[PATCH v3] lib/crypto: blake2b: Limit frame size workaround to GCC

[PATCH v3] lib/crypto: blake2b: Limit frame size workaround to GCC

[Thorsten Blum]

The GCC regression only affected i386 and has been fixed since GCC 12.2.
However, modern GCC versions still generate large stack frames on other
architectures (e.g., 3440 bytes for blake2b_compress_generic() on m68k
with GCC 15.1.0). Clang handles these functions efficiently and should
work fine with the default warning threshold.

Limit the frame size workaround to GCC only.

Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
---
Changes in v3:
- Add a comment and remove the end marker (Nathan)
- Link to v2: https://lore.kernel.org/lkml/20251123182515.548471-3-thorsten.blum@linux.dev/

Changes in v2:
- Restrict frame size workaround to GCC independent of its version or
  the architecture
- Update patch title and description
- Link to v1: https://lore.kernel.org/lkml/20251122105530.441350-2-thorsten.blum@linux.dev/
---
 lib/crypto/Makefile | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/lib/crypto/Makefile b/lib/crypto/Makefile
index b5346cebbb55..79315717fb43 100644
--- a/lib/crypto/Makefile
+++ b/lib/crypto/Makefile
@@ -33,7 +33,12 @@ obj-$(CONFIG_CRYPTO_LIB_GF128MUL)		+= gf128mul.o
 
 obj-$(CONFIG_CRYPTO_LIB_BLAKE2B) += libblake2b.o
 libblake2b-y := blake2b.o
+ifeq ($(CONFIG_CC_IS_GCC),y)
+# Please note that the bug affected only i386 and has been fixed since GCC 12.2.
+# However, modern GCC versions still generate very large stack frames on other
+# architectures.
 CFLAGS_blake2b.o := -Wframe-larger-than=4096 #  https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105930
+endif
 ifeq ($(CONFIG_CRYPTO_LIB_BLAKE2B_ARCH),y)
 CFLAGS_blake2b.o += -I$(src)/$(SRCARCH)
 libblake2b-$(CONFIG_ARM) += arm/blake2b-neon-core.o
-- 
Thorsten Blum
GPG: 1D60 735E 8AEF 3BE4 73B6  9D84 7336 78FD 8DFE EAD4