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Date:      Thu, 27 Oct 2016 15:08:01 -0700
From:      John Baldwin <jhb@freebsd.org>
To:        src-committers@freebsd.org
Cc:        svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   Re: svn commit: r307971 - head/sys/mips/include
Message-ID:  <11698910.Akp5I7OyZ5@ralph.baldwin.cx>
In-Reply-To: <201610261737.u9QHb8Ps036831@repo.freebsd.org>
References:  <201610261737.u9QHb8Ps036831@repo.freebsd.org>

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On Wednesday, October 26, 2016 05:37:08 PM John Baldwin wrote:
> Author: jhb
> Date: Wed Oct 26 17:37:08 2016
> New Revision: 307971
> URL: https://svnweb.freebsd.org/changeset/base/307971
> 
> Log:
>   Correct definition of 'struct sigcontext' on MIPS.
>   
>   Add missing fields ('sr' and 'mc_tls') to 'struct sigcontext'.
>   
>   The kernel doesn't use 'struct sigcontext' but instead uses 'ucontext_t'
>   which includes 'mcontext_t' in 'struct sigframe' to build the signal frame.
>   As a result, this change is not an ABI change but simply making
>   'struct sigcontext' correct.  Note that 'struct sigcontext' is only used
>   for "Traditional BSD style" signal handlers.
>   
>   While here, rename the 'xxx' field to '__spare__' to match 'mcontext_t'.
>   
>   Sponsored by:	DARPA, AFRL

We should perhaps a static assertion somewhere that
sizeof(sigset_t) + sizeof(ucontext_t) == sizeof(struct sigcontext) if
that is really true of all of our architectures.

Alternatively, we might consider retiring 'struct sigcontext' altogether.
It's purpose has been superseded by SA_SIGINFO (which is more portable)
which has been around for quite a while now.  As a first step I guess
we could try an exp-run with 'struct sigcontext' removed.  (We should
have ditched this in 5.0 since we have a separate sendsig/sigreturn path
for FreeBSD 4.x already.  Oh well.)

-- 
John Baldwin



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