On Mon, May 30, 2022 at 1:04 AM Johannes Berg <johannes@xxxxxxxxxxxxxxxx> wrote: > > On Fri, 2022-05-27 at 11:56 -0700, David Gow wrote: > > > > The UML-specific KASAN initializer uses mmap to map the roughly 2.25TB > > You say 2.25TB here, and > > > +config KASAN_SHADOW_OFFSET > > + hex > > + depends on KASAN > > + default 0x100000000000 > > + help > > + This is the offset at which the ~2.25TB of shadow memory is > > here too, of course. > > But I notice that I get ~16TB address space use when running, > > > +/* used in kasan_mem_to_shadow to divide by 8 */ > > +#define KASAN_SHADOW_SCALE_SHIFT 3 > > + > > +#ifdef CONFIG_X86_64 > > +#define KASAN_HOST_USER_SPACE_END_ADDR 0x00007fffffffffffUL > > +/* KASAN_SHADOW_SIZE is the size of total address space divided by 8 */ > > +#define KASAN_SHADOW_SIZE ((KASAN_HOST_USER_SPACE_END_ADDR + 1) >> \ > > + KASAN_SHADOW_SCALE_SHIFT) > > because this ends up being 0x100000000000, i.e. 16 TiB. > > Is that intentional? Was something missed? Maybe > KASAN_HOST_USER_SPACE_END_ADDR was too big? > > It doesn't really matter, but I guess then the documentation should be > updated. Whoops, the amount of shadow memory allocated was changed for v1 of this patch (it was ~2.25 TB in the original RFC). I've updated these comments in v3: https://lore.kernel.org/lkml/20220630074757.2739000-2-davidgow@xxxxxxxxxx/ -- David
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