Re: [Qemu-devel] [PATCH V7 2/4] tests/migration: Convert the boot block compilation script into Makefile

[Wei Huang <wei@redhat.com>]

On 03/02/2018 09:25 AM, Laurent Vivier wrote:
> On 28/02/2018 19:02, Wei Huang wrote:
>> The x86 boot block header currently is generated with a shell script.
>> To better support other CPUs (e.g. aarch64), we convert the script
>> into Makefile. This allows us to 1) support cross-compilation easily,
>> and 2) avoid creating a script file for every architecture.
>>
>> Signed-off-by: Wei Huang <wei@redhat.com>
>> Reviewed-by: Andrew Jones <drjones@redhat.com>
>> ---
>>  tests/migration/Makefile                 | 36 ++++++++++++++++++++++++++++++++
>>  tests/migration/rebuild-x86-bootblock.sh | 33 -----------------------------
>>  tests/migration/x86-a-b-bootblock.h      |  2 +-
>>  tests/migration/x86-a-b-bootblock.s      |  5 ++---
>>  4 files changed, 39 insertions(+), 37 deletions(-)
>>  create mode 100644 tests/migration/Makefile
>>  delete mode 100755 tests/migration/rebuild-x86-bootblock.sh
>>
>> diff --git a/tests/migration/Makefile b/tests/migration/Makefile
>> new file mode 100644
>> index 0000000000..8fbedaa8b8
>> --- /dev/null
>> +++ b/tests/migration/Makefile
>> @@ -0,0 +1,36 @@
>> +#
>> +# Copyright (c) 2016-2018 Red Hat, Inc. and/or its affiliates
>> +#
>> +# Authors:
>> +#   Dave Gilbert <dgilbert@redhat.com>
>> +#
>> +# This work is licensed under the terms of the GNU GPL, version 2 or later.
>> +# See the COPYING file in the top-level directory.
>> +#
>> +export __note
>> +override define __note
>> +/* This file is automatically generated from
>> + * tests/migration/$<, edit that and then run
>> + * "make $@" inside tests/migration to update,
>> + * and then remember to send both in your patch submission.
>> + */
>> +endef
>> +
>> +all: x86-a-b-bootblock.h
>> +# Dummy command so that make thinks it has done something
>> +	@true
>> +
>> +SRC_PATH=../..
>> +include $(SRC_PATH)/rules.mak
> 
> does it work in not in-tree build?

Yes, I tried it with a out-of-tree build and it worked. More
specifically, because .h file (e.g. x86-a-b-bootblock.h) is provided,
this Makefile is disjoint from the main build system and it has to be
invoked explicitly. So it won't be affected by out-of-tree build.

> 
>> +
>> +x86_64_cross_prefix := $(call find-cross-prefix,x86_64)
>> +
>> +x86-a-b-bootblock.h: x86-a-b-bootblock.s
>> +	$(x86_64_cross_prefix)as --32 -march=i486 $< -o x86.o
>> +	$(x86_64_cross_prefix)objcopy -O binary x86.o x86.boot
>> +	dd if=x86.boot of=x86.bootsect bs=256 count=2 skip=124
>> +	echo "$$__note" > $@
>> +	xxd -i x86.bootsect | sed -e 's/.*int.*//' >> $@
> 
> To be really in the spirit of a makefile, you should have a rule by target:
> 
> x86.o: x86-a-b-bootblock.s
> 	$(x86_64_cross_prefix)as --32 -march=i486 $< -o x86.o
> 
> x86.boot: x86.o
> 	$(x86_64_cross_prefix)objcopy -O binary x86.o x86.boot
> 
> x86.bootsect: x86.boot
> 	dd if=x86.boot of=x86.bootsect bs=256 count=2 skip=124
> 
> x86-a-b-bootblock.h: x86.bootsect
> 	echo "$$__note" > header.tmp
> 	xxd -i x86.bootsect | sed -e 's/.*int.*//' >> header.tmp
> 	mv header.tmp $@
> 

It is cleaner, I agree. But it will make the Makefile quite bulky
(remember that we have to do the same for aarch64 and others).

> Thanks,
> Laurent
>