mtd: map: fixed bug in 64-bit systems

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Gitweb:     http://git.infradead.org/?p=mtd-2.6.git;a=commit;h=a4d62babf988fe5dfde24437fa135ef147bc7aa0
Commit:     a4d62babf988fe5dfde24437fa135ef147bc7aa0
Parent:     f83c3838b9146b891d0405d3a83660e8f6aed02f
Author:     Wang Haitao <wang.haitao1 at zte.com.cn>
AuthorDate: Thu Aug 22 19:32:38 2013 +0800
Committer:  Brian Norris <computersforpeace at gmail.com>
CommitDate: Wed Nov 6 23:32:59 2013 -0800

    mtd: map: fixed bug in 64-bit systems
    
    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 at zte.com.cn>
    Signed-off-by: Zhang Yi <zhang.yi20 at zte.com.cn>
    Signed-off-by: Lu Zhongjun <lu.zhongjun at zte.com.cn>
    Cc: <stable at vger.kernel.org>
    Signed-off-by: Brian Norris <computersforpeace at gmail.com>
---
 include/linux/mtd/map.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/linux/mtd/map.h b/include/linux/mtd/map.h
index 4b02512..5f487d7 100644
--- a/include/linux/mtd/map.h
+++ b/include/linux/mtd/map.h
@@ -365,7 +365,7 @@ static inline map_word map_word_load_partial(struct map_info *map, map_word orig
 			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(struct map_info *map)
 
 	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;