linux-kernel - Re: [PATCH 1/2] mm: introduce put_user

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Fri, 14 Dec 2018 11:53:31 -0800
From:   Dave Hansen <dave.hansen@...el.com>
To:     Matthew Wilcox <willy@...radead.org>,
        Dan Williams <dan.j.williams@...el.com>
Cc:     John Hubbard <jhubbard@...dia.com>, david <david@...morbit.com>,
        Jérôme Glisse <jglisse@...hat.com>,
        Jan Kara <jack@...e.cz>, John Hubbard <john.hubbard@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux MM <linux-mm@...ck.org>, tom@...pey.com,
        Al Viro <viro@...iv.linux.org.uk>, benve@...co.com,
        Christoph Hellwig <hch@...radead.org>,
        Christopher Lameter <cl@...ux.com>,
        "Dalessandro, Dennis" <dennis.dalessandro@...el.com>,
        Doug Ledford <dledford@...hat.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Michal Hocko <mhocko@...nel.org>,
        Mike Marciniszyn <mike.marciniszyn@...el.com>,
        rcampbell@...dia.com,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>
Subject: Re: [PATCH 1/2] mm: introduce put_user_page*(), placeholder versions

On 12/14/18 11:48 AM, Matthew Wilcox wrote:
> I think we can do better than a proxy object with bit 0 set.  I'd go
> for allocating something like this:
> 
> struct dynamic_page {
> 	struct page;
> 	unsigned long vaddr;
> 	unsigned long pfn;
> 	...
> };
> 
> and use a bit in struct page to indicate that this is a dynamic page.

That might be fun.  We'd just need a fast/static and slow/dynamic path
in page_to_pfn()/pfn_to_page().  We'd also need some kind of auxiliary
pfn-to-page structure since we could not fit that^ structure in vmemmap[].