[PATCH] crypto: ccree - reduce kernel stack usage with clang

[PATCH] crypto: ccree - reduce kernel stack usage with clang

[Arnd Bergmann]

Building with clang for a 32-bit architecture runs over the stack
frame limit in the setkey function:

drivers/crypto/ccree/cc_cipher.c:318:12: error: stack frame size of 1152 bytes in function 'cc_cipher_setkey' [-Werror,-Wframe-larger-than=]

The problem is that there are two large variables: the temporary
'tmp' array and the SHASH_DESC_ON_STACK() declaration. Moving
the first into the block in which it is used reduces the
total frame size to 768 bytes, which seems more reasonable
and is under the warning limit.

Fixes: 63ee04c8b491 ("crypto: ccree - add skcipher support")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 drivers/crypto/ccree/cc_cipher.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/crypto/ccree/cc_cipher.c b/drivers/crypto/ccree/cc_cipher.c
index d9c17078517b..0abcdc224ab0 100644
--- a/drivers/crypto/ccree/cc_cipher.c
+++ b/drivers/crypto/ccree/cc_cipher.c
@@ -321,7 +321,6 @@ static int cc_cipher_setkey(struct crypto_skcipher *sktfm, const u8 *key,
 	struct crypto_tfm *tfm = crypto_skcipher_tfm(sktfm);
 	struct cc_cipher_ctx *ctx_p = crypto_tfm_ctx(tfm);
 	struct device *dev = drvdata_to_dev(ctx_p->drvdata);
-	u32 tmp[DES3_EDE_EXPKEY_WORDS];
 	struct cc_crypto_alg *cc_alg =
 			container_of(tfm->__crt_alg, struct cc_crypto_alg,
 				     skcipher_alg.base);
@@ -347,6 +346,7 @@ static int cc_cipher_setkey(struct crypto_skcipher *sktfm, const u8 *key,
 	 * HW does the expansion on its own.
 	 */
 	if (ctx_p->flow_mode == S_DIN_to_DES) {
+		u32 tmp[DES3_EDE_EXPKEY_WORDS];
 		if (keylen == DES3_EDE_KEY_SIZE &&
 		    __des3_ede_setkey(tmp, &tfm->crt_flags, key,
 				      DES3_EDE_KEY_SIZE)) {
-- 
2.20.0

Re: [PATCH] crypto: ccree - reduce kernel stack usage with clang

[Gilad Ben-Yossef]

On Thu, Mar 14, 2019 at 11:10 AM Arnd Bergmann <arnd@arndb.de> wrote:
>
> Building with clang for a 32-bit architecture runs over the stack
> frame limit in the setkey function:
>
> drivers/crypto/ccree/cc_cipher.c:318:12: error: stack frame size of 1152 bytes in function 'cc_cipher_setkey' [-Werror,-Wframe-larger-than=]
>
> The problem is that there are two large variables: the temporary
> 'tmp' array and the SHASH_DESC_ON_STACK() declaration. Moving
> the first into the block in which it is used reduces the
> total frame size to 768 bytes, which seems more reasonable
> and is under the warning limit.
>

Thank you , Ard.

I will also revisit splitting that function to further reduce stack
usage after I finish tackling the fallout of the new testmgr... :-)

Acked-By: Gilad Ben-Yossef <gilad@benyossef.com>

Gilad
-- 
Gilad Ben-Yossef
Chief Coffee Drinker

values of β will give rise to dom!

Re: [PATCH] crypto: ccree - reduce kernel stack usage with clang

[Herbert Xu]

On Thu, Mar 14, 2019 at 10:09:44AM +0100, Arnd Bergmann wrote:
> Building with clang for a 32-bit architecture runs over the stack
> frame limit in the setkey function:
> 
> drivers/crypto/ccree/cc_cipher.c:318:12: error: stack frame size of 1152 bytes in function 'cc_cipher_setkey' [-Werror,-Wframe-larger-than=]
> 
> The problem is that there are two large variables: the temporary
> 'tmp' array and the SHASH_DESC_ON_STACK() declaration. Moving
> the first into the block in which it is used reduces the
> total frame size to 768 bytes, which seems more reasonable
> and is under the warning limit.
> 
> Fixes: 63ee04c8b491 ("crypto: ccree - add skcipher support")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
>  drivers/crypto/ccree/cc_cipher.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

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