RFR(M): 8139864: Improve handling of stack protection zones.

Sat Dec 5 09:49:28 UTC 2015

Hi Goetz,

thanks for this change! I'm a bit late to review this, so feel free to work
in my suggestions or not. They are not terribly important, mostly just
cosmetics:

http://cr.openjdk.java.net/~goetz/webrevs/8139864-StackZones/webrev.01/src/share/vm/runtime/thread.hpp.udiff.html

There is no reason to publish set_stack_xxxx_zone_size(). They could be
file local in thread.cpp (if _stack_xxx_zone_size were made file local too)
or at least made class private.

---

http://cr.openjdk.java.net/~goetz/webrevs/8139864-StackZones/webrev.01/src/cpu/aarch64/vm/macroAssembler_aarch64.cpp.udiff.html
http://cr.openjdk.java.net/~goetz/webrevs/8139864-StackZones/webrev.01/src/cpu/sparc/vm/macroAssembler_sparc.cpp.udiff.html
http://cr.openjdk.java.net/~goetz/webrevs/8139864-StackZones/webrev.01/src/cpu/sparc/vm/sharedRuntime_sparc.cpp.udiff.html
etc

All places where you calculate the number of real shadow pages by
(JavaThread::stack_shadow_zone_size() / os::vm_page_size()) could be made
more readable with another method like
"JavaThread::num_stack_shadow_pages()", which would return the number of
real stack shadow pages.

----

http://cr.openjdk.java.net/~goetz/webrevs/8139864-StackZones/webrev.01/src/cpu/aarch64/vm/templateInterpreter_aarch64.cpp.udiff.html

http://cr.openjdk.java.net/~goetz/webrevs/8139864-StackZones/webrev.01/src/cpu/x86/vm/cppInterpreter_x86.cpp.udiff.html

http://cr.openjdk.java.net/~goetz/webrevs/8139864-StackZones/webrev.01/src/cpu/x86/vm/templateInterpreter_x86_32.cpp.udiff.html

etc.

All places where max_bang_size is calculated could be made more readable by
using MAX2.

----

http://cr.openjdk.java.net/~goetz/webrevs/8139864-StackZones/webrev.01/src/share/vm/runtime/globals.hpp.udiff.html

missing period after "If pages are bigger yellow zone is aligned up" on
StackYellowPages/StackRedPages.

missing period after "This should exceed the depth of the VM and native
call stack" for StackShadowPages.

----

Apart from that, I would second Coleen's request for a compile-time check
against using the old StackXXXPages parameters directly.

Kind Regards, Thomas

On Tue, Dec 1, 2015 at 5:10 PM, Lindenmaier, Goetz <
goetz.lindenmaier at sap.com> wrote:

> Hi,
>
> I ran the change through our night builds - all jtreg tests are clean.
> (and the other tests as well.)
> I prepared a complete and - from my side - final webrev:
> http://cr.openjdk.java.net/~goetz/webrevs/8139864-StackZones/webrev.01/
> This includes the fixes proposed by David as well as some minor fixes to
> get it compiling on windows.
>
> So to capture the change still the split webrevs might be a good starting
> point:
>
> http://cr.openjdk.java.net/~goetz/webrevs/8139864-StackZones/webrev.00-basic/
>
> http://cr.openjdk.java.net/~goetz/webrevs/8139864-StackZones/webrev.00-spread/
>
> David, can I consider this reviewed?
> I please need a second reviewer and a sponsor.
>
> Best regards,
>   Goetz.
>
>
> > -----Original Message-----
> > From: hotspot-runtime-dev [mailto:hotspot-runtime-dev-
> > bounces at openjdk.java.net] On Behalf Of Lindenmaier, Goetz
> > Sent: Freitag, 27. November 2015 10:28
> > To: David Holmes <david.holmes at oracle.com>; Coleen Phillimore
> > (coleen.phillimore at oracle.com) <coleen.phillimore at oracle.com>; hotspot-
> > runtime-dev at openjdk.java.net
> > Subject: RE: RFR(M): 8139864: Improve handling of stack protection zones.
> >
> > Hi David,
> >
> > thanks for looking at this change!
> > I edited the thinks you remarked, thanks for spotting that.
> >
> > I'll run the change through our testing to assure I catch all
> > issues with jtreg.  We have some systems with other page sizes.
> >
> > Best regards,
> >   Goetz.
> >
> > > -----Original Message-----
> > > From: David Holmes [mailto:david.holmes at oracle.com]
> > > Sent: Freitag, 27. November 2015 06:33
> > > To: Lindenmaier, Goetz <goetz.lindenmaier at sap.com>; Coleen Phillimore
> > > (coleen.phillimore at oracle.com) <coleen.phillimore at oracle.com>;
> > hotspot-
> > > runtime-dev at openjdk.java.net
> > > Subject: Re: RFR(M): 8139864: Improve handling of stack protection
> zones.
> > >
> > > Hi Goetz,
> > >
> > > On 26/11/2015 1:55 AM, Lindenmaier, Goetz wrote:
> > > > Hi,
> > > >
> > > > For a description of the problem see
> > > https://bugs.openjdk.java.net/browse/JDK-8139864
> > > >
> > > > This is a first version of my implementation of the proposal '3'
> that was
> > > discussed here:
> > > > http://mail.openjdk.java.net/pipermail/hotspot-runtime-dev/2015-
> > > October/016085.html
> > > > which is continued here
> > > > http://mail.openjdk.java.net/pipermail/hotspot-runtime-dev/2015-
> > > November/016805.html
> > > >
> > > > Opposed to my original proposal, I did not introduce new flags. I
> > > documented the
> > > > old flags to specify 4K pages, and save the ergonomic values in
> static
> > fields
> > > of JavaThread.
> > > > This avoids two sets of similar flags.
> > >
> > > That seems like a good compromise. Though not sure about placement in
> > > JavaThread when everything else stack-related seems to be in os class.
> > >
> > > > To simplify reviewing, I made two webrevs for the first round:
> > > > The basic changes to determining the sizes of the zones to protect
> are in
> > > this partial webrev:
> > > > http://cr.openjdk.java.net/~goetz/webrevs/8139864-
> > > StackZones/webrev.00-basic/
> > > > This contains the functional change.
> > >
> > > This seems okay to me - though I don't claim expertise in this area.
> > >
> > > A couple of minor nits:
> > >
> > > src/share/vm/runtime/thread.hpp
> > >
> > > 1364   static size_t stack_yellow_zone_size() {
> > > 1365     assert(_stack_red_zone_size > 0, "Don't call this before the
> > > field is initialized.");
> > >
> > > The assert should check yellow size
> > >
> > > 1383   static size_t stack_shadow_zone_size() {
> > > 1384     assert(_stack_red_zone_size > 0, "Don't call this before the
> > > field is initialized.");
> > >
> > > The assert should check shadow size.
> > >
> > > ---
> > >
> > > src/share/vm/runtime/globals.hpp
> > >
> > > kB -> KB
> > >
> > > > I also fixed the bounds of ThreadStackSize and
> CompilerThreadStackSize
> > > which
> > > > allowed to specify stacks >> max_intx.
> > >
> > > Ok - not sure how this was missed given we do the same for
> > > VMThreadStackSize :)
> > >
> > >
> > > > If we agree on this, I need to replace all occurrences of the three
> flags by
> > > accessor calls.
> > > > This allows to simplify all the platform code which computed the
> space
> > > required
> > > > over and over again:
> > > > http://cr.openjdk.java.net/~goetz/webrevs/8139864-
> > > StackZones/webrev.00-spread/
> > >
> > > That all seems okay to me.
> > >
> > > > Actually I think there is no need that the shadow zone is page
> aligned.
> > > There are no
> > > > pages to allocate or protect.  The size of this zone is only used for
> > banging.
> > > In most
> > > > places only the upper bound of the zone is banged.  In few places,
> all
> > pages
> > > within
> > > > this zone are banged.  But this code also does not depend on a page
> > > aligned size.
> > > > Removing the rounding to page sizes here could free up stack space
> for
> > real
> > > usage.
> > > > But I think that should be done in an extra change.
> > > >
> > > > I also fixed the bounds of ThreadStackSize and
> CompilerThreadStackSize
> > > which
> > > > allowed to specify stacks >> max_intx.
> > > >
> > > > If this is agreed on, I will check for jtreg tests that fail on
> systems with
> > stack
> > > > pages > 4K and add the fixes to this change.
> > >
> > > You may also need to check the tests for valid command-line args given
> > > the range adjustments on the stack sizes.
> > >
> > > Thanks,
> > > David
> > > -----
> > >
> > > > Best regards,
> > > >    Goetz.
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
>