linux-kernel - Re: NVM Mapping API

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] [day] [month] [year] [list]

Message-ID: <CALCETrUmajOtdSKNqQgfJtbMRe9GZBM52vBZ9rHW=swbcbzAaQ@mail.gmail.com>
Date:	Thu, 31 May 2012 10:53:06 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Matthew Wilcox <willy@...ux.intel.com>
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: NVM Mapping API

On Wed, May 16, 2012 at 9:02 AM, Matthew Wilcox <willy@...ux.intel.com> wrote:
> On Tue, May 15, 2012 at 04:02:01PM -0700, Andy Lutomirski wrote:
>> I would love to use this from userspace.  If I could carve out a little
>> piece of NVM as a file (or whatever) and mmap it, I could do all kinds
>> of fun things with that.  It would be nice if it had well-defined, or at
>> least configurable or discoverable, caching properties (e.g. WB, WT, WC,
>> UC, etc.).
>
> Yes, usage from userspace is definitely planned; again through a
> filesystem interface.  Treating it like a regular file will work as
> expected; the question is how to expose the interesting properties
> (eg is there a lighter weight mechanism than calling msync()).

clfush?  vdso system call?

If there's a proliferation of different technologies like this, we
could have an opaque struct nvm_mapping and a vdso call like

void __vdso_nvm_flush_writes(struct nvm_mapping *mapping, void
*address, size_t len);

that would read the struct nvm_mapping to figure out whether it should
do a clflush, sfence, mfence, posting read, or whatever else the
particular device needs.  (This would also give a much better chance
of portability to architectures other than x86.)

>
> My hope was that by having a discussion of how to use this stuff within
> the kernel, we might come up with some usage models that would inform
> how we design a user space library.
>
>> (Even better would be a way to make a clone of an fd that only allows
>> mmap, but that's a mostly unrelated issue.)
>
> O_MMAP_ONLY?  And I'm not sure why you'd want to forbid reads and writes.

I don't want to forbid reads and writes; I want to forbid ftruncate.
That way I don't need to worry about malicious / obnoxious programs
sharing the fd causing SIGBUS.

--Andy
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/