[uml-devel] Re: Some changes in SKAS0

[Bodo Stroesser <bstroesser@fujitsu-siemens.com>]

Jeff Dike wrote:
> 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
Sorry, late reply: you are right.

	Bodo


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