On Thu, Apr 07, 2022 at 11:58:55AM +0200, Pali Rohár wrote: > On Thursday 07 April 2022 11:54:55 Miquel Raynal wrote: > > Hi Pali, > > > > p...@kernel.org wrote on Thu, 7 Apr 2022 11:41:59 +0200: > > > > > On Thursday 07 April 2022 09:54:21 Miquel Raynal wrote: > > > > Hi Pali, > > > > > > > > p...@kernel.org wrote on Wed, 6 Apr 2022 23:31:53 +0200: > > > > > > > > Would you mind explaining a little bit how this change fixes it? It > > > > does not look straightforward to me. > > > > > > Yes! I though that it is straightforward this change... > > > byteorder/little_endian.h defines cpu_to_le* macros for Little Endian > > > systems and byteorder/big_endian.h for Big Endian systems. > > > > > > File asm/byteorder.h is then ARCH-specific and implements macros for the > > > current architecture (by including the correct header file). > > > > > > So currently if you try to compile squashfs for big endian systems you > > > get compile error: > > > > > > In file included from ./arch/powerpc/include/asm/byteorder.h:82, > > > from include/linux/unaligned/access_ok.h:4, > > > from ./arch/powerpc/include/asm/unaligned.h:9, > > > from fs/squashfs/sqfs_filesystem.h:11, > > > from fs/squashfs/sqfs_dir.c:16: > > > include/linux/byteorder/big_endian.h:34: warning: "__cpu_to_le32" > > > redefined > > > #define __cpu_to_le32(x) ((__force __le32)__swab32((x))) > > > > > > In file included from fs/squashfs/sqfs_dir.c:10: > > > include/linux/byteorder/little_endian.h:34: note: this is the location > > > of the previous definition > > > #define __cpu_to_le32(x) ((__force __le32)(__u32)(x)) > > > > > > Or: > > > > > > In file included from fs/squashfs/sqfs.c:14: > > > include/linux/byteorder/little_endian.h:89:21: error: redefinition of > > > ‘__be16_to_cpup’ > > > static inline __u16 __be16_to_cpup(const __be16 *p) > > > ^~~~~~~~~~~~~~ > > > In file included from ./arch/powerpc/include/asm/byteorder.h:82, > > > from include/linux/unaligned/access_ok.h:4, > > > from ./arch/powerpc/include/asm/unaligned.h:9, > > > from fs/squashfs/sqfs.c:10: > > > include/linux/byteorder/big_endian.h:89:21: note: previous definition > > > of ‘__be16_to_cpup’ was here > > > static inline __u16 __be16_to_cpup(const __be16 *p) > > > ^~~~~~~~~~~~~~ > > > > > > As some header files include correct asm/byteorder.h file and this > > > squashfs includes additional little_endian.h. > > > > Great, thanks for the thorough explanation. Based on what you said, > > wouldn't it be cleaner to just get rid of the little_endian.h include > > rather than also use the ARCH specific byteorder.h header? > > I think that this is not possible. squashfs code uses le16_to_cpu() > macro and its correct definition is provided only by arch specific > asm/byteorder.h.
Miquel, is this sufficient explanation? Thanks. -- Tom
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