Re: [Qemu-devel] RFC: [0/11] EFAULT patch

[Stuart Anderson <anderson@netsweng.com>]

On Wed, 19 Sep 2007, J. Mayer wrote:

> The idea is great but there seem to be a problem in those patches:
> you directly cast syscall arguments, which are (or should be)
> target_ulong to pointers in the host environment. You should to use the
> g2h / h2g macros to get the pointer in the host memory from the offset
> in the target address space.

I was explicitly told to _not_ use these in this code.

> Offset in the target address  space can not
> be assumed to be the same size as an address in the host address space,

And in fact, they definitely are not the same in certain cobinations.

> thus can never be casted directly to host pointer.

At some point, we have to convert things from target_long to a host
pointer. If we can agree on what that right mechanism it to do this, I'd
be glad to use it. So far, everything I've seen involved some form of
type casting.


> This used to be handled by the lock_user functions and should be handled
> in your patch too...

It was handled by g2h() which was just a typecast hidden behind the
macro.


                                 Stuart

Stuart R. Anderson                               anderson@netsweng.com
Network & Software Engineering                   http://www.netsweng.com/
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