2: the clean up phase
return unwind_phase2(exception_object);
}
/// When _Unwind_RaiseException() is in phase2, it hands control
/// to the personality function at each frame. The personality
/// may force a jump to a landing pad in that function, the landing
/// pad code may then call _Unwind_Resume() to continue with the
/// unwinding. Note: the call to _Unwind_Resume() is from compiler
/// geneated user code. All other _Unwind_* routines are called
/// by the C++ runtime __cxa_* routines.
///
/// Re-throwing an exception is implemented by having the code call
/// __cxa_rethrow() which in turn calls _Unwind_Resume_or_Rethrow()
_LIBUNWIND_EXPORT void
_Unwind_SjLj_Resume(struct _Unwind_Exception *exception_object) {
_LIBUNWIND_TRACE_API("_Unwind_SjLj_Resume(ex_obj=%p)\n", exception_object);
if (exception_object->private_1 != 0)
unwind_phase2_forced(exception_object,
(_Unwind_Stop_Fn) exception_object->private_1,
(void *)exception_object->private_2);
else
unwind_phase2(exception_object);
// clients assume _Unwind_Resume() does not return, so all we can do is abort.
_LIBUNWIND_ABORT("_Unwind_SjLj_Resume() can't return");
}
/// Called by __cxa_rethrow().
_LIBUNWIND_EXPORT _Unwind_Reason_Code
_Unwind_SjLj_Resume_or_Rethrow(struct _Unwind_Exception *exception_object) {
_LIBUNWIND_TRACE_API("__Unwind_SjLj_Resume_or_Rethrow(ex_obj=%p), "
"private_1=%ld\n",
exception_object, exception_object->private_1);
// If this is non-forced and a stopping place was found, then this is a
// re-throw.
// Call _Unwind_RaiseException() as if this was a new exception.
if (exception_object->private_1 == 0) {
return _Unwind_SjLj_RaiseException(exception_object);
// should return if there is no catch clause, so that __cxa_rethrow can call
// std::terminate()
}
// Call through to _Unwind_Resume() which distiguishes between forced and
// regular exceptions.
_Unwind_SjLj_Resume(exception_object);
_LIBUNWIND_ABORT("__Unwind_SjLj_Resume_or_Rethrow() called "
"_Unwind_SjLj_Resume() which unexpectedly returned");
}
/// Called by personality handler during phase 2 to get LSDA for current frame.
_LIBUNWIND_EXPORT uintptr_t
_Unwind_GetLanguageSpecificData(struct _Unwind_Context *context) {
_Unwind_FunctionContext_t ufc = (_Unwind_FunctionContext_t) context;
_LIBUNWIND_TRACE_API("_Unwind_GetLanguageSpecificData(context=%p) "
"=> 0x%0lX\n", context, ufc->lsda);
return ufc->lsda;
}
/// Called by personality handler during phase 2 to get register values.
_LIBUNWIND_EXPORT uintptr_t _Unwind_GetGR(struct _Unwind_Context *context,
int index) {
_LIBUNWIND_TRACE_API("_Unwind_GetGR(context=%p, reg=%d)\n",
context, index);
_Unwind_FunctionContext_t ufc = (_Unwind_FunctionContext_t) context;
return ufc->resumeParameters[index];
}
/// Called by personality handler during phase 2 to alter register values.
_LIBUNWIND_EXPORT void _Unwind_SetGR(struct _Unwind_Context *context, int index,
uintptr_t new_value) {
_LIBUNWIND_TRACE_API("_Unwind_SetGR(context=%p, reg=%d, value=0x%0lX)\n"
, context, index, new_value);
_Unwind_FunctionContext_t ufc = (_Unwind_FunctionContext_t) context;
ufc->resumeParameters[index] = new_value;
}
/// Called by personality handler during phase 2 to get instruction pointer.
_LIBUNWIND_EXPORT uintptr_t _Unwind_GetIP(struct _Unwind_Context *context) {
_Unwind_FunctionContext_t ufc = (_Unwind_FunctionContext_t) context;
_LIBUNWIND_TRACE_API("_Unwind_GetIP(context=%p) => 0x%lX\n", context,
ufc->resumeLocation + 1);
return ufc->resumeLocation + 1;
}
/// Called by personality handler during phase 2 to get instruction pointer.
/// ipBefore is a boolean that says if IP is already adjusted to be the call
/// site address. Normally IP is the return address.
_LIBUNWIND_EXPORT uintptr_t _Unwind_GetIPInfo(struct _Unwind_Context *context,
int *ipBefore) {
_Unwind_FunctionContext_t ufc = (_Unwind_FunctionContext_t) context;
*ipBefore = 0;
_LIBUNWIND_TRACE_API("_Unwind_GetIPInfo(context=%p, %p) => 0x%lX\n",
context, ipBefore, ufc->resumeLocation + 1);
return ufc->resumeLocation + 1;
}
/// Called by personality handler during phase 2 to alter instruction pointer.
_LIBUNWIND_EXPORT void _Unwind_SetIP(struct _Unwind_Context *context,
uintptr_t new_value) {
_LIBUNWIND_TRACE_API("_Unwind_SetIP(context=%p, value=0x%0lX)\n",
context, new_value);
_Unwind_FunctionContext_t ufc = (_Unwind_FunctionContext_t) context;
ufc->resumeLocation = new_value - 1;
}
/// Called by personality handler during phase 2 to find the start of the
/// function.
_LIBUNWIND_EXPORT uintptr_t
_Unwind_GetRegionStart(struct _Unwind_Context *context) {
// Not supported or needed for sjlj based unwinding
(void)context;
_LIBUNWIND_TRACE_API("_Unwind_GetRegionStart(context=%p)\n", context);
return 0;
}
/// Called by personality handler during phase 2 if a foreign exception
/// is caught.
_LIBUNWIND_EXPORT void
_Unwind_DeleteException(struct _Unwind_Exception *exception_object) {
_LIBUNWIND_TRACE_API("_Unwind_DeleteException(ex_obj=%p)\n",
exception_object);
if (exception_object->exception_cleanup != NULL)
(*exception_object->exception_cleanup)(_URC_FOREIGN_EXCEPTION_CAUGHT,
exception_object);
}
/// Called by personality handler during phase 2 to get base address for data
/// relative encodings.
_LIBUNWIND_EXPORT uintptr_t
_Unwind_GetDataRelBase(struct _Unwind_Context *context) {
// Not supported or needed for sjlj based unwinding
(void)context;
_LIBUNWIND_TRACE_API("_Unwind_GetDataRelBase(context=%p)\n", context);
_LIBUNWIND_ABORT("_Unwind_GetDataRelBase() not implemented");
}
/// Called by personality handler during phase 2 to get base address for text
/// relative encodings.
_LIBUNWIND_EXPORT uintptr_t
_Unwind_GetTextRelBase(struct _Unwind_Context *context) {
// Not supported or needed for sjlj based unwinding
(void)context;
_LIBUNWIND_TRACE_API("_Unwind_GetTextRelBase(context=%p)\n", context);
_LIBUNWIND_ABORT("_Unwind_GetTextRelBase() not implemented");
}
/// Called by personality handler to get "Call Frame Area" for current frame.
_LIBUNWIND_EXPORT uintptr_t _Unwind_GetCFA(struct _Unwind_Context *context) {
_LIBUNWIND_TRACE_API("_Unwind_GetCFA(context=%p)\n", context);
if (context != NULL) {
_Unwind_FunctionContext_t ufc = (_Unwind_FunctionContext_t) context;
// Setjmp/longjmp based exceptions don't have a true CFA.
// Instead, the SP in the jmpbuf is the closest approximation.
return (uintptr_t) ufc->jbuf[2];
}
return 0;
}
#endif // _LIBUNWIND_BUILD_SJLJ_APIS