Re: RFC: named anonymous vmas

[Colin Cross]

On Sat, Jun 22, 2013 at 3:31 AM, Christoph Hellwig <hch@xxxxxxxxxxxxx> 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.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/