linux-kernel - Re: [PATCH] mm: extend prefault helpers to fault in more than PAGE

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]

Message-ID: <CAMuHMdXBEiDGyJQ+szoBKxo0pS=n3xKfpb=F+rNkMQUv4SdTQA@mail.gmail.com>
Date:	Fri, 13 Apr 2012 21:12:21 +0200
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Daniel Vetter <daniel.vetter@...ll.ch>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Intel Graphics Development <intel-gfx@...ts.freedesktop.org>,
	DRI Development <dri-devel@...ts.freedesktop.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux MM <linux-mm@...ck.org>,
	Linux-Next <linux-next@...r.kernel.org>
Subject: Re: [PATCH] mm: extend prefault helpers to fault in more than PAGE_SIZE

On Thu, Mar 1, 2012 at 20:22, Daniel Vetter <daniel.vetter@...ll.ch> wrote:
> +/* Multipage variants of the above prefault helpers, useful if more than
> + * PAGE_SIZE of date needs to be prefaulted. These are separate from the above
> + * functions (which only handle up to PAGE_SIZE) to avoid clobbering the
> + * filemap.c hotpaths. */
> +static inline int fault_in_multipages_writeable(char __user *uaddr, int size)
> +{
> +       int ret;
> +       const char __user *end = uaddr + size - 1;

Please drop the const.

> +
> +       if (unlikely(size == 0))
> +               return 0;
> +
> +       /*
> +        * Writing zeroes into userspace here is OK, because we know that if
> +        * the zero gets there, we'll be overwriting it.
> +        */
> +       while (uaddr <= end) {
> +               ret = __put_user(0, uaddr);
> +               if (ret != 0)
> +                       return ret;
> +               uaddr += PAGE_SIZE;
> +       }
> +
> +       /* Check whether the range spilled into the next page. */
> +       if (((unsigned long)uaddr & PAGE_MASK) ==
> +                       ((unsigned long)end & PAGE_MASK))
> +               ret = __put_user(0, end);

include/linux/pagemap.h:483:3: error: read-only location '*end' used
as 'asm' output

Now in -next:

http://kisskb.ellerman.id.au/kisskb/buildresult/6100650/
http://kisskb.ellerman.id.au/kisskb/buildresult/6100673/
http://kisskb.ellerman.id.au/kisskb/buildresult/6100860/

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
--
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/