Message-ID: <CAK7LNAQ7GqCNc008ZZ4K0_BdTVMdwwVUgnfqBO-kDBmw4ikr3w@mail.gmail.com>
Date:   Thu, 21 Feb 2019 23:34:41 +0900
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     Joel Fernandes <joel@...lfernandes.org>
Cc:     Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Networking <netdev@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Alexei Starovoitov <ast@...nel.org>,
        atish patra <atishp04@...il.com>,
        Daniel Colascione <dancol@...gle.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jonathan Corbet <corbet@....net>,
        Karim Yaghmour <karim.yaghmour@...rsys.com>,
        Kees Cook <keescook@...omium.org>, kernel-team@...roid.com,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>,
        Manoj Rao <linux@...ojrajarao.com>,
        Paul McKenney <paulmck@...ux.vnet.ibm.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Randy Dunlap <rdunlap@...radead.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Shuah Khan <shuah@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Yonghong Song <yhs@...com>
Subject: Re: [PATCH v2 1/2] Provide in-kernel headers for making it easy to
 extend the kernel

On Wed, Feb 20, 2019 at 12:17 AM Joel Fernandes <joel@...lfernandes.org> wrote:

>
> Firstly, I want to apologize for not testing this and other corner cases you
> brought up. I should have known better. Since my build was working, I assumed
> that the feature is working. For that, I am very sorry.


You do not need to apologize. 0day bot usually catches build errors.
I guess 0day bot performs compile-tests only incrementally
and that is why we did not get any report.



> Secondly, it turns out Module.symvers circularly dependency problem also
> exists with another use case.
> If one does 'make modules_prepare' in a base kernel tree and then tries to
> build modules with that tree, a warning like this is printed but the module
> still gets built:
>
>   WARNING: Symbol version dump ./Module.symvers
>            is missing; modules will have no dependencies and modversions.
>
>   CC [M]  /tmp/testmod/test.o
>   Building modules, stage 2.
>   MODPOST 1 modules
>   CC      /tmp/testmod/test.mod.o
>   LD [M]  /tmp/testmod/test.ko
>
> So, I am thinking that at least for first pass I will just drop the inclusion
> of Module.symvers in the archive and allow any modules built using
> /proc/kheaders.tar.xz to not use it.
>
> Kbuild will print a warning anyway when anyone tries to build using
> /proc/kheaders.tar.xz, so if the user really wants module symbol versioning
> then they should probably use a full kernel source tree with Module.symvers
> available. For our usecase, kernel symbol versioning is a bit useless when
> using /proc/kheaders.tar.gz because the proc file is generated with the same
> kernel that the module is being built against, and subsequently loaded into
> the kernel. So it is not likely that the CRC of a kernel symbol will be
> different from what the module expects.


Without Module.symver, modpost cannot check whether references are
resolvable or not.

You will see "WARNING ... undefined" for every symbol referenced from
the module.


I am not an Android developer.
So, I will leave this judge to other people.




One more request if you have a chance to submit the next version.
Please do not hide error messages.

I wondered why you redirected stdout/stderr from the script.

I applied the following patch, and I tested.  Then I see why.

Please fix your code instead of hiding underlying problems.


diff --git a/kernel/Makefile b/kernel/Makefile
index 1d13a7a..a76ccbd 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -148,7 +148,7 @@ $(obj)/kheaders.o: $(obj)/kheaders_data.h
 targets += kheaders_data.txz

 quiet_cmd_genikh = GEN     $(obj)/kheaders_data.txz
-cmd_genikh = $(srctree)/scripts/gen_ikh_data.sh $@ $^ >/dev/null 2>&1
+cmd_genikh = $(srctree)/scripts/gen_ikh_data.sh $@ $^
 $(obj)/kheaders_data.txz: $(ikh_file_list) FORCE
        $(call cmd,genikh)






masahiro@...ver:~/workspace/linux-yamada$ make
  CALL    scripts/checksyscalls.sh
  DESCEND  objtool
  CHK     include/generated/compile.h
  GEN     kernel/kheaders_data.txz
find: ‘FORCE’: No such file or directory
70106 blocks
Can't do inplace edit: kernel/kheaders_data.txz.tmp is not a regular file.
Can't do inplace edit: kernel/kheaders_data.txz.tmp/arch is not a regular file.
Can't do inplace edit: kernel/kheaders_data.txz.tmp/arch/x86 is not a
regular file.
Can't do inplace edit: kernel/kheaders_data.txz.tmp/arch/x86/include
is not a regular file.
Can't do inplace edit:
kernel/kheaders_data.txz.tmp/arch/x86/include/uapi is not a regular
file.
Can't do inplace edit:
kernel/kheaders_data.txz.tmp/arch/x86/include/uapi/asm is not a
regular file.
Can't do inplace edit:
kernel/kheaders_data.txz.tmp/arch/x86/include/generated is not a
regular file.
Can't do inplace edit:
kernel/kheaders_data.txz.tmp/arch/x86/include/generated/uapi is not a
regular file.
Can't do inplace edit:
kernel/kheaders_data.txz.tmp/arch/x86/include/generated/uapi/asm is
not a regular file.
Can't do inplace edit:
kernel/kheaders_data.txz.tmp/arch/x86/include/generated/asm is not a
regular file.
Can't do inplace edit:
kernel/kheaders_data.txz.tmp/arch/x86/include/asm is not a regular
file.
Can't do inplace edit:
kernel/kheaders_data.txz.tmp/arch/x86/include/asm/xen is not a regular
file.
Can't do inplace edit:
kernel/kheaders_data.txz.tmp/arch/x86/include/asm/uv is not a regular
file.
Can't do inplace edit:
kernel/kheaders_data.txz.tmp/arch/x86/include/asm/numachip is not a
regular file.
Can't do inplace edit:
kernel/kheaders_data.txz.tmp/arch/x86/include/asm/e820 is not a
regular file.
Can't do inplace edit:
kernel/kheaders_data.txz.tmp/arch/x86/include/asm/fpu is not a regular
file.
Can't do inplace edit:
kernel/kheaders_data.txz.tmp/arch/x86/include/asm/crypto is not a
regular file.
Can't do inplace edit:
kernel/kheaders_data.txz.tmp/arch/x86/include/asm/trace is not a
regular file.
Can't do inplace edit: kernel/kheaders_data.txz.tmp/scripts is not a
regular file.
Can't do inplace edit: kernel/kheaders_data.txz.tmp/scripts/genksyms
is not a regular file.
Can't do inplace edit: kernel/kheaders_data.txz.tmp/scripts/ksymoops
is not a regular file.
Can't do inplace edit: kernel/kheaders_data.txz.tmp/scripts/gdb is not
a regular file.
Can't do inplace edit: kernel/kheaders_data.txz.tmp/scripts/gdb/linux
is not a regular file.
Can't do inplace edit: kernel/kheaders_data.txz.tmp/scripts/basic is
not a regular file.
Can't do inplace edit: kernel/kheaders_data.txz.tmp/scripts/dtc is not
a regular file.
Can't do inplace edit: kernel/kheaders_data.txz.tmp/scripts/dtc/libfdt
is not a regular file.
Can't do inplace edit:
kernel/kheaders_data.txz.tmp/scripts/dtc/include-prefixes is not a
regular file.
Can't open kernel/kheaders_data.txz.tmp/scripts/dtc/include-prefixes/arm64:
No such file or directory.
Can't open kernel/kheaders_data.txz.tmp/scripts/dtc/include-prefixes/xtensa:
No such file or directory.
Can't open kernel/kheaders_data.txz.tmp/scripts/dtc/include-prefixes/openrisc:
No such file or directory.
Can't open kernel/kheaders_data.txz.tmp/scripts/dtc/include-prefixes/nios2:
No such file or directory.
Can't open kernel/kheaders_data.txz.tmp/scripts/dtc/include-prefixes/mips:
No such file or directory.
Can't open kernel/kheaders_data.txz.tmp/scripts/dtc/include-prefixes/arm:
No such file or directory.
Can't open kernel/kheaders_data.txz.tmp/scripts/dtc/include-prefixes/microblaze:
No such file or directory.
Can't open kernel/kheaders_data.txz.tmp/scripts/dtc/include-prefixes/arc:
No such file or directory.
Can't open kernel/kheaders_data.txz.tmp/scripts/dtc/include-prefixes/sh:
No such file or directory.
Can't open kernel/kheaders_data.txz.tmp/scripts/dtc/include-prefixes/powerpc:
No such file or directory.
Can't do inplace edit:
kernel/kheaders_data.txz.tmp/scripts/dtc/include-prefixes/dt-bindings
is not a regular file.

  [ massive amount of error messages continues ]






> I can't think any other ways at the moment to break the circular dependency
> so I'm thinking this is good enough for now especially since Kbuild will
> print a proper warning. Let me know what you think?
>
> thanks,
>
>  - Joel
>
--
Best Regards
Masahiro Yamada

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