Messages in this thread | | | Date | Wed, 28 May 2014 14:45:18 -0700 | From | "H. Peter Anvin" <> | Subject | Re: Pondering per-process vsyscall disablement |
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On 05/23/2014 09:40 AM, Andy Lutomirski wrote: > > I don't think this should be something configured by the > administrator, unless the administrator is the builder of a kiosky > thing like Chromium OS. In that case, the administrator can use > vsyscall=none. > > I think this should be handled by either libc or the toolchain, hence > the suggestions of a syscall or an ELF header. >
We could mimic the NX stack stuff, but it would have a lot of false negatives, simply because very few things would actually poke at the vsyscall page.
The NX stuff uses a dummy program header in the ELF image.
On the other hand, you could make the argument that anything compiled with a new toolchain simply should not use the vsyscall page, and just unconditionally set the opt-out bit (header) in question.
It might be better to have some kind of flags field (which a number of architectures use) than keep using dummy program headers, though.
-hpa
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