01.02.2016 21:52, Oleg Nesterov пишет:
Stas, I probably missed something, but I don't understand your concerns,
On 02/01, Stas Sergeev wrote:
01.02.2016 21:04, Oleg Nesterov пишет:
Yes, and SS_FORCE means "I know what I do", looks very simple.
But to me its not because I don't know what to do with
uc_stack after SS_FORCE is applied.
Nothing? restore_sigaltstack() should work as expected?
That's likely the reason for EPERM: restore_sigaltstack()
does the job, so manual modifications are disallowed.
Allowing them will bring in the surprises where the changes
done by the user are ignored.
I won't argue, but to me it would be better to keep this EPERM if !force.
Just because we should avoid the incompatible changes if possible.
Ok then. Lets implement SS_FORCE.
What semantic should it have wrt uc_stack?
sigaltstack(SS_DISABLE | SS_FORCE);
swapcontext();
sigaltstack(set up new_sas);
rt_sigreturn();
Yes, or
sigaltstack({ DISABLE | FORCE}, &old_ss);
swapcontext();
sigaltstack(&old_ss, NULL);
rt_sigreturn();
and if you are going to return from sighandler you do not even need the 2nd
sigaltstack(), you can rely on sigreturn.
Yes, that's what I do in my app already.
But its only there when SA_SIGINFO is used.
What's at the end? Do we want a surprise for the user
that he's new_sas got ignored?
Can't understand.... do you mean "set up new_sas" will be ignored because
rt_sigreturn() does restore_sigaltstack() ? I see no problem here...
Allowing the modifications that were previously EPERMed
but will now be silently ignored, may be seen as a problem.
But if it isn't - fine, lets code that.
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