Re: v3.18.86 build: 0 failures 1 warnings (v3.18.86)

Re: v3.18.86 build: 0 failures 1 warnings (v3.18.86)

[Arnd Bergmann]

On Wed, Dec 6, 2017 at 1:18 AM, Build bot for Mark Brown
<broonie@kernel.org> wrote:

> -------------------------------------------------------------------------------
> x86_64-defconfig : PASS, 0 errors, 2 warnings, 0 section mismatches
>
> Warnings:
>         ../include/linux/ftrace.h:632:36: warning: calling '__builtin_return_address' with a nonzero argument is unsafe [-Wframe-address]
>         ../include/linux/ftrace.h:632:36: warning: calling '__builtin_return_address' with a nonzero argument is unsafe [-Wframe-address]
> -------------------------------------------------------------------------------

This warning keeps coming up in 3.18 and 4.1 builds, which lack a backport of

ef6000b4c670 ("Disable the __builtin_return_address() warning globally
after all")

The other build bots use different gcc versions that don't report the
warning here,
so only Mark's bot triggers it. The warning in this file is harmless,
and the patch
only turns off the warning flag.

       Arnd

Re: v3.18.86 build: 0 failures 1 warnings (v3.18.86)

[Greg KH]

On Wed, Jan 03, 2018 at 12:24:12AM +0100, Arnd Bergmann wrote:
> On Wed, Dec 6, 2017 at 1:18 AM, Build bot for Mark Brown
> <broonie@kernel.org> wrote:
> 
> > -------------------------------------------------------------------------------
> > x86_64-defconfig : PASS, 0 errors, 2 warnings, 0 section mismatches
> >
> > Warnings:
> >         ../include/linux/ftrace.h:632:36: warning: calling '__builtin_return_address' with a nonzero argument is unsafe [-Wframe-address]
> >         ../include/linux/ftrace.h:632:36: warning: calling '__builtin_return_address' with a nonzero argument is unsafe [-Wframe-address]
> > -------------------------------------------------------------------------------
> 
> This warning keeps coming up in 3.18 and 4.1 builds, which lack a backport of
> 
> ef6000b4c670 ("Disable the __builtin_return_address() warning globally
> after all")
> 
> The other build bots use different gcc versions that don't report the
> warning here,
> so only Mark's bot triggers it. The warning in this file is harmless,
> and the patch
> only turns off the warning flag.

Ah, I tried to figure this one out in the past, thanks for this, I'll
queue it up soon.  Hm, this isn't in 4.4.y, why is it not showing up
there?  Due to a different backport of this type of thing?

odd,

greg k-h

Re: v3.18.86 build: 0 failures 1 warnings (v3.18.86)

[Greg KH]

On Wed, Jan 03, 2018 at 10:54:16AM +0100, Greg KH wrote:
> On Wed, Jan 03, 2018 at 12:24:12AM +0100, Arnd Bergmann wrote:
> > On Wed, Dec 6, 2017 at 1:18 AM, Build bot for Mark Brown
> > <broonie@kernel.org> wrote:
> > 
> > > -------------------------------------------------------------------------------
> > > x86_64-defconfig : PASS, 0 errors, 2 warnings, 0 section mismatches
> > >
> > > Warnings:
> > >         ../include/linux/ftrace.h:632:36: warning: calling '__builtin_return_address' with a nonzero argument is unsafe [-Wframe-address]
> > >         ../include/linux/ftrace.h:632:36: warning: calling '__builtin_return_address' with a nonzero argument is unsafe [-Wframe-address]
> > > -------------------------------------------------------------------------------
> > 
> > This warning keeps coming up in 3.18 and 4.1 builds, which lack a backport of
> > 
> > ef6000b4c670 ("Disable the __builtin_return_address() warning globally
> > after all")
> > 
> > The other build bots use different gcc versions that don't report the
> > warning here,
> > so only Mark's bot triggers it. The warning in this file is harmless,
> > and the patch
> > only turns off the warning flag.
> 
> Ah, I tried to figure this one out in the past, thanks for this, I'll
> queue it up soon.  Hm, this isn't in 4.4.y, why is it not showing up
> there?  Due to a different backport of this type of thing?

Nope, doesn't apply to 3.18 at all, as the main part of this patch is
already in there.  I don't really understand it, it seems that the
cc-disable-warning option isn't working for me for 3.18 at all in my
local builds.  I spent a few hours on it last week, but gave up in the
end :(

thanks,

greg k-h

Re: v3.18.86 build: 0 failures 1 warnings (v3.18.86)

[Arnd Bergmann]

On Wed, Jan 3, 2018 at 10:57 AM, Greg KH <gregkh@linuxfoundation.org> wrote:
> On Wed, Jan 03, 2018 at 10:54:16AM +0100, Greg KH wrote:
>> On Wed, Jan 03, 2018 at 12:24:12AM +0100, Arnd Bergmann wrote:
>> > On Wed, Dec 6, 2017 at 1:18 AM, Build bot for Mark Brown
>> > <broonie@kernel.org> wrote:
>> >
>> > > -------------------------------------------------------------------------------
>> > > x86_64-defconfig : PASS, 0 errors, 2 warnings, 0 section mismatches
>> > >
>> > > Warnings:
>> > >         ../include/linux/ftrace.h:632:36: warning: calling '__builtin_return_address' with a nonzero argument is unsafe [-Wframe-address]
>> > >         ../include/linux/ftrace.h:632:36: warning: calling '__builtin_return_address' with a nonzero argument is unsafe [-Wframe-address]
>> > > -------------------------------------------------------------------------------
>> >
>> > This warning keeps coming up in 3.18 and 4.1 builds, which lack a backport of
>> >
>> > ef6000b4c670 ("Disable the __builtin_return_address() warning globally
>> > after all")
>> >
>> > The other build bots use different gcc versions that don't report the
>> > warning here,
>> > so only Mark's bot triggers it. The warning in this file is harmless,
>> > and the patch
>> > only turns off the warning flag.
>>
>> Ah, I tried to figure this one out in the past, thanks for this, I'll
>> queue it up soon.  Hm, this isn't in 4.4.y, why is it not showing up
>> there?  Due to a different backport of this type of thing?
>
> Nope, doesn't apply to 3.18 at all, as the main part of this patch is
> already in there.  I don't really understand it, it seems that the
> cc-disable-warning option isn't working for me for 3.18 at all in my
> local builds.  I spent a few hours on it last week, but gave up in the
> end :(

Right, this is more mysterious than I thought. I see now that the original
patch 124a3d88fa20 ("Disable "frame-address" warning") was backported
into 3.18, just not the revert 377ccbb48373 ("Makefile: Mute warning for
__builtin_return_address(>0) for tracing only") and the subsequent
revert^2 ef6000b4c670 ("Disable the __builtin_return_address() warning
globally after all").

I have checked that on my build box, the warning is successfully
disabled with gcc-6 and higher (tried 6.1.1, 6.3.1, 7.0.0, 7.1.1)
and older compilers have neither the warning nor the option
to disable it.
I also tried reproducing the warning on arm and aarch64 with some
other modifications but I get a different warning there:

kernel/sched/core.c: In function 'preempt_count_sub':
include/linux/ftrace.h:632:36: warning: unsupported argument to
'__builtin_return_address'

Greg and Mark, which x86-64 compiler versions do you use?

       Arnd

Re: v3.18.86 build: 0 failures 1 warnings (v3.18.86)

[Mark Brown]

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On Wed, Jan 03, 2018 at 03:52:12PM +0100, Arnd Bergmann wrote:

> Greg and Mark, which x86-64 compiler versions do you use?

gcc (Debian 6.3.0-18) 6.3.0 20170516

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Re: v3.18.86 build: 0 failures 1 warnings (v3.18.86)

[Arnd Bergmann]

On Wed, Jan 3, 2018 at 3:59 PM, Mark Brown <broonie@kernel.org> wrote:
> On Wed, Jan 03, 2018 at 03:52:12PM +0100, Arnd Bergmann wrote:
>
>> Greg and Mark, which x86-64 compiler versions do you use?
>
> gcc (Debian 6.3.0-18) 6.3.0 20170516

I installed that version here, same as my other gcc-6 versions, the
"-Wno-frame-address" option gets set and interpreted correctly:

$ git checkout v3.18.91 ; touch kernel/sched/core.c ; make V=1
defconfig kernel/sched/core.o CC=gcc-6 2>&1 | tail
...
gcc-6 -Wp,-MD,kernel/sched/.core.o.d  -nostdinc -isystem
/usr/lib/gcc/x86_64-linux-gnu/6/include -I./arch/x86/include
-Iarch/x86/include/generated  -Iinclude -I./arch/x86/include/uapi
-Iarch/x86/include/generated/uapi -I./include/uapi
-Iinclude/generated/uapi -include ./include/linux/kconfig.h
-D__KERNEL__ -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs
-fno-strict-aliasing -fno-common -Werror-implicit-function-declaration
-Wno-format-security -std=gnu89 -m64 -mno-80387 -mno-fp-ret-in-387
-mtune=generic -mno-red-zone -mcmodel=kernel -funit-at-a-time
-maccumulate-outgoing-args -DCONFIG_AS_CFI=1
-DCONFIG_AS_CFI_SIGNAL_FRAME=1 -DCONFIG_AS_CFI_SECTIONS=1
-DCONFIG_AS_FXSAVEQ=1 -DCONFIG_AS_CRC32=1 -DCONFIG_AS_AVX=1
-DCONFIG_AS_AVX2=1 -pipe -Wno-sign-compare
-fno-asynchronous-unwind-tables -mno-sse -mno-mmx -mno-sse2 -mno-3dnow
-mno-avx -fno-delete-null-pointer-checks -Wno-frame-address -fno-PIE
-O2 --param=allow-store-data-races=0 -Wframe-larger-than=2048
-fno-stack-protector -Wno-unused-but-set-variable
-Wno-unused-const-variable -fno-omit-frame-pointer
-fno-optimize-sibling-calls -fno-var-tracking-assignments
-Wdeclaration-after-statement -Wno-pointer-sign -fno-strict-overflow
-fno-stack-check -fconserve-stack -Werror=implicit-int
-Werror=strict-prototypes -Werror=date-time -DCC_HAVE_ASM_GOTO
-D"KBUILD_STR(s)=#s" -D"KBUILD_BASENAME=KBUILD_STR(core)"
-D"KBUILD_MODNAME=KBUILD_STR(core)" -c -o kernel/sched/core.o
kernel/sched/core.c

It might be a problem with different 'make' versions, or something else
in the environment that leads to "-Wno-frame-address" not being set
on the command line instead.

     Arnd

Re: v3.18.86 build: 0 failures 1 warnings (v3.18.86)

[Mark Brown]

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On Wed, Jan 03, 2018 at 04:32:35PM +0100, Arnd Bergmann wrote:

> It might be a problem with different 'make' versions, or something else
> in the environment that leads to "-Wno-frame-address" not being set
> on the command line instead.

I'm using "GNU Make 4.1" - this is all just the default Debian stuff,
I've not customized my x86 host environment.

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Re: v3.18.86 build: 0 failures 1 warnings (v3.18.86)

[Greg KH]

On Wed, Jan 03, 2018 at 03:41:21PM +0000, Mark Brown wrote:
> On Wed, Jan 03, 2018 at 04:32:35PM +0100, Arnd Bergmann wrote:
> 
> > It might be a problem with different 'make' versions, or something else
> > in the environment that leads to "-Wno-frame-address" not being set
> > on the command line instead.
> 
> I'm using "GNU Make 4.1" - this is all just the default Debian stuff,
> I've not customized my x86 host environment.

Make 4.2.1 here with gcc 7.2.1 and I get tons of build warnings on my
3.18.y tree on my laptop, but my build machine running Fedora (make
4.2.1 and gcc 7.2.1) I get no build warnings at all.

I've given up trying to track it down for my laptop, something is
preventing the compiler flag from being added to the gcc command line,
and I don't care anymore...

thanks,

greg k-h