On Thu, Nov 06, 2025 at 12:31:28PM +0100, Christophe Leroy wrote: > On 32 bits it is more tricky. In theory user space can go up to > 0xbfffffff while kernel will usually start at 0xc0000000. So a gap > needs to be added in-between. Allthough in theory a single 4k page > would suffice, it is easier and more efficient to enforce a 128k gap > below kernel, as it simplifies the masking.
Do we have the requirement that the first access of a masked pointer is within 4k of the initial address? Suppose the pointer is to an 16k array, and the memcpy happens to like going backwards. Then a 4k hole just won't do.
