On 14 February 2017 at 21:27, Arnd Bergmann <[email protected]> wrote: > With 4 levels of 16KB pages, we get this warning about the fact that we are > copying a whole page into an array that is declared as having only two > pointers > for the top level of the page table: > > arch/arm64/mm/mmu.c: In function 'paging_init': > arch/arm64/mm/mmu.c:528:2: error: 'memcpy' writing 16384 bytes into a region > of size 16 overflows the destination [-Werror=stringop-overflow=] > > This is harmless since we actually reserve a whole page in the definition of > the > array that comes from, and just the extern declaration is short. The pgdir > is initialized to zero either way, so copying the actual entries here seems > like the best solution. > > Signed-off-by: Arnd Bergmann <[email protected]>
We should see the same issue with 64k/3 levels, since its PGD_SIZE is also much smaller than its PAGE_SIZE. This is a much more common configuration, so I am surprised you found it on 16k/4 levels first. In any case, the fix is correct IMO, so Acked-by: Ard Biesheuvel <[email protected]> > --- > arch/arm64/mm/mmu.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c > index 2131521ddc24..b805c017f789 100644 > --- a/arch/arm64/mm/mmu.c > +++ b/arch/arm64/mm/mmu.c > @@ -525,7 +525,7 @@ void __init paging_init(void) > * To do this we need to go via a temporary pgd. > */ > cpu_replace_ttbr1(__va(pgd_phys)); > - memcpy(swapper_pg_dir, pgd, PAGE_SIZE); > + memcpy(swapper_pg_dir, pgd, PGD_SIZE); > cpu_replace_ttbr1(lm_alias(swapper_pg_dir)); > > pgd_clear_fixmap(); > -- > 2.9.0 >
