linux-kernel - Re: [PATCH] lib/xz: Fix powerpc build with KERNEL

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Date:   Wed, 19 Sep 2018 07:52:42 +0200
From:   Christophe LEROY <christophe.leroy@....fr>
To:     Joel Stanley <joel@....id.au>,
        Krzysztof Kozlowski <krzk@...nel.org>
Cc:     linuxppc-dev@...ts.ozlabs.org,
        Oliver O'Halloran <oohall@...il.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] lib/xz: Fix powerpc build with KERNEL_XZ



Le 19/09/2018 à 01:07, Joel Stanley a écrit :
> 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@....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 = 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

Christophe

>   
>   	uint32_t i;
>   	uint32_t j;
>