[uml-devel] Re: Some changes in SKAS0

[Jeff Dike <jdike@addtoit.com>]

From our discussion yesterday, ...

On Fri, Jul 15, 2005 at 05:36:34PM +0200, Bodo Stroesser wrote:
> So I thought about avoiding the sigreturn at all. Working on
> this I found out some small points:

I kept this patch

> - there is a bug (typo) in wait_stub_done()

but dropped these two, plus my dont-save-fpregs patch.  Correct?

> - stopping stub_segv_handler with a "breakpoint" without
>   calling sigreturn, lets SIGSEGV being blocked after that.
>   At the next SIGSEGV, I see stub_wait_done() calling panic
>   just as with Rob's problem. And I see the child being gone!
>   I understand, that the host unblocks SIGSEGV and sets the
>   handler to SIG_DFL. But I don't understand, why the child
>   already is gone after the waitpid(), without resuming it.
>   I guess, this is the reason for Rob not being able to debug
>   the problem.
>   Thus I added SA_NOMASK to the flags for the handler.
> 
> - I changed the additional mask for the handler to be empty.
>   The only exception is x86_64, that currently must use sigreturn
>   and therefore still masks SIGUSR1 while the handler runs.
>   In skas, userspace shouldn't receive SIGIO or SIGWINCH (I hope
>   I'm right here?), SIGVTALRM already is handled by wait_stub_done.
>   Then I changed i386's stub_segv_handler to stop using "int3"
>   immediately after saving faultinfo.
>   This new method saves some syscalls on i386 and s390 and
>   simplifies s390.

				Jeff


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