Re: [linux-stable-rc:linux-5.4.y 7045/7049] mipsel-linux-ld: decompress.c:undefined reference to `memmove'

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Fri, Jul 09, 2021 at 03:20:41PM +0800, Gao Xiang wrote:
> Hi Greg, stable all,
> 
> On Fri, Jul 09, 2021 at 01:50:16PM +0800, Gao Xiang wrote:
> > On Wed, Jul 07, 2021 at 01:15:28AM +0800, kernel test robot wrote:
> > > tree:   https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git linux-5.4.y
> > > head:   3909e2374335335c9504467caabc906d3f7487e4
> > > commit: defcc2b5e54a4724fb5733f802edf5dd596018b6 [7045/7049] lib/lz4: explicitly support in-place decompression
> > > config: mips-randconfig-r036-20210706 (attached as .config)
> > > compiler: mipsel-linux-gcc (GCC) 9.3.0
> > > reproduce (this is a W=1 build):
> > >         wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
> > >         chmod +x ~/bin/make.cross
> > >         # https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git/commit/?id=defcc2b5e54a4724fb5733f802edf5dd596018b6
> > >         git remote add linux-stable-rc https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git
> > >         git fetch --no-tags linux-stable-rc linux-5.4.y
> > >         git checkout defcc2b5e54a4724fb5733f802edf5dd596018b6
> > >         # save the attached .config to linux build tree
> > >         mkdir build_dir
> > >         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross O=build_dir ARCH=mips SHELL=/bin/bash
> > > 
> > > If you fix the issue, kindly add following tag as appropriate
> > > Reported-by: kernel test robot <lkp@intel.com>
> > 
> > Which is weird, does the preboot environment miss memmove() on mipsel?
> > Just a guess, I may look into that myself later...
> > 
> 
> After manually checking, I found memmove() for the mips preboot environment
> was incidentally introduced by commit a510b616131f ("MIPS: Add support for
> ZSTD-compressed kernels") which wasn't included in v5.4, but included in
> v5.10 as below (so v5.10.y is fine):
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/arch/mips/boot/compressed?h=v5.10&id=a510b616131f85215ba156ed67e5ed1c0701f80f
> 
> And when I applied the following patch partially from the original
> commit, the compile error with the command lines mentioned above was gone:
> 
> diff --git a/arch/mips/boot/compressed/string.c b/arch/mips/boot/compressed/string.c
> index 43beecc3587c..e9ab7ea592ba 100644
> --- a/arch/mips/boot/compressed/string.c
> +++ b/arch/mips/boot/compressed/string.c
> @@ -27,3 +27,19 @@ void *memset(void *s, int c, size_t n)
>  		ss[i] = c;
>  	return s;
>  }
> +
> +void * __weak memmove(void *dest, const void *src, size_t n)
> +{
> +	unsigned int i;
> +	const char *s = src;
> +	char *d = dest;
> +
> +	if ((uintptr_t)dest < (uintptr_t)src) {
> +		for (i = 0; i < n; i++)
> +			d[i] = s[i];
> +	} else {
> +		for (i = n; i > 0; i--)
> +			d[i - 1] = s[i - 1];
> +	}
> +	return dest;
> +}
> 
> How to backport such commit partially to the v5.4.y stable kernel?

Please submit it in a format which we can apply it.

> ... Also, it would be better to check other mips compile combinations
> automatically since it's hard for me to check all such combinations
> one-by-one...

That's what kernelci is for, can you use that?

thanks,

greg k-h