linux-kernel - Re: [PATCH] crypto: ccp - Reduce maximum stack usage

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Date:   Fri, 26 Jul 2019 22:34:28 +1000
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     thomas.lendacky@....com, gary.hook@....com, davem@...emloft.net,
        arnd@...db.de, linux-crypto@...r.kernel.org,
        linux-kernel@...r.kernel.org, clang-built-linux@...glegroups.com
Subject: Re: [PATCH] crypto: ccp - Reduce maximum stack usage

Arnd Bergmann <arnd@...db.de> wrote:
> Each of the operations in ccp_run_cmd() needs several hundred
> bytes of kernel stack. Depending on the inlining, these may
> need separate stack slots that add up to more than the warning
> limit, as shown in this clang based build:
> 
> drivers/crypto/ccp/ccp-ops.c:871:12: error: stack frame size of 1164 bytes in function 'ccp_run_aes_cmd' [-Werror,-Wframe-larger-than=]
> static int ccp_run_aes_cmd(struct ccp_cmd_queue *cmd_q, struct ccp_cmd *cmd)
> 
> The problem may also happen when there is no warning, e.g. in the
> ccp_run_cmd()->ccp_run_aes_cmd()->ccp_run_aes_gcm_cmd() call chain with
> over 2000 bytes.
> 
> Mark each individual function as 'noinline_for_stack' to prevent
> this from happening, and move the calls to the two special cases for aes
> into the top-level function. This will keep the actual combined stack
> usage to the mimimum: 828 bytes for ccp_run_aes_gcm_cmd() and
> at most 524 bytes for each of the other cases.
> 
> Fixes: 63b945091a07 ("crypto: ccp - CCP device driver and interface support")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
> drivers/crypto/ccp/ccp-ops.c | 52 +++++++++++++++++++++---------------
> 1 file changed, 31 insertions(+), 21 deletions(-)

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