Re: [PATCH] Only construct ucontext for SA_SIGINFO signal handlers

[Corinna Vinschen <corinna-cygwin@cygwin.com>]

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On Apr  2 20:30, Jon TURNEY wrote:
> 	* exceptions.cc (call_signal_handler): Only bother to construct
> 	the ucontext for signal handlers with SA_SIGINFO set.

Looks good, except...

> +      ucontext_t context;
> +      ucontext_t *thiscontext = NULL;
> +
> +      /* Only make a context for SA_SIGINFO handlers */
> +      if (this_sa_flags & SA_SIGINFO)
> +        {
> +          context.uc_link = 0;
> +          context.uc_flags = 0;
> +          if (thissi.si_cyg)
> +            memcpy (&context.uc_mcontext, ((cygwin_exception *)thissi.si_cyg)->context(), sizeof(CONTEXT));
> +          else
> +            RtlCaptureContext ((CONTEXT *)&context.uc_mcontext);
> +            /* FIXME: Really this should be the context which the signal interrupted? */
> +
> +          /* FIXME: If/when sigaltstack is implemented, this will need to do
> +             something more complicated */
> +          context.uc_stack.ss_sp = NtCurrentTeb ()->Tib.StackBase;
> +          context.uc_stack.ss_flags = 0;
> +          if (!NtCurrentTeb ()->DeallocationStack)
> +            context.uc_stack.ss_size = (uintptr_t)NtCurrentTeb ()->Tib.StackLimit - (uintptr_t)NtCurrentTeb ()->Tib.StackBase;
> +          else
> +            context.uc_stack.ss_size = (uintptr_t)NtCurrentTeb ()->DeallocationStack - (uintptr_t)NtCurrentTeb ()->Tib.StackBase;
> +
> +          thiscontext = &context;
> +        }


>        sigset_t this_oldmask = set_process_mask_delta ();
> -      thiscontext.uc_sigmask = this_oldmask;
> +      context.uc_sigmask = this_oldmask;
         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

This call to set_process_mask_delta() should occur before constructing
the context, so that filling in uc_sigmask can be moved into the above
`'if' branch.

On second thought, isn't this slightly wrong anyway?  Shouldn't that be

         context.uc_sigmask = _my_tls.sigmask;
	 context.uc_mcontext.oldmask = this_oldmask;

?


Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Maintainer                 cygwin AT cygwin DOT com
Red Hat

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