[PATCH AUTOSEL 6.19-5.10] modpost: Amend ppc64 save/restfpr symnames for -Os build

[Sasha Levin <sashal@kernel.org>]

From: René Rebe <rene@exactco.de>

[ Upstream commit 3cd9763ce4ad999d015cf0734e6b968cead95077 ]

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>
Link: https://patch.msgid.link/20251123.131330.407910684435629198.rene@exactco.de
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---

LLM Generated explanations, may be completely bogus:

The base code is present and the patch should apply cleanly to any
stable tree that has the PPC64 symbol allowlist in
`ignore_undef_symbol()`, which has been there for many years.

### Summary

- **What it fixes**: Build failure on ppc64 with `-Os` optimization
- **Severity**: Build breakage (prevents kernel compilation in a valid
  configuration)
- **Risk**: Minimal — adds 4 trivial string checks following existing
  patterns
- **Scope**: Tiny, contained to one function
- **Dependencies**: None — standalone fix
- **Stable criteria**: Meets all criteria — obviously correct, fixes a
  real build issue, small and contained, no new features

This is a textbook build fix suitable for stable backporting. It's
small, obviously correct, follows existing patterns, has no risk of
regression, and fixes a real build failure.

**YES**

 scripts/mod/modpost.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index 755b842f1f9b7..88ad227f87cd1 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)
-- 
2.51.0