linux-kernel - [PATCH] crypto: jitterentropy: build without sanitizer

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Message-Id: <20190724185207.4023459-1-arnd@arndb.de>
Date:   Wed, 24 Jul 2019 20:51:55 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>
Cc:     kasan-dev@...glegroups.com,
        Stephan Müller <smueller@...onox.de>,
        Arnd Bergmann <arnd@...db.de>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Eric Biggers <ebiggers@...gle.com>,
        Vitaly Chikunov <vt@...linux.org>,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
        clang-built-linux@...glegroups.com
Subject: [PATCH] crypto: jitterentropy: build without sanitizer

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@...db.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