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From: Denys Vlasenko <vda.linux@googlemail.com>
To: Ralf Baechle <ralf@linux-mips.org>
Subject: Re: [PATCH v3] kernel/signal.c: fix BUG_ON with SIG128 (MIPS)
Date: Fri, 28 Jun 2013 22:09:21 +0200
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Cc: Oleg Nesterov <oleg@redhat.com>, James Hogan <james.hogan@imgtec.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        David Daney <ddaney@caviumnetworks.com>,
        David Daney <ddaney.cavm@gmail.com>,
        LKML <linux-kernel@vger.kernel.org>, Al Viro <viro@zeniv.linux.org.uk>,
        Kees Cook <keescook@chromium.org>,
        David Daney <david.daney@cavium.com>,
        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        David Howells <dhowells@redhat.com>, Dave Jones <davej@redhat.com>,
        linux-mips@linux-mips.org, stable@vger.kernel.org
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On Wednesday 26 June 2013 18:59, Ralf Baechle wrote:
> On Wed, Jun 26, 2013 at 06:14:52PM +0200, Oleg Nesterov wrote:
> 
> > Or simply remove the BUG_ON(), this can equally confuse wait(status).
> > 128 & 0x7f == 0.
> > 
> > Still I think it would be better to change _NSIG on mips.
> 
> If it was that easy.  That's going to outright break binary compatibility,
> see kernel/signal.c:
> 
> SYSCALL_DEFINE4(rt_sigprocmask, int, how, sigset_t __user *, nset,
>                 sigset_t __user *, oset, size_t, sigsetsize)
> {
>         sigset_t old_set, new_set;
>         int error;
> 
>         /* XXX: Don't preclude handling different sized sigset_t's.  */
>         if (sigsetsize != sizeof(sigset_t))
>                 return -EINVAL;
> 
> There are several more more syscalls performing tests like the above.

Reducing _NSIG to 127 (or 126) doesn't change sigset_t, so should be fine wrt above.