On Tue, May 16, 2017 at 09:03:08PM -0700, Eric Biggers wrote: > From: Eric Biggers <ebiggers@xxxxxxxxxx> > > 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@xxxxxxxxxx> Reviewed-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx> -- Josh
