Date: Mon, 24 Sep 2001 22:40:06 -0700 (PDT) From: Matt Dillon <dillon@earth.backplane.com> To: Peter Wemm <peter@wemm.org> Cc: Ian Dowse <iedowse@maths.tcd.ie>, Julian Elischer <julian@elischer.org>, hackers@FreeBSD.ORG Subject: Re: Patch to test kstack usage. Message-ID: <200109250540.f8P5e6499443@earth.backplane.com> References: <20010925051923.6CA2F3808@overcee.netplex.com.au>
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:
:Matt Dillon wrote:
:> This isn't perfect but it should be a good start in regards to
:> testing kstack use. This patch is against -stable. It reports
:> kernel stack use on process exit and will generate a 'Kernel stack
:> underflow' message if it detects an underflow. It doesn't panic,
:> so for a fun time you can leave UPAGES at 2 and watch in horror.
:
:It is checking against the wrong guard value. It should be u_guard2.
:
:FWIW; the max stack available is 4688 bytes on a standard 4.x system. Yes,
:that is too freaking close. Also, the maximum usage depends on what sort
:of cards you have in the system.. If you have a heavy tty user (eg: a 32+
I looked at it fairly carefully. It has got to be u_guard... at the
end of struct user, at least until you do that MFC. The ptrace code
appears to mess around with u_kproc quite a bit. And when you rip out
u_kproc it still needs to be at the end, after the coredump structure
(though for i386 the coredump structure is empty)... because interrupts
can occur during a core dump.
:port serial card) then you have lots of tty interrupts nesting as well.
:Having the ppp/sl/plip drivers in the system partly negates the effect of
:this though since it wires the net/tty interrupt masks together.
:...
:Cheers,
:-Peter
:--
:Peter Wemm - peter@FreeBSD.org; peter@yahoo-inc.com; peter@netplex.com.au
:"All of this is for nothing if we don't go to the stars" - JMS/B5
:
Yah... the test I ran was just a couple of seconds worth of playing
around over ssh. I expect the worst case to be a whole lot worse.
We're going to have to bump up UPAGES to 3 in 4.x, there's no question
about it. I'm going to do it tonight.
-Matt
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