On Wed, Sep 19, 2018 at 3:52 PM, Christophe LEROY
[off-list ref] wrote:

Le 19/09/2018 =C3=A0 01:07, Joel Stanley a =C3=A9crit :

quoted

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@jms.id.au>
---
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 =3D CRC32_POLY_LE;
+       const uint32_t poly =3D 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.

Christophe

quoted

        uint32_t i;
        uint32_t j;