linux-kernel - Re: [PATCH 0/3] kbuild: remove many tool coverage variables

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Message-ID: <CAK7LNARZuqxWyxn2peMCCt0gbsRdWjri=Pd9-HvpK7bcOB-9dA@mail.gmail.com>
Date: Tue, 14 May 2024 07:39:31 +0900
From: Masahiro Yamada <masahiroy@...nel.org>
To: Kees Cook <keescook@...omium.org>
Cc: linux-kbuild@...r.kernel.org, linux-arch@...r.kernel.org, 
	linux-kernel@...r.kernel.org, Andrey Ryabinin <ryabinin.a.a@...il.com>, 
	Alexander Potapenko <glider@...gle.com>, Andrey Konovalov <andreyknvl@...il.com>, 
	Dmitry Vyukov <dvyukov@...gle.com>, Vincenzo Frascino <vincenzo.frascino@....com>, 
	Marco Elver <elver@...gle.com>, Josh Poimboeuf <jpoimboe@...nel.org>, 
	Peter Zijlstra <peterz@...radead.org>, Peter Oberparleiter <oberpar@...ux.ibm.com>, 
	Roberto Sassu <roberto.sassu@...weicloud.com>, Johannes Berg <johannes@...solutions.net>, 
	kasan-dev@...glegroups.com, linux-hardening@...r.kernel.org
Subject: Re: [PATCH 0/3] kbuild: remove many tool coverage variables

On Tue, May 14, 2024 at 3:48 AM Kees Cook <keescook@...omium.org> wrote:
>
> In the future can you CC the various maintainers of the affected
> tooling? :)


Sorry, I was too lazy to add CC for treewide changes like this.
Anyway, thanks for adding CC.




> On Mon, May 06, 2024 at 10:35:41PM +0900, Masahiro Yamada wrote:
> >
> > This patch set removes many instances of the following variables:
> >
> >   - OBJECT_FILES_NON_STANDARD
> >   - KASAN_SANITIZE
> >   - UBSAN_SANITIZE
> >   - KCSAN_SANITIZE
> >   - KMSAN_SANITIZE
> >   - GCOV_PROFILE
> >   - KCOV_INSTRUMENT
> >
> > Such tools are intended only for kernel space objects, most of which
> > are listed in obj-y, lib-y, or obj-m.
>
> This is a reasonable assertion, and the changes really simplify things
> now and into the future. Thanks for finding such a clean solution! I
> note that it also immediately fixes the issue noticed and fixed here:
> https://lore.kernel.org/all/20240513122754.1282833-1-roberto.sassu@huaweicloud.com/
>
> > The best guess is, objects in $(obj-y), $(lib-y), $(obj-m) can opt in
> > such tools. Otherwise, not.
> >
> > This works in most places.
>
> I am worried about the use of "guess" and "most", though. :) Before, we
> had some clear opt-out situations, and now it's more of a side-effect. I
> think this is okay, but I'd really like to know more about your testing.


- defconfig for arc, hexagon, loongarch, microblaze, sh, xtensa
- allmodconfig for the other architectures


(IIRC, allmodconfig failed for the first case, for reasons unrelated
to this patch set, so I used defconfig instead.
I do not remember what errors I observed)


I checked the diff of .*.cmd files.





>
> It seems like you did build testing comparing build flags, since you
> call out some of the explicit changes in patch 2, quoting:
>
> >  - include arch/mips/vdso/vdso-image.o into UBSAN, GCOV, KCOV
> >  - include arch/sparc/vdso/vdso-image-*.o into UBSAN
> >  - include arch/sparc/vdso/vma.o into UBSAN
> >  - include arch/x86/entry/vdso/extable.o into KASAN, KCSAN, UBSAN, GCOV, KCOV
> >  - include arch/x86/entry/vdso/vdso-image-*.o into KASAN, KCSAN, UBSAN, GCOV, KCOV
> >  - include arch/x86/entry/vdso/vdso32-setup.o into KASAN, KCSAN, UBSAN, GCOV, KCOV
> >  - include arch/x86/entry/vdso/vma.o into GCOV, KCOV
> >  - include arch/x86/um/vdso/vma.o into KASAN, GCOV, KCOV
>
> I would agree that these cases are all likely desirable.
>
> Did you find any cases where you found that instrumentation was _removed_
> where not expected?




See the commit log of 1/3.


> Note:
>
> The coverage for some objects will be changed:
>
>   - exclude .vmlinux.export.o from UBSAN, KCOV
>   - exclude arch/csky/kernel/vdso/vgettimeofday.o from UBSAN
>   - exclude arch/parisc/kernel/vdso32/vdso32.so from UBSAN
>   - exclude arch/parisc/kernel/vdso64/vdso64.so from UBSAN
>   - exclude arch/x86/um/vdso/um_vdso.o from UBSAN
>   - exclude drivers/misc/lkdtm/rodata.o from UBSAN, KCOV
>   - exclude init/version-timestamp.o from UBSAN, KCOV
>   - exclude lib/test_fortify/*.o from all santizers and profilers
>
> I believe these are positive effects.




-- 
Best Regards
Masahiro Yamada