kbuild: add variables for compression tools

Allow user to use alternative implementations of compression tools,
such as pigz, pbzip2, pxz. For example, multi-threaded tools to
speed up the build:
$ make GZIP=pigz BZIP2=pbzip2

Variables _GZIP, _BZIP2, _LZOP are used internally because original env
vars are reserved by the tools. The use of GZIP in gzip tool is obsolete
since 2015. However, alternative implementations (e.g., pigz) still rely
on it. BZIP2, BZIP, LZOP vars are not obsolescent.

The credit goes to @grsecurity.

As a sidenote, for multi-threaded lzma, xz compression one can use:
$ export XZ_OPT="--threads=0"
Signed-off-by: Denis Efremov <efremov@linux.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

Makefile

@@ -458,6 +458,26 @@ PYTHON		= python
 PYTHON3		= python3
 CHECK		= sparse
 BASH		= bash
+GZIP		= gzip
+BZIP2		= bzip2
+LZOP		= lzop
+LZMA		= lzma
+LZ4		= lz4c
+XZ		= xz
+
+# GZIP, BZIP2, LZOP env vars are used by the tools. Support them as the command
+# line interface, but use _GZIP, _BZIP2, _LZOP internally.
+_GZIP          := $(GZIP)
+_BZIP2         := $(BZIP2)
+_LZOP          := $(LZOP)
+
+# Reset GZIP, BZIP2, LZOP in this Makefile
+override GZIP=
+override BZIP2=
+override LZOP=
+
+# Reset GZIP, BZIP2, LZOP in recursive invocations
+MAKEOVERRIDES += GZIP= BZIP2= LZOP=
 
 CHECKFLAGS     := -D__linux__ -Dlinux -D__STDC__ -Dunix -D__unix__ \
 		  -Wbitwise -Wno-return-void -Wno-unknown-attribute $(CF)
@@ -506,6 +526,7 @@ CLANG_FLAGS :=
 export ARCH SRCARCH CONFIG_SHELL BASH HOSTCC KBUILD_HOSTCFLAGS CROSS_COMPILE LD CC
 export CPP AR NM STRIP OBJCOPY OBJDUMP OBJSIZE READELF PAHOLE LEX YACC AWK INSTALLKERNEL
 export PERL PYTHON PYTHON3 CHECK CHECKFLAGS MAKE UTS_MACHINE HOSTCXX
+export _GZIP _BZIP2 _LZOP LZMA LZ4 XZ
 export KBUILD_HOSTCXXFLAGS KBUILD_HOSTLDFLAGS KBUILD_HOSTLDLIBS LDFLAGS_MODULE
 
 export KBUILD_CPPFLAGS NOSTDINC_FLAGS LINUXINCLUDE OBJCOPYFLAGS KBUILD_LDFLAGS
@@ -1020,10 +1041,10 @@ export mod_strip_cmd
 mod_compress_cmd = true
 ifdef CONFIG_MODULE_COMPRESS
   ifdef CONFIG_MODULE_COMPRESS_GZIP
-    mod_compress_cmd = gzip -n -f
+    mod_compress_cmd = $(_GZIP) -n -f
   endif # CONFIG_MODULE_COMPRESS_GZIP
   ifdef CONFIG_MODULE_COMPRESS_XZ
-    mod_compress_cmd = xz -f
+    mod_compress_cmd = $(XZ) -f
   endif # CONFIG_MODULE_COMPRESS_XZ
 endif # CONFIG_MODULE_COMPRESS
 export mod_compress_cmd

arch/arm/boot/deflate_xip_data.sh

@@ -56,7 +56,7 @@ trap 'rm -f "$XIPIMAGE.tmp"; exit 1' 1 2 3
 # substitute the data section by a compressed version
 $DD if="$XIPIMAGE" count=$data_start iflag=count_bytes of="$XIPIMAGE.tmp"
 $DD if="$XIPIMAGE"  skip=$data_start iflag=skip_bytes |
-gzip -9 >> "$XIPIMAGE.tmp"
+$_GZIP -9 >> "$XIPIMAGE.tmp"
 
 # replace kernel binary
 mv -f "$XIPIMAGE.tmp" "$XIPIMAGE"

arch/ia64/Makefile

@@ -40,7 +40,7 @@ $(error Sorry, you need a newer version of the assember, one that is built from
 endif
 
 quiet_cmd_gzip = GZIP    $@
-cmd_gzip = cat $(real-prereqs) | gzip -n -f -9 > $@
+cmd_gzip = cat $(real-prereqs) | $(_GZIP) -n -f -9 > $@
 
 quiet_cmd_objcopy = OBJCOPY $@
 cmd_objcopy = $(OBJCOPY) $(OBJCOPYFLAGS) $(OBJCOPYFLAGS_$(@F)) $< $@

arch/m68k/Makefile

@@ -135,10 +135,10 @@ vmlinux.gz: vmlinux
 ifndef CONFIG_KGDB
 	cp vmlinux vmlinux.tmp
 	$(STRIP) vmlinux.tmp
-	gzip -9c vmlinux.tmp >vmlinux.gz
+	$(_GZIP) -9c vmlinux.tmp >vmlinux.gz
 	rm vmlinux.tmp
 else
-	gzip -9c vmlinux >vmlinux.gz
+	$(_GZIP) -9c vmlinux >vmlinux.gz
 endif
 
 bzImage: vmlinux.bz2
@@ -148,10 +148,10 @@ vmlinux.bz2: vmlinux
 ifndef CONFIG_KGDB
 	cp vmlinux vmlinux.tmp
 	$(STRIP) vmlinux.tmp
-	bzip2 -1c vmlinux.tmp >vmlinux.bz2
+	$(_BZIP2) -1c vmlinux.tmp >vmlinux.bz2
 	rm vmlinux.tmp
 else
-	bzip2 -1c vmlinux >vmlinux.bz2
+	$(_BZIP2) -1c vmlinux >vmlinux.bz2
 endif
 
 archclean:

arch/parisc/Makefile

@@ -162,7 +162,7 @@ vmlinuz: bzImage
 	$(OBJCOPY) $(boot)/bzImage $@
 else
 vmlinuz: vmlinux
-	@gzip -cf -9 $< > $@
+	@$(_GZIP) -cf -9 $< > $@
 endif
 
 install:

kernel/gen_kheaders.sh

@@ -88,7 +88,7 @@ find $cpio_dir -type f -print0 |
 find $cpio_dir -printf "./%P\n" | LC_ALL=C sort | \
     tar "${KBUILD_BUILD_TIMESTAMP:+--mtime=$KBUILD_BUILD_TIMESTAMP}" \
     --owner=0 --group=0 --numeric-owner --no-recursion \
-    -Jcf $tarfile -C $cpio_dir/ -T - > /dev/null
+    -I $XZ -cf $tarfile -C $cpio_dir/ -T - > /dev/null
 
 echo $headers_md5 > kernel/kheaders.md5
 echo "$this_file_md5" >> kernel/kheaders.md5

scripts/Makefile.lib

@@ -244,7 +244,7 @@ cmd_objcopy = $(OBJCOPY) $(OBJCOPYFLAGS) $(OBJCOPYFLAGS_$(@F)) $< $@
 # ---------------------------------------------------------------------------
 
 quiet_cmd_gzip = GZIP    $@
-      cmd_gzip = cat $(real-prereqs) | gzip -n -f -9 > $@
+      cmd_gzip = cat $(real-prereqs) | $(_GZIP) -n -f -9 > $@
 
 # DTC
 # ---------------------------------------------------------------------------
@@ -337,19 +337,19 @@ printf "%08x\n" $$dec_size |						\
 )
 
 quiet_cmd_bzip2 = BZIP2   $@
-      cmd_bzip2 = { cat $(real-prereqs) | bzip2 -9; $(size_append); } > $@
+      cmd_bzip2 = { cat $(real-prereqs) | $(_BZIP2) -9; $(size_append); } > $@
 
 # Lzma
 # ---------------------------------------------------------------------------
 
 quiet_cmd_lzma = LZMA    $@
-      cmd_lzma = { cat $(real-prereqs) | lzma -9; $(size_append); } > $@
+      cmd_lzma = { cat $(real-prereqs) | $(LZMA) -9; $(size_append); } > $@
 
 quiet_cmd_lzo = LZO     $@
-      cmd_lzo = { cat $(real-prereqs) | lzop -9; $(size_append); } > $@
+      cmd_lzo = { cat $(real-prereqs) | $(_LZOP) -9; $(size_append); } > $@
 
 quiet_cmd_lz4 = LZ4     $@
-      cmd_lz4 = { cat $(real-prereqs) | lz4c -l -c1 stdin stdout; \
+      cmd_lz4 = { cat $(real-prereqs) | $(LZ4) -l -c1 stdin stdout; \
                   $(size_append); } > $@
 
 # U-Boot mkimage
@@ -396,7 +396,7 @@ quiet_cmd_xzkern = XZKERN  $@
                      $(size_append); } > $@
 
 quiet_cmd_xzmisc = XZMISC  $@
-      cmd_xzmisc = cat $(real-prereqs) | xz --check=crc32 --lzma2=dict=1MiB > $@
+      cmd_xzmisc = cat $(real-prereqs) | $(XZ) --check=crc32 --lzma2=dict=1MiB > $@
 
 # ASM offsets
 # ---------------------------------------------------------------------------

scripts/Makefile.package

@@ -45,7 +45,7 @@ if test "$(objtree)" != "$(srctree)"; then \
 	false; \
 fi ; \
 $(srctree)/scripts/setlocalversion --save-scmversion; \
-tar -cz $(RCS_TAR_IGNORE) -f $(2).tar.gz \
+tar -I $(_GZIP) -c $(RCS_TAR_IGNORE) -f $(2).tar.gz \
 	--transform 's:^:$(2)/:S' $(TAR_CONTENT) $(3); \
 rm -f $(objtree)/.scmversion
 
@@ -127,9 +127,9 @@ util/PERF-VERSION-GEN $(CURDIR)/$(perf-tar)/);              \
 tar rf $(perf-tar).tar $(perf-tar)/HEAD $(perf-tar)/PERF-VERSION-FILE; \
 rm -r $(perf-tar);                                                  \
 $(if $(findstring tar-src,$@),,                                     \
-$(if $(findstring bz2,$@),bzip2,                                    \
-$(if $(findstring gz,$@),gzip,                                      \
-$(if $(findstring xz,$@),xz,                                        \
+$(if $(findstring bz2,$@),$(_BZIP2),                                 \
+$(if $(findstring gz,$@),$(_GZIP),                                  \
+$(if $(findstring xz,$@),$(XZ),                                     \
 $(error unknown target $@))))                                       \
 	-f -9 $(perf-tar).tar)
 

scripts/package/buildtar

@@ -28,15 +28,15 @@ case "${1}" in
 		opts=
 		;;
 	targz-pkg)
-		opts=--gzip
+		opts="-I ${_GZIP}"
 		tarball=${tarball}.gz
 		;;
 	tarbz2-pkg)
-		opts=--bzip2
+		opts="-I ${_BZIP2}"
 		tarball=${tarball}.bz2
 		;;
 	tarxz-pkg)
-		opts=--xz
+		opts="-I ${XZ}"
 		tarball=${tarball}.xz
 		;;
 	*)

scripts/xz_wrap.sh

@@ -20,4 +20,4 @@ case $SRCARCH in
 	sparc)          BCJ=--sparc ;;
 esac
 
-exec xz --check=crc32 $BCJ --lzma2=$LZMA2OPTS,dict=32MiB
+exec $XZ --check=crc32 $BCJ --lzma2=$LZMA2OPTS,dict=32MiB