why scripts/link-vmlinux.sh has a final build of init/

Commit Message

Cao jin Feb. 13, 2018, 7:08 a.m. UTC

On 02/12/2018 10:48 PM, Masahiro Yamada wrote:
> 2018-02-12 13:22 GMT+09:00 Cao jin <[e-mail]>:
>> Hi Masahiro-san,
>>
>>   As I remember, init/ is already built during recursive make, and I did
>> a clean build(make mrproper, make localmodconfig) with all plugins
>> included on x86_64 with following patch, the kernel can boot without any
>> obvious problem. So, I don't figure out why we need this final build?
>>
>>
>> diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
>> index e6818b8e7141..086b2efd4d53 100755
>> --- a/scripts/link-vmlinux.sh
>> +++ b/scripts/link-vmlinux.sh
>> @@ -247,9 +247,6 @@ else
>>         expr 0$(cat .old_version) + 1 >.version;
>>  fi;
>>
>> -# final build of init/
>> -${MAKE} -f "${srctree}/scripts/Makefile.build" obj=init
>> GCC_PLUGINS_CFLAGS="${GCC_PLUGINS_CFLAGS}"
>> -
>>  archive_builtin
>>
>>  #link vmlinux.o
>>
> 
> 
> link-vmlinux.sh increments '.version'
> so it must descend into init/
> to update include/generated/compile.h
> and re-compile init/version.o
> 
> We do not increment '.version'
> at the first descend into init/
> because we never know whether the kernel
> is updated or not before the final link stage.
> 

Oh, I wasn't aware of this process, now understood. Thanks Masahiro-san.

BTW, I still have 2 questions.

1. In final build, why need

   GCC_PLUGINS_CFLAGS="${GCC_PLUGINS_CFLAGS}"

Doesn't GCC_PLUGINS_CFLAGS already exist in the environment?

I also tested the Randomizing Structure Layout plugin with this patch,
the plugin seems works in my test.

2. scripts/link-vmlinux.sh seems just handle only one argument: clean.
So why shouldn't it be:

 vmlinux: scripts/link-vmlinux.sh vmlinux_prereq $(vmlinux-deps) FORCE

Comments

Masahiro Yamada Feb. 14, 2018, 11:31 a.m. UTC | #1

2018-02-13 16:08 GMT+09:00 Cao jin <[e-mail]>:

> BTW, I still have 2 questions.
>
> 1. In final build, why need
>
>    GCC_PLUGINS_CFLAGS="${GCC_PLUGINS_CFLAGS}"
>
> Doesn't GCC_PLUGINS_CFLAGS already exist in the environment?
>
> I also tested the Randomizing Structure Layout plugin with this patch,
> the plugin seems works in my test.


I have not tested, but GCC_PLUGINS_CFLAGS="${GCC_PLUGINS_CFLAGS}"
is probably unnecessary.



> 2. scripts/link-vmlinux.sh seems just handle only one argument: clean.
> So why shouldn't it be:


To detect the change of $(LD) $(LDFLAGS) $(LDFLAGS_vmlinux)
because link-vmlinux.sh depends on them.



> diff --git a/Makefile b/Makefile
> index ccd981892ef2..21d93b545381 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -998,7 +998,7 @@ ARCH_POSTLINK := $(wildcard
> $(srctree)/arch/$(SRCARCH)/Makefile.postlink)
>
>  # Final link of vmlinux with optional arch pass after final link
>  cmd_link-vmlinux =                                                 \
> -       $(CONFIG_SHELL) $< $(LD) $(LDFLAGS) $(LDFLAGS_vmlinux) ;    \
> +       $(CONFIG_SHELL) $<;                                         \
>         $(if $(ARCH_POSTLINK), $(MAKE) -f $(ARCH_POSTLINK) $@, true)
>
>  vmlinux: scripts/link-vmlinux.sh vmlinux_prereq $(vmlinux-deps) FORCE

Cao jin Feb. 21, 2018, 3:20 a.m. UTC | #2

Sorry for late.

On 02/14/2018 07:31 PM, Masahiro Yamada wrote:
> 2018-02-13 16:08 GMT+09:00 Cao jin <[e-mail]>:
> 
>> BTW, I still have 2 questions.
>>
>> 1. In final build, why need
>>
>>    GCC_PLUGINS_CFLAGS="${GCC_PLUGINS_CFLAGS}"
>>
>> Doesn't GCC_PLUGINS_CFLAGS already exist in the environment?
>>
>> I also tested the Randomizing Structure Layout plugin with this patch,
>> the plugin seems works in my test.
> 
> 
> I have not tested, but GCC_PLUGINS_CFLAGS="${GCC_PLUGINS_CFLAGS}"
> is probably unnecessary.
> 
> 
> 
>> 2. scripts/link-vmlinux.sh seems just handle only one argument: clean.
>> So why shouldn't it be:
> 
> 
> To detect the change of $(LD) $(LDFLAGS) $(LDFLAGS_vmlinux)
> because link-vmlinux.sh depends on them.
> 

I understood, I missed the existence of .vmlinux.cmd file.
Thanks very much, Masahiro-san.

Patch

diff --git a/Makefile b/Makefile
index ccd981892ef2..21d93b545381 100644
--- a/Makefile
+++ b/Makefile
@@ -998,7 +998,7 @@  ARCH_POSTLINK := $(wildcard
$(srctree)/arch/$(SRCARCH)/Makefile.postlink)

 # Final link of vmlinux with optional arch pass after final link
 cmd_link-vmlinux =                                                 \
-       $(CONFIG_SHELL) $< $(LD) $(LDFLAGS) $(LDFLAGS_vmlinux) ;    \
+       $(CONFIG_SHELL) $<;                                         \
        $(if $(ARCH_POSTLINK), $(MAKE) -f $(ARCH_POSTLINK) $@, true)