On Thu, Nov 08, 2012 at 10:53:07AM -0500, Theodore Ts'o wrote: > Hey Darrick, > > I was looking at this code a bit more closely while applying the > revised version of this patch --- and this in particular raised a red > flag for me: > > *(u32 *)desc.ctx = crc; > ... > return *(u32 *)desc.ctx; > > Does this raise any byte swapping issues? Looking at how the crc32 > code in crypto/ works, I'm almost certain this is broken on big-endian > systems, and we need to add le32_to_cup() and cpu_to_le32() calls here. > > Am I missing something? crc32_[bl]e_generic() in lib/crc32.c contains the appropriate be/le-to-cpu conversion calls to ensure that the results are always returned in cpu-endian format. The crypto/crc32.c file is basically just a crypto-hash wrapper around the lib/crc32.c code, and don't touch the endianness at all. The ext4 code receives the results from the crypto code in cpu-endian format and always converts it to (or from) little-endian format when accessing disk structures. As far as e2fsprogs, it leaves the checksums in le format, only converting it to cpu-endian format when verifying or setting the checksum. --D > > - Ted -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
