On Thu, Jan 23, 2025 at 11:09:47PM +0200, Costa Shulyupin wrote: > Hi. I've found this: > > Pointers are __u64, cast from/to a uintptr_t on the userspace side and > from/to a void __user * in the kernel. Try really hard not to delay this > conversion or worse, fiddle the raw __u64 through your code since that > diminishes the checking tools like sparse can provide. The macro > u64_to_user_ptr can be used in the kernel to avoid warnings about integers > and pointers of different sizes. > > https://origin.kernel.org/doc/html/latest/process/botching-up-ioctls.html#:~:text=Pointers%20are%20__u64 That is talking about the ioctl user/kernel boundry and passing pointers across it. Not the use of pointers directly in the kernel tree. The goal of that paragraph is to tell people to always use a 64bit value for a pointer they are putting into an ioctl, which ensures that the structure remains the same size no matter if you are running on a system that has 32bit or 64bit pointers. So while this is great advice, and should be followed, it doesn't really discuss the implicit rule that "unsigned long can always hold a pointer" that Linux relies on. hope this helps, greg k-h _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
