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

[David Holmes]

On 24/04/2019 11:33 pm, Florian Weimer wrote:
> * Severin Gehwolf:
> 
>> 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,
> 
> Do you mean actual x32, or i386?  These two are different.

The code is selected based on the IA32 define which is set for a 
detected architecture of "i?86" as returned by uname I presume.

I had assumed this was simply equivalent to 32-but x86, but apparently 
x32 is something else.

> Can you actually verify changes in this area?  I think it's pretty hard
> these days to find a machine that actually uses the CS hack to avoid
> universal read-implies-exec.  I don't think this was ever part of any
> mainline kernel.

According to:

https://bugs.openjdk.java.net/browse/JDK-8023956

A number of mainline kernels were affected:

"RHEL 5 & 6 are affected, and earlier Ubuntu releases 10.04 (LTS), 
11.04, and 12.04 have also taken in the patch. "

David
-----

> Thanks,
> Florian
>