On Tue, Aug 23, 2022 at 11:42:33AM +0100, Robin Murphy wrote: > On 2022-08-23 03:51, Alyssa Rosenzweig wrote: > > > -static size_t get_pgsize(u64 addr, size_t size) > > > +static size_t get_pgsize(u64 addr, size_t size, size_t *count) > > > { > > > - if (addr & (SZ_2M - 1) || size < SZ_2M) > > > - return SZ_4K; > > > + size_t blk_offset = -addr % SZ_2M; > > > > addr is unsigned. if this is correct, it's magic. > > Eh, it's just well-defined unsigned integer overflow. Take "SZ_2M - (addr % > SZ_2M)", realise the first term can be anything that's zero modulo SZ_2M, > including zero, then also that the operations can be done in either order to > give the same result, and there you go. Shrug. It still seems voodoo to me but if this is normal kernel style I'm not going to complain, Acked-by for the patch regardless.