[4.9-stable 7/9] arm64: fix warning about swapper_pg_dir overflow

Arnd Bergmann arnd at arndb.de
Mon Feb 19 02:13:26 PST 2018

commit 12f043ff2b28fa64c9123b454cbe30a8a9e1967e upstream.

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.

Acked-by: Ard Biesheuvel <ard.biesheuvel at linaro.org>
Acked-by: Mark Rutland <mark.rutland at arm.com>
Signed-off-by: Arnd Bergmann <arnd at arndb.de>
Signed-off-by: Will Deacon <will.deacon at arm.com>
[slightly adapted to apply on 4.9]
Signed-off-by: Arnd Bergmann <arnd at arndb.de>
 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 05615a3fdc6f..d5cc6d73c2c4 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -479,7 +479,7 @@ void __init paging_init(void)
 	 * To do this we need to go via a temporary pgd.
-	memcpy(swapper_pg_dir, pgd, PAGE_SIZE);
+	memcpy(swapper_pg_dir, pgd, PGD_SIZE);

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