Messages in this thread | | | Date | Tue, 7 May 2013 13:38:10 +0200 | From | Andrew Jones <> | Subject | Re: [Qemu-devel] [PATCH 0/4] madvise(MADV_USERFAULT) & sys_remap_anon_pages() |
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On Mon, May 06, 2013 at 09:56:57PM +0200, Andrea Arcangeli wrote: > > The current behavior of remap_anon_pages is very strict to avoid any > chance of memory corruption going unnoticed, and it will return > -EFAULT at the first sign of something unexpected (like a page already > mapped in the destination pmd/pte, potentially signaling an userland > thread race condition with two threads userfaulting on the same > destination address). mremap is not strict like that: it would drop > the destination range silently and it would succeed in such a > condition. So on the API side, I wonder if I should add a flag to > remap_anon_pages to provide non-strict behavior more similar to > mremap. OTOH not providing the permissive mremap behavior may actually > be better to force userland to be strict and be sure it knows what it > is doing (otherwise it should use mremap in the first place?). >
What about instead of adding a new syscall (remap_anon_pages) to instead extend mremap with new flags giving it a strict mode?
drew
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