[<prev] [next>] [<thread-prev] [day] [month] [year] [list]
Message-ID: <20170523050127.GD17569@gondor.apana.org.au>
Date: Tue, 23 May 2017 13:01:27 +0800
From: Herbert Xu <herbert@...dor.apana.org.au>
To: Eric Biggers <ebiggers3@...il.com>
Cc: linux-crypto@...r.kernel.org,
"David S . Miller" <davem@...emloft.net>, x86@...nel.org,
linux-kernel@...r.kernel.org, Josh Poimboeuf <jpoimboe@...hat.com>,
Eric Biggers <ebiggers@...gle.com>
Subject: Re: [PATCH] crypto: x86/aes - Don't use %rbp as temporary register
On Tue, May 16, 2017 at 09:03:08PM -0700, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@...gle.com>
>
> When using the "aes-asm" implementation of AES (*not* the AES-NI
> implementation) on an x86_64, v4.12-rc1 kernel with lockdep enabled, the
> following warning was reported, along with a long unwinder dump:
>
> WARNING: kernel stack regs at ffffc90000643558 in kworker/u4:2:155 has bad 'bp' value 000000000000001c
>
> The problem is that aes_enc_block() and aes_dec_block() use %rbp as a
> temporary register, which breaks stack traces if an interrupt occurs.
>
> Fix this by replacing %rbp with %r9, which was being used to hold the
> saved value of %rbp. This required rearranging the AES round macro
> slightly since %r9d cannot be used as the target of a move from %ah-%dh.
>
> Performance is essentially unchanged --- actually about 0.2% faster than
> before. Interestingly, I also measured aes-generic as being nearly 7%
> faster than aes-asm, so perhaps aes-asm has outlived its usefulness...
>
> Signed-off-by: Eric Biggers <ebiggers@...gle.com>
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
Powered by blists - more mailing lists