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From: Pavel Machek <pavel@ucw.cz>
To: Mike Rapoport <rppt@kernel.org>
Cc: linux-kernel@vger.kernel.org, Alan Cox <alan@linux.intel.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Andy Lutomirski <luto@kernel.org>,
	Christopher Lameter <cl@linux.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Idan Yaniv <idan.yaniv@ibm.com>,
	James Bottomley <jejb@linux.ibm.com>,
	"Kirill A. Shutemov" <kirill@shutemov.name>,
	Matthew Wilcox <willy@infradead.org>,
	Peter Zijlstra <peterz@infradead.org>,
	"Reshetova, Elena" <elena.reshetova@intel.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Tycho Andersen <tycho@tycho.ws>,
	linux-api@vger.kernel.org, linux-mm@kvack.org,
	Mike Rapoport <rppt@linux.ibm.com>
Subject: Re: [RFC PATCH v2 0/5] mm: extend memfd with ability to create "secret" memory areas
Date: Fri, 17 Jul 2020 10:36:02 +0200	[thread overview]
Message-ID: <20200717083601.GB1027@bug> (raw)
In-Reply-To: <20200706172051.19465-1-rppt@kernel.org>

Hi!

> This is a second version of "secret" mappings implementation backed by a
> file descriptor. 
> 
> The file descriptor is created using memfd_create() syscall with a new
> MFD_SECRET flag. The file descriptor should be configured using ioctl() to
> define the desired protection and then mmap() of the fd will create a
> "secret" memory mapping. The pages in that mapping will be marked as not
> present in the direct map and will have desired protection bits set in the
> user page table. For instance, current implementation allows uncached
> mappings.
> 
> Hiding secret memory mappings behind an anonymous file allows (ab)use of
> the page cache for tracking pages allocated for the "secret" mappings as
> well as using address_space_operations for e.g. page migration callbacks.
> 
> The anonymous file may be also used implicitly, like hugetlb files, to
> implement mmap(MAP_SECRET) and use the secret memory areas with "native" mm
> ABIs.

I believe unix userspace normally requires mappings to be... well... protected from
other users. How is this "secret" thing different? How do you explain the difference
to userland programmers?

Best regards,
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

  parent reply	other threads:[~2020-07-17  8:36 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-06 17:20 Mike Rapoport
2020-07-06 17:20 ` [RFC PATCH v2 1/5] mm: make HPAGE_PxD_{SHIFT,MASK,SIZE} always available Mike Rapoport
2020-07-07  5:07   ` Hugh Dickins
2020-07-07  6:47     ` Mike Rapoport
2020-07-10 16:40     ` Andrea Arcangeli
2020-07-10 16:57       ` Matthew Wilcox
2020-07-10 17:08         ` Andrea Arcangeli
2020-07-10 17:12         ` Mike Rapoport
2020-07-06 17:20 ` [RFC PATCH v2 2/5] mmap: make mlock_future_check() global Mike Rapoport
2020-07-06 17:20 ` [RFC PATCH v2 3/5] mm: extend memfd with ability to create "secret" memory areas Mike Rapoport
2020-07-13 10:58   ` Kirill A. Shutemov
2020-07-13 15:31     ` Mike Rapoport
2020-07-06 17:20 ` [RFC PATCH v2 4/5] mm: secretmem: use PMD-size pages to amortize direct map fragmentation Mike Rapoport
2020-07-13 11:05   ` Kirill A. Shutemov
2020-07-13 15:32     ` Mike Rapoport
2020-07-06 17:20 ` [RFC PATCH v2 5/5] mm: secretmem: add ability to reserve memory at boot Mike Rapoport
2020-07-17  8:36 ` Pavel Machek [this message]
2020-07-17 14:43   ` [RFC PATCH v2 0/5] mm: extend memfd with ability to create "secret" memory areas James Bottomley

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