From: Colin Cross <ccross@google.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: lkml <linux-kernel@vger.kernel.org>,
Linux-MM <linux-mm@kvack.org>,
Android Kernel Team <kernel-team@android.com>,
John Stultz <john.stultz@linaro.org>
Subject: Re: RFC: named anonymous vmas
Date: Sat, 22 Jun 2013 10:30:30 -0700 [thread overview]
Message-ID: <CAMbhsRTz246dWPQOburNor2HvrgbN-AWb2jT_AEywtJHFbKWsA@mail.gmail.com> (raw)
In-Reply-To: <20130622103158.GA16304@infradead.org>
On Sat, Jun 22, 2013 at 3:31 AM, Christoph Hellwig <hch@infradead.org> wrote:
> On Fri, Jun 21, 2013 at 04:42:41PM -0700, Colin Cross wrote:
>> ranges, which John Stultz has been implementing. The second is
>> anonymous shareable memory without having a world-writable tmpfs that
>> untrusted apps could fill with files.
>
> I still haven't seen any explanation of what ashmem buys over a shared
> mmap of /dev/zero in that respect, btw.
I believe the difference is that ashmem ties the memory to an fd, so
it can be passed to another process and mmaped to get to the same
memory, but /dev/zero does not. Passing a /dev/zero fd and mmaping it
would result in a brand new region of zeroed memory. Opening a tmpfs
file would allow sharing memory by passing the fd, but we don't want a
world-writable tmpfs.
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next prev parent reply other threads:[~2013-06-22 17:30 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-06-21 23:42 RFC: named anonymous vmas Colin Cross
2013-06-22 5:12 ` Kyungmin Park
2013-06-22 5:20 ` Colin Cross
2013-06-22 10:31 ` Christoph Hellwig
2013-06-22 17:30 ` Colin Cross [this message]
2013-06-22 19:47 ` Alex Elsayed
2013-06-24 11:48 ` Christoph Hellwig
2013-06-24 17:26 ` Colin Cross
2013-06-24 23:45 ` John Stultz
2013-06-26 18:53 ` Alex Elsayed
2013-07-14 0:57 ` Sam Ben
2013-08-01 8:29 ` Christoph Hellwig
2013-08-01 8:36 ` Rich Felker
2013-08-02 15:11 ` Christoph Hellwig
2013-08-03 23:54 ` KOSAKI Motohiro
2013-07-14 0:27 ` Sam Ben
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