Re: [PATCH] tools: fix cross-compile var export

Martin Kelly <martin@xxxxxxxxxxxxxxxx> · Sun, 7 Jan 2018 10:51:21 -0800

On 01/07/2018 10:31 AM, Martin Kelly wrote:
On 01/07/2018 08:11 AM, Paul Gortmaker wrote:
[[PATCH] tools: fix cross-compile var export] On 06/01/2018 (Sat 
12:16) Martin Kelly wrote:

From: Martin Kelly <martin@xxxxxxxxxxxxxxxx>

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@xxxxxxxxxxxxxxxx>
---
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.

I think you will have better luck if you go subsystem by subsystem, e.g.
send gpio change to gpio maintainer, usb change to usb maintainer and so
on.  In addition, you'll want to try and understand/explain why those
lines were added in the 1st place and how it won't break other existing
use cases by removing them.  Maybe "git blame" will help for that...

P.
--


I can send patches subsystem-by-subsystem, but this patch fixes a single 
bug that applies to many Makefiles. It fixes it by putting the correct 
logic into tools/scripts/Makefile.include, which each Makefiles 
includes. If I do this subsystem-by-subsystem, we will just duplicate 
these lines into every Makefile:

+$(call allow-override,CC,$(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)

We could do this, but it's a lot of code duplication and means that 
anyone making a new Makefile must also copy the lines or their Makefile 
will have this bug. Since the bug fix generically applies everywhere, I 
think it's most correct for it to go into the common Makefile.

If there is really no maintainer for the tools/scripts/Makefile.include 
file, then maybe I have to send subsystem-by-subsystem, but that seems 
less than ideal.

I do understand why the CC = $(CROSS_COMPILE)gcc lines exist; it is to 
enable cross-compile when you set the $CROSS_COMPILE env var and to use 
native gcc when that is not set. The bug is that if you already have $CC 
set to your cross-compiler (which is what the Yocto SDK and other 
toolchains do), then most of your command-line gets clobbered. Here's an 
example from an ARM Yocto SDK I have:

$ echo $CC
arm-poky-linux-gnueabi-gcc -march=armv7-a -mfpu=neon -mfloat-abi=hard 
-mcpu=cortex-a8 
--sysroot=/home/martin/src/poky/build/sdk/sysroots/cortexa8hf-neon-poky-linux-gnueabi 


$ echo $CROSS_COMPILE
arm-poky-linux-gnueabi-

$ echo ${CROSS_COMPILE}gcc
arm-poky-linux-gnueabi-gcc

Although arm-poky-linux-gnueabi-gcc is a cross-compiler, we've lost many 
build flags, notably --sysroot, which enables us to find the right 
libraries to link against. Without this change, I get this kind of error 
in all the affected Makefiles:

martin@cascade:~/src/linux/tools$ make iio
[snip]
iio_event_monitor.c:18:10: fatal error: unistd.h: No such file or directory
  #include <unistd.h>
           ^~~~~~~~~~

This occurs because unistd.h is in the sysroot, but we've dropped the 
--sysroot flag:
$ find /home/martin/src/poky/build/sdk/sysroots -path 
'*/usr/include/unistd.h'
/home/martin/src/poky/build/sdk/sysroots/cortexa8hf-neon-poky-linux-gnueabi/usr/include/unistd.h 


With the change, we add do CC = $(CROSS_COMPILE)gcc if and only if CC is 
not already set. I'm happy to add all these details to the commit 
description.


Urg, I accidentally sent to kernel-kbuild instead of linux-kbuild, 
changed now. It appears that past changes to 
tools/scripts/Makefile.include have been handled by linux-kbuild and 
often Masahiro Yamada.

Perhaps the best sequence here is to send a patch to kbuild adding the 
call-override function and calls to it to the main common Makefile. Then 
I can send individual subsystem patches dropping the individual CC = 
lines and similar. It will be 13 patches instead of 1 but will 
eventually result in the same thing.

Paul, any thoughts?


  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


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