New warning in linus/master

New warning in linus/master

[Ricardo Ribalda]

Hi Thomas

Media-CI has found a couple of new warnings in the latest kernel
version for aarch64 and powerpc. They get fixed with this patch and
before moving I wanted to know if this was under your radar.



diff --git a/arch/arm64/kernel/vdso/Makefile b/arch/arm64/kernel/vdso/Makefile
index 7dec05dd33b7..65914842fae0 100644
--- a/arch/arm64/kernel/vdso/Makefile
+++ b/arch/arm64/kernel/vdso/Makefile
@@ -50,7 +50,7 @@ CFLAGS_vgettimeofday.o = $(CC_FLAGS_ADD_VDSO)
 CFLAGS_vgetrandom.o = $(CC_FLAGS_ADD_VDSO)

 ifneq ($(c-gettimeofday-y),)
-  CFLAGS_vgettimeofday.o += -include $(c-gettimeofday-y)
+  CFLAGS_vgettimeofday.o += -include $(c-gettimeofday-y)
-Wno-maybe-uninitialized
 endif

 ifneq ($(c-getrandom-y),)
diff --git a/arch/powerpc/kernel/vdso/Makefile
b/arch/powerpc/kernel/vdso/Makefile
index 8834dfe9d727..4b8d40b1dfeb 100644
--- a/arch/powerpc/kernel/vdso/Makefile
+++ b/arch/powerpc/kernel/vdso/Makefile
@@ -12,12 +12,12 @@ obj-vdso32 += getrandom-32.o vgetrandom-chacha-32.o
 obj-vdso64 += getrandom-64.o vgetrandom-chacha-64.o

 ifneq ($(c-gettimeofday-y),)
-  CFLAGS_vgettimeofday-32.o += -include $(c-gettimeofday-y)
+  CFLAGS_vgettimeofday-32.o += -include $(c-gettimeofday-y)
-Wno-maybe-uninitialized
 # Go prior to 1.16.x assumes r30 is not clobbered by any VDSO code.
That used to be true
 # by accident when the VDSO was hand-written asm code, but may not be
now that the VDSO is
 # compiler generated. To avoid breaking Go tell GCC not to use r30.
Impact on code
 # generation is minimal, it will just use r29 instead.
-  CFLAGS_vgettimeofday-64.o += -include $(c-gettimeofday-y) $(call
cc-option, -ffixed-r30)
+  CFLAGS_vgettimeofday-64.o += -include $(c-gettimeofday-y) $(call
cc-option, -ffixed-r30) -Wno-maybe-uninitialized
 endif

 ifneq ($(c-getrandom-y),)


https://gitlab.freedesktop.org/linux-media/users/ribalda/-/pipelines/1649144/test_report?job_name=cross-gcc


CONFIG_CC_VERSION_TEXT="aarch64-linux-gnu-gcc (Debian 15.2.0-16) 15.2.0"
  SYNC    include/config/auto.conf
  CC      arch/arm64/kernel/vdso/vgettimeofday.o
In file included from <command-line>:
In function ‘vdso_set_timespec’,
    inlined from ‘do_aux’ at /workdir/lib/vdso/gettimeofday.c:266:2,
    inlined from ‘__cvdso_clock_gettime_common’ at
/workdir/lib/vdso/gettimeofday.c:293:10,
    inlined from ‘__cvdso_clock_gettime_data.constprop’ at
/workdir/lib/vdso/gettimeofday.c:306:7:
/workdir/lib/vdso/gettimeofday.c:104:26: warning: ‘sec’ may be used
uninitialized [-Wmaybe-uninitialized]
  104 |         ts->tv_sec = sec + __iter_div_u64_rem(ns, NSEC_PER_SEC, &ns);
      |                      ~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/workdir/lib/vdso/gettimeofday.c: In function
‘__cvdso_clock_gettime_data.constprop’:
/workdir/lib/vdso/gettimeofday.c:242:13: note: ‘sec’ was declared here
  242 |         u64 sec, ns;
      |             ^~~
In file included from /workdir/lib/vdso/gettimeofday.c:11:
In function ‘__iter_div_u64_rem’,
    inlined from ‘vdso_set_timespec’ at /workdir/lib/vdso/gettimeofday.c:104:21,
    inlined from ‘do_aux’ at /workdir/lib/vdso/gettimeofday.c:266:2,
    inlined from ‘__cvdso_clock_gettime_common’ at
/workdir/lib/vdso/gettimeofday.c:293:10,
    inlined from ‘__cvdso_clock_gettime_data.constprop’ at
/workdir/lib/vdso/gettimeofday.c:306:7:
./include/vdso/math64.h:10:25: warning: ‘ns’ may be used uninitialized
[-Wmaybe-uninitialized]
   10 |         while (dividend >= divisor) {
      |                ~~~~~~~~~^~~~~~~~~~
/workdir/lib/vdso/gettimeofday.c: In function
‘__cvdso_clock_gettime_data.constprop’:
/workdir/lib/vdso/gettimeofday.c:242:18: note: ‘ns’ was declared here
  242 |         u64 sec, ns;
      |                  ^~
  LD      arch/arm64/kernel/vdso/vdso.so.dbg
  VDSOSYM include/generated/vdso-offsets.h
  OBJCOPY arch/arm64/kernel/vdso/vdso.so
/workdir/lib/vdso/gettimeofday.c:104:26: warning: ‘sec’ may be used
uninitialized [-Wmaybe-uninitialized]
./include/vdso/math64.h:10:25: warning: ‘ns’ may be used uninitialized
[-Wmaybe-uninitialized]

CONFIG_CC_VERSION_TEXT="powerpc64-linux-gnu-gcc (Debian 15.2.0-15) 15.2.0"
  SYNC    include/config/auto.conf
  VDSO32C arch/powerpc/kernel/vdso/vgettimeofday-32.o
In file included from <command-line>:
In function ‘vdso_set_timespec’,
    inlined from ‘do_aux’ at /workdir/lib/vdso/gettimeofday.c:266:2,
    inlined from ‘__cvdso_clock_gettime_common’ at
/workdir/lib/vdso/gettimeofday.c:293:10,
    inlined from ‘__cvdso_clock_gettime32_data’ at
/workdir/lib/vdso/gettimeofday.c:327:7:
/workdir/lib/vdso/gettimeofday.c:104:26: warning: ‘sec’ may be used
uninitialized [-Wmaybe-uninitialized]
  104 |         ts->tv_sec = sec + __iter_div_u64_rem(ns, NSEC_PER_SEC, &ns);
      |                      ~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/workdir/lib/vdso/gettimeofday.c: In function ‘__cvdso_clock_gettime32_data’:
/workdir/lib/vdso/gettimeofday.c:242:13: note: ‘sec’ was declared here
  242 |         u64 sec, ns;
      |             ^~~
In file included from /workdir/lib/vdso/gettimeofday.c:11:
In function ‘__iter_div_u64_rem’,
    inlined from ‘vdso_set_timespec’ at /workdir/lib/vdso/gettimeofday.c:104:21,
    inlined from ‘do_aux’ at /workdir/lib/vdso/gettimeofday.c:266:2,
    inlined from ‘__cvdso_clock_gettime_common’ at
/workdir/lib/vdso/gettimeofday.c:293:10,
    inlined from ‘__cvdso_clock_gettime32_data’ at
/workdir/lib/vdso/gettimeofday.c:327:7:
./include/vdso/math64.h:10:25: warning: ‘ns’ may be used uninitialized
[-Wmaybe-uninitialized]
   10 |         while (dividend >= divisor) {
      |                ~~~~~~~~~^~~~~~~~~~
/workdir/lib/vdso/gettimeofday.c: In function ‘__cvdso_clock_gettime32_data’:
/workdir/lib/vdso/gettimeofday.c:242:18: note: ‘ns’ was declared here
  242 |         u64 sec, ns;
      |                  ^~
In function ‘vdso_set_timespec’,
    inlined from ‘do_aux’ at /workdir/lib/vdso/gettimeofday.c:266:2,
    inlined from ‘__cvdso_clock_gettime_common’ at
/workdir/lib/vdso/gettimeofday.c:293:10,
    inlined from ‘__cvdso_clock_gettime_data’ at
/workdir/lib/vdso/gettimeofday.c:306:7:
/workdir/lib/vdso/gettimeofday.c:104:26: warning: ‘sec’ may be used
uninitialized [-Wmaybe-uninitialized]
  104 |         ts->tv_sec = sec + __iter_div_u64_rem(ns, NSEC_PER_SEC, &ns);
      |                      ~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/workdir/lib/vdso/gettimeofday.c: In function ‘__cvdso_clock_gettime_data’:
/workdir/lib/vdso/gettimeofday.c:242:13: note: ‘sec’ was declared here
  242 |         u64 sec, ns;
      |             ^~~
In function ‘__iter_div_u64_rem’,
    inlined from ‘vdso_set_timespec’ at /workdir/lib/vdso/gettimeofday.c:104:21,
    inlined from ‘do_aux’ at /workdir/lib/vdso/gettimeofday.c:266:2,
    inlined from ‘__cvdso_clock_gettime_common’ at
/workdir/lib/vdso/gettimeofday.c:293:10,
    inlined from ‘__cvdso_clock_gettime_data’ at
/workdir/lib/vdso/gettimeofday.c:306:7:
./include/vdso/math64.h:10:25: warning: ‘ns’ may be used uninitialized
[-Wmaybe-uninitialized]
   10 |         while (dividend >= divisor) {
      |                ~~~~~~~~~^~~~~~~~~~
/workdir/lib/vdso/gettimeofday.c: In function ‘__cvdso_clock_gettime_data’:
/workdir/lib/vdso/gettimeofday.c:242:18: note: ‘ns’ was declared here
  242 |         u64 sec, ns;
      |                  ^~
  VDSO32L arch/powerpc/kernel/vdso/vdso32.so.dbg
  VDSO32SYM include/generated/vdso32-offsets.h
  CC      arch/powerpc/kernel/vdso/vgettimeofday-64.o
  VDSO64L arch/powerpc/kernel/vdso/vdso64.so.dbg
  VDSO64SYM include/generated/vdso64-offsets.h
/workdir/lib/vdso/gettimeofday.c:104:26: warning: ‘sec’ may be used
uninitialized [-Wmaybe-uninitialized]
./include/vdso/math64.h:10:25: warning: ‘ns’ may be used uninitialized
[-Wmaybe-uninitialized]
/workdir/lib/vdso/gettimeofday.c:104:26: warning: ‘sec’ may be used
uninitialized [-Wmaybe-uninitialized]
./include/vdso/math64.h:10:25: warning: ‘ns’ may be used uninitialized
[-Wmaybe-uninitialized]

Thanks

-- 
Ricardo Ribalda

Re: New warning in linus/master

[Thomas Weißschuh]

Hi Ricardo,

On Wed, Apr 22, 2026 at 11:51:45AM +0800, Ricardo Ribalda wrote:
> Media-CI has found a couple of new warnings in the latest kernel
> version for aarch64 and powerpc. They get fixed with this patch and
> before moving I wanted to know if this was under your radar.

Thanks for the report. I was not aware of these so far.

> diff --git a/arch/arm64/kernel/vdso/Makefile b/arch/arm64/kernel/vdso/Makefile
> index 7dec05dd33b7..65914842fae0 100644
> --- a/arch/arm64/kernel/vdso/Makefile
> +++ b/arch/arm64/kernel/vdso/Makefile
> @@ -50,7 +50,7 @@ CFLAGS_vgettimeofday.o = $(CC_FLAGS_ADD_VDSO)
>  CFLAGS_vgetrandom.o = $(CC_FLAGS_ADD_VDSO)
> 
>  ifneq ($(c-gettimeofday-y),)
> -  CFLAGS_vgettimeofday.o += -include $(c-gettimeofday-y)
> +  CFLAGS_vgettimeofday.o += -include $(c-gettimeofday-y)
> -Wno-maybe-uninitialized
>  endif

(...)

I'd like to know exactly what is going on before suppressing the warning.
It is a non-standard warning, only enabled by *some* of the vDSO builds
for some reason.

> https://gitlab.freedesktop.org/linux-media/users/ribalda/-/pipelines/1649144/test_report?job_name=cross-gcc

While I was able to download a configuration from this job and also use the
same container image, I can not reproduce the issue. Is the configuration the
full one or only the template?

Could you provide full reproduction steps?

> CONFIG_CC_VERSION_TEXT="aarch64-linux-gnu-gcc (Debian 15.2.0-16) 15.2.0"

The linked test log shows GCC 14.2, not 15.2.
Not that I could reproduce it with either one...

>   SYNC    include/config/auto.conf
>   CC      arch/arm64/kernel/vdso/vgettimeofday.o
> In file included from <command-line>:
> In function ‘vdso_set_timespec’,
>     inlined from ‘do_aux’ at /workdir/lib/vdso/gettimeofday.c:266:2,
>     inlined from ‘__cvdso_clock_gettime_common’ at
> /workdir/lib/vdso/gettimeofday.c:293:10,
>     inlined from ‘__cvdso_clock_gettime_data.constprop’ at
> /workdir/lib/vdso/gettimeofday.c:306:7:
> /workdir/lib/vdso/gettimeofday.c:104:26: warning: ‘sec’ may be used
> uninitialized [-Wmaybe-uninitialized]
>   104 |         ts->tv_sec = sec + __iter_div_u64_rem(ns, NSEC_PER_SEC, &ns);
>       |                      ~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> /workdir/lib/vdso/gettimeofday.c: In function
> ‘__cvdso_clock_gettime_data.constprop’:
> /workdir/lib/vdso/gettimeofday.c:242:13: note: ‘sec’ was declared here
>   242 |         u64 sec, ns;
>       |             ^~~

The same pattern is used in some other do_ handlers, which do not generate this
warning. I also can't immediately see what is wrong.

(...)


Thomas

Re: New warning in linus/master

[Ricardo Ribalda]

Hi Thomas

Thanks for the prompt reply

On Wed, 22 Apr 2026 at 13:57, Thomas Weißschuh
<thomas.weissschuh@linutronix.de> wrote:
>
> Hi Ricardo,
>
> On Wed, Apr 22, 2026 at 11:51:45AM +0800, Ricardo Ribalda wrote:
> > Media-CI has found a couple of new warnings in the latest kernel
> > version for aarch64 and powerpc. They get fixed with this patch and
> > before moving I wanted to know if this was under your radar.
>
> Thanks for the report. I was not aware of these so far.
>
> > diff --git a/arch/arm64/kernel/vdso/Makefile b/arch/arm64/kernel/vdso/Makefile
> > index 7dec05dd33b7..65914842fae0 100644
> > --- a/arch/arm64/kernel/vdso/Makefile
> > +++ b/arch/arm64/kernel/vdso/Makefile
> > @@ -50,7 +50,7 @@ CFLAGS_vgettimeofday.o = $(CC_FLAGS_ADD_VDSO)
> >  CFLAGS_vgetrandom.o = $(CC_FLAGS_ADD_VDSO)
> >
> >  ifneq ($(c-gettimeofday-y),)
> > -  CFLAGS_vgettimeofday.o += -include $(c-gettimeofday-y)
> > +  CFLAGS_vgettimeofday.o += -include $(c-gettimeofday-y)
> > -Wno-maybe-uninitialized
> >  endif
>
> (...)
>
> I'd like to know exactly what is going on before suppressing the warning.
> It is a non-standard warning, only enabled by *some* of the vDSO builds
> for some reason.
>
> > https://gitlab.freedesktop.org/linux-media/users/ribalda/-/pipelines/1649144/test_report?job_name=cross-gcc
>
> While I was able to download a configuration from this job and also use the
> same container image, I can not reproduce the issue. Is the configuration the
> full one or only the template?
>
> Could you provide full reproduction steps?

You can try repro with:

work/linux $ podman run -v .:/workdir/ --rm -it
registry.freedesktop.org/linux-media/media-ci/build:latest
$ cd /workdir
$ CROSS_COMPILE=aarch64-linux-gnu- ARCH=arm64 make allyesconfig
$ CROSS_COMPILE=aarch64-linux-gnu- ARCH=arm64 make
arch/arm64/kernel/vdso/vgettimeofday.o

The gcc version discrepancy is because I the error was due to old gcc
version and I was playing around with that... but it fails in both
gcc14 and gcc15

You can try with debian testing with
work/linux$ podman run -v .:/workdir/ --rm -it debian:testing
$ apt-get update
$ apt-get install gcc-aarch64-linux-gnu build-essential flex bison libssl-dev bc
$ cd /workdir
$ CROSS_COMPILE=aarch64-linux-gnu- ARCH=arm64 make allyesconfig
$ CROSS_COMPILE=aarch64-linux-gnu- ARCH=arm64 make
arch/arm64/kernel/vdso/vgettimeofday.o

Regards!

>
> > CONFIG_CC_VERSION_TEXT="aarch64-linux-gnu-gcc (Debian 15.2.0-16) 15.2.0"
>
> The linked test log shows GCC 14.2, not 15.2.
> Not that I could reproduce it with either one...
>
> >   SYNC    include/config/auto.conf
> >   CC      arch/arm64/kernel/vdso/vgettimeofday.o
> > In file included from <command-line>:
> > In function ‘vdso_set_timespec’,
> >     inlined from ‘do_aux’ at /workdir/lib/vdso/gettimeofday.c:266:2,
> >     inlined from ‘__cvdso_clock_gettime_common’ at
> > /workdir/lib/vdso/gettimeofday.c:293:10,
> >     inlined from ‘__cvdso_clock_gettime_data.constprop’ at
> > /workdir/lib/vdso/gettimeofday.c:306:7:
> > /workdir/lib/vdso/gettimeofday.c:104:26: warning: ‘sec’ may be used
> > uninitialized [-Wmaybe-uninitialized]
> >   104 |         ts->tv_sec = sec + __iter_div_u64_rem(ns, NSEC_PER_SEC, &ns);
> >       |                      ~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > /workdir/lib/vdso/gettimeofday.c: In function
> > ‘__cvdso_clock_gettime_data.constprop’:
> > /workdir/lib/vdso/gettimeofday.c:242:13: note: ‘sec’ was declared here
> >   242 |         u64 sec, ns;
> >       |             ^~~
>
> The same pattern is used in some other do_ handlers, which do not generate this
> warning. I also can't immediately see what is wrong.
>
> (...)
>
>
> Thomas



-- 
Ricardo Ribalda

Re: New warning in linus/master

[Christophe Leroy (CS GROUP)]

Le 22/04/2026 à 07:56, Thomas Weißschuh a écrit :
> Hi Ricardo,
> 
> On Wed, Apr 22, 2026 at 11:51:45AM +0800, Ricardo Ribalda wrote:
>> Media-CI has found a couple of new warnings in the latest kernel
>> version for aarch64 and powerpc. They get fixed with this patch and
>> before moving I wanted to know if this was under your radar.
> 
> Thanks for the report. I was not aware of these so far.
> 
>> diff --git a/arch/arm64/kernel/vdso/Makefile b/arch/arm64/kernel/vdso/Makefile
>> index 7dec05dd33b7..65914842fae0 100644
>> --- a/arch/arm64/kernel/vdso/Makefile
>> +++ b/arch/arm64/kernel/vdso/Makefile
>> @@ -50,7 +50,7 @@ CFLAGS_vgettimeofday.o = $(CC_FLAGS_ADD_VDSO)
>>   CFLAGS_vgetrandom.o = $(CC_FLAGS_ADD_VDSO)
>>
>>   ifneq ($(c-gettimeofday-y),)
>> -  CFLAGS_vgettimeofday.o += -include $(c-gettimeofday-y)
>> +  CFLAGS_vgettimeofday.o += -include $(c-gettimeofday-y)
>> -Wno-maybe-uninitialized
>>   endif
> 
> (...)
> 
> I'd like to know exactly what is going on before suppressing the warning.
> It is a non-standard warning, only enabled by *some* of the vDSO builds
> for some reason.
> 
>> https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgitlab.freedesktop.org%2Flinux-media%2Fusers%2Fribalda%2F-%2Fpipelines%2F1649144%2Ftest_report%3Fjob_name%3Dcross-gcc&data=05%7C02%7Cchristophe.leroy2%40cs-soprasteria.com%7C5c0f15ee20a44072f47108dea0340304%7C8b87af7d86474dc78df45f69a2011bb5%7C0%7C0%7C639124342424606113%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=9Tvp2aYfB02ijxVGLzCOYcMwZlPvqVDufxEporLl1mc%3D&reserved=0
> 
> While I was able to download a configuration from this job and also use the
> same container image, I can not reproduce the issue. Is the configuration the
> full one or only the template?
> 
> Could you provide full reproduction steps?
> 
>> CONFIG_CC_VERSION_TEXT="aarch64-linux-gnu-gcc (Debian 15.2.0-16) 15.2.0"
> 
> The linked test log shows GCC 14.2, not 15.2.
> Not that I could reproduce it with either one...
> 
>>    SYNC    include/config/auto.conf
>>    CC      arch/arm64/kernel/vdso/vgettimeofday.o
>> In file included from <command-line>:
>> In function ‘vdso_set_timespec’,
>>      inlined from ‘do_aux’ at /workdir/lib/vdso/gettimeofday.c:266:2,
>>      inlined from ‘__cvdso_clock_gettime_common’ at
>> /workdir/lib/vdso/gettimeofday.c:293:10,
>>      inlined from ‘__cvdso_clock_gettime_data.constprop’ at
>> /workdir/lib/vdso/gettimeofday.c:306:7:
>> /workdir/lib/vdso/gettimeofday.c:104:26: warning: ‘sec’ may be used
>> uninitialized [-Wmaybe-uninitialized]
>>    104 |         ts->tv_sec = sec + __iter_div_u64_rem(ns, NSEC_PER_SEC, &ns);
>>        |                      ~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> /workdir/lib/vdso/gettimeofday.c: In function
>> ‘__cvdso_clock_gettime_data.constprop’:
>> /workdir/lib/vdso/gettimeofday.c:242:13: note: ‘sec’ was declared here
>>    242 |         u64 sec, ns;
>>        |             ^~~
> 
> The same pattern is used in some other do_ handlers, which do not generate this
> warning. I also can't immediately see what is wrong.

You are likely in a special case where vdso_get_timestamp() returns 
false without setting &sec, and some versions of GCC and/or CLANG fail 
to see that vdso_set_timespec() is not called when vdso_get_timestamp() 
returns false.

Christophe

Re: New warning in linus/master

[Thomas Weißschuh]

On Wed, Apr 22, 2026 at 03:00:11PM +0800, Ricardo Ribalda wrote:
> On Wed, 22 Apr 2026 at 13:57, Thomas Weißschuh
> <thomas.weissschuh@linutronix.de> wrote:
> > On Wed, Apr 22, 2026 at 11:51:45AM +0800, Ricardo Ribalda wrote:
> > > Media-CI has found a couple of new warnings in the latest kernel
> > > version for aarch64 and powerpc. They get fixed with this patch and
> > > before moving I wanted to know if this was under your radar.
> >
> > Thanks for the report. I was not aware of these so far.
> >
> > > diff --git a/arch/arm64/kernel/vdso/Makefile b/arch/arm64/kernel/vdso/Makefile
> > > index 7dec05dd33b7..65914842fae0 100644
> > > --- a/arch/arm64/kernel/vdso/Makefile
> > > +++ b/arch/arm64/kernel/vdso/Makefile
> > > @@ -50,7 +50,7 @@ CFLAGS_vgettimeofday.o = $(CC_FLAGS_ADD_VDSO)
> > >  CFLAGS_vgetrandom.o = $(CC_FLAGS_ADD_VDSO)
> > >
> > >  ifneq ($(c-gettimeofday-y),)
> > > -  CFLAGS_vgettimeofday.o += -include $(c-gettimeofday-y)
> > > +  CFLAGS_vgettimeofday.o += -include $(c-gettimeofday-y)
> > > -Wno-maybe-uninitialized
> > >  endif
> >
> > (...)
> >
> > I'd like to know exactly what is going on before suppressing the warning.
> > It is a non-standard warning, only enabled by *some* of the vDSO builds
> > for some reason.
> >
> > > https://gitlab.freedesktop.org/linux-media/users/ribalda/-/pipelines/1649144/test_report?job_name=cross-gcc
> >
> > While I was able to download a configuration from this job and also use the
> > same container image, I can not reproduce the issue. Is the configuration the
> > full one or only the template?
> >
> > Could you provide full reproduction steps?
> 
> You can try repro with:
> 
> work/linux $ podman run -v .:/workdir/ --rm -it
> registry.freedesktop.org/linux-media/media-ci/build:latest
> $ cd /workdir
> $ CROSS_COMPILE=aarch64-linux-gnu- ARCH=arm64 make allyesconfig
> $ CROSS_COMPILE=aarch64-linux-gnu- ARCH=arm64 make
> arch/arm64/kernel/vdso/vgettimeofday.o
> 
> The gcc version discrepancy is because I the error was due to old gcc
> version and I was playing around with that... but it fails in both
> gcc14 and gcc15

Ack.

> You can try with debian testing with
> work/linux$ podman run -v .:/workdir/ --rm -it debian:testing
> $ apt-get update
> $ apt-get install gcc-aarch64-linux-gnu build-essential flex bison libssl-dev bc
> $ cd /workdir
> $ CROSS_COMPILE=aarch64-linux-gnu- ARCH=arm64 make allyesconfig
> $ CROSS_COMPILE=aarch64-linux-gnu- ARCH=arm64 make
> arch/arm64/kernel/vdso/vgettimeofday.o

Both reproducers do *not* reproduce the issue for me.
(It is more or less exactly what I tried before)

Please note that this line does not work in general:
$ CROSS_COMPILE=aarch64-linux-gnu- ARCH=arm64 make arch/arm64/kernel/vdso/vgettimeofday.o

The vDSO object files can not be built in this way like regular kernel object
files and will produce a compiler error, but not the one under discussion.
Instead the vDSO on arm64 is built during the 'make prepare' phase.
(Other architectures work differently, of course...)

(...)


Thomas

Re: New warning in linus/master

[Ricardo Ribalda]

Hi Thomas

On Wed, 22 Apr 2026 at 15:32, Thomas Weißschuh
<thomas.weissschuh@linutronix.de> wrote:
>
> On Wed, Apr 22, 2026 at 03:00:11PM +0800, Ricardo Ribalda wrote:
> > On Wed, 22 Apr 2026 at 13:57, Thomas Weißschuh
> > <thomas.weissschuh@linutronix.de> wrote:
> > > On Wed, Apr 22, 2026 at 11:51:45AM +0800, Ricardo Ribalda wrote:
> > > > Media-CI has found a couple of new warnings in the latest kernel
> > > > version for aarch64 and powerpc. They get fixed with this patch and
> > > > before moving I wanted to know if this was under your radar.
> > >
> > > Thanks for the report. I was not aware of these so far.
> > >
> > > > diff --git a/arch/arm64/kernel/vdso/Makefile b/arch/arm64/kernel/vdso/Makefile
> > > > index 7dec05dd33b7..65914842fae0 100644
> > > > --- a/arch/arm64/kernel/vdso/Makefile
> > > > +++ b/arch/arm64/kernel/vdso/Makefile
> > > > @@ -50,7 +50,7 @@ CFLAGS_vgettimeofday.o = $(CC_FLAGS_ADD_VDSO)
> > > >  CFLAGS_vgetrandom.o = $(CC_FLAGS_ADD_VDSO)
> > > >
> > > >  ifneq ($(c-gettimeofday-y),)
> > > > -  CFLAGS_vgettimeofday.o += -include $(c-gettimeofday-y)
> > > > +  CFLAGS_vgettimeofday.o += -include $(c-gettimeofday-y)
> > > > -Wno-maybe-uninitialized
> > > >  endif
> > >
> > > (...)
> > >
> > > I'd like to know exactly what is going on before suppressing the warning.
> > > It is a non-standard warning, only enabled by *some* of the vDSO builds
> > > for some reason.
> > >
> > > > https://gitlab.freedesktop.org/linux-media/users/ribalda/-/pipelines/1649144/test_report?job_name=cross-gcc
> > >
> > > While I was able to download a configuration from this job and also use the
> > > same container image, I can not reproduce the issue. Is the configuration the
> > > full one or only the template?
> > >
> > > Could you provide full reproduction steps?
> >
> > You can try repro with:
> >
> > work/linux $ podman run -v .:/workdir/ --rm -it
> > registry.freedesktop.org/linux-media/media-ci/build:latest
> > $ cd /workdir
> > $ CROSS_COMPILE=aarch64-linux-gnu- ARCH=arm64 make allyesconfig
> > $ CROSS_COMPILE=aarch64-linux-gnu- ARCH=arm64 make
> > arch/arm64/kernel/vdso/vgettimeofday.o
> >
> > The gcc version discrepancy is because I the error was due to old gcc
> > version and I was playing around with that... but it fails in both
> > gcc14 and gcc15
>
> Ack.
>
> > You can try with debian testing with
> > work/linux$ podman run -v .:/workdir/ --rm -it debian:testing
> > $ apt-get update
> > $ apt-get install gcc-aarch64-linux-gnu build-essential flex bison libssl-dev bc
> > $ cd /workdir
> > $ CROSS_COMPILE=aarch64-linux-gnu- ARCH=arm64 make allyesconfig
> > $ CROSS_COMPILE=aarch64-linux-gnu- ARCH=arm64 make
> > arch/arm64/kernel/vdso/vgettimeofday.o
>
> Both reproducers do *not* reproduce the issue for me.
> (It is more or less exactly what I tried before)


Ok, I think I found what is going on. media-ci was forcing
KCFLAGS=-Wmaybe-uninitialized

https://gitlab.freedesktop.org/linux-media/media-ci/-/blob/main/test-build.sh?ref_type=heads#L29

And something has changed in the kernel in the last version that
triggers a (hopefully) false positive.

can you try with:

CROSS_COMPILE=aarch64-linux-gnu- ARCH=arm64 make
KCFLAGS=-Wmaybe-uninitialized  allyesconfig
CROSS_COMPILE=aarch64-linux-gnu- ARCH=arm64 make
KCFLAGS=-Wmaybe-uninitialized  prepare

?


>
> Please note that this line does not work in general:
> $ CROSS_COMPILE=aarch64-linux-gnu- ARCH=arm64 make arch/arm64/kernel/vdso/vgettimeofday.o
>
> The vDSO object files can not be built in this way like regular kernel object
> files and will produce a compiler error, but not the one under discussion.
> Instead the vDSO on arm64 is built during the 'make prepare' phase.
> (Other architectures work differently, of course...)
>
> (...)
>
>
> Thomas



-- 
Ricardo Ribalda

Re: New warning in linus/master

[Thomas Weißschuh]

On Wed, Apr 22, 2026 at 04:06:45PM +0800, Ricardo Ribalda wrote:
> On Wed, 22 Apr 2026 at 15:32, Thomas Weißschuh
> <thomas.weissschuh@linutronix.de> wrote:
> >
> > On Wed, Apr 22, 2026 at 03:00:11PM +0800, Ricardo Ribalda wrote:
> > > On Wed, 22 Apr 2026 at 13:57, Thomas Weißschuh
> > > <thomas.weissschuh@linutronix.de> wrote:
> > > > On Wed, Apr 22, 2026 at 11:51:45AM +0800, Ricardo Ribalda wrote:
> > > > > Media-CI has found a couple of new warnings in the latest kernel
> > > > > version for aarch64 and powerpc. They get fixed with this patch and
> > > > > before moving I wanted to know if this was under your radar.
> > > >
> > > > Thanks for the report. I was not aware of these so far.
> > > >
> > > > > diff --git a/arch/arm64/kernel/vdso/Makefile b/arch/arm64/kernel/vdso/Makefile
> > > > > index 7dec05dd33b7..65914842fae0 100644
> > > > > --- a/arch/arm64/kernel/vdso/Makefile
> > > > > +++ b/arch/arm64/kernel/vdso/Makefile
> > > > > @@ -50,7 +50,7 @@ CFLAGS_vgettimeofday.o = $(CC_FLAGS_ADD_VDSO)
> > > > >  CFLAGS_vgetrandom.o = $(CC_FLAGS_ADD_VDSO)
> > > > >
> > > > >  ifneq ($(c-gettimeofday-y),)
> > > > > -  CFLAGS_vgettimeofday.o += -include $(c-gettimeofday-y)
> > > > > +  CFLAGS_vgettimeofday.o += -include $(c-gettimeofday-y)
> > > > > -Wno-maybe-uninitialized
> > > > >  endif
> > > >
> > > > (...)
> > > >
> > > > I'd like to know exactly what is going on before suppressing the warning.
> > > > It is a non-standard warning, only enabled by *some* of the vDSO builds
> > > > for some reason.
> > > >
> > > > > https://gitlab.freedesktop.org/linux-media/users/ribalda/-/pipelines/1649144/test_report?job_name=cross-gcc
> > > >
> > > > While I was able to download a configuration from this job and also use the
> > > > same container image, I can not reproduce the issue. Is the configuration the
> > > > full one or only the template?
> > > >
> > > > Could you provide full reproduction steps?
> > >
> > > You can try repro with:
> > >
> > > work/linux $ podman run -v .:/workdir/ --rm -it
> > > registry.freedesktop.org/linux-media/media-ci/build:latest
> > > $ cd /workdir
> > > $ CROSS_COMPILE=aarch64-linux-gnu- ARCH=arm64 make allyesconfig
> > > $ CROSS_COMPILE=aarch64-linux-gnu- ARCH=arm64 make
> > > arch/arm64/kernel/vdso/vgettimeofday.o
> > >
> > > The gcc version discrepancy is because I the error was due to old gcc
> > > version and I was playing around with that... but it fails in both
> > > gcc14 and gcc15
> >
> > Ack.
> >
> > > You can try with debian testing with
> > > work/linux$ podman run -v .:/workdir/ --rm -it debian:testing
> > > $ apt-get update
> > > $ apt-get install gcc-aarch64-linux-gnu build-essential flex bison libssl-dev bc
> > > $ cd /workdir
> > > $ CROSS_COMPILE=aarch64-linux-gnu- ARCH=arm64 make allyesconfig
> > > $ CROSS_COMPILE=aarch64-linux-gnu- ARCH=arm64 make
> > > arch/arm64/kernel/vdso/vgettimeofday.o
> >
> > Both reproducers do *not* reproduce the issue for me.
> > (It is more or less exactly what I tried before)
> 
> 
> Ok, I think I found what is going on. media-ci was forcing
> KCFLAGS=-Wmaybe-uninitialized
> 
> https://gitlab.freedesktop.org/linux-media/media-ci/-/blob/main/test-build.sh?ref_type=heads#L29
> 
> And something has changed in the kernel in the last version that
> triggers a (hopefully) false positive.
> 
> can you try with:
> 
> CROSS_COMPILE=aarch64-linux-gnu- ARCH=arm64 make
> KCFLAGS=-Wmaybe-uninitialized  allyesconfig
> CROSS_COMPILE=aarch64-linux-gnu- ARCH=arm64 make
> KCFLAGS=-Wmaybe-uninitialized  prepare

That works!

The warning was introduced in ed78b7b2c5ae ("vdso/gettimeofday: Add a helper to
read the sequence lock of a time namespace aware clock").

It is *not* a false-positive, specifically:

do {
	if (vdso_read_begin_timens(vc, &seq)) {
		vd = __arch_get_vdso_u_timens_data(vd);
		vc = &vd->aux_clock_data[idx];
		/* Re-read from the real time data page */
		continue;

This 'continue' jumps to the end of the loop body and if the real vDSO datapage
by chance has a sequence counter of '1' will exit the loop, leaving 'sec' and
'nsec' uninitialized. My believe was that the 'continue' would jump to the
*beginning* of the loop body, which is cleary wrong. Previously there was an
inner while loop() which would make the 'continue' effectively start at the
beginning of the outer do-while loop.

	}

	/* Auxclock disabled? */
	if (vc->clock_mode == VDSO_CLOCKMODE_NONE)
		return false;

	if (!vdso_get_timestamp(vd, vc, VDSO_BASE_AUX, &sec, &ns))
		return false;

} while (vdso_read_retry(vc, seq));

vdso_set_timespec(ts, sec, ns);


I'm working on a fix.


Thomas

Re: New warning in linus/master

[Christophe Leroy (CS GROUP)]

Le 22/04/2026 à 10:45, Thomas Weißschuh a écrit :
> On Wed, Apr 22, 2026 at 04:06:45PM +0800, Ricardo Ribalda wrote:
>> On Wed, 22 Apr 2026 at 15:32, Thomas Weißschuh
>> <thomas.weissschuh@linutronix.de> wrote:
>>>
>>> On Wed, Apr 22, 2026 at 03:00:11PM +0800, Ricardo Ribalda wrote:
>>>> On Wed, 22 Apr 2026 at 13:57, Thomas Weißschuh
>>>> <thomas.weissschuh@linutronix.de> wrote:
>>>>> On Wed, Apr 22, 2026 at 11:51:45AM +0800, Ricardo Ribalda wrote:
>>>>>> Media-CI has found a couple of new warnings in the latest kernel
>>>>>> version for aarch64 and powerpc. They get fixed with this patch and
>>>>>> before moving I wanted to know if this was under your radar.
>>>>>
>>>>> Thanks for the report. I was not aware of these so far.
>>>>>
>>>>>> diff --git a/arch/arm64/kernel/vdso/Makefile b/arch/arm64/kernel/vdso/Makefile
>>>>>> index 7dec05dd33b7..65914842fae0 100644
>>>>>> --- a/arch/arm64/kernel/vdso/Makefile
>>>>>> +++ b/arch/arm64/kernel/vdso/Makefile
>>>>>> @@ -50,7 +50,7 @@ CFLAGS_vgettimeofday.o = $(CC_FLAGS_ADD_VDSO)
>>>>>>   CFLAGS_vgetrandom.o = $(CC_FLAGS_ADD_VDSO)
>>>>>>
>>>>>>   ifneq ($(c-gettimeofday-y),)
>>>>>> -  CFLAGS_vgettimeofday.o += -include $(c-gettimeofday-y)
>>>>>> +  CFLAGS_vgettimeofday.o += -include $(c-gettimeofday-y)
>>>>>> -Wno-maybe-uninitialized
>>>>>>   endif
>>>>>
>>>>> (...)
>>>>>
>>>>> I'd like to know exactly what is going on before suppressing the warning.
>>>>> It is a non-standard warning, only enabled by *some* of the vDSO builds
>>>>> for some reason.
>>>>>
>>>>>> https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgitlab.freedesktop.org%2Flinux-media%2Fusers%2Fribalda%2F-%2Fpipelines%2F1649144%2Ftest_report%3Fjob_name%3Dcross-gcc&data=05%7C02%7Cchristophe.leroy2%40cs-soprasteria.com%7C7cbf9009269d4ddc16d208dea04b86f1%7C8b87af7d86474dc78df45f69a2011bb5%7C0%7C0%7C639124443421115079%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=O4r8HjaUn7KEgW8tDE9GEC9e8CWyJBpCfhVTJZZ%2BFHs%3D&reserved=0
>>>>>
>>>>> While I was able to download a configuration from this job and also use the
>>>>> same container image, I can not reproduce the issue. Is the configuration the
>>>>> full one or only the template?
>>>>>
>>>>> Could you provide full reproduction steps?
>>>>
>>>> You can try repro with:
>>>>
>>>> work/linux $ podman run -v .:/workdir/ --rm -it
>>>> registry.freedesktop.org/linux-media/media-ci/build:latest
>>>> $ cd /workdir
>>>> $ CROSS_COMPILE=aarch64-linux-gnu- ARCH=arm64 make allyesconfig
>>>> $ CROSS_COMPILE=aarch64-linux-gnu- ARCH=arm64 make
>>>> arch/arm64/kernel/vdso/vgettimeofday.o
>>>>
>>>> The gcc version discrepancy is because I the error was due to old gcc
>>>> version and I was playing around with that... but it fails in both
>>>> gcc14 and gcc15
>>>
>>> Ack.
>>>
>>>> You can try with debian testing with
>>>> work/linux$ podman run -v .:/workdir/ --rm -it debian:testing
>>>> $ apt-get update
>>>> $ apt-get install gcc-aarch64-linux-gnu build-essential flex bison libssl-dev bc
>>>> $ cd /workdir
>>>> $ CROSS_COMPILE=aarch64-linux-gnu- ARCH=arm64 make allyesconfig
>>>> $ CROSS_COMPILE=aarch64-linux-gnu- ARCH=arm64 make
>>>> arch/arm64/kernel/vdso/vgettimeofday.o
>>>
>>> Both reproducers do *not* reproduce the issue for me.
>>> (It is more or less exactly what I tried before)
>>
>>
>> Ok, I think I found what is going on. media-ci was forcing
>> KCFLAGS=-Wmaybe-uninitialized
>>
>> https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgitlab.freedesktop.org%2Flinux-media%2Fmedia-ci%2F-%2Fblob%2Fmain%2Ftest-build.sh%3Fref_type%3Dheads%23L29&data=05%7C02%7Cchristophe.leroy2%40cs-soprasteria.com%7C7cbf9009269d4ddc16d208dea04b86f1%7C8b87af7d86474dc78df45f69a2011bb5%7C0%7C0%7C639124443421146576%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=%2FpTHYfCn5ob42%2Fm6FVOZ32PVzuXBNBT3rlMVWslCfhw%3D&reserved=0
>>
>> And something has changed in the kernel in the last version that
>> triggers a (hopefully) false positive.
>>
>> can you try with:
>>
>> CROSS_COMPILE=aarch64-linux-gnu- ARCH=arm64 make
>> KCFLAGS=-Wmaybe-uninitialized  allyesconfig
>> CROSS_COMPILE=aarch64-linux-gnu- ARCH=arm64 make
>> KCFLAGS=-Wmaybe-uninitialized  prepare
> 
> That works!
> 
> The warning was introduced in ed78b7b2c5ae ("vdso/gettimeofday: Add a helper to
> read the sequence lock of a time namespace aware clock").
> 
> It is *not* a false-positive, specifically:
> 
> do {
> 	if (vdso_read_begin_timens(vc, &seq)) {
> 		vd = __arch_get_vdso_u_timens_data(vd);
> 		vc = &vd->aux_clock_data[idx];
> 		/* Re-read from the real time data page */
> 		continue;
> 
> This 'continue' jumps to the end of the loop body and if the real vDSO datapage
> by chance has a sequence counter of '1' will exit the loop, leaving 'sec' and
> 'nsec' uninitialized. My believe was that the 'continue' would jump to the
> *beginning* of the loop body, which is cleary wrong. Previously there was an
> inner while loop() which would make the 'continue' effectively start at the
> beginning of the outer do-while loop.

Well spotted. I missed it too while reviewing.

A 'retry:' label at the begining of the loop with a 'goto retry' instead 
of the 'continue' should make it.

Christophe

> 
> 	}
> 
> 	/* Auxclock disabled? */
> 	if (vc->clock_mode == VDSO_CLOCKMODE_NONE)
> 		return false;
> 
> 	if (!vdso_get_timestamp(vd, vc, VDSO_BASE_AUX, &sec, &ns))
> 		return false;
> 
> } while (vdso_read_retry(vc, seq));
> 
> vdso_set_timespec(ts, sec, ns);
> 
> 
> I'm working on a fix.
> 
> 
> Thomas
>