regarding privilege levels of pentium 4

Artūras Moskvinas arturas.moskvinas@gmail.com
Sat Sep 30 22:28:00 GMT 2006


> --- Sven Eschenberg <eschenb@cs.uni-frankfurt.de>
> wrote:
> 
>> Hi Ranjith,
>>
>> I might be wrong on this, but I think the question
>> is, if the Operating 
>> System permits it or under which circumstances. It's
>> neither a question 
>> of what gcc or the hardware does, but what the OS
>> you are using allows 
>> to which processes.
> Thanks. I am sending more details of my problem.
> 
> The OS I am using       : Linux.
> The language in which the program is written : C(I am
> attaching the program)
> The compiler : gcc 3.2.3
> Processor   : Pentium 4
> I know password for root login. I logged in as root
> and compiled my program. When compiled no errors were
> reported. But when I run the program it simply shows
> "Segmentation fault". 
> 
> My goal is to measure performance parameters (for
> example the number of branch instructions that were
> mispredicted), on Pentium 4, using "RDMSR" and "WRMSR"
> instructions. Also I want to disble interrupts while
> running my program.
> The problem is that those instructions can be run only
> at privilege level zero.
You should consider using Kernel mode linux (kernel recompilation
needed) or write kernel module:
kernel mode linux:
http://web.yl.is.s.u-tokyo.ac.jp/~tosh/kml/


Arturas M.



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