"arm64: vdso: Substitute gettimeofday() with C implementation" breaks clang build

"arm64: vdso: Substitute gettimeofday() with C implementation" breaks clang build

[Qian Cai]

The linux-next commit "arm64: vdso: Substitute gettimeofday() with C
implementation" [1] breaks clang build.

error: invalid value 'tiny' in '-mcode-model tiny'
make[1]: *** [scripts/Makefile.build:279:
arch/arm64/kernel/vdso/vgettimeofday.o] Error 1
make[1]: *** Waiting for unfinished jobs....
make: *** [arch/arm64/Makefile:180: vdso_prepare] Error 2

[1] https://patchwork.kernel.org/patch/11009663/

Re: "arm64: vdso: Substitute gettimeofday() with C implementation" breaks clang build

[Vincenzo Frascino]

Hi Qian,

On 25/06/2019 13:16, Qian Cai wrote:
> The linux-next commit "arm64: vdso: Substitute gettimeofday() with C
> implementation" [1] breaks clang build.
> 
> error: invalid value 'tiny' in '-mcode-model tiny'
> make[1]: *** [scripts/Makefile.build:279:
> arch/arm64/kernel/vdso/vgettimeofday.o] Error 1
> make[1]: *** Waiting for unfinished jobs....
> make: *** [arch/arm64/Makefile:180: vdso_prepare] Error 2
> 
> [1] https://patchwork.kernel.org/patch/11009663/
> 

I am not sure what does exactly break from your report. Could you please provide
more details?

On my env:

$ make mrproper && make defconfig && make CC=clang HOSTCC=clang -j$(nproc)

...

arch/arm64/Makefile:56: CROSS_COMPILE_COMPAT is clang, the compat vDSO will not
be built

...

  LDS     arch/arm64/kernel/vdso/vdso.lds
  AS      arch/arm64/kernel/vdso/note.o
  AS      arch/arm64/kernel/vdso/sigreturn.o
  CC      arch/arm64/kernel/vdso/vgettimeofday.o
  LD      arch/arm64/kernel/vdso/vdso.so.dbg
  VDSOCHK arch/arm64/kernel/vdso/vdso.so.dbg
  VDSOSYM include/generated/vdso-offsets.h

...

  LD      vmlinux.o
  MODPOST vmlinux.o
  MODINFO modules.builtin.modinfo
  KSYM    .tmp_kallsyms1.o
  KSYM    .tmp_kallsyms2.o
  LD      vmlinux
  SORTEX  vmlinux
  SYSMAP  System.map
  Building modules, stage 2.
  OBJCOPY arch/arm64/boot/Image
  MODPOST 483 modules

-- 
Regards,
Vincenzo

Re: "arm64: vdso: Substitute gettimeofday() with C implementation" breaks clang build

[Qian Cai]

On Tue, 2019-06-25 at 13:47 +0100, Vincenzo Frascino wrote:
> Hi Qian,
> 
> On 25/06/2019 13:16, Qian Cai wrote:
> > The linux-next commit "arm64: vdso: Substitute gettimeofday() with C
> > implementation" [1] breaks clang build.
> > 
> > error: invalid value 'tiny' in '-mcode-model tiny'
> > make[1]: *** [scripts/Makefile.build:279:
> > arch/arm64/kernel/vdso/vgettimeofday.o] Error 1
> > make[1]: *** Waiting for unfinished jobs....
> > make: *** [arch/arm64/Makefile:180: vdso_prepare] Error 2
> > 
> > [1] https://patchwork.kernel.org/patch/11009663/
> > 
> 
> I am not sure what does exactly break from your report. Could you please
> provide
> more details?

Here is the config to reproduce.

https://raw.githubusercontent.com/cailca/linux-mm/master/arm64.config

# make CC=clang -j $(nr_cpus)

I can get it working again by removing "-mcmodel=tiny" in
arch/arm64/kernel/vdso/Makefile

> 
> On my env:
> 
> $ make mrproper && make defconfig && make CC=clang HOSTCC=clang -j$(nproc)
> 
> ...
> 
> arch/arm64/Makefile:56: CROSS_COMPILE_COMPAT is clang, the compat vDSO will
> not
> be built
> 
> ...
> 
>   LDS     arch/arm64/kernel/vdso/vdso.lds
>   AS      arch/arm64/kernel/vdso/note.o
>   AS      arch/arm64/kernel/vdso/sigreturn.o
>   CC      arch/arm64/kernel/vdso/vgettimeofday.o
>   LD      arch/arm64/kernel/vdso/vdso.so.dbg
>   VDSOCHK arch/arm64/kernel/vdso/vdso.so.dbg
>   VDSOSYM include/generated/vdso-offsets.h
> 
> ...
> 
>   LD      vmlinux.o
>   MODPOST vmlinux.o
>   MODINFO modules.builtin.modinfo
>   KSYM    .tmp_kallsyms1.o
>   KSYM    .tmp_kallsyms2.o
>   LD      vmlinux
>   SORTEX  vmlinux
>   SYSMAP  System.map
>   Building modules, stage 2.
>   OBJCOPY arch/arm64/boot/Image
>   MODPOST 483 modules
> 

Re: "arm64: vdso: Substitute gettimeofday() with C implementation" breaks clang build

[Vincenzo Frascino]

Hi Qin,

On 25/06/2019 13:56, Qian Cai wrote:
> On Tue, 2019-06-25 at 13:47 +0100, Vincenzo Frascino wrote:
>> Hi Qian,
>>
>> On 25/06/2019 13:16, Qian Cai wrote:
>>> The linux-next commit "arm64: vdso: Substitute gettimeofday() with C
>>> implementation" [1] breaks clang build.
>>>
>>> error: invalid value 'tiny' in '-mcode-model tiny'
>>> make[1]: *** [scripts/Makefile.build:279:
>>> arch/arm64/kernel/vdso/vgettimeofday.o] Error 1
>>> make[1]: *** Waiting for unfinished jobs....
>>> make: *** [arch/arm64/Makefile:180: vdso_prepare] Error 2
>>>
>>> [1] https://patchwork.kernel.org/patch/11009663/
>>>
>>
>> I am not sure what does exactly break from your report. Could you please
>> provide
>> more details?
> 
> Here is the config to reproduce.
> 
> https://raw.githubusercontent.com/cailca/linux-mm/master/arm64.config
> 
> # make CC=clang -j $(nr_cpus)
> 
> I can get it working again by removing "-mcmodel=tiny" in
> arch/arm64/kernel/vdso/Makefile
> 

With your defconfig I can't still reproduce the problem. Which version of clang
are you using?

>>
>> On my env:
>>
>> $ make mrproper && make defconfig && make CC=clang HOSTCC=clang -j$(nproc)
>>
>> ...
>>
>> arch/arm64/Makefile:56: CROSS_COMPILE_COMPAT is clang, the compat vDSO will
>> not
>> be built
>>
>> ...
>>
>>   LDS     arch/arm64/kernel/vdso/vdso.lds
>>   AS      arch/arm64/kernel/vdso/note.o
>>   AS      arch/arm64/kernel/vdso/sigreturn.o
>>   CC      arch/arm64/kernel/vdso/vgettimeofday.o
>>   LD      arch/arm64/kernel/vdso/vdso.so.dbg
>>   VDSOCHK arch/arm64/kernel/vdso/vdso.so.dbg
>>   VDSOSYM include/generated/vdso-offsets.h
>>
>> ...
>>
>>   LD      vmlinux.o
>>   MODPOST vmlinux.o
>>   MODINFO modules.builtin.modinfo
>>   KSYM    .tmp_kallsyms1.o
>>   KSYM    .tmp_kallsyms2.o
>>   LD      vmlinux
>>   SORTEX  vmlinux
>>   SYSMAP  System.map
>>   Building modules, stage 2.
>>   OBJCOPY arch/arm64/boot/Image
>>   MODPOST 483 modules
>>

-- 
Regards,
Vincenzo

Re: "arm64: vdso: Substitute gettimeofday() with C implementation" breaks clang build

[Qian Cai]

On Tue, 2019-06-25 at 14:40 +0100, Vincenzo Frascino wrote:
> On 25/06/2019 13:56, Qian Cai wrote:
> > On Tue, 2019-06-25 at 13:47 +0100, Vincenzo Frascino wrote:
> > > Hi Qian,
> > > 
> > > On 25/06/2019 13:16, Qian Cai wrote:
> > > > The linux-next commit "arm64: vdso: Substitute gettimeofday() with C
> > > > implementation" [1] breaks clang build.
> > > > 
> > > > error: invalid value 'tiny' in '-mcode-model tiny'
> > > > make[1]: *** [scripts/Makefile.build:279:
> > > > arch/arm64/kernel/vdso/vgettimeofday.o] Error 1
> > > > make[1]: *** Waiting for unfinished jobs....
> > > > make: *** [arch/arm64/Makefile:180: vdso_prepare] Error 2
> > > > 
> > > > [1] https://patchwork.kernel.org/patch/11009663/
> > > > 
> > > 
> > > I am not sure what does exactly break from your report. Could you please
> > > provide
> > > more details?
> > 
> > Here is the config to reproduce.
> > 
> > https://raw.githubusercontent.com/cailca/linux-mm/master/arm64.config
> > 
> > # make CC=clang -j $(nr_cpus)
> > 
> > I can get it working again by removing "-mcmodel=tiny" in
> > arch/arm64/kernel/vdso/Makefile
> > 
> 
> With your defconfig I can't still reproduce the problem. Which version of
> clang
> are you using?

Compiler: clang version 7.0.1 (tags/RELEASE_701/final)

> 
> > > 
> > > On my env:
> > > 
> > > $ make mrproper && make defconfig && make CC=clang HOSTCC=clang -j$(nproc)
> > > 
> > > ...
> > > 
> > > arch/arm64/Makefile:56: CROSS_COMPILE_COMPAT is clang, the compat vDSO
> > > will
> > > not
> > > be built
> > > 
> > > ...
> > > 
> > >   LDS     arch/arm64/kernel/vdso/vdso.lds
> > >   AS      arch/arm64/kernel/vdso/note.o
> > >   AS      arch/arm64/kernel/vdso/sigreturn.o
> > >   CC      arch/arm64/kernel/vdso/vgettimeofday.o
> > >   LD      arch/arm64/kernel/vdso/vdso.so.dbg
> > >   VDSOCHK arch/arm64/kernel/vdso/vdso.so.dbg
> > >   VDSOSYM include/generated/vdso-offsets.h
> > > 
> > > ...
> > > 
> > >   LD      vmlinux.o
> > >   MODPOST vmlinux.o
> > >   MODINFO modules.builtin.modinfo
> > >   KSYM    .tmp_kallsyms1.o
> > >   KSYM    .tmp_kallsyms2.o
> > >   LD      vmlinux
> > >   SORTEX  vmlinux
> > >   SYSMAP  System.map
> > >   Building modules, stage 2.
> > >   OBJCOPY arch/arm64/boot/Image
> > >   MODPOST 483 modules
> > > 
> 
> 

Re: "arm64: vdso: Substitute gettimeofday() with C implementation" breaks clang build

[Vincenzo Frascino]

Hi Qian,

On 25/06/2019 14:51, Qian Cai wrote:
> On Tue, 2019-06-25 at 14:40 +0100, Vincenzo Frascino wrote:
>> On 25/06/2019 13:56, Qian Cai wrote:
>>> On Tue, 2019-06-25 at 13:47 +0100, Vincenzo Frascino wrote:
>>>> Hi Qian,
>>>>
>>>> On 25/06/2019 13:16, Qian Cai wrote:
>>>>> The linux-next commit "arm64: vdso: Substitute gettimeofday() with C
>>>>> implementation" [1] breaks clang build.
>>>>>
>>>>> error: invalid value 'tiny' in '-mcode-model tiny'
>>>>> make[1]: *** [scripts/Makefile.build:279:
>>>>> arch/arm64/kernel/vdso/vgettimeofday.o] Error 1
>>>>> make[1]: *** Waiting for unfinished jobs....
>>>>> make: *** [arch/arm64/Makefile:180: vdso_prepare] Error 2
>>>>>
>>>>> [1] https://patchwork.kernel.org/patch/11009663/
>>>>>
>>>>
>>>> I am not sure what does exactly break from your report. Could you please
>>>> provide
>>>> more details?
>>>
>>> Here is the config to reproduce.
>>>
>>> https://raw.githubusercontent.com/cailca/linux-mm/master/arm64.config
>>>
>>> # make CC=clang -j $(nr_cpus)
>>>
>>> I can get it working again by removing "-mcmodel=tiny" in
>>> arch/arm64/kernel/vdso/Makefile
>>>
>>
>> With your defconfig I can't still reproduce the problem. Which version of
>> clang
>> are you using?
> 
> Compiler: clang version 7.0.1 (tags/RELEASE_701/final)
> 

I am using clang 8.0.0. Could you please try with it and see if the issue goes away?

Thanks,
Vincenzo

>>
>>>>
>>>> On my env:
>>>>
>>>> $ make mrproper && make defconfig && make CC=clang HOSTCC=clang -j$(nproc)
>>>>
>>>> ...
>>>>
>>>> arch/arm64/Makefile:56: CROSS_COMPILE_COMPAT is clang, the compat vDSO
>>>> will
>>>> not
>>>> be built
>>>>
>>>> ...
>>>>
>>>>   LDS     arch/arm64/kernel/vdso/vdso.lds
>>>>   AS      arch/arm64/kernel/vdso/note.o
>>>>   AS      arch/arm64/kernel/vdso/sigreturn.o
>>>>   CC      arch/arm64/kernel/vdso/vgettimeofday.o
>>>>   LD      arch/arm64/kernel/vdso/vdso.so.dbg
>>>>   VDSOCHK arch/arm64/kernel/vdso/vdso.so.dbg
>>>>   VDSOSYM include/generated/vdso-offsets.h
>>>>
>>>> ...
>>>>
>>>>   LD      vmlinux.o
>>>>   MODPOST vmlinux.o
>>>>   MODINFO modules.builtin.modinfo
>>>>   KSYM    .tmp_kallsyms1.o
>>>>   KSYM    .tmp_kallsyms2.o
>>>>   LD      vmlinux
>>>>   SORTEX  vmlinux
>>>>   SYSMAP  System.map
>>>>   Building modules, stage 2.
>>>>   OBJCOPY arch/arm64/boot/Image
>>>>   MODPOST 483 modules
>>>>
>>
>>

-- 
Regards,
Vincenzo

Re: "arm64: vdso: Substitute gettimeofday() with C implementation" breaks clang build

[Qian Cai]

On Tue, 2019-06-25 at 15:11 +0100, Vincenzo Frascino wrote:
> Hi Qian,
> 
> On 25/06/2019 14:51, Qian Cai wrote:
> > On Tue, 2019-06-25 at 14:40 +0100, Vincenzo Frascino wrote:
> > > On 25/06/2019 13:56, Qian Cai wrote:
> > > > On Tue, 2019-06-25 at 13:47 +0100, Vincenzo Frascino wrote:
> > > > > Hi Qian,
> > > > > 
> > > > > On 25/06/2019 13:16, Qian Cai wrote:
> > > > > > The linux-next commit "arm64: vdso: Substitute gettimeofday() with C
> > > > > > implementation" [1] breaks clang build.
> > > > > > 
> > > > > > error: invalid value 'tiny' in '-mcode-model tiny'
> > > > > > make[1]: *** [scripts/Makefile.build:279:
> > > > > > arch/arm64/kernel/vdso/vgettimeofday.o] Error 1
> > > > > > make[1]: *** Waiting for unfinished jobs....
> > > > > > make: *** [arch/arm64/Makefile:180: vdso_prepare] Error 2
> > > > > > 
> > > > > > [1] https://patchwork.kernel.org/patch/11009663/
> > > > > > 
> > > > > 
> > > > > I am not sure what does exactly break from your report. Could you
> > > > > please
> > > > > provide
> > > > > more details?
> > > > 
> > > > Here is the config to reproduce.
> > > > 
> > > > https://raw.githubusercontent.com/cailca/linux-mm/master/arm64.config
> > > > 
> > > > # make CC=clang -j $(nr_cpus)
> > > > 
> > > > I can get it working again by removing "-mcmodel=tiny" in
> > > > arch/arm64/kernel/vdso/Makefile
> > > > 
> > > 
> > > With your defconfig I can't still reproduce the problem. Which version of
> > > clang
> > > are you using?
> > 
> > Compiler: clang version 7.0.1 (tags/RELEASE_701/final)
> > 
> 
> I am using clang 8.0.0. Could you please try with it and see if the issue goes
> away?

Looks like the "tiny" was added since clang 8.0.

https://reviews.llvm.org/D49674

but clang 7.0 is still use in many distros by default, so maybe this commit can
be fixed by adding a conditional check to use "small" if clang version < 8.0.

> 
> Thanks,
> Vincenzo
> 
> > > 
> > > > > 
> > > > > On my env:
> > > > > 
> > > > > $ make mrproper && make defconfig && make CC=clang HOSTCC=clang
> > > > > -j$(nproc)
> > > > > 
> > > > > ...
> > > > > 
> > > > > arch/arm64/Makefile:56: CROSS_COMPILE_COMPAT is clang, the compat vDSO
> > > > > will
> > > > > not
> > > > > be built
> > > > > 
> > > > > ...
> > > > > 
> > > > >   LDS     arch/arm64/kernel/vdso/vdso.lds
> > > > >   AS      arch/arm64/kernel/vdso/note.o
> > > > >   AS      arch/arm64/kernel/vdso/sigreturn.o
> > > > >   CC      arch/arm64/kernel/vdso/vgettimeofday.o
> > > > >   LD      arch/arm64/kernel/vdso/vdso.so.dbg
> > > > >   VDSOCHK arch/arm64/kernel/vdso/vdso.so.dbg
> > > > >   VDSOSYM include/generated/vdso-offsets.h
> > > > > 
> > > > > ...
> > > > > 
> > > > >   LD      vmlinux.o
> > > > >   MODPOST vmlinux.o
> > > > >   MODINFO modules.builtin.modinfo
> > > > >   KSYM    .tmp_kallsyms1.o
> > > > >   KSYM    .tmp_kallsyms2.o
> > > > >   LD      vmlinux
> > > > >   SORTEX  vmlinux
> > > > >   SYSMAP  System.map
> > > > >   Building modules, stage 2.
> > > > >   OBJCOPY arch/arm64/boot/Image
> > > > >   MODPOST 483 modules
> > > > > 
> > > 
> > > 
> 
> 

Re: "arm64: vdso: Substitute gettimeofday() with C implementation" breaks clang build

[Vincenzo Frascino]

Hi Qian,

On 25/06/2019 15:28, Qian Cai wrote:
> On Tue, 2019-06-25 at 15:11 +0100, Vincenzo Frascino wrote:
>> Hi Qian,
>>
>> On 25/06/2019 14:51, Qian Cai wrote:
>>> On Tue, 2019-06-25 at 14:40 +0100, Vincenzo Frascino wrote:
>>>> On 25/06/2019 13:56, Qian Cai wrote:
>>>>> On Tue, 2019-06-25 at 13:47 +0100, Vincenzo Frascino wrote:
>>>>>> Hi Qian,
>>>>>>
>>>>>> On 25/06/2019 13:16, Qian Cai wrote:
>>>>>>> The linux-next commit "arm64: vdso: Substitute gettimeofday() with C
>>>>>>> implementation" [1] breaks clang build.
>>>>>>>
>>>>>>> error: invalid value 'tiny' in '-mcode-model tiny'
>>>>>>> make[1]: *** [scripts/Makefile.build:279:
>>>>>>> arch/arm64/kernel/vdso/vgettimeofday.o] Error 1
>>>>>>> make[1]: *** Waiting for unfinished jobs....
>>>>>>> make: *** [arch/arm64/Makefile:180: vdso_prepare] Error 2
>>>>>>>
>>>>>>> [1] https://patchwork.kernel.org/patch/11009663/
>>>>>>>
>>>>>>
>>>>>> I am not sure what does exactly break from your report. Could you
>>>>>> please
>>>>>> provide
>>>>>> more details?
>>>>>
>>>>> Here is the config to reproduce.
>>>>>
>>>>> https://raw.githubusercontent.com/cailca/linux-mm/master/arm64.config
>>>>>
>>>>> # make CC=clang -j $(nr_cpus)
>>>>>
>>>>> I can get it working again by removing "-mcmodel=tiny" in
>>>>> arch/arm64/kernel/vdso/Makefile
>>>>>
>>>>
>>>> With your defconfig I can't still reproduce the problem. Which version of
>>>> clang
>>>> are you using?
>>>
>>> Compiler: clang version 7.0.1 (tags/RELEASE_701/final)
>>>
>>
>> I am using clang 8.0.0. Could you please try with it and see if the issue goes
>> away?
> 
> Looks like the "tiny" was added since clang 8.0.
> 
> https://reviews.llvm.org/D49674
> 
> but clang 7.0 is still use in many distros by default, so maybe this commit can
> be fixed by adding a conditional check to use "small" if clang version < 8.0.
> 

It is what I thought that's why I asked to cross-check. I did not want to remove
tiny.

Thanks for your support, I will post a patch adding your tag as reported-by if
you are ok with that.

>>
>> Thanks,
>> Vincenzo
>>
>>>>
>>>>>>
>>>>>> On my env:
>>>>>>
>>>>>> $ make mrproper && make defconfig && make CC=clang HOSTCC=clang
>>>>>> -j$(nproc)
>>>>>>
>>>>>> ...
>>>>>>
>>>>>> arch/arm64/Makefile:56: CROSS_COMPILE_COMPAT is clang, the compat vDSO
>>>>>> will
>>>>>> not
>>>>>> be built
>>>>>>
>>>>>> ...
>>>>>>
>>>>>>   LDS     arch/arm64/kernel/vdso/vdso.lds
>>>>>>   AS      arch/arm64/kernel/vdso/note.o
>>>>>>   AS      arch/arm64/kernel/vdso/sigreturn.o
>>>>>>   CC      arch/arm64/kernel/vdso/vgettimeofday.o
>>>>>>   LD      arch/arm64/kernel/vdso/vdso.so.dbg
>>>>>>   VDSOCHK arch/arm64/kernel/vdso/vdso.so.dbg
>>>>>>   VDSOSYM include/generated/vdso-offsets.h
>>>>>>
>>>>>> ...
>>>>>>
>>>>>>   LD      vmlinux.o
>>>>>>   MODPOST vmlinux.o
>>>>>>   MODINFO modules.builtin.modinfo
>>>>>>   KSYM    .tmp_kallsyms1.o
>>>>>>   KSYM    .tmp_kallsyms2.o
>>>>>>   LD      vmlinux
>>>>>>   SORTEX  vmlinux
>>>>>>   SYSMAP  System.map
>>>>>>   Building modules, stage 2.
>>>>>>   OBJCOPY arch/arm64/boot/Image
>>>>>>   MODPOST 483 modules
>>>>>>
>>>>
>>>>
>>
>>

-- 
Regards,
Vincenzo

Re: "arm64: vdso: Substitute gettimeofday() with C implementation" breaks clang build

[Vincenzo Frascino]

[-- Attachment #1: Type: text/plain, Size: 274 bytes --]

Hi Qian,

...

> 
> but clang 7.0 is still use in many distros by default, so maybe this commit can
> be fixed by adding a conditional check to use "small" if clang version < 8.0.
> 

Could you please verify that the patch below works for you?

Thanks,
Vincenzo

--->8----


[-- Attachment #2: 0001-arm64-vdso-Fix-compilation-with-clang-8.patch --]
[-- Type: text/x-patch, Size: 1130 bytes --]

From 0546f3bbea910cd26df8c2ff9ed1a59945bb1bec Mon Sep 17 00:00:00 2001
From: Vincenzo Frascino <vincenzo.frascino@arm.com>
Date: Tue, 25 Jun 2019 15:49:37 +0100
Subject: [PATCH] arm64: vdso: Fix compilation with clang < 8

clang versions previous to 8 do not support -mcmodel=tiny.

Add a check to the vDSO Makefile for arm64 to remove the flag when these
versions of the compiler are detected.

Reported-by: Qian Cai <cai@lca.pw>
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
---
 arch/arm64/kernel/vdso/Makefile | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/arm64/kernel/vdso/Makefile b/arch/arm64/kernel/vdso/Makefile
index ec81d28aeb5d..c11cbf71073f 100644
--- a/arch/arm64/kernel/vdso/Makefile
+++ b/arch/arm64/kernel/vdso/Makefile
@@ -38,6 +38,11 @@ else
 CFLAGS_vgettimeofday.o = -O2 -mcmodel=tiny -include $(c-gettimeofday-y)
 endif
 
+# Clang versions less than 8 do not support -mcmodel=tiny
+ifeq ($(shell test $(CONFIG_CLANG_VERSION) -lt 80000; echo $$?),0)
+CFLAGS_REMOVE_vgettimeofday.o = -mcmodel=tiny
+endif
+
 # Disable gcov profiling for VDSO code
 GCOV_PROFILE := n
 
-- 
2.22.0

Re: "arm64: vdso: Substitute gettimeofday() with C implementation" breaks clang build

[Qian Cai]

On Tue, 2019-06-25 at 15:54 +0100, Vincenzo Frascino wrote:
> Hi Qian,
> 
> ...
> 
> > 
> > but clang 7.0 is still use in many distros by default, so maybe this commit
> > can
> > be fixed by adding a conditional check to use "small" if clang version <
> > 8.0.
> > 
> 
> Could you please verify that the patch below works for you?
> 
> Thanks,
> Vincenzo
> 
> --->8----
> 

It does not work unfortunately.

# make CC=clang -j 256 2>/tmp/warn3.txt
  HOSTCC  scripts/basic/fixdep
  HOSTCC  scripts/dtc/dtc.o
  HOSTCC  scripts/dtc/flattree.o
  HOSTCC  scripts/dtc/fstree.o
  HOSTCC  scripts/dtc/data.o
  HOSTCC  scripts/dtc/livetree.o
  HOSTCC  scripts/dtc/treesource.o
  HOSTCC  scripts/dtc/srcpos.o
  HOSTCC  scripts/dtc/checks.o
  HOSTCC  scripts/dtc/util.o
  LEX     scripts/dtc/dtc-lexer.lex.c
  YACC    scripts/dtc/dtc-parser.tab.h
  YACC    scripts/dtc/dtc-parser.tab.c
  HOSTCC  scripts/dtc/dtc-parser.tab.o
  HOSTCC  scripts/dtc/dtc-lexer.lex.o
  HOSTLD  scripts/dtc/dtc
  HOSTCC  scripts/kallsyms
  HOSTCC  scripts/recordmcount
  HOSTCC  scripts/sortextable
  DTC     arch/arm64/boot/dts/arm/foundation-v8.dtb
  DTC     arch/arm64/boot/dts/arm/foundation-v8-psci.dtb
  DTC     arch/arm64/boot/dts/arm/foundation-v8-gicv3.dtb
  DTC     arch/arm64/boot/dts/arm/foundation-v8-gicv3-psci.dtb
  DTC     arch/arm64/boot/dts/arm/juno.dtb
  DTC     arch/arm64/boot/dts/arm/juno-r1.dtb
  DTC     arch/arm64/boot/dts/arm/juno-r2.dtb
  DTC     arch/arm64/boot/dts/arm/rtsm_ve-aemv8a.dtb
  DTC     arch/arm64/boot/dts/arm/vexpress-v2f-1xv7-ca53x2.dtb
  DTC     arch/arm64/boot/dts/arm/fvp-base-revc.dtb
  DTC     arch/arm64/boot/dts/cavium/thunder2-99xx.dtb
  DTC     arch/arm64/boot/dts/hisilicon/hi3660-hikey960.dtb
  DTC     arch/arm64/boot/dts/hisilicon/hi3670-hikey970.dtb
  DTC     arch/arm64/boot/dts/hisilicon/hi3798cv200-poplar.dtb
  DTC     arch/arm64/boot/dts/hisilicon/hi6220-hikey.dtb
  DTC     arch/arm64/boot/dts/hisilicon/hip05-d02.dtb
  DTC     arch/arm64/boot/dts/hisilicon/hip06-d03.dtb
  DTC     arch/arm64/boot/dts/hisilicon/hip07-d05.dtb
  HOSTCC  scripts/mod/mk_elfconfig
  CC      scripts/mod/devicetable-offsets.s
  CC      scripts/mod/empty.o
  MKELF   scripts/mod/elfconfig.h
  HOSTCC  scripts/mod/modpost.o
  HOSTCC  scripts/mod/file2alias.o
  HOSTCC  scripts/mod/sumversion.o
  HOSTLD  scripts/mod/modpost
  CC      kernel/bounds.s
  CALL    scripts/atomic/check-atomics.sh
  CC      arch/arm64/kernel/asm-offsets.s
  CALL    scripts/checksyscalls.sh
  LDS     arch/arm64/kernel/vdso/vdso.lds
  AS      arch/arm64/kernel/vdso/note.o
  AS      arch/arm64/kernel/vdso/sigreturn.o
  CC      arch/arm64/kernel/vdso/vgettimeofday.o
  LD      arch/arm64/kernel/vdso/vdso.so.dbg
  VDSOCHK arch/arm64/kernel/vdso/vdso.so.dbg
00000000000009d0 R_AARCH64_JUMP_SLOT  _mcount

arch/arm64/kernel/vdso/vdso.so.dbg: dynamic relocations are not supported
make[1]: *** [arch/arm64/kernel/vdso/Makefile:59:
arch/arm64/kernel/vdso/vdso.so.dbg] Error 1
make: *** [arch/arm64/Makefile:180: vdso_prepare] Error 2

Re: "arm64: vdso: Substitute gettimeofday() with C implementation" breaks clang build

[Nick Desaulniers]

On Tue, Jun 25, 2019 at 7:54 AM Vincenzo Frascino
<vincenzo.frascino@arm.com> wrote:
>
> Hi Qian,
>
> ...
>
> >
> > but clang 7.0 is still use in many distros by default, so maybe this commit can
> > be fixed by adding a conditional check to use "small" if clang version < 8.0.
> >
>
> Could you please verify that the patch below works for you?

Should it be checking against CONFIG_CLANG_VERSION, or better yet be
using cc-option macro?
-- 
Thanks,
~Nick Desaulniers

Re: "arm64: vdso: Substitute gettimeofday() with C implementation" breaks clang build

[Vincenzo Frascino]

[-- Attachment #1: Type: text/plain, Size: 1241 bytes --]

Hi Nick,

On 25/06/2019 17:26, Nick Desaulniers wrote:
> On Tue, Jun 25, 2019 at 7:54 AM Vincenzo Frascino
> <vincenzo.frascino@arm.com> wrote:
>>
>> Hi Qian,
>>
>> ...
>>
>>>
>>> but clang 7.0 is still use in many distros by default, so maybe this commit can
>>> be fixed by adding a conditional check to use "small" if clang version < 8.0.
>>>
>>
>> Could you please verify that the patch below works for you?
> 
> Should it be checking against CONFIG_CLANG_VERSION, or better yet be
> using cc-option macro?
> 

This is what I did in my proposed patch, but I was surprised that clang-7
generates relocations that clang-8 does not.

  LD      arch/arm64/kernel/vdso/vdso.so.dbg
  VDSOCHK arch/arm64/kernel/vdso/vdso.so.dbg
00000000000009d0 R_AARCH64_JUMP_SLOT  _mcount

arch/arm64/kernel/vdso/vdso.so.dbg: dynamic relocations are not supported
make[1]: *** [arch/arm64/kernel/vdso/Makefile:59:
arch/arm64/kernel/vdso/vdso.so.dbg] Error 1
make: *** [arch/arm64/Makefile:180: vdso_prepare] Error 2

This is the the result of the macro I introduced in lib/vdso/Makefile.

And I just found out why. I forgot to add a "+" in the patch provided :)

@Qian: Could you please retry with the one provided below?

-- 
Regards,
Vincenzo

--->8----




[-- Attachment #2: 0001-arm64-vdso-Fix-compilation-with-clang-8.patch --]
[-- Type: text/x-patch, Size: 1131 bytes --]

From eed9ea23cf999d31b87db4b98a8e9de209706132 Mon Sep 17 00:00:00 2001
From: Vincenzo Frascino <vincenzo.frascino@arm.com>
Date: Tue, 25 Jun 2019 15:49:37 +0100
Subject: [PATCH] arm64: vdso: Fix compilation with clang < 8

clang versions previous to 8 do not support -mcmodel=tiny.

Add a check to the vDSO Makefile for arm64 to remove the flag when these
versions of the compiler are detected.

Reported-by: Qian Cai <cai@lca.pw>
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
---
 arch/arm64/kernel/vdso/Makefile | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/arm64/kernel/vdso/Makefile b/arch/arm64/kernel/vdso/Makefile
index ec81d28aeb5d..5154f50aff2d 100644
--- a/arch/arm64/kernel/vdso/Makefile
+++ b/arch/arm64/kernel/vdso/Makefile
@@ -38,6 +38,11 @@ else
 CFLAGS_vgettimeofday.o = -O2 -mcmodel=tiny -include $(c-gettimeofday-y)
 endif
 
+# Clang versions less than 8 do not support -mcmodel=tiny
+ifeq ($(shell test $(CONFIG_CLANG_VERSION) -lt 80000; echo $$?),0)
+CFLAGS_REMOVE_vgettimeofday.o += -mcmodel=tiny
+endif
+
 # Disable gcov profiling for VDSO code
 GCOV_PROFILE := n
 
-- 
2.22.0

Re: "arm64: vdso: Substitute gettimeofday() with C implementation" breaks clang build

[Qian Cai]

On Tue, 2019-06-25 at 18:00 +0100, Vincenzo Frascino wrote:
> Hi Nick,
> 
> On 25/06/2019 17:26, Nick Desaulniers wrote:
> > On Tue, Jun 25, 2019 at 7:54 AM Vincenzo Frascino
> > <vincenzo.frascino@arm.com> wrote:
> > > 
> > > Hi Qian,
> > > 
> > > ...
> > > 
> > > > 
> > > > but clang 7.0 is still use in many distros by default, so maybe this
> > > > commit can
> > > > be fixed by adding a conditional check to use "small" if clang version <
> > > > 8.0.
> > > > 
> > > 
> > > Could you please verify that the patch below works for you?
> > 
> > Should it be checking against CONFIG_CLANG_VERSION, or better yet be
> > using cc-option macro?
> > 
> 
> This is what I did in my proposed patch, but I was surprised that clang-7
> generates relocations that clang-8 does not.
> 
>   LD      arch/arm64/kernel/vdso/vdso.so.dbg
>   VDSOCHK arch/arm64/kernel/vdso/vdso.so.dbg
> 00000000000009d0 R_AARCH64_JUMP_SLOT  _mcount
> 
> arch/arm64/kernel/vdso/vdso.so.dbg: dynamic relocations are not supported
> make[1]: *** [arch/arm64/kernel/vdso/Makefile:59:
> arch/arm64/kernel/vdso/vdso.so.dbg] Error 1
> make: *** [arch/arm64/Makefile:180: vdso_prepare] Error 2
> 
> This is the the result of the macro I introduced in lib/vdso/Makefile.
> 
> And I just found out why. I forgot to add a "+" in the patch provided :)
> 
> @Qian: Could you please retry with the one provided below?
> 

It works fine.

Re: "arm64: vdso: Substitute gettimeofday() with C implementation" breaks clang build

[Vincenzo Frascino]

Hi Qian,

On 25/06/2019 18:31, Qian Cai wrote:
> On Tue, 2019-06-25 at 18:00 +0100, Vincenzo Frascino wrote:
>> Hi Nick,
>>
>> On 25/06/2019 17:26, Nick Desaulniers wrote:
>>> On Tue, Jun 25, 2019 at 7:54 AM Vincenzo Frascino
>>> <vincenzo.frascino@arm.com> wrote:
>>>>
>>>> Hi Qian,
>>>>
>>>> ...
>>>>
>>>>>
>>>>> but clang 7.0 is still use in many distros by default, so maybe this
>>>>> commit can
>>>>> be fixed by adding a conditional check to use "small" if clang version <
>>>>> 8.0.
>>>>>
>>>>
>>>> Could you please verify that the patch below works for you?
>>>
>>> Should it be checking against CONFIG_CLANG_VERSION, or better yet be
>>> using cc-option macro?
>>>
>>
>> This is what I did in my proposed patch, but I was surprised that clang-7
>> generates relocations that clang-8 does not.
>>
>>   LD      arch/arm64/kernel/vdso/vdso.so.dbg
>>   VDSOCHK arch/arm64/kernel/vdso/vdso.so.dbg
>> 00000000000009d0 R_AARCH64_JUMP_SLOT  _mcount
>>
>> arch/arm64/kernel/vdso/vdso.so.dbg: dynamic relocations are not supported
>> make[1]: *** [arch/arm64/kernel/vdso/Makefile:59:
>> arch/arm64/kernel/vdso/vdso.so.dbg] Error 1
>> make: *** [arch/arm64/Makefile:180: vdso_prepare] Error 2
>>
>> This is the the result of the macro I introduced in lib/vdso/Makefile.
>>
>> And I just found out why. I forgot to add a "+" in the patch provided :)
>>
>> @Qian: Could you please retry with the one provided below?
>>
> 
> It works fine.
> 

Thanks for the confirmation, I will push the patch in a short while.

-- 
Regards,
Vincenzo

Re: "arm64: vdso: Substitute gettimeofday() with C implementation" breaks clang build

[Will Deacon]

On Tue, Jun 25, 2019 at 06:00:27PM +0100, Vincenzo Frascino wrote:
> On 25/06/2019 17:26, Nick Desaulniers wrote:
> > On Tue, Jun 25, 2019 at 7:54 AM Vincenzo Frascino
> > <vincenzo.frascino@arm.com> wrote:
> >>> but clang 7.0 is still use in many distros by default, so maybe this commit can
> >>> be fixed by adding a conditional check to use "small" if clang version < 8.0.
> >>>
> >>
> >> Could you please verify that the patch below works for you?
> > 
> > Should it be checking against CONFIG_CLANG_VERSION, or better yet be
> > using cc-option macro?
> > 
> 
> This is what I did in my proposed patch, but I was surprised that clang-7
> generates relocations that clang-8 does not.
> 
>   LD      arch/arm64/kernel/vdso/vdso.so.dbg
>   VDSOCHK arch/arm64/kernel/vdso/vdso.so.dbg
> 00000000000009d0 R_AARCH64_JUMP_SLOT  _mcount

Hmm. It would be nice to understand where the reference to _mcount is coming
from, since that sounds like ftrace is getting involved where it shouldn't
be.

Will

Re: "arm64: vdso: Substitute gettimeofday() with C implementation" breaks clang build

[Vincenzo Frascino]

On 26/06/2019 10:38, Will Deacon wrote:
> On Tue, Jun 25, 2019 at 06:00:27PM +0100, Vincenzo Frascino wrote:
>> On 25/06/2019 17:26, Nick Desaulniers wrote:
>>> On Tue, Jun 25, 2019 at 7:54 AM Vincenzo Frascino
>>> <vincenzo.frascino@arm.com> wrote:
>>>>> but clang 7.0 is still use in many distros by default, so maybe this commit can
>>>>> be fixed by adding a conditional check to use "small" if clang version < 8.0.
>>>>>
>>>>
>>>> Could you please verify that the patch below works for you?
>>>
>>> Should it be checking against CONFIG_CLANG_VERSION, or better yet be
>>> using cc-option macro?
>>>
>>
>> This is what I did in my proposed patch, but I was surprised that clang-7
>> generates relocations that clang-8 does not.
>>
>>   LD      arch/arm64/kernel/vdso/vdso.so.dbg
>>   VDSOCHK arch/arm64/kernel/vdso/vdso.so.dbg
>> 00000000000009d0 R_AARCH64_JUMP_SLOT  _mcount
> 
> Hmm. It would be nice to understand where the reference to _mcount is coming
> from, since that sounds like ftrace is getting involved where it shouldn't
> be.
> 

That's very true, it was a mistake in the Makefile change that I provided with
the original iteration of this patch, that had as a side effect of having ftrace
involved (_mcount is defined in entry-ftrace.c).

I was overriding:

CFLAGS_REMOVE_vgettimeofday.o = $(CC_FLAGS_FTRACE) -Os

with:

CFLAGS_REMOVE_vgettimeofday.o = -mcmodel=tiny (selected if clang is < 8)

that's why I said that I missed a "+" in my previous patch.

Having:

CFLAGS_REMOVE_vgettimeofday.o += -mcmodel=tiny

restores the wanted behavior.

Sorry for not being clear in my explanation.

> Will
> 

-- 
Regards,
Vincenzo