Re: [linux-next:master] BUILD REGRESSION 0a6f624a86e766a27d23cbb73c23be62231d10ff

[Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>]

On Fri, 06 Nov 2020 08:19:36 +0800 kernel test robot <lkp@xxxxxxxxx> wrote:

> tree/branch: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git  master
> branch HEAD: 0a6f624a86e766a27d23cbb73c23be62231d10ff  Add linux-next specific files for 20201105
> 
> Error/Warning reports:
> 
> https://lore.kernel.org/linux-mm/202010281624.9m2gZw45-lkp@xxxxxxxxx
> https://lore.kernel.org/linux-mm/202010290238.M1tDrV8p-lkp@xxxxxxxxx
> https://lore.kernel.org/linux-mm/202010291054.WEZO3olr-lkp@xxxxxxxxx
> https://lore.kernel.org/linux-mm/202011020749.5XQ3Hfzc-lkp@xxxxxxxxx
> 
> ...
>
> mm/kasan/init.c:318:9: warning: variable 'pud' set but not used [-Wunused-but-set-variable]
> 

This is because mm/kasan/init.c does

static void kasan_free_pud(pud_t *pud_start, p4d_t *p4d)
{
	pud_t *pud;
	int i;

	for (i = 0; i < PTRS_PER_PUD; i++) {
		pud = pud_start + i;
		if (!pud_none(*pud))
			return;
	}

	pud_free(&init_mm, (pud_t *)page_to_virt(p4d_page(*p4d)));
	p4d_clear(p4d);
}

but arch/arm/include/asm/pgtable-2level.h does

#define pud_none(pud)           (0)

The solution here is for the arm implementation to reference `pud'. 
Typically this is done via the use of an empty static inline C function
rather than a macro.  But really all of these

#define pud_none(pud)           (0)
#define pud_bad(pud)            (0)
#define pud_present(pud)        (1)
#define pud_clear(pudp)         do { } while (0)
#define set_pud(pud,pudp)       do { } while (0)

should be thus converted.

Could someone in arm world please attend to this?

Thanks.