kbuild: add support for zstd compressed modules

kmod 28 supports modules compressed in zstd format so let's add this
possibility to kernel.
Signed-off-by: Piotr Gorski <lucjan.lucjanov@gmail.com>
Reviewed-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

init/Kconfig

@@ -2242,7 +2242,7 @@ choice
 
 	  Please note that the tool used to load modules needs to support the
 	  corresponding algorithm. module-init-tools MAY support gzip, and kmod
-	  MAY support gzip and xz.
+	  MAY support gzip, xz and zstd.
 
 	  Your build system needs to provide the appropriate compression tool
 	  to compress the modules.
@@ -2267,6 +2267,12 @@ config MODULE_COMPRESS_XZ
 	  Compress modules with XZ. The installed modules are suffixed
 	  with .ko.xz.
 
+config MODULE_COMPRESS_ZSTD
+	bool "ZSTD"
+	help
+	  Compress modules with ZSTD. The installed modules are suffixed
+	  with .ko.zst.
+
 endchoice
 
 config MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS

scripts/Makefile.modinst

@@ -21,6 +21,7 @@ endif
 suffix-y				:=
 suffix-$(CONFIG_MODULE_COMPRESS_GZIP)	:= .gz
 suffix-$(CONFIG_MODULE_COMPRESS_XZ)	:= .xz
+suffix-$(CONFIG_MODULE_COMPRESS_ZSTD)	:= .zst
 
 modules := $(patsubst $(extmod_prefix)%, $(dst)/%$(suffix-y), $(modules))
 
@@ -95,6 +96,8 @@ quiet_cmd_gzip = GZIP    $@
       cmd_gzip = $(KGZIP) -n -f $<
 quiet_cmd_xz = XZ      $@
       cmd_xz = $(XZ) --lzma2=dict=2MiB -f $<
+quiet_cmd_zstd = ZSTD    $@
+      cmd_zstd = $(ZSTD) -T0 --rm -f -q $<
 
 $(dst)/%.ko.gz: $(dst)/%.ko FORCE
 	$(call cmd,gzip)
@@ -102,6 +105,9 @@ $(dst)/%.ko.gz: $(dst)/%.ko FORCE
 $(dst)/%.ko.xz: $(dst)/%.ko FORCE
 	$(call cmd,xz)
 
+$(dst)/%.ko.zst: $(dst)/%.ko FORCE
+	$(call cmd,zstd)
+
 PHONY += FORCE
 FORCE: