Subject: Re: [PATCH v3] kbuild: add support for zstd compressed modules

[Piotr Gorski <lucjan.lucjanov@gmail.com>]

I originally posted the patch in a different form [1] even before Masahiro's changes. 
I've been testing this solution since December last year and posted it in March this year, 
after I made sure everything was working fine. This patch was tested by Oleksandr and he also didn't report any objections. [2]

Masahiro notified me about the planned changes [3] and asked me to resend this patch, adjusted to those changes, which I did.

My current logs:

lucjan@archlinux ~ $ zgrep CONFIG_DEBUG_INFO /proc/config.gz
CONFIG_DEBUG_INFO=y
# CONFIG_DEBUG_INFO_REDUCED is not set
# CONFIG_DEBUG_INFO_COMPRESSED is not set
# CONFIG_DEBUG_INFO_SPLIT is not set
CONFIG_DEBUG_INFO_DWARF4=y
CONFIG_DEBUG_INFO_BTF=y
CONFIG_DEBUG_INFO_BTF_MODULES=y
lucjan@archlinux ~ $ zgrep CONFIG_MODULE_COMPRESS_ZSTD /proc/config.gz
CONFIG_MODULE_COMPRESS_ZSTD=y
CONFIG_MODULE_COMPRESS_ZSTD_LEVEL=19

Pay no attention to CONFIG_MODULE_COMPRESS_ZSTD_LEVEL as this is not in the upstream, it's an additional patch I use. 

The only difference - I don't use clang. Maybe those who use will comment on this. 
I relied on the opinions of Oleksander and a dozen other users who reported no errors in using zstd module compression.  

[1] https://marc.info/?l=linux-kbuild&m=161710402402989&w=2

[2] https://marc.info/?l=linux-kbuild&m=161710503403517&w=2

[3] https://marc.info/?l=linux-kbuild&m=161780602730829&w=2