Le dimanche 07 août 2011 à 18:30 +0900, Akinobu Mita a écrit :
> The check_bytes() function is used by slub debugging. It returns a pointer
> to the first unmatching byte for a character in the given memory area.
>
> If the character for matching byte is greater than 0x80, check_bytes()
> doesn't work. Becuase 64-bit pattern is generated as below.
>
> value64 = value | value << 8 | value << 16 | value << 24;
> value64 = value64 | value64 << 32;
>
> The integer promotions are performed and sign-extended as the type of value
> is u8. The upper 32 bits of value64 is 0xffffffff in the first line, and
> the second line has no effect.
>
> This fixes the 64-bit pattern generation.
>
> Signed-off-by: Akinobu Mita <akinobu.mita@xxxxxxxxx>
> Cc: Christoph Lameter <cl@xxxxxxxxxxxxxxxxxxxx>
> Cc: Pekka Enberg <penberg@xxxxxxxxxx>
> Cc: Matt Mackall <mpm@xxxxxxxxxxx>
> Cc: linux-mm@xxxxxxxxx
> ---
> mm/slub.c | 2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/mm/slub.c b/mm/slub.c
> index eb5a8f9..5695f92 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -701,7 +701,7 @@ static u8 *check_bytes(u8 *start, u8 value, unsigned int bytes)
> return check_bytes8(start, value, bytes);
>
> value64 = value | value << 8 | value << 16 | value << 24;
> - value64 = value64 | value64 << 32;
> + value64 = (value64 & 0xffffffff) | value64 << 32;
> prefix = 8 - ((unsigned long)start) % 8;
>
> if (prefix) {
Still buggy I am afraid. Could we use the following ?
value64 = value;
value64 |= value64 << 8;
value64 |= value64 << 16;
value64 |= value64 << 32;
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