On Tue, Feb 21, 2012 at 11:37 AM, H. Peter Anvin <hpa@xxxxxxxxx> 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-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
