Date:   Sun, 7 Jan 2018 10:51:21 -0800
From:   Martin Kelly <martin@...tingkelly.com>
To:     Paul Gortmaker <paul.gortmaker@...driver.com>
Cc:     linux-kbuild@...r.kernel.org, kernel-janitors@...r.kernel.org,
        linux-embedded@...r.kernel.org,
        David Woodhouse <dwmw2@...radead.org>,
        Matt Mackall <mpm@...enic.com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Michal Marek <michal.lkml@...kovi.net>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] tools: fix cross-compile var export

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@...tingkelly.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@...tingkelly.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.
>>
>> 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 ${CROSS_COMPILE}gcc
> arm-poky-linux-gnueabi-gcc
> 
> Although arm-poky-linux-gnueabi-gcc is a cross-compiler, we've lost many 
> build flags, notably --sysroot, which enables us to find the right 
> libraries to link against. Without this change, I get this kind of error 
> in all the affected Makefiles:
> 
> martin@...cade:~/src/linux/tools$ 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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