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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@google.com> Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.