On Thu, Jul 29, 2021 at 03:29:19PM +0200, Vasily Gorbik wrote:
> zstd decompression uses __builtin_clz() which fails back to __clzdi2()
> when the kernel is built for older hardware like z900. This leads to
> build failures like the following:
> s390x-11.1.0-ld: /devel/src/kernel/arch/s390/boot/compressed/../../../../lib/zstd/bitstream.h:148: undefined reference to `__clzdi2'
> 
> Fix that by optionally including lib/clz_ctz.c into the decompressor.
> 
> Reported-by: kernel test robot <lkp@intel.com>
> Fixes: 7b034d9c1b08 ("s390/boot: add zstd support")
> Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
> ---
>  arch/s390/boot/compressed/Makefile  | 1 +
>  arch/s390/boot/compressed/clz_ctz.c | 2 ++
>  2 files changed, 3 insertions(+)
>  create mode 100644 arch/s390/boot/compressed/clz_ctz.c

Applied, thanks!