Re: [PATCH] lib/xz: Fix powerpc build with KERNEL_XZ

[Christophe LEROY]

Le 19/09/2018 Ã 08:44, Oliver a ÃcritÂ:
> On Wed, Sep 19, 2018 at 3:52 PM, Christophe LEROY
> <christophe.leroy@xxxxxx> wrote:
> > Le 19/09/2018 Ã 01:07, Joel Stanley a Ãcrit :
> > > This partially reverts faa16bc404d72a5 ("lib: Use existing define with
> > > polynomial").
> > >
> > > The cleanup added a dependency on include/linux, which broke the PowerPC
> > > boot wrapper/decompresser when KERNEL_XZ is enabled:
> > >
> > >     BOOTCC  arch/powerpc/boot/decompress.o
> > >    In file included from
> > > arch/powerpc/boot/../../../lib/decompress_unxz.c:233,
> > >                    from arch/powerpc/boot/decompress.c:42:
> > >    arch/powerpc/boot/../../../lib/xz/xz_crc32.c:18:10: fatal error:
> > >    linux/crc32poly.h: No such file or directory
> > >     #include <linux/crc32poly.h>
> > >              ^~~~~~~~~~~~~~~~~~~
> > >
> > > The powerpc decompressor is a hairy corner of the kernel. Even while
> > > building
> > > a 64-bit kernel it needs to build a 32-bit binary and therefore avoid
> > > including
> > > files from include/linux.
> > >
> > > Fixes: faa16bc404d7 ("lib: Use existing define with polynomial")
> > > Signed-off-by: Joel Stanley <joel@xxxxxxxxx>
> > > ---
> > > We need to clean up the powerpc boot decompresser but that work will be
> > > more involved than we would include in a late -rc. Please consider
> > > merging this fix for 4.19. Thanks!
> > >
> > >    lib/xz/xz_crc32.c | 3 +--
> > >    1 file changed, 1 insertion(+), 2 deletions(-)
> > >
> > > diff --git a/lib/xz/xz_crc32.c b/lib/xz/xz_crc32.c
> > > index 25a5d87e2e4c..34532d14fd4c 100644
> > > --- a/lib/xz/xz_crc32.c
> > > +++ b/lib/xz/xz_crc32.c
> > > @@ -15,7 +15,6 @@
> > >     * but they are bigger and use more memory for the lookup table.
> > >     */
> > >    -#include <linux/crc32poly.h>
> > >    #include "xz_private.h"
> > >      /*
> > > @@ -30,7 +29,7 @@ STATIC_RW_DATA uint32_t xz_crc32_table[256];
> > >      XZ_EXTERN void xz_crc32_init(void)
> > >    {
> > > -       const uint32_t poly = CRC32_POLY_LE;
> > > +       const uint32_t poly = 0xEDB88320;
> >
> >
> > Maybe avoid capital letters ?
> >
> > What about adding something like the following in xz_private.h instead:
> >
> > #define CRC32_POLY_LE 0xedb88320
>
> The problem is that it's pulling in linux/crc32poly.h. To support old
> systems with a 32bit Open Firmware we boot wrapper we build the boot
> wrapper as a 32bit ELF even for a 64 bit kernel. The headers generated
> by Kbuild are only valid for the 64bit kernel so we have to avoid
> pulling them into the boot wrapper.

Yes I understood, hence my proposal to redefine CRC32_POLY_LE in 
xz_private.h instead of including linux/crc32poly.h

It avoids modifying the C code.

Christophe

> > Christophe
> >
> > >          uint32_t i;
> > >          uint32_t j;