From: Nathan Chancellor <nathan@kernel.org>
To: Nick Desaulniers <ndesaulniers@google.com>
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 09:13:29 -0700 [thread overview]
Message-ID: <Ys7vKYJ9tyih8Cng@dev-arch.thelio-3990X> (raw)
In-Reply-To: <CAKwvOd=kqfAZoywsOFbvvzUJD+zVgFgmDAAcb7h0U8LGzfG33A@mail.gmail.com>
On Wed, Jul 13, 2022 at 09:01:58AM -0700, Nick Desaulniers wrote:
> 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
Sure thing.
With KASAN:
$ llvm-objdump -r --disassemble-symbols=asan.module_ctor,asan.module_dtor build/arch/x86/kernel/fpu/bugs.o
build/arch/x86/kernel/fpu/bugs.o: file format elf64-x86-64
Disassembly of section .text.asan.module_ctor:
0000000000000000 <asan.module_ctor>:
0: be 01 00 00 00 movl $1, %esi
5: 48 c7 c7 00 00 00 00 movq $0, %rdi
0000000000000008: R_X86_64_32S .data
c: e8 00 00 00 00 callq 0x11 <asan.module_ctor+0x11>
000000000000000d: R_X86_64_PLT32 __asan_register_globals-0x4
11: c3 retq
Disassembly of section .text.asan.module_dtor:
0000000000000000 <asan.module_dtor>:
0: be 01 00 00 00 movl $1, %esi
5: 48 c7 c7 00 00 00 00 movq $0, %rdi
0000000000000008: R_X86_64_32S .data
c: e8 00 00 00 00 callq 0x11 <asan.module_dtor+0x11>
000000000000000d: R_X86_64_PLT32 __asan_unregister_globals-0x4
11: c3 retq
With KCSAN:
$ llvm-objdump -r --disassemble-symbols=tsan.module_ctor build/arch/x86/kernel/fpu/bugs.o
build/arch/x86/kernel/fpu/bugs.o: file format elf64-x86-64
Disassembly of section .text.tsan.module_ctor:
0000000000000000 <tsan.module_ctor>:
0: e8 00 00 00 00 callq 0x5 <tsan.module_ctor+0x5>
0000000000000001: R_X86_64_PLT32 __tsan_init-0x4
5: c3 retq
Cheers,
Nathan
next prev parent reply other threads:[~2022-07-13 16:13 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
2022-07-13 16:13 ` Nathan Chancellor [this message]
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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