[PATCH V2] modpost: Amend ppc64 save/restfpr symnames for -Os build

[PATCH V2] modpost: Amend ppc64 save/restfpr symnames for -Os build

[René Rebe]

Building a size optimized ppc64 kernel (-Os), gcc emits more FP
save/restore symbols, that the linker generates on demand into the
.sfpr section. Explicitly allow-list those in scripts/mod/modpost.c,
too. They are needed for the amdgpu in-kernel floating point support.

MODPOST Module.symvers
ERROR: modpost: "_restfpr_20" [drivers/gpu/drm/amd/amdgpu/amdgpu.ko] undefined!
ERROR: modpost: "_restfpr_26" [drivers/gpu/drm/amd/amdgpu/amdgpu.ko] undefined!
ERROR: modpost: "_restfpr_22" [drivers/gpu/drm/amd/amdgpu/amdgpu.ko] undefined!
ERROR: modpost: "_savegpr1_27" [drivers/gpu/drm/amd/amdgpu/amdgpu.ko] undefined!
ERROR: modpost: "_savegpr1_25" [drivers/gpu/drm/amd/amdgpu/amdgpu.ko] undefined!
ERROR: modpost: "_restfpr_28" [drivers/gpu/drm/amd/amdgpu/amdgpu.ko] undefined!
ERROR: modpost: "_savegpr1_29" [drivers/gpu/drm/amd/amdgpu/amdgpu.ko] undefined!
ERROR: modpost: "_savefpr_20" [drivers/gpu/drm/amd/amdgpu/amdgpu.ko] undefined!
ERROR: modpost: "_savefpr_22" [drivers/gpu/drm/amd/amdgpu/amdgpu.ko] undefined!
ERROR: modpost: "_restfpr_15" [drivers/gpu/drm/amd/amdgpu/amdgpu.ko] undefined!
WARNING: modpost: suppressed 56 unresolved symbol warnings because there were too many)

Signed-off-by: René Rebe <rene@exactco.de>
---
V2: description
Theoretically for -stable, but no previous commit that broke it.
---
 scripts/mod/modpost.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index 47c8aa2a6939..133dfa16308a 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -602,6 +602,10 @@ static int ignore_undef_symbol(struct elf_info *info, const char *symname)
 		/* Special register function linked on all modules during final link of .ko */
 		if (strstarts(symname, "_restgpr0_") ||
 		    strstarts(symname, "_savegpr0_") ||
+		    strstarts(symname, "_restgpr1_") ||
+		    strstarts(symname, "_savegpr1_") ||
+		    strstarts(symname, "_restfpr_") ||
+		    strstarts(symname, "_savefpr_") ||
 		    strstarts(symname, "_restvr_") ||
 		    strstarts(symname, "_savevr_") ||
 		    strcmp(symname, ".TOC.") == 0)
-- 
2.46.0

-- 
René Rebe, ExactCODE GmbH, Berlin, Germany
https://exactco.de • https://t2linux.com • https://patreon.com/renerebe

Re: [PATCH V2] modpost: Amend ppc64 save/restfpr symnames for -Os build

[Christophe Leroy (CS GROUP)]

Le 23/11/2025 à 13:13, René Rebe a écrit :
> Building a size optimized ppc64 kernel (-Os), gcc emits more FP
> save/restore symbols, that the linker generates on demand into the
> .sfpr section. Explicitly allow-list those in scripts/mod/modpost.c,
> too. They are needed for the amdgpu in-kernel floating point support.

Would have been interested to know with which version of GCC the problem 
started.

By the way you seem to fix the problem for modules, but does it also 
work when amdgpu is in kernel ? I would have expected a need to add 
functions in arch/powerpc/lib/crtsavres.S as well, just like following 
commits:

8fe9c93e7453 ("powerpc: Add vr save/restore functions")
7fca5dc8aa7a ("powerpc: Fix module building for gcc 4.5 and 64 bit")
da3de6df33f5 ("[POWERPC] Fix -Os kernel builds with newer gcc versions")


> 
> MODPOST Module.symvers
> ERROR: modpost: "_restfpr_20" [drivers/gpu/drm/amd/amdgpu/amdgpu.ko] undefined!
> ERROR: modpost: "_restfpr_26" [drivers/gpu/drm/amd/amdgpu/amdgpu.ko] undefined!
> ERROR: modpost: "_restfpr_22" [drivers/gpu/drm/amd/amdgpu/amdgpu.ko] undefined!
> ERROR: modpost: "_savegpr1_27" [drivers/gpu/drm/amd/amdgpu/amdgpu.ko] undefined!
> ERROR: modpost: "_savegpr1_25" [drivers/gpu/drm/amd/amdgpu/amdgpu.ko] undefined!
> ERROR: modpost: "_restfpr_28" [drivers/gpu/drm/amd/amdgpu/amdgpu.ko] undefined!
> ERROR: modpost: "_savegpr1_29" [drivers/gpu/drm/amd/amdgpu/amdgpu.ko] undefined!
> ERROR: modpost: "_savefpr_20" [drivers/gpu/drm/amd/amdgpu/amdgpu.ko] undefined!
> ERROR: modpost: "_savefpr_22" [drivers/gpu/drm/amd/amdgpu/amdgpu.ko] undefined!
> ERROR: modpost: "_restfpr_15" [drivers/gpu/drm/amd/amdgpu/amdgpu.ko] undefined!
> WARNING: modpost: suppressed 56 unresolved symbol warnings because there were too many)
> 
> Signed-off-by: René Rebe <rene@exactco.de>
> ---
> V2: description
> Theoretically for -stable, but no previous commit that broke it.

In that case you have to add Cc: stable@vger.kernel.org
Add indeed it is likely a gcc upgrade that broke it, not a previous commit.

> ---
>   scripts/mod/modpost.c | 4 ++++
>   1 file changed, 4 insertions(+)
> 
> diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
> index 47c8aa2a6939..133dfa16308a 100644
> --- a/scripts/mod/modpost.c
> +++ b/scripts/mod/modpost.c
> @@ -602,6 +602,10 @@ static int ignore_undef_symbol(struct elf_info *info, const char *symname)
>   		/* Special register function linked on all modules during final link of .ko */
>   		if (strstarts(symname, "_restgpr0_") ||
>   		    strstarts(symname, "_savegpr0_") ||
> +		    strstarts(symname, "_restgpr1_") ||
> +		    strstarts(symname, "_savegpr1_") ||
> +		    strstarts(symname, "_restfpr_") ||
> +		    strstarts(symname, "_savefpr_") ||
>   		    strstarts(symname, "_restvr_") ||
>   		    strstarts(symname, "_savevr_") ||
>   		    strcmp(symname, ".TOC.") == 0)

Re: [PATCH V2] modpost: Amend ppc64 save/restfpr symnames for -Os build

[René Rebe]

Hi,

On Sun, 23 Nov 2025 15:57:24 +0100, "Christophe Leroy (CS GROUP)" <chleroy@kernel.org> wrote:

> Le 23/11/2025 à 13:13, René Rebe a écrit :
> > Building a size optimized ppc64 kernel (-Os), gcc emits more FP
> > save/restore symbols, that the linker generates on demand into the
> > .sfpr section. Explicitly allow-list those in scripts/mod/modpost.c,
> > too. They are needed for the amdgpu in-kernel floating point support.
> 
> Would have been interested to know with which version of GCC the
> problem started.

idk, maybe forever, or at least a decade fo GCC? Most devs probably
don't build size optimized, and addtionally we only use in kernel
floating point for amdgpu since recently? Should I add Fixes: for the
in-kernel FP hash?

> By the way you seem to fix the problem for modules, but does it also
> work when amdgpu is in kernel ? I would have expected a need to add
> functions in arch/powerpc/lib/crtsavres.S as well, just like following
> commits:
> 
> 8fe9c93e7453 ("powerpc: Add vr save/restore functions")
> 7fca5dc8aa7a ("powerpc: Fix module building for gcc 4.5 and 64 bit")
> da3de6df33f5 ("[POWERPC] Fix -Os kernel builds with newer gcc
> versions")

idk, I avoid linking that big stuff directly into the kernel and would
need to specically test that, too. I guess I go do that now, too, ...

> > MODPOST Module.symvers
> > ERROR: modpost: "_restfpr_20" [drivers/gpu/drm/amd/amdgpu/amdgpu.ko]
> > undefined!
> > ERROR: modpost: "_restfpr_26" [drivers/gpu/drm/amd/amdgpu/amdgpu.ko]
> > undefined!
> > ERROR: modpost: "_restfpr_22" [drivers/gpu/drm/amd/amdgpu/amdgpu.ko]
> > undefined!
> > ERROR: modpost: "_savegpr1_27" [drivers/gpu/drm/amd/amdgpu/amdgpu.ko]
> > undefined!
> > ERROR: modpost: "_savegpr1_25" [drivers/gpu/drm/amd/amdgpu/amdgpu.ko]
> > undefined!
> > ERROR: modpost: "_restfpr_28" [drivers/gpu/drm/amd/amdgpu/amdgpu.ko]
> > undefined!
> > ERROR: modpost: "_savegpr1_29" [drivers/gpu/drm/amd/amdgpu/amdgpu.ko]
> > undefined!
> > ERROR: modpost: "_savefpr_20" [drivers/gpu/drm/amd/amdgpu/amdgpu.ko]
> > undefined!
> > ERROR: modpost: "_savefpr_22" [drivers/gpu/drm/amd/amdgpu/amdgpu.ko]
> > undefined!
> > ERROR: modpost: "_restfpr_15" [drivers/gpu/drm/amd/amdgpu/amdgpu.ko]
> > undefined!
> > WARNING: modpost: suppressed 56 unresolved symbol warnings because
> > there were too many)
> > Signed-off-by: René Rebe <rene@exactco.de>
> > ---
> > V2: description
> > Theoretically for -stable, but no previous commit that broke it.
> 
> In that case you have to add Cc: stable@vger.kernel.org
> Add indeed it is likely a gcc upgrade that broke it, not a previous
> commit.

Should I then simply use enabling amdgpu dc_fp and in-kernel FP as the
breaking commit for Fixes:?

Thanks!

	René

> > ---
> >   scripts/mod/modpost.c | 4 ++++
> >   1 file changed, 4 insertions(+)
> > diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
> > index 47c8aa2a6939..133dfa16308a 100644
> > --- a/scripts/mod/modpost.c
> > +++ b/scripts/mod/modpost.c
> > @@ -602,6 +602,10 @@ static int ignore_undef_symbol(struct elf_info
> > *info, const char *symname)
> >   		/* Special register function linked on all modules during final link of
> >   		.ko */
> >   		if (strstarts(symname, "_restgpr0_") ||
> >   		    strstarts(symname, "_savegpr0_") ||
> > +		    strstarts(symname, "_restgpr1_") ||
> > +		    strstarts(symname, "_savegpr1_") ||
> > +		    strstarts(symname, "_restfpr_") ||
> > +		    strstarts(symname, "_savefpr_") ||
> >   		    strstarts(symname, "_restvr_") ||
> >   		    strstarts(symname, "_savevr_") ||
> >   		    strcmp(symname, ".TOC.") == 0)
> 

-- 
René Rebe, ExactCODE GmbH, Berlin, Germany
https://exactco.de • https://t2linux.com • https://patreon.com/renerebe

Re: [PATCH V2] modpost: Amend ppc64 save/restfpr symnames for -Os build

[René Rebe]

Hey,

On Sun, 23 Nov 2025 16:09:41 +0100 (CET), René Rebe <rene@exactco.de> wrote:

> On Sun, 23 Nov 2025 15:57:24 +0100, "Christophe Leroy (CS GROUP)" <chleroy@kernel.org> wrote:
> 
> > Le 23/11/2025 à 13:13, René Rebe a écrit :
> > > Building a size optimized ppc64 kernel (-Os), gcc emits more FP
> > > save/restore symbols, that the linker generates on demand into the
> > > .sfpr section. Explicitly allow-list those in scripts/mod/modpost.c,
> > > too. They are needed for the amdgpu in-kernel floating point support.
> > 
> > Would have been interested to know with which version of GCC the
> > problem started.
> 
> idk, maybe forever, or at least a decade fo GCC? Most devs probably
> don't build size optimized, and addtionally we only use in kernel
> floating point for amdgpu since recently? Should I add Fixes: for the
> in-kernel FP hash?
> 
> > By the way you seem to fix the problem for modules, but does it also
> > work when amdgpu is in kernel ? I would have expected a need to add
> > functions in arch/powerpc/lib/crtsavres.S as well, just like following
> > commits:
> > 
> > 8fe9c93e7453 ("powerpc: Add vr save/restore functions")
> > 7fca5dc8aa7a ("powerpc: Fix module building for gcc 4.5 and 64 bit")
> > da3de6df33f5 ("[POWERPC] Fix -Os kernel builds with newer gcc
> > versions")
> 
> idk, I avoid linking that big stuff directly into the kernel and would
> need to specically test that, too. I guess I go do that now, too, ...

It appears built-in amdgpu FP somehow magically works for me:

debug-linux:[linux-6.17]# grep DRM.*AMD .config
CONFIG_DRM_AMDGPU=y
CONFIG_DRM_AMDGPU_SI=y
CONFIG_DRM_AMDGPU_CIK=y
CONFIG_DRM_AMDGPU_USERPTR=y
CONFIG_DRM_AMD_ACP=y
CONFIG_DRM_AMD_DC=y
CONFIG_DRM_AMD_DC_FP=y
CONFIG_DRM_AMD_DC_SI=y
...
  CC      drivers/gpu/drm/amd/amdgpu/../display/modules/hdcp/hdcp_ddc.o
  CC      drivers/gpu/drm/amd/amdgpu/../display/modules/hdcp/hdcp_log.o
  CC      drivers/gpu/drm/amd/amdgpu/../display/modules/hdcp/hdcp_psp.o
  CC      drivers/gpu/drm/amd/amdgpu/../display/modules/hdcp/hdcp.o
  CC      drivers/gpu/drm/amd/amdgpu/../display/modules/hdcp/hdcp1_execution.o
  CC      drivers/gpu/drm/amd/amdgpu/../display/modules/hdcp/hdcp1_transition.o
  CC      drivers/gpu/drm/amd/amdgpu/../display/modules/hdcp/hdcp2_execution.o
  CC      drivers/gpu/drm/amd/amdgpu/../display/modules/hdcp/hdcp2_transition.o
  AR      drivers/gpu/drm/amd/amdgpu/built-in.a
  AR      drivers/gpu/drm/built-in.a
  AR      drivers/gpu/built-in.a
  AR      drivers/built-in.a
  AR      built-in.a
  AR      vmlinux.a
  LD      vmlinux.o
  GEN     modules.builtin.modinfo
  GEN     modules.builtin
  MODPOST vmlinux.symvers
  CC      .vmlinux.export.o
  UPD     include/generated/utsversion.h
  CC      init/version-timestamp.o
  KSYMS   .tmp_vmlinux0.kallsyms.S
  AS      .tmp_vmlinux0.kallsyms.o
  LD      .tmp_vmlinux1
  NM      .tmp_vmlinux1.syms
  KSYMS   .tmp_vmlinux1.kallsyms.S
  AS      .tmp_vmlinux1.kallsyms.o
  LD      .tmp_vmlinux2
  NM      .tmp_vmlinux2.syms
  KSYMS   .tmp_vmlinux2.kallsyms.S
  AS      .tmp_vmlinux2.kallsyms.o
  LD      vmlinux.unstripped
  NM      System.map
  SORTTAB vmlinux.unstripped
make[3]: Nothing to be done for 'vmlinux.unstripped'.
  OBJCOPY vmlinux

So I guess the patch is good to go after clarifying which kind of
Fixes: to use?

Thanks!
       René

> > > MODPOST Module.symvers
> > > ERROR: modpost: "_restfpr_20" [drivers/gpu/drm/amd/amdgpu/amdgpu.ko]
> > > undefined!
> > > ERROR: modpost: "_restfpr_26" [drivers/gpu/drm/amd/amdgpu/amdgpu.ko]
> > > undefined!
> > > ERROR: modpost: "_restfpr_22" [drivers/gpu/drm/amd/amdgpu/amdgpu.ko]
> > > undefined!
> > > ERROR: modpost: "_savegpr1_27" [drivers/gpu/drm/amd/amdgpu/amdgpu.ko]
> > > undefined!
> > > ERROR: modpost: "_savegpr1_25" [drivers/gpu/drm/amd/amdgpu/amdgpu.ko]
> > > undefined!
> > > ERROR: modpost: "_restfpr_28" [drivers/gpu/drm/amd/amdgpu/amdgpu.ko]
> > > undefined!
> > > ERROR: modpost: "_savegpr1_29" [drivers/gpu/drm/amd/amdgpu/amdgpu.ko]
> > > undefined!
> > > ERROR: modpost: "_savefpr_20" [drivers/gpu/drm/amd/amdgpu/amdgpu.ko]
> > > undefined!
> > > ERROR: modpost: "_savefpr_22" [drivers/gpu/drm/amd/amdgpu/amdgpu.ko]
> > > undefined!
> > > ERROR: modpost: "_restfpr_15" [drivers/gpu/drm/amd/amdgpu/amdgpu.ko]
> > > undefined!
> > > WARNING: modpost: suppressed 56 unresolved symbol warnings because
> > > there were too many)
> > > Signed-off-by: René Rebe <rene@exactco.de>
> > > ---
> > > V2: description
> > > Theoretically for -stable, but no previous commit that broke it.
> > 
> > In that case you have to add Cc: stable@vger.kernel.org
> > Add indeed it is likely a gcc upgrade that broke it, not a previous
> > commit.
> 
> Should I then simply use enabling amdgpu dc_fp and in-kernel FP as the
> breaking commit for Fixes:?
> 
> Thanks!
> 
> 	René
> 
> > > ---
> > >   scripts/mod/modpost.c | 4 ++++
> > >   1 file changed, 4 insertions(+)
> > > diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
> > > index 47c8aa2a6939..133dfa16308a 100644
> > > --- a/scripts/mod/modpost.c
> > > +++ b/scripts/mod/modpost.c
> > > @@ -602,6 +602,10 @@ static int ignore_undef_symbol(struct elf_info
> > > *info, const char *symname)
> > >   		/* Special register function linked on all modules during final link of
> > >   		.ko */
> > >   		if (strstarts(symname, "_restgpr0_") ||
> > >   		    strstarts(symname, "_savegpr0_") ||
> > > +		    strstarts(symname, "_restgpr1_") ||
> > > +		    strstarts(symname, "_savegpr1_") ||
> > > +		    strstarts(symname, "_restfpr_") ||
> > > +		    strstarts(symname, "_savefpr_") ||
> > >   		    strstarts(symname, "_restvr_") ||
> > >   		    strstarts(symname, "_savevr_") ||
> > >   		    strcmp(symname, ".TOC.") == 0)
> > 
> 
> -- 
> René Rebe, ExactCODE GmbH, Berlin, Germany
> https://exactco.de • https://t2linux.com • https://patreon.com/renerebe

-- 
René Rebe, ExactCODE GmbH, Berlin, Germany
https://exactco.de • https://t2linux.com • https://patreon.com/renerebe

Re: [PATCH V2] modpost: Amend ppc64 save/restfpr symnames for -Os build

[Erhard Furtner]

On 11/23/25 15:57, Christophe Leroy (CS GROUP) wrote:
> 
> 
> Le 23/11/2025 à 13:13, René Rebe a écrit :
>> Building a size optimized ppc64 kernel (-Os), gcc emits more FP
>> save/restore symbols, that the linker generates on demand into the
>> .sfpr section. Explicitly allow-list those in scripts/mod/modpost.c,
>> too. They are needed for the amdgpu in-kernel floating point support.
> 
> Would have been interested to know with which version of GCC the problem 
> started.

I can reproduce the modpost errors on GCC 15.2 and GCC 11.5.

Same kernel .config builds ok with CLANG 20.1.8 however.

> By the way you seem to fix the problem for modules, but does it also 
> work when amdgpu is in kernel ? I would have expected a need to add 
> functions in arch/powerpc/lib/crtsavres.S as well, just like following 
> commits:

If I build amdgpu statically into the kernel I don't get the modpost 
errors, the build finishes successfully. Only building amdgpu as module 
leads to these errors Rene reported.

Regards,
Erhard