[CRIU] [PATCH 7/8] restore: Add restoration of alternative signal stack

[Cyrill Gorcunov]

On Tue, Jun 18, 2013 at 06:15:58PM +0400, Andrew Vagin wrote:
> > 
> > We call sigaltstack in only one case -- on dump, to fetch the value(s)
> > dumpee has. On restore we have 2 ways
> > 
> >  - either call for sigaltstack explicitly in restorer.c right before
> >    we call for sigreturn
> You use this way in these patches.
> > 
> >  - either pass stack value to sigreturn call and allow the kernel to
> >    restore stack for us
> > 
> > I chose second way and simply tune up sigframe. Sounds reasonable?
> You are going to implement the second way...
> 
> I vote for the second way too.

Nope :-)

[patch dump: Add dumping of alternative signal stack]

	init_thread
		...
		ret = sys_sigaltstack(NULL, &args->sas);
		...

	init
		...
		ret = sys_sigaltstack(NULL, &args->sas);
		...

[patch restore: Add restoration of alternative signal stack]

	__export_restore_task
		...
		if (args->has_sas)
			setup_sas(rt_sigframe, &args->sas);

	construct_sigframe
		...
		setup_sas(sigframe, core->sas);

ie explicit sys_sigaltstack are only on dump. restore simply
tunes up sigframe but doesn't call for sys_sigaltstack.