RFR: 8221639: [x32] expand_exec_shield_cs_limit workaround is undefined code after JDK-8199717

[Severin Gehwolf]

Hi David,

On Fri, 2019-04-19 at 00:02 +1000, David Holmes wrote:
> Hi Severin,
> 
> I'll have to delve into this more deeply (but I'm on Easter break for 
> the next 4 days). I don't recall ever being aware of 
> "suppress_primordial_thread_resolution"!

So any more thoughts about this?

Thanks,
Severin

> David
> 
> On 18/04/2019 11:41 pm, Severin Gehwolf wrote:
> > Hi,
> > 
> > Could I please get reviews for this Linux x32 fix? JDK-8199717 added a
> > performance optimization to only capture the initial stack size when
> > launched via non-java launchers. However, on Linux x32, there is old
> > code being executed to work around the exec shield CS limit. That code
> > depends on the initial stack size being captured. Right now this is
> > undefined code: Pointer artithmetic on NULL pointer.
> > 
> > src/hotspot/os_cpu/linux_x86/os_linux_x86.cpp:884:73: runtime error: pointer index expression with base 0x00000000 overflowed to 0xffffb000
> > 
> > I propose to not perform the optimization of JDK-8199717 for Linux x32.
> > 
> > Bug: https://bugs.openjdk.java.net/browse/JDK-8221639
> > webrev: http://cr.openjdk.java.net/~sgehwolf/webrevs/JDK-8221639/01/webrev/
> > 
> > Testing: release/fastdebug builds on x32 Linux, inspecting
> > -Xlog:os=info messages, currently running through jdkd/submit. Tier 1
> > tests on Linux x86_64
> > 
> > Thoughts?
> > 
> > Thanks,
> > Severin
> >