linux-kernel - [PATCH -v2 02/10] m68k,mm: Fix ColdFire pgd

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Message-Id: <20200131125403.540057688@infradead.org>
Date:   Fri, 31 Jan 2020 13:45:33 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     linux-m68k@...ts.linux-m68k.org, linux-kernel@...r.kernel.org,
        Will Deacon <will@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Michael Schmitz <schmitzmic@...il.com>,
        Greg Ungerer <gerg@...ux-m68k.org>
Subject: [PATCH -v2 02/10] m68k,mm: Fix ColdFire pgd_alloc()

From: Will Deacon <will@...nel.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@...nel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.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;
 }