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[Qemu-devel] Re: linux-user issues
From: |
Paul Brook |
Subject: |
[Qemu-devel] Re: linux-user issues |
Date: |
Sun, 14 Mar 2010 15:11:30 +0000 |
User-agent: |
KMail/1.12.4 (Linux/2.6.32-trunk-amd64; KDE/4.3.4; x86_64; ; ) |
> On Sat, 13 Mar 2010, Paul Brook wrote:
> > > a) elfload.c:859
> > >
> > > #define TARGET_ELF_PAGESTART(_v) ((_v) & ~(unsigned
> > > long)(TARGET_ELF_EXEC_PAGESIZE-1))
> > >
> > > This means that for 64bit guest on a 32bit host the _v's value is
> > > silently reduced to 32bit, the cast should be abi_ulong.
> > >
> > > b) mmap.c:428
> > >
> > > real_start = start & qemu_host_page_mask;
> > >
> > > Same thing basically qemu_host_page_mask is unsigned long and so
> > > the upper bits are sliently cleared. Again qemu_host_page_mask
> > > should probably be abi_ulong.
> > >
> > > The above two make elf binary with one of the segments above 4G load
> > > and run on 32bit guest only to fail well into execution and without
> > > any indication that it shouldn't have been allowed to run in the first
> > > place.
> >
> > I'd be amazed if these are the only two issues, and expect 64-bit guests
> > on 32-bit hosts to be generally unsafe.
>
> These are the two issues i've been bitten by while trying to solve
> x86_64's far jumps, if you are okay with code silently misbehaving
> fine by me.
I never said this was ok behavior. Only that you've probably only discovered
the tip of the iceberg.
Paul