RFR: 8199323: hsdis could not be loaded which are located on long path

[David Holmes]

Hi Yasumasa,

On 8/03/2018 11:21 PM, Yasumasa Suenaga wrote:
> Hi all,
> 
> Could you review and sponsor it?
> 
>                            webrev: 
> http://cr.openjdk.java.net/~ysuenaga/JDK-8199323/webrev.00/
>                               JBS: 
> https://bugs.openjdk.java.net/browse/JDK-8199323
> Mach5 test result on submit repo: 
> mach5-one-ysuenaga-JDK-8199323-20180308-1027-13701
> 
> I encountered DebuggerException when hsdis is located on long path as 
> below:
> 
> Location of hsdis:
> /home/yasuenag/work/xxxxxx/xxxxxxxxxxxxxx/xxxxxxxxxxxxx/workspace/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.101-3.b13.el6_8.x86_64/jre/lib/amd64/hsdis-amd64.so 
> 
> 
> Exception:
> sun.jvm.hotspot.debugger.DebuggerException: 
> /home/yasuenag/work/xxxxxx/xxxxxxxxxxxxxx/xxxxxxxxxxxxx/workspace/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.101-3.b13.el6_8.x86_64/j: 
> cannot open shared object file: No such file or directory
> 
> In Java_sun_jvm_hotspot_asm_Disassembler_load_1library(), buffer which 
> uses for library path is defined as below:
> 
> ```
> char buffer[128];
> ```
> 
> I copied JVM_MAXPATHLEN related code to sadis.c from 
> os/posix/include/jvm_md.h and os/windows/include/jvm_md.h .

I don't think this code has the same concern that the code in jvm_md.h 
claims** to have, so a simple use of MAXPATHLEN should be fine on all 
non-windows platforms.

** The posix jvm_md.h code is historical and I don't think we have to be 
concerned either about a 4095 definition of MAXPATHLEN or that the VM 
and libraries may have been compiled on different Linux versions!

My only concern with the current change is whether a 4K on stack buffer 
might cause any issues?

Thanks,
David
-----

> 
> I added noreg-hard label on this ticket because this issue is available 
> when disassembling on coredump.
> 
> 
> Thanks,
> 
> Yasumasa