Problems building ppc images in v4.14.y and v4.16.y using gcc 7.3.0 / 8.1.0 from kernel.org

Problems building ppc images in v4.14.y and v4.16.y using gcc 7.3.0 / 8.1.0 from kernel.org

[Guenter Roeck]

Hi Arnd,

when using the ppc64 compiler from kernel.org, I see the following problems
when trying to compile ppc:allnoconfig in v4.14.y or v4.16.y.

gcc 7.3.0: Compilation of kernel.cpu.o hangs

The problem goes away if I apply the following two patches (tested with 4.16.y)

17a2f1ced028 cpu/hotplug: Merge cpuhp_bp_states and cpuhp_ap_states
fcb3029a8d89 cpu/hotplug: Fix unused function warning

gcc 8.1.0: Compilation of kernel/cpu.o results in the following error

powerpc64-linux-gcc: error: unrecognized command line option '-mno-spe'; did you mean '-fno-see'?
powerpc64-linux-gcc: error: unrecognized command line option '-mspe=no'; did you mean '-misel=no'?

This problem is also seen with mainline.

With ppc:defconfig, kernel/cpu.o builds fine with both compiler versions.

Have you seen similar problems ? Any idea what to do about it, other than sticking
with older compilers ?

Thanks,
Guenter

Re: Problems building ppc images in v4.14.y and v4.16.y using gcc 7.3.0 / 8.1.0 from kernel.org

[Arnd Bergmann]

On Tue, Jun 5, 2018 at 3:52 PM, Guenter Roeck <linux@roeck-us.net> wrote:
> Hi Arnd,
>
> when using the ppc64 compiler from kernel.org, I see the following problems
> when trying to compile ppc:allnoconfig in v4.14.y or v4.16.y.
>
> gcc 7.3.0: Compilation of kernel.cpu.o hangs
>
> The problem goes away if I apply the following two patches (tested with
> 4.16.y)
>
> 17a2f1ced028 cpu/hotplug: Merge cpuhp_bp_states and cpuhp_ap_states
> fcb3029a8d89 cpu/hotplug: Fix unused function warning

This is probably the same as
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84038

I thought I had included the fix in my builds.

> gcc 8.1.0: Compilation of kernel/cpu.o results in the following error
>
> powerpc64-linux-gcc: error: unrecognized command line option '-mno-spe'; did
> you mean '-fno-see'?
> powerpc64-linux-gcc: error: unrecognized command line option '-mspe=no'; did
> you mean '-misel=no'?
>
> This problem is also seen with mainline.

I've seen it, but couldn't figure out what the right fix is. I ended
up commenting
out those two lines in my private builds:

--- a/arch/powerpc/Makefile
+++ b/arch/powerpc/Makefile
@@ -215,8 +215,8 @@ KBUILD_CFLAGS += $(call cc-option,-mno-vsx)

 # No SPE instruction when building kernel
 # (We use all available options to help semi-broken compilers)
-KBUILD_CFLAGS += $(call cc-option,-mno-spe)
-KBUILD_CFLAGS += $(call cc-option,-mspe=no)
+#KBUILD_CFLAGS += $(call cc-option,-mno-spe)
+#KBUILD_CFLAGS += $(call cc-option,-mspe=no)

 # Enable unit-at-a-time mode when possible. It shrinks the
 # kernel considerably.

I think there were some changes in how cc-option gets evaluated, maybe
those rely on something else to be enabled or disabled first?

        Arnd

Re: Problems building ppc images in v4.14.y and v4.16.y using gcc 7.3.0 / 8.1.0 from kernel.org

[Guenter Roeck]

On Tue, Jun 05, 2018 at 04:31:00PM +0200, Arnd Bergmann wrote:
> On Tue, Jun 5, 2018 at 3:52 PM, Guenter Roeck <linux@roeck-us.net> wrote:
> > Hi Arnd,
> >
> > when using the ppc64 compiler from kernel.org, I see the following problems
> > when trying to compile ppc:allnoconfig in v4.14.y or v4.16.y.
> >
> > gcc 7.3.0: Compilation of kernel.cpu.o hangs
> >
> > The problem goes away if I apply the following two patches (tested with
> > 4.16.y)
> >
> > 17a2f1ced028 cpu/hotplug: Merge cpuhp_bp_states and cpuhp_ap_states
> > fcb3029a8d89 cpu/hotplug: Fix unused function warning
> 
> This is probably the same as
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84038
> 
> I thought I had included the fix in my builds.
> 
Guess not.

> > gcc 8.1.0: Compilation of kernel/cpu.o results in the following error
> >
> > powerpc64-linux-gcc: error: unrecognized command line option '-mno-spe'; did
> > you mean '-fno-see'?
> > powerpc64-linux-gcc: error: unrecognized command line option '-mspe=no'; did
> > you mean '-misel=no'?
> >
> > This problem is also seen with mainline.
> 
> I've seen it, but couldn't figure out what the right fix is. I ended
> up commenting
> out those two lines in my private builds:
> 
> --- a/arch/powerpc/Makefile
> +++ b/arch/powerpc/Makefile
> @@ -215,8 +215,8 @@ KBUILD_CFLAGS += $(call cc-option,-mno-vsx)
> 
>  # No SPE instruction when building kernel
>  # (We use all available options to help semi-broken compilers)
> -KBUILD_CFLAGS += $(call cc-option,-mno-spe)
> -KBUILD_CFLAGS += $(call cc-option,-mspe=no)
> +#KBUILD_CFLAGS += $(call cc-option,-mno-spe)
> +#KBUILD_CFLAGS += $(call cc-option,-mspe=no)
> 
>  # Enable unit-at-a-time mode when possible. It shrinks the
>  # kernel considerably.
> 
> I think there were some changes in how cc-option gets evaluated, maybe
> those rely on something else to be enabled or disabled first?
> 
I think it may have cached the flags from the other compiler version.
"make mrproper" prior to "make defconfig" took care of the issue.

However, that doesn't really help - I get lots of
	error: 'sys_spu_create' alias between functions of incompatible types
	error: 'strncpy' output truncated before terminating nul
if I try to use gcc 8.1.0.

Oh well. I'll try gcc 6.4.0 next.

Thanks,
Guenter

Re: Problems building ppc images in v4.14.y and v4.16.y using gcc 7.3.0 / 8.1.0 from kernel.org

[Arnd Bergmann]

On Tue, Jun 5, 2018 at 6:06 PM, Guenter Roeck <linux@roeck-us.net> wrote:
> On Tue, Jun 05, 2018 at 04:31:00PM +0200, Arnd Bergmann wrote:
>> On Tue, Jun 5, 2018 at 3:52 PM, Guenter Roeck <linux@roeck-us.net> wrote:
>> > Hi Arnd,
>> >
>> > when using the ppc64 compiler from kernel.org, I see the following problems
>> > when trying to compile ppc:allnoconfig in v4.14.y or v4.16.y.
>> >
>> > gcc 7.3.0: Compilation of kernel.cpu.o hangs
>> >
>> > The problem goes away if I apply the following two patches (tested with
>> > 4.16.y)
>> >
>> > 17a2f1ced028 cpu/hotplug: Merge cpuhp_bp_states and cpuhp_ap_states
>> > fcb3029a8d89 cpu/hotplug: Fix unused function warning
>>
>> This is probably the same as
>> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84038
>>
>> I thought I had included the fix in my builds.
>>
> Guess not.

I probably had it in one build and then forgot about it when I did a
rebuild of 7.3 :(

I'm still planning to do a new set of gcc-7.3 binaries (or maybe 7.4
if that gets
released soon) and should try to remember doing that.

>>
> I think it may have cached the flags from the other compiler version.
> "make mrproper" prior to "make defconfig" took care of the issue.
>
> However, that doesn't really help - I get lots of
>         error: 'sys_spu_create' alias between functions of incompatible types
>         error: 'strncpy' output truncated before terminating nul
> if I try to use gcc 8.1.0.
>
> Oh well. I'll try gcc 6.4.0 next.

On the upside, those two errors are just a result of arch/power/*/*.c getting
built with -Werror, they are warnings that gcc-8 introduced that we should
either shut up or fix.

        Arnd

Re: Problems building ppc images in v4.14.y and v4.16.y using gcc 7.3.0 / 8.1.0 from kernel.org

[Christophe LEROY]

Le 05/06/2018 à 21:47, Arnd Bergmann a écrit :
> On Tue, Jun 5, 2018 at 6:06 PM, Guenter Roeck <linux@roeck-us.net> wrote:
>> On Tue, Jun 05, 2018 at 04:31:00PM +0200, Arnd Bergmann wrote:
>>> On Tue, Jun 5, 2018 at 3:52 PM, Guenter Roeck <linux@roeck-us.net> wrote:
>>>> Hi Arnd,
>>>>
>>>> when using the ppc64 compiler from kernel.org, I see the following problems
>>>> when trying to compile ppc:allnoconfig in v4.14.y or v4.16.y.
>>>>
>>>> gcc 7.3.0: Compilation of kernel.cpu.o hangs
>>>>
>>>> The problem goes away if I apply the following two patches (tested with
>>>> 4.16.y)
>>>>
>>>> 17a2f1ced028 cpu/hotplug: Merge cpuhp_bp_states and cpuhp_ap_states
>>>> fcb3029a8d89 cpu/hotplug: Fix unused function warning
>>>
>>> This is probably the same as
>>> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84038
>>>
>>> I thought I had included the fix in my builds.
>>>
>> Guess not.
> 
> I probably had it in one build and then forgot about it when I did a
> rebuild of 7.3 :(
> 
> I'm still planning to do a new set of gcc-7.3 binaries (or maybe 7.4
> if that gets
> released soon) and should try to remember doing that.
> 
>>>
>> I think it may have cached the flags from the other compiler version.
>> "make mrproper" prior to "make defconfig" took care of the issue.
>>
>> However, that doesn't really help - I get lots of
>>          error: 'sys_spu_create' alias between functions of incompatible types
>>          error: 'strncpy' output truncated before terminating nul
>> if I try to use gcc 8.1.0.
>>
>> Oh well. I'll try gcc 6.4.0 next.
> 
> On the upside, those two errors are just a result of arch/power/*/*.c getting
> built with -Werror, they are warnings that gcc-8 introduced that we should
> either shut up or fix.

They are fixed in next:

https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?id=2479bfc9bc600dcce7f932d52dcfa8d677c41f93
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?id=c95998811807d897ca112ea62d66716ed733d058

Christophe

> 
>          Arnd
>