Date: Fri, 2 Feb 2018 12:43:25 -0600 (CST) From: Christopher Lameter <cl@...ux.com> To: Igor Stoppa <igor.stoppa@...wei.com> cc: jglisse@...hat.com, keescook@...omium.org, mhocko@...nel.org, labbott@...hat.com, hch@...radead.org, willy@...radead.org, linux-security-module@...r.kernel.org, linux-mm@...ck.org, linux-kernel@...r.kernel.org, kernel-hardening@...ts.openwall.com Subject: Re: [PATCH 3/6] struct page: add field for vm_struct On Thu, 1 Feb 2018, Igor Stoppa wrote: > > Would it not be better to use compound page allocations here? > > page_head(whatever) gets you the head page where you can store all sorts > > of information about the chunk of memory. > > Can you please point me to this function/macro? I don't seem to be able > to find it, at least not in 4.15 Ok its compound_head(). See also the use in the SLAB and SLUB allocator. > During hardened user copy permission check, I need to confirm if the > memory range that would be exposed to userspace is a legitimate > sub-range of a pmalloc allocation. If you save the size in the head page struct then you could do that pretty fast. > I cannot comment on your proposal because I do not know where to find > the reference you made, or maybe I do not understand what you mean :-( compund pages are higher order pages that are handled as a single page by the VM. See https://lwn.net/Articles/619514/
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