mirror of
https://github.com/matrix-construct/construct
synced 2024-05-18 10:53:48 +02:00
ircd::fpe: Condition experimental asynchronous exception use.
This commit is contained in:
Jason Volk
parent
451dbe5def
commit
19ef3cfb67
37
configure.ac
37
configure.ac
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@ -366,6 +366,33 @@ AM_COND_IF([GENERIC],
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CXXFLAGS+=" -march=native"
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])
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dnl !!! Experimental !!!
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dnl
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dnl Allows a signal handler to throw a C++ exception if the signal is from
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dnl a CPU trap on an instruction (ex. SIGFPE from a floating point divide
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dnl by zero). This allows the signal handler to transfer control to the
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dnl catch block wrapping the area which errored, thereby aborting any further
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dnl execution after the signal was received which would have to manually check
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dnl for such an error after each floating point operation and throw.
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AC_ARG_ENABLE(asyncexcept, AC_HELP_STRING([--enable-asyncexcept], [Enable experimental asynchronous exceptions]),
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[
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asyncexcept="yes"
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], [
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asyncexcept="no"
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])
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dnl CHARYBDIS_C_GCC_TRY_FLAGS([-fnon-call-exceptions], charybdis_cv_c_gcc_f_non_call_exceptions)
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if test "$asyncexcept" = "yes"; then
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IRCD_DEFINE(USE_ASYNC_EXCEPTIONS, [1], [Experimental asynchronous exceptions are supported])
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CXXFLAGS+=" -fasynchronous-unwind-tables"
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CXXFLAGS+=" -fnon-call-exceptions"
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fi
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AM_CONDITIONAL([ASYNCEXCEPT], [[[[ $asyncexcept = "yes" ]]]])
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dnl
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dnl Optimization
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dnl
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@ -415,15 +442,6 @@ dnl CXXFLAGS+=" -fcheck-pointer-bounds"
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CXXFLAGS+=" -fchkp-instrument-marked-only"
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CXXFLAGS+=" -fstack-protector-explicit"
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dnl !!! Experimental !!!
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dnl Allows a signal handler to throw a C++ exception if the signal is from
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dnl a CPU trap on an instruction (ex. SIGFPE from a floating point divide
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dnl by zero). This allows the signal handler to transfer control to the
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dnl catch block wrapping the area which errored, thereby aborting any further
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dnl execution after the SIGFPE was received which would have to manually check
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dnl for such an error after each floating point operation and throw.
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CXXFLAGS+=" -fnon-call-exceptions"
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dnl -ffriend-injection allows us to deduplicate declarations of friend
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dnl functions in both the friend class and the enclosing namespace
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CXXFLAGS+=" -ffriend-injection"
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@ -636,6 +654,7 @@ RB_CHK_SYSHEADER(regex, [REGEX])
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dnl unix platform
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RB_CHK_SYSHEADER(unistd.h, [UNISTD_H])
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RB_CHK_SYSHEADER(signal.h, [SIGNAL_H])
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RB_CHK_SYSHEADER(sys/time.h, [SYS_TIME_H])
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RB_CHK_SYSHEADER(sys/stat.h, [SYS_STAT_H])
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RB_CHK_SYSHEADER(sys/statvfs.h, [SYS_STATVFS_H])
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@ -11,11 +11,6 @@
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#pragma once
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#define HAVE_IRCD_FPE_H
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extern "C"
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{
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struct sigaction;
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};
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namespace ircd::fpe
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{
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struct errors_handle;
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@ -27,6 +22,9 @@ namespace ircd::fpe
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void throw_errors(const ushort &flags);
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}
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/// Perform a single floating point operation at a time within the scope
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/// of fpe::errors_handle. After each operation check the floating point
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/// unit for an error status flag and throw a C++ exception.
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struct ircd::fpe::errors_handle
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{
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fexcept_t theirs;
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@ -40,6 +38,18 @@ struct ircd::fpe::errors_handle
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~errors_handle() noexcept(false);
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};
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// We don't include <signal.h> in IRCd's standard include list. Instead that
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// is conditionally included in the appropriate .cc file. All we require here
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// is a forward declaration.
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extern "C"
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{
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struct sigaction;
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};
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/// Experimental floating-point error handling strategy which throws
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/// a C++ exception directly from the instruction which faulted the FPU.
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/// The stack will unwind directly from that point in the execution and
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/// control will be transferred to the appropriate catch block.
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struct ircd::fpe::errors_throw
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{
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custom_ptr<struct sigaction> their_sa;
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75
ircd/fpe.cc
75
ircd/fpe.cc
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@ -8,7 +8,7 @@
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// copyright notice and this permission notice is present in all copies. The
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// full license for this software is available in the LICENSE file.
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#include <signal.h>
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#include <RB_INC_SIGNAL_H
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#ifndef __GNUC__
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#pragma STDC FENV_ACCESS on
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@ -18,34 +18,38 @@
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// errors_throw
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//
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#if defined(IRCD_USE_ASYNC_EXCEPTIONS) \
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&& defined(HAVE_SIGNAL_H) \
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&& defined(__GNUC__) \
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namespace ircd::fpe
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{
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constexpr const size_t &SA_HEAP_MAX {64};
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/// The maximum number of sigactions we can maintain in our internal space.
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constexpr const size_t &SA_HEAP_MAX {48};
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/// This internal buffer is used for holding instances of struct sigaction
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/// as our external interface only has a forward-declaration and our class
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/// only maintains a pointer member for it.
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thread_local allocator::fixed<struct sigaction, SA_HEAP_MAX> sa_heap;
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extern const std::exception_ptr sigfpe_eptr;
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extern "C" void ircd_fpe_handle_sigfpe(int signum, siginfo_t *const si, void *const uctx);
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}
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decltype(ircd::fpe::sigfpe_eptr)
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ircd::fpe::sigfpe_eptr
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{
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std::make_exception_ptr(std::domain_error
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{
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"Floating Point Exception"
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})
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};
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__attribute__((noreturn))
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void
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[[noreturn]] void
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ircd::fpe::ircd_fpe_handle_sigfpe(int signum,
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siginfo_t *const si,
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void *const uctx)
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{
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assert(si);
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assert(signum == SIGFPE);
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std::rethrow_exception(sigfpe_eptr); //TODO: still malloc()'s :/
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//TODO: due to __cxa_allocate_exception() this still malloc()'s :/
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// We can't have a floating point error within malloc() and family
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// or this signal will cleave it at an intermediate state and reenter.
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throw std::domain_error
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{
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reflect_sicode(si->si_code)
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};
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}
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//
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@ -86,6 +90,29 @@ noexcept
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syscall(std::fesetexceptflag, &their_fe, FE_ALL_EXCEPT);
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}
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#else // IRCD_USE_ASYNC_EXCEPTIONS
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//
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// errors_throw::errors_throw
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//
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__attribute__((noreturn))
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ircd::fpe::errors_throw::errors_throw()
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{
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throw assertive
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{
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"Not implemented in this environment."
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};
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}
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ircd::fpe::errors_throw::~errors_throw()
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noexcept
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{
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assert(0);
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}
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#endif // IRCD_USE_ASYNC_EXCEPTIONS
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//
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// errors_handle
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//
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@ -182,14 +209,16 @@ ircd::fpe::reflect_sicode(const int &code)
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{
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switch(code)
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{
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case FPE_INTDIV: return "INTDIV";
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case FPE_INTOVF: return "INTOVF";
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case FPE_FLTDIV: return "FLTDIV";
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case FPE_FLTOVF: return "FLTOVF";
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case FPE_FLTUND: return "FLTUND";
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case FPE_FLTRES: return "FLTRES";
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case FPE_FLTINV: return "FLTINV";
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case FPE_FLTSUB: return "FLTSUB";
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#ifdef HAVE_SIGNAL_H
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case FPE_INTDIV: return "INTDIV";
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case FPE_INTOVF: return "INTOVF";
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case FPE_FLTDIV: return "FLTDIV";
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case FPE_FLTOVF: return "FLTOVF";
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case FPE_FLTUND: return "FLTUND";
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case FPE_FLTRES: return "FLTRES";
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case FPE_FLTINV: return "FLTINV";
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case FPE_FLTSUB: return "FLTSUB";
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#endif // HAVE_SIGNAL_H
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}
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return "?????";
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