On Wed, Jul 05, 2023 at 04:08:08PM -0700, Mike Kravetz wrote: > I was recently asked about the behavior of mprotect on a hugetlb > mapping where addr or addr+len is not hugetlb page size aligned. As > one might expect, EINVAL is returned in such cases. However, the man > page makes no mention of alignment requirements for hugetlb mappings. > > I am happy to submit man page updates if people agree this is the correct > behavior. We might even want to check alignment earlier in the code > path as we fail when trying to split the vma today. > > An alternative behavior would be to operate on whole hugetlb pages within > the range addr - addr+len. After a careful re-reading of the mprotect() man page, I suggest the following behaviour ... addr must be a multiple of the hpage size. Otherwise -EINVAL. len should be rounded up to hpage size. I wonder how likely this change would be to break userspace code. Maybe some test cases.
