=============================================================================== GENIV Template cipher ===============================================================================
Currently, the iv generation algorithms are implemented in dm-crypt.c. The goal is to move these algorithms from the dm layer to the kernel crypto layer by implementing them as template ciphers so they can be used in relation with algorithms like aes, and with multiple modes like cbc, ecb etc. As part of this patchset, the iv-generation code is moved from the dm layer to the crypto layer and adapt the dm-layer to send a whole 'bio' (as defined in the block layer) at a time. Each bio contains the in memory representation of physically contiguous disk blocks. Since the bio itself may not be contiguous in main memory, the dm layer sets up a chained scatterlist of these blocks split into physically contiguous segments in memory so that DMA can be performed. One challenge in doing so is that the IVs are generated based on a 512-byte sector number. This infact limits the block sizes to 512 bytes. But this should not be a problem if a hardware with iv generation support is used. The geniv itself splits the segments into sectors so it could choose the IV based on sector number. But it could be modelled in hardware effectively by not splitting up the segments in the bio. Another challenge faced is that dm-crypt has an option to use multiple keys. The key selection is done based on the sector number. If the whole bio is encrypted / decrypted with the same key, the encrypted volumes will not be compatible with the original dm-crypt [without the changes]. So, the key selection code is moved to crypto layer so the neighboring sectors are encrypted with a different key. The dm layer allocates space for iv. The hardware drivers can choose to make use of this space to generate their IVs sequentially or allocate it on their own. This can be moved to crypto layer too. Postponing this decision until the requirement to integrate milan's changes are clear. Interface to the crypto layer - include/crypto/geniv.h Revisions: v1: https://patchwork.kernel.org/patch/9439175 v2: https://patchwork.kernel.org/patch/9471923 v2 --> v3 ---------- 1. Moved iv algorithms in dm-crypt.c for control 2. Key management code moved from dm layer to cryto layer so that cipher instance selection can be made depending on key_index 3. The revision v2 had scatterlist nodes created for every sector in the bio. It is modified to create only once scatterlist node to reduce memory foot print. Synchronous requests are processed sequentially. Asynchronous requests are processed in parallel and is freed in the async callback. 4. Changed allocation for sub-requests using mempool v1 --> v2 ---------- 1. dm-crypt changes to process larger block sizes (one segment in a bio) 2. Incorporated changes w.r.t. comments from Herbert. Binoy Jayan (1): crypto: Add IV generation algorithms drivers/md/dm-crypt.c | 1891 ++++++++++++++++++++++++++++++++++-------------- include/crypto/geniv.h | 47 ++ 2 files changed, 1399 insertions(+), 539 deletions(-) create mode 100644 include/crypto/geniv.h -- Binoy Jayan -- To unsubscribe from this list: send the line "unsubscribe linux-crypto" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
