linux-kernel - Re: [PATCH] kdb: use memmove instead of overlapping memcpy

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Date:   Fri, 2 Feb 2018 09:08:40 -0600
From:   Jason Wessel <jason.wessel@...driver.com>
To:     Arnd Bergmann <arnd@...db.de>,
        Daniel Thompson <daniel.thompson@...aro.org>
CC:     Nicolas Pitre <nico@...aro.org>, Andi Kleen <ak@...ux.intel.com>,
        <kgdb-bugreport@...ts.sourceforge.net>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] kdb: use memmove instead of overlapping memcpy

On 02/02/2018 08:59 AM, Arnd Bergmann wrote:
> gcc discovered that the memcpy() arguments in kdbnearsym() overlap, so
> we should really use memmove(), which is defined to handle that correctly:
> 
> In function 'memcpy',
>      inlined from 'kdbnearsym' at /git/arm-soc/kernel/debug/kdb/kdb_support.c:132:4:
> /git/arm-soc/include/linux/string.h:353:9: error: '__builtin_memcpy' accessing 792 bytes at offsets 0 and 8 overlaps 784 bytes at offset 8 [-Werror=restrict]
>    return __builtin_memcpy(p, q, size);
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>   kernel/debug/kdb/kdb_support.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/debug/kdb/kdb_support.c b/kernel/debug/kdb/kdb_support.c
> index 5d8ef3a07ecd..1ad4370ccbf0 100644
> --- a/kernel/debug/kdb/kdb_support.c
> +++ b/kernel/debug/kdb/kdb_support.c
> @@ -129,13 +129,13 @@ int kdbnearsym(unsigned long addr, kdb_symtab_t *symtab)
>   		}
>   		if (i >= ARRAY_SIZE(kdb_name_table)) {
>   			debug_kfree(kdb_name_table[0]);
> -			memcpy(kdb_name_table, kdb_name_table+1,
> +			memmove(kdb_name_table, kdb_name_table+1,
>   			       sizeof(kdb_name_table[0]) *
>   			       (ARRAY_SIZE(kdb_name_table)-1));
>   		} else {
>   			debug_kfree(knt1);
>   			knt1 = kdb_name_table[i];
> -			memcpy(kdb_name_table+i, kdb_name_table+i+1,
> +			memmove(kdb_name_table+i, kdb_name_table+i+1,
>   			       sizeof(kdb_name_table[0]) *
>   			       (ARRAY_SIZE(kdb_name_table)-i-1));
>   		}
> 


That is good by me.   Many thanks!  Added to queue.

Reviewed-by: Jason Wessel <jason.wessel@...driver.com>

Jason.