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
If there is any additional information I can provide or patches I can
test, I am happy to do so!
Cheers,
Nathan
On Wed, Jul 13, 2022 at 8:48 AM Nathan Chancellor <[email protected]> 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
On Wed, Jul 13, 2022 at 09:13:29AM -0700, Nathan Chancellor wrote:
> On Wed, Jul 13, 2022 at 09:01:58AM -0700, Nick Desaulniers wrote:
> > On Wed, Jul 13, 2022 at 8:48 AM Nathan Chancellor <[email protected]> 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
As Nick said; this should be: 'jmp __x86_return_thunk', on those builds.
On Wed, Jul 13, 2022 at 09:01:58AM -0700, Nick Desaulniers wrote:
> On Wed, Jul 13, 2022 at 8:48 AM Nathan Chancellor <[email protected]> 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
On Wed, Jul 13, 2022 at 9:25 AM Peter Zijlstra <[email protected]> wrote:
>
> On Wed, Jul 13, 2022 at 09:13:29AM -0700, Nathan Chancellor wrote:
> > On Wed, Jul 13, 2022 at 09:01:58AM -0700, Nick Desaulniers wrote:
> > > On Wed, Jul 13, 2022 at 8:48 AM Nathan Chancellor <[email protected]> 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
>
> As Nick said; this should be: 'jmp __x86_return_thunk', on those builds.
https://github.com/llvm/llvm-project/issues/56514
--
Thanks,
~Nick Desaulniers
On Wed, Jul 13, 2022 at 9:42 AM Nick Desaulniers
<[email protected]> wrote:
>
> On Wed, Jul 13, 2022 at 9:25 AM Peter Zijlstra <[email protected]> wrote:
> >
> > On Wed, Jul 13, 2022 at 09:13:29AM -0700, Nathan Chancellor wrote:
> > > On Wed, Jul 13, 2022 at 09:01:58AM -0700, Nick Desaulniers wrote:
> > > > On Wed, Jul 13, 2022 at 8:48 AM Nathan Chancellor <[email protected]> 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
It's not just the sanitizers, `CONFIG_GCOV_KERNEL=y` +
`CONFIG_GCOV_PROFILE_ALL=y` also has this issue:
```
...
drivers/base/platform.o: warning: objtool: __llvm_gcov_reset+0xa94:
'naked' return found in RETHUNK build
net/core/netpoll.o: warning: objtool: __llvm_gcov_reset+0xde3: 'naked'
return found in RETHUNK build
net/netfilter/nf_conntrack_netlink.o: warning: objtool:
__llvm_gcov_reset+0x1b94: 'naked' return found in RETHUNK build
fs/fs_parser.o: warning: objtool: __llvm_gcov_reset+0x344: 'naked'
return found in RETHUNK build
drivers/acpi/debugfs.o: warning: objtool: __llvm_gcov_reset+0xb:
'naked' return found in RETHUNK build
mm/pagewalk.o: warning: objtool: __llvm_gcov_reset+0x77f: 'naked'
return found in RETHUNK build
drivers/tty/serial/8250/8250_pnp.o: warning: objtool:
__llvm_gcov_reset+0x231: 'naked' return found in RETHUNK build
fs/init.o: warning: objtool: __llvm_gcov_reset+0x2f7: 'naked' return
found in RETHUNK build
drivers/gpu/drm/drm_fourcc.o: warning: objtool:
__llvm_gcov_reset+0x1ce: '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
> >
> > As Nick said; this should be: 'jmp __x86_return_thunk', on those builds.
>
> https://github.com/llvm/llvm-project/issues/56514
>
> --
> Thanks,
> ~Nick Desaulniers
--
Thanks,
~Nick Desaulniers
On Wed, Jul 13, 2022 at 3:05 PM Nick Desaulniers
<[email protected]> wrote:
>
> On Wed, Jul 13, 2022 at 9:42 AM Nick Desaulniers
> <[email protected]> wrote:
> >
> > On Wed, Jul 13, 2022 at 9:25 AM Peter Zijlstra <[email protected]> wrote:
> > >
> > > On Wed, Jul 13, 2022 at 09:13:29AM -0700, Nathan Chancellor wrote:
> > > > On Wed, Jul 13, 2022 at 09:01:58AM -0700, Nick Desaulniers wrote:
> > > > > On Wed, Jul 13, 2022 at 8:48 AM Nathan Chancellor <[email protected]> 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
>
> It's not just the sanitizers, `CONFIG_GCOV_KERNEL=y` +
> `CONFIG_GCOV_PROFILE_ALL=y` also has this issue:
> ```
> ...
> drivers/base/platform.o: warning: objtool: __llvm_gcov_reset+0xa94:
> 'naked' return found in RETHUNK build
> net/core/netpoll.o: warning: objtool: __llvm_gcov_reset+0xde3: 'naked'
> return found in RETHUNK build
> net/netfilter/nf_conntrack_netlink.o: warning: objtool:
> __llvm_gcov_reset+0x1b94: 'naked' return found in RETHUNK build
> fs/fs_parser.o: warning: objtool: __llvm_gcov_reset+0x344: 'naked'
> return found in RETHUNK build
> drivers/acpi/debugfs.o: warning: objtool: __llvm_gcov_reset+0xb:
> 'naked' return found in RETHUNK build
> mm/pagewalk.o: warning: objtool: __llvm_gcov_reset+0x77f: 'naked'
> return found in RETHUNK build
> drivers/tty/serial/8250/8250_pnp.o: warning: objtool:
> __llvm_gcov_reset+0x231: 'naked' return found in RETHUNK build
> fs/init.o: warning: objtool: __llvm_gcov_reset+0x2f7: 'naked' return
> found in RETHUNK build
> drivers/gpu/drm/drm_fourcc.o: warning: objtool:
> __llvm_gcov_reset+0x1ce: 'naked' return found in RETHUNK build
> ...
> ```
https://reviews.llvm.org/D129709
>
> > > > >
> > > > > 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
> > >
> > > As Nick said; this should be: 'jmp __x86_return_thunk', on those builds.
> >
> > https://github.com/llvm/llvm-project/issues/56514
> >
> > --
> > Thanks,
> > ~Nick Desaulniers
>
>
>
> --
> Thanks,
> ~Nick Desaulniers
--
Thanks,
~Nick Desaulniers