On Tue, 18 Dec 2018 14:30:33 +0100 Andrey Konovalov <andreyknvl@xxxxxxxxxx> wrote: > Instead of changing cache->align to be aligned to KASAN_SHADOW_SCALE_SIZE > in kasan_cache_create() we can reuse the ARCH_SLAB_MINALIGN macro. > > ... > > --- a/arch/arm64/include/asm/kasan.h > +++ b/arch/arm64/include/asm/kasan.h > @@ -36,6 +36,10 @@ > #define KASAN_SHADOW_OFFSET (KASAN_SHADOW_END - (1ULL << \ > (64 - KASAN_SHADOW_SCALE_SHIFT))) > > +#ifdef CONFIG_KASAN_SW_TAGS > +#define ARCH_SLAB_MINALIGN (1ULL << KASAN_SHADOW_SCALE_SHIFT) > +#endif > + > void kasan_init(void); > void kasan_copy_shadow(pgd_t *pgdir); > asmlinkage void kasan_early_init(void); This looks unreliable. include/linux/slab.h has /* * Setting ARCH_SLAB_MINALIGN in arch headers allows a different alignment. * Intended for arches that get misalignment faults even for 64 bit integer * aligned buffers. */ #ifndef ARCH_SLAB_MINALIGN #define ARCH_SLAB_MINALIGN __alignof__(unsigned long long) #endif so if a .c file includes arch/arm64/include/asm/kasan.h after include/linux/slab.h, it can get a macro-redefined warning. If the .c file includes those headers in the other order, ARCH_SLAB_MINALIGN will get a different value compared to other .c files. Or something like that. Different architectures define ARCH_SLAB_MINALIGN in different place: ./arch/microblaze/include/asm/page.h:#define ARCH_SLAB_MINALIGN L1_CACHE_BYTES ./arch/arm/include/asm/cache.h:#define ARCH_SLAB_MINALIGN 8 ./arch/sh/include/asm/page.h:#define ARCH_SLAB_MINALIGN 8 ./arch/c6x/include/asm/cache.h:#define ARCH_SLAB_MINALIGN L1_CACHE_BYTES ./arch/sparc/include/asm/cache.h:#define ARCH_SLAB_MINALIGN __alignof__(unsigned long long) ./arch/xtensa/include/asm/processor.h:#define ARCH_SLAB_MINALIGN STACK_ALIGN which is rather bad of us. But still. I think your definition should occur in an arch header file which is reliably included from slab.h. And kasan code should get its definition of ARCH_SLAB_MINALIGN by including slab.h.
