Messages in this thread | | | Date | Fri, 25 Oct 2013 15:59:23 +0100 | From | "H. Peter Anvin" <> | Subject | Re: RW and executable hole in page tables on x86_64 |
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On 10/25/2013 02:34 PM, Kees Cook wrote: > Hi, > > I've noticed there's a chunk of kernel memory still marked RW and x. See > 0xffffffff82956000 below... > > ---[ High Kernel Mapping ]--- > 0xffffffff80000000-0xffffffff81000000 16M pmd > 0xffffffff81000000-0xffffffff81a00000 10M ro PSE GLB x pmd > 0xffffffff81a00000-0xffffffff81e00000 4M ro PSE GLB NX pmd > 0xffffffff81e00000-0xffffffff82200000 4M RW GLB NX pte > 0xffffffff82200000-0xffffffff82800000 6M RW PSE GLB NX pmd > 0xffffffff82800000-0xffffffff82956000 1368K RW GLB NX pte > 0xffffffff82956000-0xffffffff82a00000 680K RW GLB x pte > 0xffffffff82a00000-0xffffffffa0000000 470M pmd > > HPA looked at it for a bit, but it wasn't obvious what was going on. It's > after the end of bss. I do note that the two adjacent regions add up to > 2MiB. Is this some kind of leftover mapping? What is this region? Is there > a sensible place to clean it up? >
It looks to be what is left after the 2 MB page for bss is broken up. It doesn't mean it isn't broken, though.
-hpa
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