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Support sigaction with SIG_DFL and SA_SIGINFO. #55673

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Jul 15, 2021
Merged

Support sigaction with SIG_DFL and SA_SIGINFO. #55673

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75 changes: 46 additions & 29 deletions src/coreclr/pal/src/exception/signal.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -344,6 +344,26 @@ bool IsRunningOnAlternateStack(void *context)
#endif // HAVE_MACH_EXCEPTIONS
}

static bool IsSaSigInfo(struct sigaction* action)
{
return (action->sa_flags & SA_SIGINFO) != 0;
}

static bool IsSigDfl(struct sigaction* action)
{
// macOS can return sigaction with SIG_DFL and SA_SIGINFO.
// SA_SIGINFO means we should use sa_sigaction, but here we want to check sa_handler.
// So we ignore SA_SIGINFO when sa_sigaction and sa_handler are at the same address.
return (&action->sa_handler == (void*)&action->sa_sigaction || !IsSaSigInfo(action)) &&
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A nit - can you please add ( ) to explicitly express the precedence in all the composite conditions? It is a preferred style in this codebase. Like this:

return ((&action->sa_handler == (void*)&action->sa_sigaction) || !IsSaSigInfo(action)) &&
(action->sa_handler == SIG_DFL));

action->sa_handler == SIG_DFL;
}

static bool IsSigIgn(struct sigaction* action)
{
return (&action->sa_handler == (void*)&action->sa_sigaction || !IsSaSigInfo(action)) &&
action->sa_handler == SIG_IGN;
}

/*++
Function :
invoke_previous_action
Expand All @@ -363,44 +383,41 @@ static void invoke_previous_action(struct sigaction* action, int code, siginfo_t
{
_ASSERTE(action != NULL);

if (action->sa_flags & SA_SIGINFO)
if (IsSigIgn(action))
{
// Directly call the previous handler.
_ASSERTE(action->sa_sigaction != NULL);
action->sa_sigaction(code, siginfo, context);
}
else
{
if (action->sa_handler == SIG_IGN)
if (signalRestarts)
{
if (signalRestarts)
{
// This signal mustn't be ignored because it will be restarted.
PROCAbort(code);
}
return;
// This signal mustn't be ignored because it will be restarted.
PROCAbort(code);
}
else if (action->sa_handler == SIG_DFL)
return;
}
else if (IsSigDfl(action))
{
if (signalRestarts)
{
if (signalRestarts)
{
// Restore the original and restart h/w exception.
restore_signal(code, action);
}
else
{
// We can't invoke the original handler because returning from the
// handler doesn't restart the exception.
PROCAbort(code);
}
// Restore the original and restart h/w exception.
restore_signal(code, action);
}
else
{
// Directly call the previous handler.
_ASSERTE(action->sa_handler != NULL);
action->sa_handler(code);
// We can't invoke the original handler because returning from the
// handler doesn't restart the exception.
PROCAbort(code);
}
}
else if (IsSaSigInfo(action))
{
// Directly call the previous handler.
_ASSERTE(action->sa_sigaction != NULL);
action->sa_sigaction(code, siginfo, context);
}
else
{
// Directly call the previous handler.
_ASSERTE(action->sa_handler != NULL);
action->sa_handler(code);
}

PROCNotifyProcessShutdown(IsRunningOnAlternateStack(context));

Expand Down
33 changes: 21 additions & 12 deletions src/libraries/Native/Unix/System.Native/pal_signal.c
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Original file line number Diff line number Diff line change
Expand Up @@ -63,16 +63,21 @@ static bool IsSaSigInfo(struct sigaction* action)
#pragma clang diagnostic pop
}

static bool IsSigIgn(struct sigaction* action)
static bool IsSigDfl(struct sigaction* action)
{
assert(action);
return !IsSaSigInfo(action) && action->sa_handler == SIG_IGN;
// macOS can return sigaction with SIG_DFL and SA_SIGINFO.
// SA_SIGINFO means we should use sa_sigaction, but here we want to check sa_handler.
// So we ignore SA_SIGINFO when sa_sigaction and sa_handler are at the same address.
return (&action->sa_handler == (void*)&action->sa_sigaction || !IsSaSigInfo(action)) &&
action->sa_handler == SIG_DFL;
}

static bool IsSigDfl(struct sigaction* action)
static bool IsSigIgn(struct sigaction* action)
{
assert(action);
return !IsSaSigInfo(action) && action->sa_handler == SIG_DFL;
return (&action->sa_handler == (void*)&action->sa_sigaction || !IsSaSigInfo(action)) &&
action->sa_handler == SIG_IGN;
}

static bool TryConvertSignalCodeToPosixSignal(int signalCode, PosixSignal* posixSignal)
Expand Down Expand Up @@ -209,15 +214,19 @@ static void SignalHandler(int sig, siginfo_t* siginfo, void* context)
if (!IsCancelableTerminationSignal(sig))
{
struct sigaction* origHandler = OrigActionFor(sig);
if (IsSaSigInfo(origHandler))
{
assert(origHandler->sa_sigaction);
origHandler->sa_sigaction(sig, siginfo, context);
}
else if (origHandler->sa_handler != SIG_IGN &&
origHandler->sa_handler != SIG_DFL)
if (!IsSigDfl(origHandler) && !IsSigIgn(origHandler))
{
origHandler->sa_handler(sig);
if (IsSaSigInfo(origHandler))
{
assert(origHandler->sa_sigaction);
origHandler->sa_sigaction(sig, siginfo, context);
}
else
{
assert(origHandler->sa_handler);
origHandler->sa_handler(sig);
}

}
}

Expand Down