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Date: Mon, 9 Jun 2008 19:19:53 +0200
From: "Laurent Desnogues" <laurent.desnogues@gmail.com>
Subject: Re: [Qemu-devel] [4710] Prevent guest reusing host memory allocations.
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To: qemu-devel@nongnu.org

On Mon, Jun 9, 2008 at 3:47 PM, Paul Brook <paul@nowt.org> wrote:
> Modified: trunk/exec.c
> ===================================================================
> --- trunk/exec.c        2008-06-09 12:10:22 UTC (rev 4709)
> +++ trunk/exec.c        2008-06-09 13:47:45 UTC (rev 4710)
> @@ -263,13 +263,33 @@
[...]
> +#if defined(CONFIG_USER_ONLY)
> +        unsigned long addr;
> +        size_t len = sizeof(PageDesc) * L2_SIZE;
> +        /* Don't use qemu_malloc because it may recurse.  */
> +        p = mmap(0, len, PROT_READ | PROT_WRITE,
> +                 MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
>         *lp = p;
> +        addr = h2g(p);
> +        if (addr == (target_ulong)addr) {
> +            page_set_flags(addr & TARGET_PAGE_MASK,
> +                           TARGET_PAGE_ALIGN(addr + len),
> +                           PAGE_RESERVED);
> +        }

I don't understand what the test is supposed to do, to me it looks
like it can't fail since we have:

#define h2g(x) ((target_ulong)(x - GUEST_BASE))

Did I miss something?


Laurent