Date: Mon, 6 Dec 1999 17:16:31 -0500 (EST) From: Luoqi Chen <luoqi@watermarkgroup.com> To: freebsd-hackers@FreeBSD.ORG, gallatin@cs.duke.edu Subject: Re: Is part of user stack always mapped? Message-ID: <199912062216.RAA09858@lor.watermarkgroup.com>
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> I was under the impression that this was a no-no & one should use > copyin/copout & friends to access memory on users's stacks. Although > this appears to work on the i386, if I try this on the alpha I take a > fatal trap when accessing *set. > > So -- how does this work on the i386? Is the user's stack always > mappeped into the kernel's address space? Should it also work on the > alpha? > On i386, under the current implementation, the kernel can directly access curproc's address space (not just the stack, stack is used because we're sure the spare space won't/shouldn't be used by the user application). I don't know if the same is true for alpha, but this should definitely be considered an implementation dependent feature. I wish there were some other ways to bypass copyin/out in ioctls. -lq To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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