From 8dfb61dcbaceb19a5ded5e9c9dcf8d05acc32294 Mon Sep 17 00:00:00 2001
From: Denis Efremov <efremov@linux.com>
Date: Fri, 5 Jun 2020 10:39:55 +0300
Subject: 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 The use of GZIP in gzip tool is obsolete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 | 25 +++++++++++++++++++++++--
 1 file changed, 23 insertions(+), 2 deletions(-)

(limited to 'Makefile')

diff --git a/Makefile b/Makefile
index 7b750dc0b2da..64ebbc1dfbef 100644
--- a/Makefile
+++ b/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
-- 
cgit