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From Gregory Shimansky <gshiman...@gmail.com>
Subject Re: [M3] NPE is thrown while debugging with M3
Date Thu, 11 Oct 2007 10:22:28 GMT
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.

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

-- 
Gregory


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