Date: Thu, 11 Feb 1999 11:12:50 -0800 From: David Greenman <dg@root.com> To: "Md. Ahsan Habib" <mhabib@vt.edu> Cc: freebsd-hackers@FreeBSD.ORG Subject: Re: /dev/kmem Message-ID: <199902111912.LAA01519@implode.root.com> In-Reply-To: Your message of "Thu, 11 Feb 1999 14:07:56 EST." <3.0.5.32.19990211140756.0090e4f0@csgrad.cs.vt.edu>
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>I am facing some problems to use /dev/kmem. I tried a lot, post it to the
>news groups but couldn't come up to a solution. In one of my experiments I
>need to write in /dev/kmem. I can't use normal file because it will consume
>more time which will affect my experiments.
>
>This is a sample code I tried to execute:
>
>#include <fcntl.h>
>#include <stdio.h>
>#include <errno.h>
>
>extern int errno;
>
>int main()
>{
> int fp,w,c;
> long l;
> char * Buff = "1234";
>
> fp = open("/dev/kmem", O_RDWR);
> if (fp == -1) {
> printf("open returned error\n");
> perror("open");
> }
> l = lseek(fp, 0x000a000,0);
> w = write(fp,Buff,4);
> c = close(fp);
> return 0;
>}
>
>It can open the file, change the file pointer, close the file but can't
>write anything in the file. The value of w is always -1. I tried with
>several locations instead of the beginning one 0x000a000.
>
>I set all necessary mod and ownership.
>
>I will be happy if anyone can help me. It's really important to me.
/dev/kmem addresses start at the kernel start address, KERNBASE. Attempts
to access memory locations below that will fail.
-DG
David Greenman
Co-founder/Principal Architect, The FreeBSD Project
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