[PATCH -v2 02/10] m68k,mm: Fix ColdFire pgd_alloc()

Peter Zijlstra
2020-01-31T12:56:42Z

From: Will Deacon <will@kernel.org>

I also notice that building for m5475evb_defconfig with vanilla v5.5
triggers this scary looking warning due to a mismatch between the pgd
size and the (8k!) page size:

| In function 'pgd_alloc.isra.111',
| inlined from 'mm_alloc_pgd' at kernel/fork.c:634:12,
| inlined from 'mm_init.isra.112' at kernel/fork.c:1043:6:
| ./arch/m68k/include/asm/string.h:72:25: warning: '__builtin_memcpy' forming offset [4097, 8192] is out of the bounds [0, 4096] of object 'kernel_pg_dir' with type 'pgd_t[1024]' {aka 'struct <anonymous>[1024]'} [-Warray-bounds]
| #define memcpy(d, s, n) __builtin_memcpy(d, s, n)
| ^~~~~~~~~~~~~~~~~~~~~~~~~
| ./arch/m68k/include/asm/mcf_pgalloc.h:93:2: note: in expansion of macro 'memcpy'
| memcpy(new_pgd, swapper_pg_dir, PAGE_SIZE);
| ^~~~~~

Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
arch/m68k/include/asm/mcf_pgalloc.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/m68k/include/asm/mcf_pgalloc.h
+++ b/arch/m68k/include/asm/mcf_pgalloc.h
@@ -90,7 +90,7 @@ static inline pgd_t *pgd_alloc(struct mm
new_pgd = (pgd_t *)__get_free_page(GFP_DMA | __GFP_NOWARN);
if (!new_pgd)
return NULL;
- memcpy(new_pgd, swapper_pg_dir, PAGE_SIZE);
+ memcpy(new_pgd, swapper_pg_dir, PTRS_PER_PGD * sizeof(pgd_t));
memset(new_pgd, 0, PAGE_OFFSET >> PGDIR_SHIFT);
return new_pgd;
}