Date: Sun, 14 Apr 2002 07:33:12 +0900 From: Katsushi Kobayashi <ikob@koganei.wide.ad.jp> To: Mikko Tyolajarvi <mikko@dynas.se> Cc: simokawa@sat.t.u-tokyo.ac.jp, hackers@FreeBSD.ORG Subject: Re: FireWire for kernel hackers Message-ID: <3CB8B228.70006@koganei.wide.ad.jp> References: <ybselhkx4r3.wl@ett.sat.t.u-tokyo.ac.jp> <200204131941.g3DJfAb18611@mikko.rsa.com>
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Mikko Tyolajarvi wrote: > >Umm... excuse a stupid question, but does this mean that a firewire >port always gives unconditional access to the host's memory? Great >for kernel debugging. Maybe not so great for a running system, from a >security point a view (ok, physical access eventually equals full >access, but plugging in a firewire cable is a heck of a lot faster >than using a screwdriver...) > Basically, firewire provides a function all host memory mapped into the unified memory space. Using this unified memory enables a connected host access to other host without CPU process. I believe access control function relys a chip implementatin. The IEEE1394 OHCI specifies two ways for the access control: 1. Host can specify the nodes capable to access its physical memory. 2. Host can specify the memory area capable to be accessed from other host. I believe the two access control ways are not enough in today. However, the currecnt firewire standard only provides limited phisical connection environment. Limited cable length and limited number of node. I think the unconditional access issues will occure at the limited situation only. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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