[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] Xen hypercall API/ABI problems
>>> On 19.06.13 at 17:43, Andrew Cooper <andrew.cooper3@xxxxxxxxxx> wrote: > In memory.c, there is a possible unsigned->signed conversion error from > max_pages to rc. That's of no concern as long as the maximum possible value can't result in the value being negative. Plus it's problematic only when the hypervisor is 32-bit (as otherwise it's a conversion from "unsigned int" to "signed long". And for the list of items to be complete - there's a similar conversion for d->tot_pages. > In compat/memory.c, there is a long->int truncation error for compat > hypercalls, although newer versions of Xen cap this at INT_{MIN,MAX} That was added precisely to avoid uncontrolled truncation. > In the privcmd driver passes the hypercall rc through as the return from > the ioctl handler, containing a possible long->int truncation error. That's an outright bug, introduced by improper code transformations when porting the XenoLinux code to the upstream kernel, or - if the porting was done long enough ago - lack of noticing linux-2.6.18-xen.hg c/s 984. > From the work with XSA-55, we have already identified that the error > handling and propagation in libxc leaves a lot to be desired. However, > the hypervisor side of things is just as problematic. Given the above I'm not clear what problematic point you see. > What policy do we have about deprecating hypercall interfaces and > introducing newer ones? At a minimum, all hypercalls should be using > -errno style errors, with a possibility of returning 0 to LONG_MAX as well. > > I realise that simply changing the hypercalls in place is not possible. > Would it be acceptable to have a step change across a Xen version (say > early in 4.4) where consumers of the public interface would have to make > use of -DXEN_LEGACY_UNSAFE_HYPERCALLS (or equivalent) in an attempt to > move them forward with the API ? That's what we have __XEN_INTERFACE_VERSION__ for - just guard stuff you don't want up-to-date consumers to use anymore with a respective #if __XEN_INTERFACE_VERSION__ < 0x040400. Of course pv-ops is lacking any such version handling so far, apparently with the original hope of only using up-to-date bits. Jan _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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