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Wed, 03 Oct 2007

HIFN driver addons and crypto stack issues.

I decided to rewrite crypto session setup in HIFN driver to allow multiple scatter-gather lists (which are now transformed into pages) in single crypto session (even though with multiple descriptor slots being used). Main goal for this step is to allow encryption of buffers, which are split into number of pages, where each chunk is not block size aligned (for example one page contains 2 bytes and another one 14 for single datablock of 16 bytes). Second revision of driver does not support such blocks yet.
To simplify this I started to use generic linux crypto helpers blkcipher_walk_* from block ciphers. But they do not allow to be called in interrupt context, although all allocations are performed like they happen in atomic context.
Rougly code looks like this (error processing ommitted):

struct blkcipher_walk walk;

blkcipher_walk_init(&walk, dst, src, nbytes);
blkcipher_walk_virt(desc, &walk);

while ((nbytes = walk.nbytes)) {
	u8 *iv = encrypt();
	memcpy(walk.iv, iv, ivsize);
	nbytes &= blocksize - 1;
	err = blkcipher_walk_done(desc, &walk, nbytes);
}

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