Re: [Qemu-devel] Re: [PATCH] efault - add data type to put_user()/get_user()

[Fabrice Bellard <fabrice@bellard.org>]

I think that using host addresses in __put_user and __get_user is not
logical. They should use target addresses as get_user and put_user. As
Paul said, It is not worth mixing get/put/copy and lock/unlock functions.

The ultimate goal of such cleanup is not only to generate -EFAULT
correctly but also to be able to have arbitrary address space changes.

In fact it would be good to be able to introduce an arbitrary address
space change (such as a translation as Paul did) so that we can verify
that all the Linux emulation stills works in this case.

Regards,

Fabrice.

Thayne Harbaugh wrote:
> On Wed, 2007-10-31 at 16:44 -0600, Thayne Harbaugh wrote:
>> This patch updates get_user() and put_user() to take a third argument of
>> data type.  get_user() and put_user() use target address which are
>> target_ulong and don't reflect the data type pointed to in target
>> memory.
>>
>> Simply casting the target_ulong to a type before passing to
>> get/put_user() is poor because target_ulong isn't always a simple cast
>> to a host type (consider 32 bit on 64 bit where address are either
>> extended or truncate).  Also, simple casting of the argument to
>> get/put_user() results in several warnings when target and long pointer
>> sizes don't match.
>>
>> This patch has additional updates to fix places where get/put_user() are
>> already used.
> 
> This is an updated patch that doesn't conflict with the
> abi_long/abi_ulong changes from a couple weeks ago.