svn commit: r307971 - head/sys/mips/include

[Konstantin Belousov]

On Thu, Oct 27, 2016 at 03:08:01PM -0700, John Baldwin wrote:
> 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.
This should be mcontext_t instead of ucontext_t.

> 
> 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 It's purpose has been superseded by SA_SIGINFO (which is more portable)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.)

I do not think that this is a practical option. I know that struct
sigcontext is used by nongnu libunwind. Quick search identifies mono and
go as consumers as well.