[PATCH] crypto: jitterentropy: build without sanitizer

[PATCH] crypto: jitterentropy: build without sanitizer

[Arnd Bergmann]

Recent clang-9 snapshots double the kernel stack usage when building
this file with -O0 -fsanitize=kernel-hwaddress, compared to clang-8
and older snapshots, this changed between commits svn364966 and
svn366056:

crypto/jitterentropy.c:516:5: error: stack frame size of 2640 bytes in function 'jent_entropy_init' [-Werror,-Wframe-larger-than=]
int jent_entropy_init(void)
    ^
crypto/jitterentropy.c:185:14: error: stack frame size of 2224 bytes in function 'jent_lfsr_time' [-Werror,-Wframe-larger-than=]
static __u64 jent_lfsr_time(struct rand_data *ec, __u64 time, __u64 loop_cnt)
             ^

I prepared a reduced test case in case any clang developers want to
take a closer look, but from looking at the earlier output it seems
that even with clang-8, something was very wrong here.

Turn off any KASAN and UBSAN sanitizing for this file, as that likely
clashes with -O0 anyway.  Turning off just KASAN avoids the warning
already, but I suspect both of these have undesired side-effects
for jitterentropy.

Link: https://godbolt.org/z/fDcwZ5
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 crypto/Makefile | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/crypto/Makefile b/crypto/Makefile
index 9479e1a45d8c..176b2623dd68 100644
--- a/crypto/Makefile
+++ b/crypto/Makefile
@@ -136,6 +136,8 @@ obj-$(CONFIG_CRYPTO_ANSI_CPRNG) += ansi_cprng.o
 obj-$(CONFIG_CRYPTO_DRBG) += drbg.o
 obj-$(CONFIG_CRYPTO_JITTERENTROPY) += jitterentropy_rng.o
 CFLAGS_jitterentropy.o = -O0
+KASAN_SANITIZE_jitterentropy.o = n
+UBSAN_SANITIZE_jitterentropy.o = n
 jitterentropy_rng-y := jitterentropy.o jitterentropy-kcapi.o
 obj-$(CONFIG_CRYPTO_TEST) += tcrypt.o
 obj-$(CONFIG_CRYPTO_GHASH) += ghash-generic.o
-- 
2.20.0

Re: [PATCH] crypto: jitterentropy: build without sanitizer

[Herbert Xu]

On Wed, Jul 24, 2019 at 08:51:55PM +0200, Arnd Bergmann wrote:
> Recent clang-9 snapshots double the kernel stack usage when building
> this file with -O0 -fsanitize=kernel-hwaddress, compared to clang-8
> and older snapshots, this changed between commits svn364966 and
> svn366056:
> 
> crypto/jitterentropy.c:516:5: error: stack frame size of 2640 bytes in function 'jent_entropy_init' [-Werror,-Wframe-larger-than=]
> int jent_entropy_init(void)
>     ^
> crypto/jitterentropy.c:185:14: error: stack frame size of 2224 bytes in function 'jent_lfsr_time' [-Werror,-Wframe-larger-than=]
> static __u64 jent_lfsr_time(struct rand_data *ec, __u64 time, __u64 loop_cnt)
>              ^
> 
> I prepared a reduced test case in case any clang developers want to
> take a closer look, but from looking at the earlier output it seems
> that even with clang-8, something was very wrong here.
> 
> Turn off any KASAN and UBSAN sanitizing for this file, as that likely
> clashes with -O0 anyway.  Turning off just KASAN avoids the warning
> already, but I suspect both of these have undesired side-effects
> for jitterentropy.
> 
> Link: https://godbolt.org/z/fDcwZ5
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
>  crypto/Makefile | 2 ++
>  1 file changed, 2 insertions(+)

Patch applied.  Thanks.
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt