After commit 6f110a5e4f ("Disable SLUB_TINY for build testing"), which
causes CONFIG_KASAN to be enabled in allmodconfig again, arm64
allmodconfig builds with clang-17 and older show an instance of
-Wframe-larger-than (which breaks the build with CONFIG_WERROR=y):
lib/crypto/curve25519-hacl64.c:757:6: error: stack frame size (2336) exceeds limit (2048) in 'curve25519_generic' [-Werror,-Wframe-larger-than]
757 | void curve25519_generic(u8 mypublic[CURVE25519_KEY_SIZE],
| ^
When KASAN is disabled, the stack usage is roughly quartered:
lib/crypto/curve25519-hacl64.c:757:6: error: stack frame size (608) exceeds limit (128) in 'curve25519_generic' [-Werror,-Wframe-larger-than]
757 | void curve25519_generic(u8 mypublic[CURVE25519_KEY_SIZE],
| ^
Using '-Rpass-analysis=stack-frame-layout' shows the following variables
and many, many 8-byte spills when KASAN is enabled:
Offset: [SP-144], Type: Variable, Align: 8, Size: 40
Offset: [SP-464], Type: Variable, Align: 8, Size: 320
Offset: [SP-784], Type: Variable, Align: 8, Size: 320
Offset: [SP-864], Type: Variable, Align: 32, Size: 80
Offset: [SP-896], Type: Variable, Align: 32, Size: 32
Offset: [SP-1016], Type: Variable, Align: 8, Size: 120
When KASAN is disabled, there are still spills but not at many and the
variables list is smaller:
Offset: [SP-192], Type: Variable, Align: 32, Size: 80
Offset: [SP-224], Type: Variable, Align: 32, Size: 32
Offset: [SP-344], Type: Variable, Align: 8, Size: 120
Disable KASAN for this file when using clang-17 or older to avoid
blowing out the stack, clearing up the warning.
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Acked-by: "Jason A. Donenfeld" <Jason@zx2c4.com>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20250609-curve25519-hacl64-disable-kasan-clang-v1-1-08ea0ac5ccff@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
2f13daee2a