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From: Nick Desaulniers <ndesaulniers@google.com>
To: Nathan Chancellor <nathan@kernel.org>
Cc: Josh Poimboeuf <jpoimboe@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	 linux-kernel@vger.kernel.org, llvm@lists.linux.dev
Subject: Re: objtool "'naked' return found in RETHUNK build" with clang + CONFIG_K{A,C}SAN=y
Date: Wed, 13 Jul 2022 09:01:58 -0700	[thread overview]
Message-ID: <CAKwvOd=kqfAZoywsOFbvvzUJD+zVgFgmDAAcb7h0U8LGzfG33A@mail.gmail.com> (raw)
In-Reply-To: <Ys7pLq+tQk5xEa/B@dev-arch.thelio-3990X>

On Wed, Jul 13, 2022 at 8:48 AM Nathan Chancellor <nathan@kernel.org> wrote:
>
> Hi Josh and Peter,
>
> After commit 9bb2ec608a20 ("objtool: Update Retpoline validation") and
> commit f43b9876e857 ("x86/retbleed: Add fine grained Kconfig knobs"), I
> see a spew of objtool warnings when building certain configurations with
> clang. Examples below, they appear to trigger in every single file.
>
> With x86_64_defconfig + CONFIG_KASAN=y:
>
> arch/x86/ia32/audit.o: warning: objtool: asan.module_ctor+0x11: 'naked' return found in RETHUNK build
> arch/x86/ia32/audit.o: warning: objtool: asan.module_dtor+0x11: 'naked' return found in RETHUNK build
> init/version.o: warning: objtool: asan.module_ctor+0x11: 'naked' return found in RETHUNK build
> init/version.o: warning: objtool: asan.module_dtor+0x11: 'naked' return found in RETHUNK build
> arch/x86/kernel/cpu/rdrand.o: warning: objtool: asan.module_ctor+0x11: 'naked' return found in RETHUNK build
> arch/x86/kernel/cpu/rdrand.o: warning: objtool: asan.module_dtor+0x11: 'naked' return found in RETHUNK build
> arch/x86/kernel/fpu/bugs.o: warning: objtool: asan.module_ctor+0x11: 'naked' return found in RETHUNK build
> arch/x86/kernel/fpu/bugs.o: warning: objtool: asan.module_dtor+0x11: 'naked' return found in RETHUNK build
> arch/x86/kernel/platform-quirks.o: warning: objtool: asan.module_ctor+0x0: 'naked' return found in RETHUNK build
> init/calibrate.o: warning: objtool: asan.module_ctor+0x11: 'naked' return found in RETHUNK build
> init/calibrate.o: warning: objtool: asan.module_dtor+0x11: 'naked' return found in RETHUNK build
>
> With x86_64_defconfig + CONFIG_KCSAN=y:
>
> arch/x86/ia32/audit.o: warning: objtool: tsan.module_ctor+0x5: 'naked' return found in RETHUNK build
> init/calibrate.o: warning: objtool: tsan.module_ctor+0x5: 'naked' return found in RETHUNK build
> init/version.o: warning: objtool: tsan.module_ctor+0x5: 'naked' return found in RETHUNK build
> arch/x86/kernel/fpu/bugs.o: warning: objtool: tsan.module_ctor+0x5: 'naked' return found in RETHUNK build
> arch/x86/kernel/cpu/rdrand.o: warning: objtool: tsan.module_ctor+0x5: 'naked' return found in RETHUNK build
> arch/x86/events/probe.o: warning: objtool: tsan.module_ctor+0x5: 'naked' return found in RETHUNK build
> arch/x86/kernel/apic/ipi.o: warning: objtool: tsan.module_ctor+0x5: 'naked' return found in RETHUNK build

Thanks for the report. I wonder if this might be a compiler bug; it
seems like the {a|t}san.module_{c|d}tor functions are being emitted
with ret instructions?

If you have one of these builds lying around still, can you provide:

$ llvm-objdump -dr --disassemble-symbols=tsan.module_ctor
arch/x86/kernel/fpu/bugs.o

(I'm about to head into a bunch of meetings now, but can check more
this afternoon; see you at Noon)

If Peter and Josh are bored, feel free to stop by
https://meet.google.com/yjf-jyqk-iaz
at Noon PDT / 19:00 UTV today.

>
> If there is any additional information I can provide or patches I can
> test, I am happy to do so!
>
> Cheers,
> Nathan
>


-- 
Thanks,
~Nick Desaulniers

  reply	other threads:[~2022-07-13 16:02 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-07-13 15:47 objtool "'naked' return found in RETHUNK build" with clang + CONFIG_K{A,C}SAN=y Nathan Chancellor
2022-07-13 16:01 ` Nick Desaulniers [this message]
2022-07-13 16:13   ` Nathan Chancellor
2022-07-13 16:25     ` Peter Zijlstra
2022-07-13 16:42       ` Nick Desaulniers
2022-07-13 22:05         ` Nick Desaulniers
2022-07-14  0:31           ` Nick Desaulniers

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