On 7/22/19 2:55 PM, Arnd Bergmann wrote:
> ARM64 randdconfig builds regularly run into a build error, especially
> when NUMA_BALANCING and SPARSEMEM are enabled but not SPARSEMEM_VMEMMAP:
>
> #error "KASAN: not enough bits in page flags for tag"
>
> The last-cpuid bits are already contitional on the available space,
> so the result of the calculation is a bit random on whether they
> were already left out or not.
>
> Adding the kasan tag bits before last-cpuid makes it much more likely
> to end up with a successful build here, and should be reliable for
> randconfig at least, as long as that does not randomize NR_CPUS
> or NODES_SHIFT but uses the defaults.
>
> In order for the modified check to not trigger in the x86 vdso32 code
> where all constants are wrong (building with -m32), enclose all the
> definitions with an #ifdef.
>
> Fixes: 2813b9c02962 ("kasan, mm, arm64: tag non slab memory allocated via
> pagealloc")
> Link: https://lore.kernel.org/lkml/20190618095347.3850490-1-a...@arndb.de/
> Reviewed-by: Andrey Konovalov <andreyk...@google.com>
> Signed-off-by: Arnd Bergmann <a...@arndb.de>
Reviewed-by: Andrey Ryabinin <aryabi...@virtuozzo.com>
