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    Subject[PATCH 3.12 070/212] mtd: map: fixed bug in 64-bit systems
    Date
    3.12-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Wang Haitao <wang.haitao1@zte.com.cn>

    commit a4d62babf988fe5dfde24437fa135ef147bc7aa0 upstream.

    Hardware:
    CPU: XLP832,the 64-bit OS
    NOR Flash:S29GL128S 128M
    Software:
    Kernel:2.6.32.41
    Filesystem:JFFS2
    When writing files, errors appear:
    Write len 182 but return retlen 180
    Write of 182 bytes at 0x072c815c failed. returned -5, retlen 180
    Write len 186 but return retlen 184
    Write of 186 bytes at 0x072caff4 failed. returned -5, retlen 184
    These errors exist only in 64-bit systems,not in 32-bit systems. After analysis, we
    found that the left shift operation is wrong in map_word_load_partial. For instance:
    unsigned char buf[3] ={0x9e,0x3a,0xea};
    map_bankwidth(map) is 4;
    for (i=0; i < 3; i++) {
    int bitpos;
    bitpos = (map_bankwidth(map)-1-i)*8;
    orig.x[0] &= ~(0xff << bitpos);
    orig.x[0] |= buf[i] << bitpos;
    }

    The value of orig.x[0] is expected to be 0x9e3aeaff, but in this situation(64-bit
    System) we'll get the wrong value of 0xffffffff9e3aeaff due to the 64-bit sign
    extension:
    buf[i] is defined as "unsigned char" and the left-shift operation will convert it
    to the type of "signed int", so when left-shift buf[i] by 24 bits, the final result
    will get the wrong value: 0xffffffff9e3aeaff.

    If the left-shift bits are less than 24, then sign extension will not occur. Whereas
    the bankwidth of the nor flash we used is 4, therefore this BUG emerges.

    Signed-off-by: Pang Xunlei <pang.xunlei@zte.com.cn>
    Signed-off-by: Zhang Yi <zhang.yi20@zte.com.cn>
    Signed-off-by: Lu Zhongjun <lu.zhongjun@zte.com.cn>
    Signed-off-by: Brian Norris <computersforpeace@gmail.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    include/linux/mtd/map.h | 4 ++--
    1 file changed, 2 insertions(+), 2 deletions(-)

    --- a/include/linux/mtd/map.h
    +++ b/include/linux/mtd/map.h
    @@ -365,7 +365,7 @@ static inline map_word map_word_load_par
    bitpos = (map_bankwidth(map)-1-i)*8;
    #endif
    orig.x[0] &= ~(0xff << bitpos);
    - orig.x[0] |= buf[i-start] << bitpos;
    + orig.x[0] |= (unsigned long)buf[i-start] << bitpos;
    }
    }
    return orig;
    @@ -384,7 +384,7 @@ static inline map_word map_word_ff(struc

    if (map_bankwidth(map) < MAP_FF_LIMIT) {
    int bw = 8 * map_bankwidth(map);
    - r.x[0] = (1 << bw) - 1;
    + r.x[0] = (1UL << bw) - 1;
    } else {
    for (i=0; i<map_words(map); i++)
    r.x[i] = ~0UL;



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