Re: [PATCH] kernel/memremap, kasan: Make ZONE_DEVICE with work with KASAN

[kbuild test robot]

Hi Andrey,

I love your patch! Yet something to improve:

[auto build test ERROR on linus/master]
[also build test ERROR on v4.18-rc2]
[cannot apply to next-20180625]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Andrey-Ryabinin/kernel-memremap-kasan-Make-ZONE_DEVICE-with-work-with-KASAN/20180626-023131
config: xtensa-allyesconfig (attached as .config)
compiler: xtensa-linux-gcc (GCC) 8.1.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # save the attached .config to linux build tree
        GCC_VERSION=8.1.0 make.cross ARCH=xtensa 

All error/warnings (new ones prefixed by >>):

   mm/kasan/kasan_init.c: In function 'kasan_populate_zero_shadow':
>> mm/kasan/kasan_init.c:267:9: error: implicit declaration of function 'p4d_alloc_one'; did you mean 'pud_alloc_one'? [-Werror=implicit-function-declaration]
        p = p4d_alloc_one(&init_mm, addr);
            ^~~~~~~~~~~~~
            pud_alloc_one
>> mm/kasan/kasan_init.c:267:7: warning: assignment to 'pgd_t *' {aka 'struct <anonymous> *'} from 'int' makes pointer from integer without a cast [-Wint-conversion]
        p = p4d_alloc_one(&init_mm, addr);
          ^
   cc1: some warnings being treated as errors

vim +267 mm/kasan/kasan_init.c

   211	
   212	/**
   213	 * kasan_populate_zero_shadow - populate shadow memory region with
   214	 *                               kasan_zero_page
   215	 * @shadow_start - start of the memory range to populate
   216	 * @shadow_end   - end of the memory range to populate
   217	 */
   218	int __ref kasan_populate_zero_shadow(const void *shadow_start,
   219					const void *shadow_end)
   220	{
   221		unsigned long addr = (unsigned long)shadow_start;
   222		unsigned long end = (unsigned long)shadow_end;
   223		pgd_t *pgd = pgd_offset_k(addr);
   224		unsigned long next;
   225	
   226		do {
   227			next = pgd_addr_end(addr, end);
   228	
   229			if (IS_ALIGNED(addr, PGDIR_SIZE) && end - addr >= PGDIR_SIZE) {
   230				p4d_t *p4d;
   231				pud_t *pud;
   232				pmd_t *pmd;
   233	
   234				/*
   235				 * kasan_zero_pud should be populated with pmds
   236				 * at this moment.
   237				 * [pud,pmd]_populate*() below needed only for
   238				 * 3,2 - level page tables where we don't have
   239				 * puds,pmds, so pgd_populate(), pud_populate()
   240				 * is noops.
   241				 *
   242				 * The ifndef is required to avoid build breakage.
   243				 *
   244				 * With 5level-fixup.h, pgd_populate() is not nop and
   245				 * we reference kasan_zero_p4d. It's not defined
   246				 * unless 5-level paging enabled.
   247				 *
   248				 * The ifndef can be dropped once all KASAN-enabled
   249				 * architectures will switch to pgtable-nop4d.h.
   250				 */
   251	#ifndef __ARCH_HAS_5LEVEL_HACK
   252				pgd_populate(&init_mm, pgd, lm_alias(kasan_zero_p4d));
   253	#endif
   254				p4d = p4d_offset(pgd, addr);
   255				p4d_populate(&init_mm, p4d, lm_alias(kasan_zero_pud));
   256				pud = pud_offset(p4d, addr);
   257				pud_populate(&init_mm, pud, lm_alias(kasan_zero_pmd));
   258				pmd = pmd_offset(pud, addr);
   259				pmd_populate_kernel(&init_mm, pmd, lm_alias(kasan_zero_pte));
   260				continue;
   261			}
   262	
   263			if (pgd_none(*pgd)) {
   264				p4d_t *p;
   265	
   266				if (slab_is_available())
 > 267					p = p4d_alloc_one(&init_mm, addr);
   268				else
   269					p = early_alloc(PAGE_SIZE, NUMA_NO_NODE);
   270				if (!p)
   271					return -ENOMEM;
   272	
   273				pgd_populate(&init_mm, pgd, p);
   274			}
   275			zero_p4d_populate(pgd, addr, next);
   276		} while (pgd++, addr = next, addr != end);
   277	
   278		return 0;
   279	}
   280	

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