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Re: regarding privilege levels of pentium 4

From: Tim Prince <timothyprince at sbcglobal dot net>
To: ArtÅras Moskvinas <arturas dot moskvinas at gmail dot com>
Cc: ranjith kumar <ranjit_kumar_b4u at yahoo dot co dot uk>, gcc-help at gcc dot gnu dot org
Date: Sat, 30 Sep 2006 18:03:24 -0700
Subject: Re: regarding privilege levels of pentium 4
References: <20060930220855.41172.qmail@web27405.mail.ukl.yahoo.com> <451EEFA1.4010007@gmail.com>
Reply-to: tprince at myrealbox dot com

ArtÅras Moskvinas wrote:

--- Sven Eschenberg <eschenb@cs.uni-frankfurt.de>
wrote:

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/

Also, consider whether you need to re-invent the wheel, when both open and closed source profilers exist for this purpose.

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