Messages in this thread | | | Date | Sun, 15 Oct 2006 22:02:19 +0200 (MEST) | From | Jan Engelhardt <> | Subject | Re: privilege levels and kernel mode |
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>Hi, > I am using pentium-4 processor. My operating >system is Linux version 2.4.22-1.2199.nptl > > I want to measure performance events like number of >memory reads, number of cache misses occured while >running a "C" program. For that I have to wright some >values into "Model specific registers of pentium-4 >processor". But those registers can be written ONLY at >privilege level of zero of pentium4 processor. > > We know that application programs we write (for >example any C program)are run at privilege >level-3(user mode). > >I know how to include assembly instructions in a C >program to wtrite into "Model specific registers". But >that program has to be run at privilege level zero. > >How to run a C program at privilege level zero??
The short answer: You can't.
The long answer: You have to write a kernel module to do what you need.
The best answer: Use /dev/cpu/0/msr.
>Can any one help me? > >Thanks in advance. > > > >Send instant messages to your online friends http://uk.messenger.yahoo.com >- >To unsubscribe from this list: send the line "unsubscribe linux-kernel" in >the body of a message to majordomo@vger.kernel.org >More majordomo info at http://vger.kernel.org/majordomo-info.html >Please read the FAQ at http://www.tux.org/lkml/ >
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