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To: StockMan who wrote (40143)	11/12/1997 1:20:00 PM
From: StockMan	Read Replies (1) \| Respond to of 186894

All, FYI found on USENET. May or maynot be authentic. I'll be damned! Just got this on BugTraq: From: Joe Ilacqua <NOSPAMBYMEspike@INDRA.COM> Subject: Intel Pentium Bug: BSDI Releases a patch To: [list name snipped by me] Apparently the issue can be addressed in software. No details on how it works are provided. ------- Forwarded Message To: NOSPAMBYMEbsdi-users@bsdi.com Subject: Beta test of Pentium hang work-around for BSD/OS 3.1 (and 3.0) Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Date: Tue, 11 Nov 1997 16:38:48 -0700 From: Jeff Polk <NOSPAMBYMEpolk@bsdi.com> Sender: NOSPAMBYMEowner-bsdi-users@mailinglists.org Precedence: bulk X-Sender: Jeff Polk <NOSPAMBYMEpolk@bsdi.com> X-UIDL: fb8659ed152bd2ba9912c603b6a1b837 As many of you probably know, a bug was recently discovered in the Pentium CPU that causes the CPU to hang when a certain instruction is executed. This bug has been widely reported in mailing lists and news groups. The bug enables an unprivileged user to hang the system, requiring the system to be reset or power-cycled. With information provided by Intel, BSDI has developed a workaround for this problem. A beta version of the mod for BSD/OS version 3.1 is now available for testing from ftp://ftp.bsdi.com/bsdi/patches/patches-3.1/M310-hangfix This mod may also be applied to 3.0 based systems. The workaround is enabled only on P5 processors, and should not be necessary on Pentium Pro, Pentium II or non-Intel CPUs. The mod is currently available only in binary form. We anticipate general release of the mod within a day or so. We are interested in hearing of any problems experienced with this change. We are also interested in hearing about testing on any non-Intel Pentium-compatible systems. Please send any reports to NOSPAMBYMEbsdi-hang-beta@BSDI.COM We are not at liberty to discuss the mechanism of the workaround at this time. If you are installing the mod in a source kernel tree, you will need to copy the files sys/i386/OBJ/{machdep.o,locore.o} to your kernel compile directory before rebuilding your kernel. Jeff - -- /\ Jeff Polk Berkeley Software Design, Inc. (BSDI) /\/ \ NOSPAMBYMEpolk@BSDI.COM 5575 Tech Center Dr. #110, Colo Spgs, CO 80919 - -- To unsubscribe from this list, send 'unsubscribe' in the body of an e-mail message to 'NOSPAMBYMEbsdi-users-request@mailinglists.org'

To: StockMan who wrote (40143)	11/12/1997 1:42:00 PM
From: Fridrik Skulason	Read Replies (1) \| Respond to of 186894

>Really, How do you think it is done in Unix/NT. I do not "think" how it is done...I know how it is done. Many OSes provide separate code segments (executable, not writable) and data segments (writable, not executable). If that is all you have, you cannot create self-modifying code. However, in real life (depending on the OS), you can usually do either of the following: 1) change the property of a code segment, making it a data segment, modify as needed and change it back to a code segment. 2) create a mixed segment, which is writable and executable, copy code there, modify it and execute. Failing this, a program may be able to modify its own disk image. Finally, any OS that includes a "DOS box" where you can run (not just emulate) DOS applications has to allow the existence of self-modifying executables.