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From Tim Ellison <t.p.elli...@gmail.com>
Subject Re: [M3] NPE is thrown while debugging with M3
Date Fri, 12 Oct 2007 15:00:40 GMT
Gregory Shimansky wrote:
> Tim Ellison wrote:
>> Andrew Zhang wrote:
>>> On 10/11/07, Tim Ellison <t.p.ellison@gmail.com> wrote:
>>>> Is that something we need to add to a technical FAQ?
>>>
>>> yeah, I think it would be really helpful!
>>
>> There is a (short) technical FAQ in this page:
>>   https://svn.apache.org/repos/asf/harmony/standard/site/xdocs/faq.xml
>>
>> Perhaps you could add in the symptoms and instructions for disabling the
>> NX bit?
> 
> Is this text ok for FAQ?
> 
> The symptom seems to be unexpected NPEs in the code that doesn't produce
> any when not debugged. This is a limitation of M3 build. Hopefully it
> will be fixed in M4.

Hmm, well if it will be fixed in M4 perhaps it should go into the M3
release notes as a known issue rather than as a permanent technical FAQ.

Regards,
Tim

> On Linux ia32 NX bit is usually disabled because enabling it requires
> CONFIG_X86_PAE that is needed to address over 4Gb of memory, and to turn
> it on it is necessary to specify "noexec=on" on kernel command line.
> 
> On Linux x86_64 NX bit is enabled by default, so if one tries to run
> DRLVM debugger in x86 emulation mode it is better to specify
> "noexec=off" on kernel command line.
> 
> On Windows x86 NX bit is controlled with a /noexecute switch to kernel
> command line in X:\boot.ini (X is boot drive letter) file. Usually it is
> set as /noexecute=optin that disables execution of kernel but allows
> execution of user level programs heap. For more details see [1]
> 
> [1] http://www.microsoft.com/technet/sysinternals/information/bootini.mspx
> 

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