On Fri, Sep 24, 2010 at 01:43:50PM +0200, Jean-Christophe PLAGNIOL-VILLARD wrote: > On 13:15 Fri 24 Sep , Sascha Hauer wrote: > > On Fri, Sep 24, 2010 at 01:00:45PM +0200, Jean-Christophe PLAGNIOL-VILLARD wrote: > > > > >>>>- | ( (uint32_t) (b)[(i) + 3] ); \ > > > > >>>>-} > > > > >>>>-#endif > > > > >>>>- > > > > >>>>-#ifndef PUT_UINT32_BE > > > > >>>>-#define PUT_UINT32_BE(n,b,i) { \ > > > > >>>>- (b)[(i) ] = (unsigned char) ( (n)>> 24 ); \ > > > > >>>>- (b)[(i) + 1] = (unsigned char) ( (n)>> 16 ); \ > > > > >>>>- (b)[(i) + 2] = (unsigned char) ( (n)>> 8 ); \ > > > > >>>>- (b)[(i) + 3] = (unsigned char) ( (n) ); \ > > > > >>>>-} > > > > >>>>-#endif > > > > >>>>+#define GET_UINT32_BE(n,b,i) (n) = be32_to_cpu(((uint32_t*)(b))[i / 4]) > > > > >>>>+#define PUT_UINT32_BE(n,b,i) ((uint32_t*)(b))[i / 4] = cpu_to_be32(n) > > > > >>>> > > > > >>>> > > > > >>> > > > > >>>The previous macros served two purposes: endian swapping and performing > > > > >>>the memory accesses byte-by-byte. New versions are unsafe for CPUs which > > > > >>>do not support misaligned 32bit memory accesses. > > > > >> > > > > >>Indeed. We have get_unaligned_be32() / put_unaligned_be32(). These should be > > > > >>the correct functions, right? > > > > > > > > > >no-nned IIRC as be32_to_cpu and cpu_to_be32 already handle this > > > > >depending on the arch > > > > > > > > > > > > > I think get_unaligned_be32() / put_unaligned_be32() are correct in > > > > this case. be32_to_cpu / cpu_to_be32 perform endian swapping (if > > > > required) with source and destination both being 32bit variables, > > > > not memory locations ? > > > no the arch have to handle this > > > > No. As Andre mentioned cpu_to_be32 operates on variables, not on > > pointers. with ((uint32_t*)(b))[i / 4] you cast b to a pointer to > > uint32_t which you dereference with [i / 4]. This has nothing to do > > with cpu_to_be32 and will crash if the architecture does not allow > > unaligned accesses. > except cpu_to_be 32 do a swapb so it's safe cpu_to_be32 does a __swap32 and not a swapb. And I can only repeat myself: The problem is *not* cpu_to_be32 but the argument you pass *to* cpu_to_be32. Let me put it in other words: x = be32_to_cpu(((uint32_t*)(b))[i / 4]) can be written as u32 y = ((uint32_t*)(b))[i / 4]; x = be32_to_cpu(y); which can also be written as: u32 *z = (uint32_t *)b; u32 y = z[i / 4]; x = be32_to_cpu(y); And this will crash in the first line if b is not aligned. Sascha -- Pengutronix e.K. | | Industrial Linux Solutions | http://www.pengutronix.de/ | Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | _______________________________________________ barebox mailing list barebox@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/barebox