Re: dd if=/dev/mem can hang a machine?
BTW, I think it was related to reading memory-mapped registers intended to put CPU into Cx states (x = 2). -- Andriy Gapon ___ freebsd-hackers@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: dd if=/dev/mem can hang a machine?
on 30/11/2008 22:14 Julian Stacey said the following: Gary Jennejohn wrote: On Fri, 28 Nov 2008 15:28:35 +0200 Andriy Gapon [EMAIL PROTECTED] wrote: I have a new machine with DG33TL mainboard (ICH9/G33). In a course of some hacking I ran dd if=/dev/mem ... to scan all memory, this caused the machine to hang. I tried to reproduce and this is 100% reproducible. I am not used to such behavior. In older days I could scan all the memory without any issues. Could this be related to some modern form of memory-mapped IO? Or to Intel Management Engine (that seems t bite into DRAM)? Or something else? Just wondering. That's what I would assume. With some hardware just reading a register can be harmful. I just crashed 3 normally stable machines trying that. I only tried for casual interest. I acknowledge Gary's comment above :-) dd if=/dev/mem of=/dev/null FreeBSD lapa.js.berklix.net 4.11-RELEASE FreeBSD 4.11-RELEASE #0: Fri Jul 7 17:56:30 CEST 2006 [EMAIL PROTECTED]:/usr/src/sys/compile/LAPA.small i386 FreeBSD laps.js.berklix.net 7.0-RELEASE FreeBSD 7.0-RELEASE #2: Mon Sep 8 15:39:53 CEST 2008 [EMAIL PROTECTED]:/usr1/ftp/pri/FreeBSD/releases/7.0-RELEASE/src/sys/i386/compile/LAPS.small i386 FreeBSD john.js.berklix.net 7.1-BETA2 FreeBSD 7.1-BETA2 #0: Sun Oct 12 20:59:28 UTC 2008 [EMAIL PROTECTED]:/usr/obj/usr/src/sys/GENERIC amd64 Thank you for going to all the trouble. I see now that I have to be more careful in this respect. -- Andriy Gapon ___ freebsd-hackers@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: dd if=/dev/mem can hang a machine?
On Fri, 28 Nov 2008 15:28:35 +0200 Andriy Gapon [EMAIL PROTECTED] wrote: I have a new machine with DG33TL mainboard (ICH9/G33). In a course of some hacking I ran dd if=/dev/mem ... to scan all memory, this caused the machine to hang. I tried to reproduce and this is 100% reproducible. I am not used to such behavior. In older days I could scan all the memory without any issues. Could this be related to some modern form of memory-mapped IO? Or to Intel Management Engine (that seems t bite into DRAM)? Or something else? Just wondering. That's what I would assume. With some hardware just reading a register can be harmful. --- Gary Jennejohn ___ freebsd-hackers@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: dd if=/dev/mem can hang a machine?
Gary Jennejohn wrote: On Fri, 28 Nov 2008 15:28:35 +0200 Andriy Gapon [EMAIL PROTECTED] wrote: I have a new machine with DG33TL mainboard (ICH9/G33). In a course of some hacking I ran dd if=/dev/mem ... to scan all memory, this caused the machine to hang. I tried to reproduce and this is 100% reproducible. I am not used to such behavior. In older days I could scan all the memory without any issues. Could this be related to some modern form of memory-mapped IO? Or to Intel Management Engine (that seems t bite into DRAM)? Or something else? Just wondering. That's what I would assume. With some hardware just reading a register can be harmful. I just crashed 3 normally stable machines trying that. I only tried for casual interest. I acknowledge Gary's comment above :-) dd if=/dev/mem of=/dev/null FreeBSD lapa.js.berklix.net 4.11-RELEASE FreeBSD 4.11-RELEASE #0: Fri Jul 7 17:56:30 CEST 2006 [EMAIL PROTECTED]:/usr/src/sys/compile/LAPA.small i386 FreeBSD laps.js.berklix.net 7.0-RELEASE FreeBSD 7.0-RELEASE #2: Mon Sep 8 15:39:53 CEST 2008 [EMAIL PROTECTED]:/usr1/ftp/pri/FreeBSD/releases/7.0-RELEASE/src/sys/i386/compile/LAPS.small i386 FreeBSD john.js.berklix.net 7.1-BETA2 FreeBSD 7.1-BETA2 #0: Sun Oct 12 20:59:28 UTC 2008 [EMAIL PROTECTED]:/usr/obj/usr/src/sys/GENERIC amd64 Cheers, Julian -- Julian Stacey: BSDUnixLinux C Prog Admin SysEng Consult Munich www.berklix.com Mail plain ASCII text. HTML Base64 text are spam. www.asciiribbon.org ___ freebsd-hackers@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to [EMAIL PROTECTED]
dd if=/dev/mem can hang a machine?
I have a new machine with DG33TL mainboard (ICH9/G33). In a course of some hacking I ran dd if=/dev/mem ... to scan all memory, this caused the machine to hang. I tried to reproduce and this is 100% reproducible. I am not used to such behavior. In older days I could scan all the memory without any issues. Could this be related to some modern form of memory-mapped IO? Or to Intel Management Engine (that seems t bite into DRAM)? Or something else? Just wondering. -- Andriy Gapon ___ freebsd-hackers@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to [EMAIL PROTECTED]
