n Fri, Dec 12, 2014 at 1:41 PM, Dave Hansen <d...@sr71.net> wrote: > On 12/12/2014 12:48 PM, Andy Lutomirski wrote: >> On Fri, Dec 12, 2014 at 12:27 PM, Dave Hansen <d...@sr71.net> wrote: >>> You want the same size structures with the same format for 32-bit and >>> 64-bit modes? >> >> Yes. Especially because programs can switch between 32-bit and 64-bit >> mode entirely in userspace. I don't know whether any do in practice, >> but programs *can*. > > So, you want a 2GB of the 32-bit address space dedicated to a bounds > directory, and half of the space for the bounds tables to be simply > zero-filled unused address bits? That seems, um, a bit unreasonable.
Fair enough. > >> Or better yet: Intel could have skipped supporting it at all in 32-bit >> mode. > > So, we should not have this security feature for 32-bit apps... because > it costs us 50 lines of code in the kernel to support? Did you look at > the diffstat? > >> Isn't mpx somewhat of an address space hog anyway? > > Yes, it will be troublesome for 32-bit apps that are already bumping up > against the virtual address space size to support it. But, really, how > many of those *are* there these days? I wonder how many 32-bit apps will end up using mpx regardless. Anyway, do your patches handle the case where a 32-bit app maliciously executes a 64-bit mpx insn with a very large address? I think it's okay, but I might have missed something. --Andy -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/