dm-crypt.c

来自「Linux Kernel 2.6.9 for OMAP1710」· C语言 代码 · 共 800 行 · 第 1/2 页

/*
 * Copyright (C) 2003 Christophe Saout <[e-mail]>
 *
 * This file is released under the GPL.
 */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/bio.h>
#include <linux/blkdev.h>
#include <linux/mempool.h>
#include <linux/slab.h>
#include <linux/crypto.h>
#include <linux/workqueue.h>
#include <asm/atomic.h>
#include <asm/scatterlist.h>

#include "dm.h"

#define PFX	"crypt: "

/*
 * per bio private data
 */
struct crypt_io {
	struct dm_target *target;
	struct bio *bio;
	struct bio *first_clone;
	struct work_struct work;
	atomic_t pending;
	int error;
};

/*
 * context holding the current state of a multi-part conversion
 */
struct convert_context {
	struct bio *bio_in;
	struct bio *bio_out;
	unsigned int offset_in;
	unsigned int offset_out;
	int idx_in;
	int idx_out;
	sector_t sector;
	int write;
};

/*
 * Crypt: maps a linear range of a block device
 * and encrypts / decrypts at the same time.
 */
struct crypt_config {
	struct dm_dev *dev;
	sector_t start;

	/*
	 * pool for per bio private data and
	 * for encryption buffer pages
	 */
	mempool_t *io_pool;
	mempool_t *page_pool;

	/*
	 * crypto related data
	 */
	struct crypto_tfm *tfm;
	sector_t iv_offset;
	int (*iv_generator)(struct crypt_config *cc, u8 *iv, sector_t sector);
	int iv_size;
	int key_size;
	u8 key[0];
};

#define MIN_IOS        256
#define MIN_POOL_PAGES 32
#define MIN_BIO_PAGES  8

static kmem_cache_t *_crypt_io_pool;

/*
 * Mempool alloc and free functions for the page
 */
static void *mempool_alloc_page(int gfp_mask, void *data)
{
	return alloc_page(gfp_mask);
}

static void mempool_free_page(void *page, void *data)
{
	__free_page(page);
}


/*
 * Different IV generation algorithms
 */
static int crypt_iv_plain(struct crypt_config *cc, u8 *iv, sector_t sector)
{
	*(u32 *)iv = cpu_to_le32(sector & 0xffffffff);
	if (cc->iv_size > sizeof(u32) / sizeof(u8))
		memset(iv + (sizeof(u32) / sizeof(u8)), 0,
		       cc->iv_size - (sizeof(u32) / sizeof(u8)));

	return 0;
}

static inline int
crypt_convert_scatterlist(struct crypt_config *cc, struct scatterlist *out,
                          struct scatterlist *in, unsigned int length,
                          int write, sector_t sector)
{
	u8 iv[cc->iv_size];
	int r;

	if (cc->iv_generator) {
		r = cc->iv_generator(cc, iv, sector);
		if (r < 0)
			return r;

		if (write)
			r = crypto_cipher_encrypt_iv(cc->tfm, out, in, length, iv);
		else
			r = crypto_cipher_decrypt_iv(cc->tfm, out, in, length, iv);
	} else {
		if (write)
			r = crypto_cipher_encrypt(cc->tfm, out, in, length);
		else
			r = crypto_cipher_decrypt(cc->tfm, out, in, length);
	}

	return r;
}

static void
crypt_convert_init(struct crypt_config *cc, struct convert_context *ctx,
                   struct bio *bio_out, struct bio *bio_in,
                   sector_t sector, int write)
{
	ctx->bio_in = bio_in;
	ctx->bio_out = bio_out;
	ctx->offset_in = 0;
	ctx->offset_out = 0;
	ctx->idx_in = bio_in ? bio_in->bi_idx : 0;
	ctx->idx_out = bio_out ? bio_out->bi_idx : 0;
	ctx->sector = sector + cc->iv_offset;
	ctx->write = write;
}

/*
 * Encrypt / decrypt data from one bio to another one (can be the same one)
 */
static int crypt_convert(struct crypt_config *cc,
                         struct convert_context *ctx)
{
	int r = 0;

	while(ctx->idx_in < ctx->bio_in->bi_vcnt &&
	      ctx->idx_out < ctx->bio_out->bi_vcnt) {
		struct bio_vec *bv_in = bio_iovec_idx(ctx->bio_in, ctx->idx_in);
		struct bio_vec *bv_out = bio_iovec_idx(ctx->bio_out, ctx->idx_out);
		struct scatterlist sg_in = {
			.page = bv_in->bv_page,
			.offset = bv_in->bv_offset + ctx->offset_in,
			.length = 1 << SECTOR_SHIFT
		};
		struct scatterlist sg_out = {
			.page = bv_out->bv_page,
			.offset = bv_out->bv_offset + ctx->offset_out,
			.length = 1 << SECTOR_SHIFT
		};

		ctx->offset_in += sg_in.length;
		if (ctx->offset_in >= bv_in->bv_len) {
			ctx->offset_in = 0;
			ctx->idx_in++;
		}

		ctx->offset_out += sg_out.length;
		if (ctx->offset_out >= bv_out->bv_len) {
			ctx->offset_out = 0;
			ctx->idx_out++;
		}

		r = crypt_convert_scatterlist(cc, &sg_out, &sg_in, sg_in.length,
		                              ctx->write, ctx->sector);
		if (r < 0)
			break;

		ctx->sector++;
	}

	return r;
}

/*
 * Generate a new unfragmented bio with the given size
 * This should never violate the device limitations
 * May return a smaller bio when running out of pages
 */
static struct bio *
crypt_alloc_buffer(struct crypt_config *cc, unsigned int size,
                   struct bio *base_bio, int *bio_vec_idx)
{
	struct bio *bio;
	int nr_iovecs = dm_div_up(size, PAGE_SIZE);
	int gfp_mask = GFP_NOIO | __GFP_HIGHMEM;
	int flags = current->flags;
	int i;

	/*
	 * Tell VM to act less aggressively and fail earlier.
	 * This is not necessary but increases throughput.
	 * FIXME: Is this really intelligent?
	 */
	current->flags &= ~PF_MEMALLOC;

	if (base_bio)
		bio = bio_clone(base_bio, GFP_NOIO);
	else
		bio = bio_alloc(GFP_NOIO, nr_iovecs);
	if (!bio) {
		if (flags & PF_MEMALLOC)
			current->flags |= PF_MEMALLOC;
		return NULL;
	}

	/* if the last bio was not complete, continue where that one ended */
	bio->bi_idx = *bio_vec_idx;
	bio->bi_vcnt = *bio_vec_idx;
	bio->bi_size = 0;
	bio->bi_flags &= ~(1 << BIO_SEG_VALID);

	/* bio->bi_idx pages have already been allocated */
	size -= bio->bi_idx * PAGE_SIZE;

	for(i = bio->bi_idx; i < nr_iovecs; i++) {
		struct bio_vec *bv = bio_iovec_idx(bio, i);

		bv->bv_page = mempool_alloc(cc->page_pool, gfp_mask);
		if (!bv->bv_page)
			break;

		/*
		 * if additional pages cannot be allocated without waiting,
		 * return a partially allocated bio, the caller will then try
		 * to allocate additional bios while submitting this partial bio
		 */
		if ((i - bio->bi_idx) == (MIN_BIO_PAGES - 1))
			gfp_mask = (gfp_mask | __GFP_NOWARN) & ~__GFP_WAIT;

		bv->bv_offset = 0;
		if (size > PAGE_SIZE)
			bv->bv_len = PAGE_SIZE;
		else
			bv->bv_len = size;

		bio->bi_size += bv->bv_len;
		bio->bi_vcnt++;
		size -= bv->bv_len;
	}

	if (flags & PF_MEMALLOC)
		current->flags |= PF_MEMALLOC;

	if (!bio->bi_size) {
		bio_put(bio);
		return NULL;
	}

	/*
	 * Remember the last bio_vec allocated to be able
	 * to correctly continue after the splitting.
	 */
	*bio_vec_idx = bio->bi_vcnt;

	return bio;
}

static void crypt_free_buffer_pages(struct crypt_config *cc,
                                    struct bio *bio, unsigned int bytes)
{
	unsigned int start, end;
	struct bio_vec *bv;
	int i;

	/*
	 * This is ugly, but Jens Axboe thinks that using bi_idx in the
	 * endio function is too dangerous at the moment, so I calculate the
	 * correct position using bi_vcnt and bi_size.
	 * The bv_offset and bv_len fields might already be modified but we
	 * know that we always allocated whole pages.
	 * A fix to the bi_idx issue in the kernel is in the works, so
	 * we will hopefully be able to revert to the cleaner solution soon.
	 */
	i = bio->bi_vcnt - 1;
	bv = bio_iovec_idx(bio, i);
	end = (i << PAGE_SHIFT) + (bv->bv_offset + bv->bv_len) - bio->bi_size;
	start = end - bytes;

	start >>= PAGE_SHIFT;
	if (!bio->bi_size)
		end = bio->bi_vcnt;
	else
		end >>= PAGE_SHIFT;

	for(i = start; i < end; i++) {
		bv = bio_iovec_idx(bio, i);
		BUG_ON(!bv->bv_page);
		mempool_free(bv->bv_page, cc->page_pool);
		bv->bv_page = NULL;
	}
}

/*
 * One of the bios was finished. Check for completion of
 * the whole request and correctly clean up the buffer.
 */
static void dec_pending(struct crypt_io *io, int error)
{
	struct crypt_config *cc = (struct crypt_config *) io->target->private;

	if (error < 0)
		io->error = error;

	if (!atomic_dec_and_test(&io->pending))
		return;

	if (io->first_clone)
		bio_put(io->first_clone);

	bio_endio(io->bio, io->bio->bi_size, io->error);

	mempool_free(io, cc->io_pool);
}

/*
 * kcryptd:
 *
 * Needed because it would be very unwise to do decryption in an
 * interrupt context, so bios returning from read requests get
 * queued here.
 */
static struct workqueue_struct *_kcryptd_workqueue;

static void kcryptd_do_work(void *data)
{
	struct crypt_io *io = (struct crypt_io *) data;
	struct crypt_config *cc = (struct crypt_config *) io->target->private;
	struct convert_context ctx;
	int r;

	crypt_convert_init(cc, &ctx, io->bio, io->bio,
	                   io->bio->bi_sector - io->target->begin, 0);
	r = crypt_convert(cc, &ctx);

	dec_pending(io, r);
}

static void kcryptd_queue_io(struct crypt_io *io)
{
	INIT_WORK(&io->work, kcryptd_do_work, io);
	queue_work(_kcryptd_workqueue, &io->work);
}

/*
 * Decode key from its hex representation
 */
static int crypt_decode_key(u8 *key, char *hex, int size)
{
	char buffer[3];
	char *endp;
	int i;

	buffer[2] = '\0';

	for(i = 0; i < size; i++) {
		buffer[0] = *hex++;
		buffer[1] = *hex++;

		key[i] = (u8)simple_strtoul(buffer, &endp, 16);

		if (endp != &buffer[2])
			return -EINVAL;
	}

	if (*hex != '\0')
		return -EINVAL;

	return 0;
}

/*
 * Encode key into its hex representation
 */
static void crypt_encode_key(char *hex, u8 *key, int size)
{
	int i;

	for(i = 0; i < size; i++) {