On 06/30/2011 06:22 PM, Alexander Graf wrote:
Regarding that. There's another option - the ioctl code embeds the
structure size. So if we extend the ioctl parsing to pad up (or
truncate down) from the user's size to our size, and similarly in the
other direction, we can get away from this ugliness.
Some years ago I posted a generic helper that did this (and also
kmalloc'ed and kfree'd the data itself), but it wasn't received
favourably. Maybe I should try again (and we can possibly use it in
kvm even if it is rejected for general use, though that's against our
principles of pushing all generic infrastructure to the wider kernel).
That does sound interesting, but requires a lot more thought to be put
into the actual code, as we basically need to read out the feature
bitmap, then provide a minimum size for the chosen features and then
decide if they fit in.
Why? just put the things you want in the structure.
old userspace -> new kernel: we auto-zero the parts userspace left out,
and zero means old behaviour, so everthing works
new userspace -> old kernel: truncate. Userspace shouldn't have used
any new features (KVM_CAP), and we can -EINVAL if the truncated section
contains a nonzero bit.
--
error compiling committee.c: too many arguments to function
_______________________________________________
Linuxppc-dev mailing list
Linuxppc-dev@lists.ozlabs.org
https://lists.ozlabs.org/listinfo/linuxppc-dev
