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SubjectRe: [PATCH] ARM: add boot image dependencies not to generate invalid images
From
Hi Russel,

No more comment?
I answered your question.




2015-07-11 1:41 GMT+09:00 Masahiro Yamada <yamada.masahiro@socionext.com>:
> Hi Russel,
>
>
> 2015-07-10 19:22 GMT+09:00 Russell King - ARM Linux <linux@arm.linux.org.uk>:
>> On Mon, Jul 06, 2015 at 09:37:04PM +0900, Masahiro Yamada wrote:
>>> [3] Then, re-build "all" and "uImage" simultaneously.
>>> You will get an invalid uImage at random.
>>> $ make -s -j8 ARCH=arm UIMAGE_LOADADDR=0x80208000 all uImage
>>> Image Name: Linux-4.2.0-rc1-00008-g1c4c715-d
>>> Created: Mon Jul 6 17:52:22 2015
>>> Image Type: ARM Linux Kernel Image (uncompressed)
>>> Data Size: 26768 Bytes = 26.14 kB = 0.03 MB
>>> Load Address: 80208000
>>> Entry Point: 80208000
>>
>> At no point in the above do I see an attempt to rebuild init/main.o,
>> which there should be as you touched the corresponding .c file -
>> because you're hiding that output with -s. Please show what's going
>> on without using -s.
>
> Please see the log attached at the end of this message.
>
>
>>> "make uImage" could descend into arch/arm/boot/Makefile before
>>> "make zImage" is completed because arch/arm/Makefile describes no
>>> dependency among boot targets.
>>
>> The uImage target should depend on vmlinux, which should force the
>> rebuild of init/main.o, and relink of the top-level vmlinux file
>> before decending into arch/arm/boot/Makefile for the
>> arch/arm/boot/uImage target.
>>
>> That makefile contains the dependencies required to order things
>> correctly - the arch/arm/boot/uImage target depends on
>> arch/arm/boot/zImage, which in turn depends on
>> arch/arm/boot/compressed/vmlinux, and then arch/arm/boot/Image.
>>
>> In other words, arch/arm/boot/Makefile deals with the dependencies
>> between the targets it's responsible for building itself.
>
> No, you do not understand what is happening in here.
>
>
> The dependencies among targets such as Image, zImage, uImage,
> are fully described in arch/arm/boot/Makefile, but it is not enough.
>
> Because arch/arm/boot/Makefile is _not_ included from the top-level Makefile,
> the top-level build cannot know the dependency between zImage and uImage.
>
> arch/arm/Makefile, which is included from the top Makefile,
> only describes that zImage depends on vmlinux,
> and uImage depends on vmlinux as well.
> But, no dependency between zImage and uImage is written in arch/arm/Makefile.
>
> Consequently, we run make with the parallel option, first Kbuild
> updates vmlinux,
> and then two different threads descends into arch/arm/boot/Makefile
> almost at the same time, one for updating zImage and the other for uImage.
>
> The is a race between the two threads.
>
> While one thread is re-generating zImage and also uImage on top of that,
> the other thread tries to re-generate zImage independently.
>
> zImage is overwritten by the slower thread, and then uImage is
> re-generated based on the broken zImage.
>
> See my detailed build log below:
>
> Please note:
> "Kernel: arch/arm/boot/zImage is ready"
> is displayed twice,
> the first one is shown before the uImage log, and the second one is
> after uImage.
>
> zImage is correct, but uImage is extremely small when this problem happens.
>
>
>
> $ git describe
> v4.2-rc1-62-gc4b5fd3
>
>
> $ touch init/main.c
> $ make -j8 ARCH=arm UIMAGE_LOADADDR=0x80208000 all uImage
> CHK include/config/kernel.release
> CHK include/generated/uapi/linux/version.h
> CHK include/generated/utsrelease.h
> make[1]: `include/generated/mach-types.h' is up to date.
> CHK include/generated/timeconst.h
> CHK include/generated/bounds.h
> CHK include/generated/asm-offsets.h
> CALL scripts/checksyscalls.sh
> CC init/main.o
> CHK include/generated/compile.h
> LD init/built-in.o
> LINK vmlinux
> LD vmlinux.o
> MODPOST vmlinux.o
> GEN .version
> CHK include/generated/compile.h
> UPD include/generated/compile.h
> CC init/version.o
> LD init/built-in.o
> KSYM .tmp_kallsyms1.o
> KSYM .tmp_kallsyms2.o
> LD vmlinux
> SORTEX vmlinux
> SYSMAP System.map
> OBJCOPY arch/arm/boot/Image
> Building modules, stage 2.
> Kernel: arch/arm/boot/Image is ready
> GZIP arch/arm/boot/compressed/piggy.gzip
> AS arch/arm/boot/compressed/piggy.gzip.o
> Kernel: arch/arm/boot/Image is ready
> GZIP arch/arm/boot/compressed/piggy.gzip
> LD arch/arm/boot/compressed/vmlinux
> OBJCOPY arch/arm/boot/zImage
> Kernel: arch/arm/boot/zImage is ready
> UIMAGE arch/arm/boot/uImage
> Image Name: Linux-4.2.0-rc1-00062-gc4b5fd3-d
> Created: Sat Jul 11 01:22:22 2015
> Image Type: ARM Linux Kernel Image (uncompressed)
> Data Size: 26472 Bytes = 25.85 kB = 0.03 MB
> Load Address: 80208000
> Entry Point: 80208000
> Image arch/arm/boot/uImage is ready
> MODPOST 192 modules
> AS arch/arm/boot/compressed/piggy.gzip.o
> LD arch/arm/boot/compressed/vmlinux
> OBJCOPY arch/arm/boot/zImage
> Kernel: arch/arm/boot/zImage is ready
> $ LANG=C ls -l arch/arm/boot/
> total 19636
> -rwxrwxr-x 1 masahiro masahiro 13766656 Jul 11 01:22 Image
> -rw-rw-r-- 1 masahiro masahiro 3137 Jul 3 01:17 Makefile
> drwxrwxr-x 2 masahiro masahiro 4096 Jul 3 01:17 bootp
> drwxrwxr-x 2 masahiro masahiro 4096 Jul 11 01:22 compressed
> drwxrwxr-x 3 masahiro masahiro 155648 Jul 11 00:58 dts
> -rw-rw-r-- 1 masahiro masahiro 1648 Jul 3 01:17 install.sh
> -rw-rw-r-- 1 masahiro masahiro 26536 Jul 11 01:22 uImage
> -rwxrwxr-x 1 masahiro masahiro 6135048 Jul 11 01:22 zImage
>
>
>
>
>
>
>
> --
> Best Regards
> Masahiro Yamada



--
Best Regards
Masahiro Yamada


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