[PATCH] tools: fix cross-compile var export

[Martin Kelly <martin@martingkelly.com>]

From: Martin Kelly <martin@martingkelly.com>

Currently in a number of Makefiles, we clobber the CC, LD, and/or STRIP env vars
when cross-compiling, which breaks any additional flags that might be set (such
as sysroot). This easily shows up by using, for instance, a Yocto SDK.

Fix this by more carefully overriding the flags in the way that the perf
Makefile does.

This patch does not fix cross-compile for all the tools (some have other bugs),
but it does appear to fix it for these:

- cgroup
- freefall
- gpio
- hv
- iio
- leds
- spi
- vm
- wmi

Signed-off-by: Martin Kelly <martin@martingkelly.com>
---
This patch touches multiple subsystems, and there doesn't appear to be a global
tools maintainer, so I sent this to linux-embedded kernel-janitors, and
linux-kbuild. Please let me know if there is a better place for it.

 tools/cgroup/Makefile            |  1 -
 tools/gpio/Makefile              |  2 --
 tools/hv/Makefile                |  1 -
 tools/iio/Makefile               |  2 --
 tools/laptop/freefall/Makefile   |  1 -
 tools/leds/Makefile              |  1 -
 tools/perf/Makefile.perf         |  6 ------
 tools/power/acpi/Makefile.config |  3 ---
 tools/scripts/Makefile.include   | 18 ++++++++++++++++++
 tools/spi/Makefile               |  2 --
 tools/usb/Makefile               |  1 -
 tools/vm/Makefile                |  1 -
 tools/wmi/Makefile               |  1 -
 13 files changed, 18 insertions(+), 22 deletions(-)

diff --git a/tools/cgroup/Makefile b/tools/cgroup/Makefile
index 860fa151640a..ffca068e4a76 100644
--- a/tools/cgroup/Makefile
+++ b/tools/cgroup/Makefile
@@ -1,7 +1,6 @@
 # SPDX-License-Identifier: GPL-2.0
 # Makefile for cgroup tools
 
-CC = $(CROSS_COMPILE)gcc
 CFLAGS = -Wall -Wextra
 
 all: cgroup_event_listener
diff --git a/tools/gpio/Makefile b/tools/gpio/Makefile
index 805a2c0cf4cd..240eda014b37 100644
--- a/tools/gpio/Makefile
+++ b/tools/gpio/Makefile
@@ -12,8 +12,6 @@ endif
 # (this improves performance and avoids hard-to-debug behaviour);
 MAKEFLAGS += -r
 
-CC = $(CROSS_COMPILE)gcc
-LD = $(CROSS_COMPILE)ld
 CFLAGS += -O2 -Wall -g -D_GNU_SOURCE -I$(OUTPUT)include
 
 ALL_TARGETS := lsgpio gpio-hammer gpio-event-mon
diff --git a/tools/hv/Makefile b/tools/hv/Makefile
index 31503819454d..68c2d7b059b3 100644
--- a/tools/hv/Makefile
+++ b/tools/hv/Makefile
@@ -1,7 +1,6 @@
 # SPDX-License-Identifier: GPL-2.0
 # Makefile for Hyper-V tools
 
-CC = $(CROSS_COMPILE)gcc
 WARNINGS = -Wall -Wextra
 CFLAGS = $(WARNINGS) -g $(shell getconf LFS_CFLAGS)
 
diff --git a/tools/iio/Makefile b/tools/iio/Makefile
index a08e7a47d6a3..332ed2f6c2c2 100644
--- a/tools/iio/Makefile
+++ b/tools/iio/Makefile
@@ -12,8 +12,6 @@ endif
 # (this improves performance and avoids hard-to-debug behaviour);
 MAKEFLAGS += -r
 
-CC = $(CROSS_COMPILE)gcc
-LD = $(CROSS_COMPILE)ld
 CFLAGS += -O2 -Wall -g -D_GNU_SOURCE -I$(OUTPUT)include
 
 ALL_TARGETS := iio_event_monitor lsiio iio_generic_buffer
diff --git a/tools/laptop/freefall/Makefile b/tools/laptop/freefall/Makefile
index 5f758c489a20..b572d94255f6 100644
--- a/tools/laptop/freefall/Makefile
+++ b/tools/laptop/freefall/Makefile
@@ -2,7 +2,6 @@
 PREFIX ?= /usr
 SBINDIR ?= sbin
 INSTALL ?= install
-CC = $(CROSS_COMPILE)gcc
 
 TARGET = freefall
 
diff --git a/tools/leds/Makefile b/tools/leds/Makefile
index c379af003807..7b6bed13daaa 100644
--- a/tools/leds/Makefile
+++ b/tools/leds/Makefile
@@ -1,7 +1,6 @@
 # SPDX-License-Identifier: GPL-2.0
 # Makefile for LEDs tools
 
-CC = $(CROSS_COMPILE)gcc
 CFLAGS = -Wall -Wextra -g -I../../include/uapi
 
 all: uledmon led_hw_brightness_mon
diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf
index 68cf1360a3f3..3035ce5f6b36 100644
--- a/tools/perf/Makefile.perf
+++ b/tools/perf/Makefile.perf
@@ -144,12 +144,6 @@ define allow-override
     $(eval $(1) = $(2)))
 endef
 
-# Allow setting CC and AR and LD, or setting CROSS_COMPILE as a prefix.
-$(call allow-override,CC,$(CROSS_COMPILE)gcc)
-$(call allow-override,AR,$(CROSS_COMPILE)ar)
-$(call allow-override,LD,$(CROSS_COMPILE)ld)
-$(call allow-override,CXX,$(CROSS_COMPILE)g++)
-
 LD += $(EXTRA_LDFLAGS)
 
 HOSTCC  ?= gcc
diff --git a/tools/power/acpi/Makefile.config b/tools/power/acpi/Makefile.config
index a1883bbb0144..2cccbba64418 100644
--- a/tools/power/acpi/Makefile.config
+++ b/tools/power/acpi/Makefile.config
@@ -56,9 +56,6 @@ INSTALL_SCRIPT = ${INSTALL_PROGRAM}
 # to compile vs uClibc, that can be done here as well.
 CROSS = #/usr/i386-linux-uclibc/usr/bin/i386-uclibc-
 CROSS_COMPILE ?= $(CROSS)
-CC = $(CROSS_COMPILE)gcc
-LD = $(CROSS_COMPILE)gcc
-STRIP = $(CROSS_COMPILE)strip
 HOSTCC = gcc
 
 # check if compiler option is supported
diff --git a/tools/scripts/Makefile.include b/tools/scripts/Makefile.include
index 3fab179b1aba..09b2d0f07f66 100644
--- a/tools/scripts/Makefile.include
+++ b/tools/scripts/Makefile.include
@@ -42,6 +42,24 @@ EXTRA_WARNINGS += -Wformat
 
 CC_NO_CLANG := $(shell $(CC) -dM -E -x c /dev/null | grep -Fq "__clang__"; echo $$?)
 
+# Makefiles suck: This macro sets a default value of $(2) for the
+# variable named by $(1), unless the variable has been set by
+# environment or command line. This is necessary for CC and AR
+# because make sets default values, so the simpler ?= approach
+# won't work as expected.
+define allow-override
+  $(if $(or $(findstring environment,$(origin $(1))),\
+            $(findstring command line,$(origin $(1)))),,\
+    $(eval $(1) = $(2)))
+endef
+
+# Allow setting various cross-compile vars or setting CROSS_COMPILE as a prefix.
+$(call allow-override,CC,$(CROSS_COMPILE)gcc)
+$(call allow-override,AR,$(CROSS_COMPILE)ar)
+$(call allow-override,LD,$(CROSS_COMPILE)ld)
+$(call allow-override,CXX,$(CROSS_COMPILE)g++)
+$(call allow-override,CXX,$(CROSS_COMPILE)strip)
+
 ifeq ($(CC_NO_CLANG), 1)
 EXTRA_WARNINGS += -Wstrict-aliasing=3
 endif
diff --git a/tools/spi/Makefile b/tools/spi/Makefile
index 90615e10c79a..815d15589177 100644
--- a/tools/spi/Makefile
+++ b/tools/spi/Makefile
@@ -11,8 +11,6 @@ endif
 # (this improves performance and avoids hard-to-debug behaviour);
 MAKEFLAGS += -r
 
-CC = $(CROSS_COMPILE)gcc
-LD = $(CROSS_COMPILE)ld
 CFLAGS += -O2 -Wall -g -D_GNU_SOURCE -I$(OUTPUT)include
 
 ALL_TARGETS := spidev_test spidev_fdx
diff --git a/tools/usb/Makefile b/tools/usb/Makefile
index 4e6506078494..01d758d73b6d 100644
--- a/tools/usb/Makefile
+++ b/tools/usb/Makefile
@@ -1,7 +1,6 @@
 # SPDX-License-Identifier: GPL-2.0
 # Makefile for USB tools
 
-CC = $(CROSS_COMPILE)gcc
 PTHREAD_LIBS = -lpthread
 WARNINGS = -Wall -Wextra
 CFLAGS = $(WARNINGS) -g -I../include
diff --git a/tools/vm/Makefile b/tools/vm/Makefile
index be320b905ea7..20f6cf04377f 100644
--- a/tools/vm/Makefile
+++ b/tools/vm/Makefile
@@ -6,7 +6,6 @@ TARGETS=page-types slabinfo page_owner_sort
 LIB_DIR = ../lib/api
 LIBS = $(LIB_DIR)/libapi.a
 
-CC = $(CROSS_COMPILE)gcc
 CFLAGS = -Wall -Wextra -I../lib/
 LDFLAGS = $(LIBS)
 
diff --git a/tools/wmi/Makefile b/tools/wmi/Makefile
index e664f1167388..e0e87239126b 100644
--- a/tools/wmi/Makefile
+++ b/tools/wmi/Makefile
@@ -2,7 +2,6 @@ PREFIX ?= /usr
 SBINDIR ?= sbin
 INSTALL ?= install
 CFLAGS += -D__EXPORTED_HEADERS__ -I../../include/uapi -I../../include
-CC = $(CROSS_COMPILE)gcc
 
 TARGET = dell-smbios-example
 
-- 
2.11.0