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.
[...]
> > + /* Allocation and free stack information. */
> > + int num_alloc_stack;
> > + int num_free_stack;
> > + unsigned long alloc_stack[KFENCE_STACK_DEPTH];
> > + unsigned long free_stack[KFENCE_STACK_DEPTH];
>
> It was a concious decision to not use stackdepot, right? Perhaps it
> makes sense to document the reason somewhere.
Yes; we want to avoid the dynamic allocations that stackdepot does.
[...]
Thanks,
-- Marco
