Files
linux/include/linux
Wang Haitao 1da42d7c5f mtd: map: fixed bug in 64-bit systems
commit a4d62babf9 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>
2013-12-04 10:56:22 -08:00
..
2013-05-17 14:31:05 -04:00
2013-07-25 14:07:23 -07:00
2013-12-04 10:56:22 -08:00
2013-05-07 19:46:02 -07:00
2013-05-01 16:36:22 +05:30
2013-07-28 16:30:11 -07:00
2013-05-07 18:38:27 -07:00
2013-04-29 18:28:40 -07:00
2013-10-13 16:08:28 -07:00
2013-07-28 16:30:05 -07:00
2013-04-30 17:04:06 -07:00
2013-04-30 17:04:00 -07:00
2013-10-13 16:08:35 -07:00
2013-07-21 18:21:29 -07:00
2013-04-29 18:28:44 -07:00
2013-05-04 14:47:26 -04:00
2013-04-29 15:54:28 -07:00
2013-05-28 11:05:08 +02:00
2013-04-29 15:54:28 -07:00
2013-04-12 10:26:23 +02:00
2013-04-09 14:13:29 -04:00
2013-04-30 15:50:12 +05:30
2013-08-20 08:43:02 -07:00
2013-07-28 16:29:55 -07:00
2013-04-29 15:54:37 -07:00