On Fri, Jan 21, 2022 at 08:32:25AM +0100, Christian Borntraeger wrote: > So in essence adding something like this and then providing raw_copy_from/to_user_key? > (whitespace damaged, just pasted in) > > diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h > index ac0394087f7d..3b6e78ee211c 100644 > --- a/include/linux/uaccess.h > +++ b/include/linux/uaccess.h > @@ -201,6 +201,59 @@ copy_to_user(void __user *to, const void *from, unsigned long n) > return n; > } > + > +#if defined(__s390x__) && defined(CONFIG_KVM) > +/* > + * Variants that pass along an access key. Uses by KVM on s390x to implement > + * key checks for guests that use storage keys Must be kept in sync with the > + * non-key variants from above. The only difference is the _key suffix when > + * calling raw_copy_from/to_user_key. > + */ This is too architecture specific, I wouldn't like to see __s390__ or KVM dependencies. This should be a bit more generic, so other architectures _might_ also make use of this interface that is: > +static inline __must_check unsigned long > +_copy_from_user_key(void *to, const void __user *from, unsigned long n, u8 key) Make key unsigned long, add support for INLINE_COPY_TO_USER, and maybe add a wrapper, so this works on all architectures, e.g. if raw_copy_to_user_key() is not defined, then fall back to raw_copy_to_user() and ignore the key parameter. Just some ideas. The _only_ concern about the previous implementation I have, is that we could run out-of-sync with common code wrt instrumentation and other options. Given how sensitive uaccess ops are, I think we should try to avoid that by all cost, if possible. Does that make sense?
