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

["René Rebe" <rene@exactco.de>]

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