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Re: [Qemu-devel] [RFC PATCH 1/1] linux-user: Probe the guest base for sh
From: |
Paul Brook |
Subject: |
Re: [Qemu-devel] [RFC PATCH 1/1] linux-user: Probe the guest base for shared objects when needed |
Date: |
Thu, 28 Jun 2012 01:47:33 +0100 |
User-agent: |
KMail/1.13.7 (Linux/3.2.0-2-amd64; KDE/4.8.3; x86_64; ; ) |
> On 28.06.2012, at 02:06, Paul Brook wrote:
> >>> openSUSE uses a version patched so that IIUC 3G are reserved.
> >>> Just today this failed on a system where swap got disabled and the
> >>> mmap() thus failed.
> >>
> >> Err... why? We map with MAP_NORESERVE, so swap shouldn't matter...
> >
> > I can't say if it's the same cause, but we fail with "ulimit -v 4046848".
> >
> > Incidentally, it seems a strange that we only reserve 0xf7000000 bytes,
> > not the full 4G.
>
> Uh, I think that was because of the vdso shared page that is allocated on
> top of -R.
That can't be right. The whole point of -R is that it defines all the guest
accessible virtual address space. The surrounding space is liable to be used
by something else, and we must not make any assumptions about it.
Further inspection shows that guest_validate_base contains some extremely
bogus code.
If the guest needs something at the top of its address space then we need to
offset address zero within the block, and ensure accesses wrap appropriately.
Paul
- Re: [Qemu-devel] [RFC PATCH 1/1] linux-user: Probe the guest base for shared objects when needed, (continued)
- Re: [Qemu-devel] [RFC PATCH 1/1] linux-user: Probe the guest base for shared objects when needed, Richard Henderson, 2012/06/12
- Re: [Qemu-devel] [RFC PATCH 1/1] linux-user: Probe the guest base for shared objects when needed, Meador Inge, 2012/06/12
- Re: [Qemu-devel] [RFC PATCH 1/1] linux-user: Probe the guest base for shared objects when needed, Meador Inge, 2012/06/27
- Re: [Qemu-devel] [RFC PATCH 1/1] linux-user: Probe the guest base for shared objects when needed, Richard Henderson, 2012/06/27
- Re: [Qemu-devel] [RFC PATCH 1/1] linux-user: Probe the guest base for shared objects when needed, Peter Maydell, 2012/06/27
- Re: [Qemu-devel] [RFC PATCH 1/1] linux-user: Probe the guest base for shared objects when needed, Andreas Färber, 2012/06/27
- Re: [Qemu-devel] [RFC PATCH 1/1] linux-user: Probe the guest base for shared objects when needed, Richard Henderson, 2012/06/27
- Re: [Qemu-devel] [RFC PATCH 1/1] linux-user: Probe the guest base for shared objects when needed, Andreas Färber, 2012/06/27
- Re: [Qemu-devel] [RFC PATCH 1/1] linux-user: Probe the guest base for shared objects when needed, Paul Brook, 2012/06/27
- Re: [Qemu-devel] [RFC PATCH 1/1] linux-user: Probe the guest base for shared objects when needed, Alexander Graf, 2012/06/27
- Re: [Qemu-devel] [RFC PATCH 1/1] linux-user: Probe the guest base for shared objects when needed,
Paul Brook <=
- Re: [Qemu-devel] [RFC PATCH 1/1] linux-user: Probe the guest base for shared objects when needed, Meador Inge, 2012/06/27
- Re: [Qemu-devel] [RFC PATCH 1/1] linux-user: Probe the guest base for shared objects when needed, Paul Brook, 2012/06/27
- Re: [Qemu-devel] [RFC PATCH 1/1] linux-user: Probe the guest base for shared objects when needed, Meador Inge, 2012/06/27