On Tue, Sep 29, 2020 at 3:11 PM Marco Elver <[email protected]> wrote: > > On Tue, Sep 29, 2020 at 02:42PM +0200, Andrey Konovalov wrote: > [...] > > > + */ > > > + index = (addr - (unsigned long)__kfence_pool) / (PAGE_SIZE * 2) - > > > 1; > > > > Why do we subtract 1 here? We do have the metadata entry reserved for > > something? > > Above the declaration of __kfence_pool it says: > > * We allocate an even number of pages, as it simplifies calculations > to map > * address to metadata indices; effectively, the very first page > serves as an > * extended guard page, but otherwise has no special purpose. > > Hopefully that clarifies the `- 1` here.
So there are two guard pages at the beginning and only then a page that holds an object?
