[Qemu-devel] Re: linux-user issues

[malc <av1474@comtv.ru>]

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.

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