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Diffstat (limited to 'src/Unwind-sjlj.c')
| -rw-r--r-- | src/Unwind-sjlj.c | 468 |
1 files changed, 468 insertions, 0 deletions
diff --git a/src/Unwind-sjlj.c b/src/Unwind-sjlj.c new file mode 100644 index 000000000000..f9256b5a9260 --- /dev/null +++ b/src/Unwind-sjlj.c @@ -0,0 +1,468 @@ +//===--------------------------- 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 |