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Date: Tue, 21 Feb 2012 11:40:38 -0800 From: Andrew Lutomirski <luto@....edu> To: "H. Peter Anvin" <hpa@...or.com> Cc: linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org, mingo@...nel.org, tglx@...utronix.de, torvalds@...ux-foundation.org, akpm@...ux-foundation.org, hjl.tools@...il.com Subject: Re: [PATCH 30/30] x32: Add x32 VDSO support On Tue, Feb 21, 2012 at 11:37 AM, H. Peter Anvin <hpa@...or.com> wrote: > On 02/21/2012 11:29 AM, Andrew Lutomirski wrote: >>> >>> The vsyscall page shouldn't be mapped for x32 tasks... >> >> How is that possible? It lives in the fixmap and is presumably >> visible from any 64-bit code. >> >> Admittedly, x32 tasks are probably somewhat difficult to trick into >> calling addresses with high bits set, but it's not necessarily >> impossible. >> > > Fair enough, and it's not necessarily all that hard either. > > And it's visible even in a 32-bit task, although a 32-bit task has to > switch into 64-bit mode. Yet another reason the vsyscall page needs to die. > > I was having delusions that we could have a task-owned PDT in negative > space, but that would require unsharing the third level, too, which is > just way too messy. I'd like to do that, too, and I'd also like to have a per-cpu kernel-only page in there, but that's even worse. If we had a separate cr3-like register for negative addresses, life would be good :) --Andy -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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