diff --git a/Documentation/device-mapper/verity.txt b/Documentation/device-mapper/verity.txt
index e15bc1a0fb98ab23563681210cc6ed1865234816..d602c801ff5907ae2d882fd924c202feed73b95c 100644
--- a/Documentation/device-mapper/verity.txt
+++ b/Documentation/device-mapper/verity.txt
@@ -18,11 +18,11 @@ Construction Parameters
0 is the original format used in the Chromium OS.
The salt is appended when hashing, digests are stored continuously and
- the rest of the block is padded with zeros.
+ the rest of the block is padded with zeroes.
1 is the current format that should be used for new devices.
The salt is prepended when hashing and each digest is
- padded with zeros to the power of two.
+ padded with zeroes to the power of two.
<dev>
This is the device containing data, the integrity of which needs to be
@@ -79,6 +79,32 @@ restart_on_corruption
not compatible with ignore_corruption and requires user space support to
avoid restart loops.
+use_fec_from_device <fec_dev>
+ Use forward error correction (FEC) to recover from corruption if hash
+ verification fails. Use encoding data from the specified device. This
+ may be the same device where data and hash blocks reside, in which case
+ fec_start must be outside data and hash areas.
+
+ If the encoding data covers additional metadata, it must be accessible
+ on the hash device after the hash blocks.
+
+ Note: block sizes for data and hash devices must match. Also, if the
+ verity <dev> is encrypted the <fec_dev> should be too.
+
+fec_roots <num>
+ Number of generator roots. This equals to the number of parity bytes in
+ the encoding data. For example, in RS(M, N) encoding, the number of roots
+ is M-N.
+
+fec_blocks <num>
+ The number of encoding data blocks on the FEC device. The block size for
+ the FEC device is <data_block_size>.
+
+fec_start <offset>
+ This is the offset, in <data_block_size> blocks, from the start of the
+ FEC device to the beginning of the encoding data.
+
+
Theory of operation
===================
@@ -98,6 +124,11 @@ per-block basis. This allows for a lightweight hash computation on first read
into the page cache. Block hashes are stored linearly, aligned to the nearest
block size.
+If forward error correction (FEC) support is enabled any recovery of
+corrupted data will be verified using the cryptographic hash of the
+corresponding data. This is why combining error correction with
+integrity checking is essential.
+
Hash Tree
---------
diff --git a/drivers/md/Kconfig b/drivers/md/Kconfig
index 1b69359461e91de6849ba8986cbdc68e1839db48..0a2e7273db9e996ea67d9d461172342aaa65d4f1 100644
--- a/drivers/md/Kconfig
+++ b/drivers/md/Kconfig
@@ -467,6 +467,18 @@ config DM_VERITY
If unsure, say N.
+config DM_VERITY_FEC
+ bool "Verity forward error correction support"
+ depends on DM_VERITY
+ select REED_SOLOMON
+ select REED_SOLOMON_DEC8
+ ---help---
+ Add forward error correction support to dm-verity. This option
+ makes it possible to use pre-generated error correction data to
+ recover from corrupted blocks.
+
+ If unsure, say N.
+
config DM_SWITCH
tristate "Switch target support (EXPERIMENTAL)"
depends on BLK_DEV_DM
diff --git a/drivers/md/Makefile b/drivers/md/Makefile
index 94e9f6bb33d15050b4f1e085bdf9d23ac69a9673..62a65764e8e0f093cede342f0eb4b7d0aec2eb4e 100644
--- a/drivers/md/Makefile
+++ b/drivers/md/Makefile
@@ -64,3 +64,7 @@ obj-$(CONFIG_DM_LOG_WRITES) += dm-log-writes.o
ifeq ($(CONFIG_DM_UEVENT),y)
dm-mod-objs += dm-uevent.o
endif
+
+ifeq ($(CONFIG_DM_VERITY_FEC),y)
+dm-verity-objs += dm-verity-fec.o
+endif
diff --git a/drivers/md/dm-verity-fec.c b/drivers/md/dm-verity-fec.c
new file mode 100644
index 0000000000000000000000000000000000000000..88143d36a1d22e90953c765dd1326838cbdbb0f1
--- /dev/null
+++ b/drivers/md/dm-verity-fec.c
@@ -0,0 +1,812 @@
+/*
+ * Copyright (C) 2015 Google, Inc.
+ *
+ * Author: Sami Tolvanen <samitolvanen@google.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 2 of the License, or (at your option)
+ * any later version.
+ */
+
+#include "dm-verity-fec.h"
+#include <linux/math64.h>
+
+#define DM_MSG_PREFIX "verity-fec"
+
+/*
+ * If error correction has been configured, returns true.
+ */
+bool verity_fec_is_enabled(struct dm_verity *v)
+{
+ return v->fec && v->fec->dev;
+}
+
+/*
+ * Return a pointer to dm_verity_fec_io after dm_verity_io and its variable
+ * length fields.
+ */
+static inline struct dm_verity_fec_io *fec_io(struct dm_verity_io *io)
+{
+ return (struct dm_verity_fec_io *) verity_io_digest_end(io->v, io);
+}
+
+/*
+ * Return an interleaved offset for a byte in RS block.
+ */
+static inline u64 fec_interleave(struct dm_verity *v, u64 offset)
+{
+ u32 mod;
+
+ mod = do_div(offset, v->fec->rsn);
+ return offset + mod * (v->fec->rounds << v->data_dev_block_bits);
+}
+
+/*
+ * Decode an RS block using Reed-Solomon.
+ */
+static int fec_decode_rs8(struct dm_verity *v, struct dm_verity_fec_io *fio,
+ u8 *data, u8 *fec, int neras)
+{
+ int i;
+ uint16_t par[DM_VERITY_FEC_RSM - DM_VERITY_FEC_MIN_RSN];
+
+ for (i = 0; i < v->fec->roots; i++)
+ par[i] = fec[i];
+
+ return decode_rs8(fio->rs, data, par, v->fec->rsn, NULL, neras,
+ fio->erasures, 0, NULL);
+}
+
+/*
+ * Read error-correcting codes for the requested RS block. Returns a pointer
+ * to the data block. Caller is responsible for releasing buf.
+ */
+static u8 *fec_read_parity(struct dm_verity *v, u64 rsb, int index,
+ unsigned *offset, struct dm_buffer **buf)
+{
+ u64 position, block;
+ u8 *res;
+
+ position = (index + rsb) * v->fec->roots;
+ block = position >> v->data_dev_block_bits;
+ *offset = (unsigned)(position - (block << v->data_dev_block_bits));
+
+ res = dm_bufio_read(v->fec->bufio, v->fec->start + block, buf);
+ if (unlikely(IS_ERR(res))) {
+ DMERR("%s: FEC %llu: parity read failed (block %llu): %ld",
+ v->data_dev->name, (unsigned long long)rsb,
+ (unsigned long long)(v->fec->start + block),
+ PTR_ERR(res));
+ *buf = NULL;
+ }
+
+ return res;
+}
+
+/* Loop over each preallocated buffer slot. */
+#define fec_for_each_prealloc_buffer(__i) \
+ for (__i = 0; __i < DM_VERITY_FEC_BUF_PREALLOC; __i++)
+
+/* Loop over each extra buffer slot. */
+#define fec_for_each_extra_buffer(io, __i) \
+ for (__i = DM_VERITY_FEC_BUF_PREALLOC; __i < DM_VERITY_FEC_BUF_MAX; __i++)
+
+/* Loop over each allocated buffer. */
+#define fec_for_each_buffer(io, __i) \
+ for (__i = 0; __i < (io)->nbufs; __i++)
+
+/* Loop over each RS block in each allocated buffer. */
+#define fec_for_each_buffer_rs_block(io, __i, __j) \
+ fec_for_each_buffer(io, __i) \
+ for (__j = 0; __j < 1 << DM_VERITY_FEC_BUF_RS_BITS; __j++)
+
+/*
+ * Return a pointer to the current RS block when called inside
+ * fec_for_each_buffer_rs_block.
+ */
+static inline u8 *fec_buffer_rs_block(struct dm_verity *v,
+ struct dm_verity_fec_io *fio,
+ unsigned i, unsigned j)
+{
+ return &fio->bufs[i][j * v->fec->rsn];
+}
+
+/*
+ * Return an index to the current RS block when called inside
+ * fec_for_each_buffer_rs_block.
+ */
+static inline unsigned fec_buffer_rs_index(unsigned i, unsigned j)
+{
+ return (i << DM_VERITY_FEC_BUF_RS_BITS) + j;
+}
+
+/*
+ * Decode all RS blocks from buffers and copy corrected bytes into fio->output
+ * starting from block_offset.
+ */
+static int fec_decode_bufs(struct dm_verity *v, struct dm_verity_fec_io *fio,
+ u64 rsb, int byte_index, unsigned block_offset,
+ int neras)
+{
+ int r, corrected = 0, res;
+ struct dm_buffer *buf;
+ unsigned n, i, offset;
+ u8 *par, *block;
+
+ par = fec_read_parity(v, rsb, block_offset, &offset, &buf);
+ if (IS_ERR(par))
+ return PTR_ERR(par);
+
+ /*
+ * Decode the RS blocks we have in bufs. Each RS block results in
+ * one corrected target byte and consumes fec->roots parity bytes.
+ */
+ fec_for_each_buffer_rs_block(fio, n, i) {
+ block = fec_buffer_rs_block(v, fio, n, i);
+ res = fec_decode_rs8(v, fio, block, &par[offset], neras);
+ if (res < 0) {
+ dm_bufio_release(buf);
+
+ r = res;
+ goto error;
+ }
+
+ corrected += res;
+ fio->output[block_offset] = block[byte_index];
+
+ block_offset++;
+ if (block_offset >= 1 << v->data_dev_block_bits)
+ goto done;
+
+ /* read the next block when we run out of parity bytes */
+ offset += v->fec->roots;
+ if (offset >= 1 << v->data_dev_block_bits) {
+ dm_bufio_release(buf);
+
+ par = fec_read_parity(v, rsb, block_offset, &offset, &buf);
+ if (unlikely(IS_ERR(par)))
+ return PTR_ERR(par);
+ }
+ }
+done:
+ r = corrected;
+error:
+ if (r < 0 && neras)
+ DMERR_LIMIT("%s: FEC %llu: failed to correct: %d",
+ v->data_dev->name, (unsigned long long)rsb, r);
+ else if (r > 0)
+ DMWARN_LIMIT("%s: FEC %llu: corrected %d errors",
+ v->data_dev->name, (unsigned long long)rsb, r);
+
+ return r;
+}
+
+/*
+ * Locate data block erasures using verity hashes.
+ */
+static int fec_is_erasure(struct dm_verity *v, struct dm_verity_io *io,
+ u8 *want_digest, u8 *data)
+{
+ if (unlikely(verity_hash(v, verity_io_hash_desc(v, io),
+ data, 1 << v->data_dev_block_bits,
+ verity_io_real_digest(v, io))))
+ return 0;
+
+ return memcmp(verity_io_real_digest(v, io), want_digest,
+ v->digest_size) != 0;
+}
+
+/*
+ * Read data blocks that are part of the RS block and deinterleave as much as
+ * fits into buffers. Check for erasure locations if @neras is non-NULL.
+ */
+static int fec_read_bufs(struct dm_verity *v, struct dm_verity_io *io,
+ u64 rsb, u64 target, unsigned block_offset,
+ int *neras)
+{
+ int i, j, target_index = -1;
+ struct dm_buffer *buf;
+ struct dm_bufio_client *bufio;
+ struct dm_verity_fec_io *fio = fec_io(io);
+ u64 block, ileaved;
+ u8 *bbuf, *rs_block;
+ u8 want_digest[v->digest_size];
+ unsigned n, k;
+
+ if (neras)
+ *neras = 0;
+
+ /*
+ * read each of the rsn data blocks that are part of the RS block, and
+ * interleave contents to available bufs
+ */
+ for (i = 0; i < v->fec->rsn; i++) {
+ ileaved = fec_interleave(v, rsb * v->fec->rsn + i);
+
+ /*
+ * target is the data block we want to correct, target_index is
+ * the index of this block within the rsn RS blocks
+ */
+ if (ileaved == target)
+ target_index = i;
+
+ block = ileaved >> v->data_dev_block_bits;
+ bufio = v->fec->data_bufio;
+
+ if (block >= v->data_blocks) {
+ block -= v->data_blocks;
+
+ /*
+ * blocks outside the area were assumed to contain
+ * zeros when encoding data was generated
+ */
+ if (unlikely(block >= v->fec->hash_blocks))
+ continue;
+
+ block += v->hash_start;
+ bufio = v->bufio;
+ }
+
+ bbuf = dm_bufio_read(bufio, block, &buf);
+ if (unlikely(IS_ERR(bbuf))) {
+ DMWARN_LIMIT("%s: FEC %llu: read failed (%llu): %ld",
+ v->data_dev->name,
+ (unsigned long long)rsb,
+ (unsigned long long)block, PTR_ERR(bbuf));
+
+ /* assume the block is corrupted */
+ if (neras && *neras <= v->fec->roots)
+ fio->erasures[(*neras)++] = i;
+
+ continue;
+ }
+
+ /* locate erasures if the block is on the data device */
+ if (bufio == v->fec->data_bufio &&
+ verity_hash_for_block(v, io, block, want_digest) == 0) {
+ /*
+ * skip if we have already found the theoretical
+ * maximum number (i.e. fec->roots) of erasures
+ */
+ if (neras && *neras <= v->fec->roots &&
+ fec_is_erasure(v, io, want_digest, bbuf))
+ fio->erasures[(*neras)++] = i;
+ }
+
+ /*
+ * deinterleave and copy the bytes that fit into bufs,
+ * starting from block_offset
+ */
+ fec_for_each_buffer_rs_block(fio, n, j) {
+ k = fec_buffer_rs_index(n, j) + block_offset;
+
+ if (k >= 1 << v->data_dev_block_bits)
+ goto done;
+
+ rs_block = fec_buffer_rs_block(v, fio, n, j);
+ rs_block[i] = bbuf[k];
+ }
+done:
+ dm_bufio_release(buf);
+ }
+
+ return target_index;
+}
+
+/*
+ * Allocate RS control structure and FEC buffers from preallocated mempools,
+ * and attempt to allocate as many extra buffers as available.
+ */
+static int fec_alloc_bufs(struct dm_verity *v, struct dm_verity_fec_io *fio)
+{
+ unsigned n;
+
+ if (!fio->rs) {
+ fio->rs = mempool_alloc(v->fec->rs_pool, 0);
+ if (unlikely(!fio->rs)) {
+ DMERR("failed to allocate RS");
+ return -ENOMEM;
+ }
+ }
+
+ fec_for_each_prealloc_buffer(n) {
+ if (fio->bufs[n])
+ continue;
+
+ fio->bufs[n] = mempool_alloc(v->fec->prealloc_pool, GFP_NOIO);
+ if (unlikely(!fio->bufs[n])) {
+ DMERR("failed to allocate FEC buffer");
+ return -ENOMEM;
+ }
+ }
+
+ /* try to allocate the maximum number of buffers */
+ fec_for_each_extra_buffer(fio, n) {
+ if (fio->bufs[n])
+ continue;
+
+ fio->bufs[n] = mempool_alloc(v->fec->extra_pool, GFP_NOIO);
+ /* we can manage with even one buffer if necessary */
+ if (unlikely(!fio->bufs[n]))
+ break;
+ }
+ fio->nbufs = n;
+
+ if (!fio->output) {
+ fio->output = mempool_alloc(v->fec->output_pool, GFP_NOIO);
+
+ if (!fio->output) {
+ DMERR("failed to allocate FEC page");
+ return -ENOMEM;
+ }
+ }
+
+ return 0;
+}
+
+/*
+ * Initialize buffers and clear erasures. fec_read_bufs() assumes buffers are
+ * zeroed before deinterleaving.
+ */
+static void fec_init_bufs(struct dm_verity *v, struct dm_verity_fec_io *fio)
+{
+ unsigned n;
+
+ fec_for_each_buffer(fio, n)
+ memset(fio->bufs[n], 0, v->fec->rsn << DM_VERITY_FEC_BUF_RS_BITS);
+
+ memset(fio->erasures, 0, sizeof(fio->erasures));
+}
+
+/*
+ * Decode all RS blocks in a single data block and return the target block
+ * (indicated by @offset) in fio->output. If @use_erasures is non-zero, uses
+ * hashes to locate erasures.
+ */
+static int fec_decode_rsb(struct dm_verity *v, struct dm_verity_io *io,
+ struct dm_verity_fec_io *fio, u64 rsb, u64 offset,
+ bool use_erasures)
+{
+ int r, neras = 0;
+ unsigned pos;
+
+ r = fec_alloc_bufs(v, fio);
+ if (unlikely(r < 0))
+ return r;
+
+ for (pos = 0; pos < 1 << v->data_dev_block_bits; ) {
+ fec_init_bufs(v, fio);
+
+ r = fec_read_bufs(v, io, rsb, offset, pos,
+ use_erasures ? &neras : NULL);
+ if (unlikely(r < 0))
+ return r;
+
+ r = fec_decode_bufs(v, fio, rsb, r, pos, neras);
+ if (r < 0)
+ return r;
+
+ pos += fio->nbufs << DM_VERITY_FEC_BUF_RS_BITS;
+ }
+
+ /* Always re-validate the corrected block against the expected hash */
+ r = verity_hash(v, verity_io_hash_desc(v, io), fio->output,
+ 1 << v->data_dev_block_bits,
+ verity_io_real_digest(v, io));
+ if (unlikely(r < 0))
+ return r;
+
+ if (memcmp(verity_io_real_digest(v, io), verity_io_want_digest(v, io),
+ v->digest_size)) {
+ DMERR_LIMIT("%s: FEC %llu: failed to correct (%d erasures)",
+ v->data_dev->name, (unsigned long long)rsb, neras);
+ return -EILSEQ;
+ }
+
+ return 0;
+}
+
+static int fec_bv_copy(struct dm_verity *v, struct dm_verity_io *io, u8 *data,
+ size_t len)
+{
+ struct dm_verity_fec_io *fio = fec_io(io);
+
+ memcpy(data, &fio->output[fio->output_pos], len);
+ fio->output_pos += len;
+
+ return 0;
+}
+
+/*
+ * Correct errors in a block. Copies corrected block to dest if non-NULL,
+ * otherwise to a bio_vec starting from iter.
+ */
+int verity_fec_decode(struct dm_verity *v, struct dm_verity_io *io,
+ enum verity_block_type type, sector_t block, u8 *dest,
+ struct bvec_iter *iter)
+{
+ int r;
+ struct dm_verity_fec_io *fio = fec_io(io);
+ u64 offset, res, rsb;
+
+ if (!verity_fec_is_enabled(v))
+ return -EOPNOTSUPP;
+
+ if (type == DM_VERITY_BLOCK_TYPE_METADATA)
+ block += v->data_blocks;
+
+ /*
+ * For RS(M, N), the continuous FEC data is divided into blocks of N
+ * bytes. Since block size may not be divisible by N, the last block
+ * is zero padded when decoding.
+ *
+ * Each byte of the block is covered by a different RS(M, N) code,
+ * and each code is interleaved over N blocks to make it less likely
+ * that bursty corruption will leave us in unrecoverable state.
+ */
+
+ offset = block << v->data_dev_block_bits;
+
+ res = offset;
+ div64_u64(res, v->fec->rounds << v->data_dev_block_bits);
+
+ /*
+ * The base RS block we can feed to the interleaver to find out all
+ * blocks required for decoding.
+ */
+ rsb = offset - res * (v->fec->rounds << v->data_dev_block_bits);
+
+ /*
+ * Locating erasures is slow, so attempt to recover the block without
+ * them first. Do a second attempt with erasures if the corruption is
+ * bad enough.
+ */
+ r = fec_decode_rsb(v, io, fio, rsb, offset, false);
+ if (r < 0) {
+ r = fec_decode_rsb(v, io, fio, rsb, offset, true);
+ if (r < 0)
+ return r;
+ }
+
+ if (dest)
+ memcpy(dest, fio->output, 1 << v->data_dev_block_bits);
+ else if (iter) {
+ fio->output_pos = 0;
+ r = verity_for_bv_block(v, io, iter, fec_bv_copy);
+ }
+
+ return r;
+}
+
+/*
+ * Clean up per-bio data.
+ */
+void verity_fec_finish_io(struct dm_verity_io *io)
+{
+ unsigned n;
+ struct dm_verity_fec *f = io->v->fec;
+ struct dm_verity_fec_io *fio = fec_io(io);
+
+ if (!verity_fec_is_enabled(io->v))
+ return;
+
+ mempool_free(fio->rs, f->rs_pool);
+
+ fec_for_each_prealloc_buffer(n)
+ mempool_free(fio->bufs[n], f->prealloc_pool);
+
+ fec_for_each_extra_buffer(fio, n)
+ mempool_free(fio->bufs[n], f->extra_pool);
+
+ mempool_free(fio->output, f->output_pool);
+}
+
+/*
+ * Initialize per-bio data.
+ */
+void verity_fec_init_io(struct dm_verity_io *io)
+{
+ struct dm_verity_fec_io *fio = fec_io(io);
+
+ if (!verity_fec_is_enabled(io->v))
+ return;
+
+ fio->rs = NULL;
+ memset(fio->bufs, 0, sizeof(fio->bufs));
+ fio->nbufs = 0;
+ fio->output = NULL;
+}
+
+/*
+ * Append feature arguments and values to the status table.
+ */
+unsigned verity_fec_status_table(struct dm_verity *v, unsigned sz,
+ char *result, unsigned maxlen)
+{
+ if (!verity_fec_is_enabled(v))
+ return sz;
+
+ DMEMIT(" " DM_VERITY_OPT_FEC_DEV " %s "
+ DM_VERITY_OPT_FEC_BLOCKS " %llu "
+ DM_VERITY_OPT_FEC_START " %llu "
+ DM_VERITY_OPT_FEC_ROOTS " %d",
+ v->fec->dev->name,
+ (unsigned long long)v->fec->blocks,
+ (unsigned long long)v->fec->start,
+ v->fec->roots);
+
+ return sz;
+}
+
+void verity_fec_dtr(struct dm_verity *v)
+{
+ struct dm_verity_fec *f = v->fec;
+
+ if (!verity_fec_is_enabled(v))
+ goto out;
+
+ mempool_destroy(f->rs_pool);
+ mempool_destroy(f->prealloc_pool);
+ mempool_destroy(f->extra_pool);
+ kmem_cache_destroy(f->cache);
+
+ if (f->data_bufio)
+ dm_bufio_client_destroy(f->data_bufio);
+ if (f->bufio)
+ dm_bufio_client_destroy(f->bufio);
+
+ if (f->dev)
+ dm_put_device(v->ti, f->dev);
+out:
+ kfree(f);
+ v->fec = NULL;
+}
+
+static void *fec_rs_alloc(gfp_t gfp_mask, void *pool_data)
+{
+ struct dm_verity *v = (struct dm_verity *)pool_data;
+
+ return init_rs(8, 0x11d, 0, 1, v->fec->roots);
+}
+
+static void fec_rs_free(void *element, void *pool_data)
+{
+ struct rs_control *rs = (struct rs_control *)element;
+
+ if (rs)
+ free_rs(rs);
+}
+
+bool verity_is_fec_opt_arg(const char *arg_name)
+{
+ return (!strcasecmp(arg_name, DM_VERITY_OPT_FEC_DEV) ||
+ !strcasecmp(arg_name, DM_VERITY_OPT_FEC_BLOCKS) ||
+ !strcasecmp(arg_name, DM_VERITY_OPT_FEC_START) ||
+ !strcasecmp(arg_name, DM_VERITY_OPT_FEC_ROOTS));
+}
+
+int verity_fec_parse_opt_args(struct dm_arg_set *as, struct dm_verity *v,
+ unsigned *argc, const char *arg_name)
+{
+ int r;
+ struct dm_target *ti = v->ti;
+ const char *arg_value;
+ unsigned long long num_ll;
+ unsigned char num_c;
+ char dummy;
+
+ if (!*argc) {
+ ti->error = "FEC feature arguments require a value";
+ return -EINVAL;
+ }
+
+ arg_value = dm_shift_arg(as);
+ (*argc)--;
+
+ if (!strcasecmp(arg_name, DM_VERITY_OPT_FEC_DEV)) {
+ r = dm_get_device(ti, arg_value, FMODE_READ, &v->fec->dev);
+ if (r) {
+ ti->error = "FEC device lookup failed";
+ return r;
+ }
+
+ } else if (!strcasecmp(arg_name, DM_VERITY_OPT_FEC_BLOCKS)) {
+ if (sscanf(arg_value, "%llu%c", &num_ll, &dummy) != 1 ||
+ ((sector_t)(num_ll << (v->data_dev_block_bits - SECTOR_SHIFT))
+ >> (v->data_dev_block_bits - SECTOR_SHIFT) != num_ll)) {
+ ti->error = "Invalid " DM_VERITY_OPT_FEC_BLOCKS;
+ return -EINVAL;
+ }
+ v->fec->blocks = num_ll;
+
+ } else if (!strcasecmp(arg_name, DM_VERITY_OPT_FEC_START)) {
+ if (sscanf(arg_value, "%llu%c", &num_ll, &dummy) != 1 ||
+ ((sector_t)(num_ll << (v->data_dev_block_bits - SECTOR_SHIFT)) >>
+ (v->data_dev_block_bits - SECTOR_SHIFT) != num_ll)) {
+ ti->error = "Invalid " DM_VERITY_OPT_FEC_START;
+ return -EINVAL;
+ }
+ v->fec->start = num_ll;
+
+ } else if (!strcasecmp(arg_name, DM_VERITY_OPT_FEC_ROOTS)) {
+ if (sscanf(arg_value, "%hhu%c", &num_c, &dummy) != 1 || !num_c ||
+ num_c < (DM_VERITY_FEC_RSM - DM_VERITY_FEC_MAX_RSN) ||
+ num_c > (DM_VERITY_FEC_RSM - DM_VERITY_FEC_MIN_RSN)) {
+ ti->error = "Invalid " DM_VERITY_OPT_FEC_ROOTS;
+ return -EINVAL;
+ }
+ v->fec->roots = num_c;
+
+ } else {
+ ti->error = "Unrecognized verity FEC feature request";
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
+/*
+ * Allocate dm_verity_fec for v->fec. Must be called before verity_fec_ctr.
+ */
+int verity_fec_ctr_alloc(struct dm_verity *v)
+{
+ struct dm_verity_fec *f;
+
+ f = kzalloc(sizeof(struct dm_verity_fec), GFP_KERNEL);
+ if (!f) {
+ v->ti->error = "Cannot allocate FEC structure";
+ return -ENOMEM;
+ }
+ v->fec = f;
+
+ return 0;
+}
+
+/*
+ * Validate arguments and preallocate memory. Must be called after arguments
+ * have been parsed using verity_fec_parse_opt_args.
+ */
+int verity_fec_ctr(struct dm_verity *v)
+{
+ struct dm_verity_fec *f = v->fec;
+ struct dm_target *ti = v->ti;
+ u64 hash_blocks;
+
+ if (!verity_fec_is_enabled(v)) {
+ verity_fec_dtr(v);
+ return 0;
+ }
+
+ /*
+ * FEC is computed over data blocks, possible metadata, and
+ * hash blocks. In other words, FEC covers total of fec_blocks
+ * blocks consisting of the following:
+ *
+ * data blocks | hash blocks | metadata (optional)
+ *
+ * We allow metadata after hash blocks to support a use case
+ * where all data is stored on the same device and FEC covers
+ * the entire area.
+ *
+ * If metadata is included, we require it to be available on the
+ * hash device after the hash blocks.
+ */
+
+ hash_blocks = v->hash_blocks - v->hash_start;
+
+ /*
+ * Require matching block sizes for data and hash devices for
+ * simplicity.
+ */
+ if (v->data_dev_block_bits != v->hash_dev_block_bits) {
+ ti->error = "Block sizes must match to use FEC";
+ return -EINVAL;
+ }
+
+ if (!f->roots) {
+ ti->error = "Missing " DM_VERITY_OPT_FEC_ROOTS;
+ return -EINVAL;
+ }
+ f->rsn = DM_VERITY_FEC_RSM - f->roots;
+
+ if (!f->blocks) {
+ ti->error = "Missing " DM_VERITY_OPT_FEC_BLOCKS;
+ return -EINVAL;
+ }
+
+ f->rounds = f->blocks;
+ if (sector_div(f->rounds, f->rsn))
+ f->rounds++;
+
+ /*
+ * Due to optional metadata, f->blocks can be larger than
+ * data_blocks and hash_blocks combined.
+ */
+ if (f->blocks < v->data_blocks + hash_blocks || !f->rounds) {
+ ti->error = "Invalid " DM_VERITY_OPT_FEC_BLOCKS;
+ return -EINVAL;
+ }
+
+ /*
+ * Metadata is accessed through the hash device, so we require
+ * it to be large enough.
+ */
+ f->hash_blocks = f->blocks - v->data_blocks;
+ if (dm_bufio_get_device_size(v->bufio) < f->hash_blocks) {
+ ti->error = "Hash device is too small for "
+ DM_VERITY_OPT_FEC_BLOCKS;
+ return -E2BIG;
+ }
+
+ f->bufio = dm_bufio_client_create(f->dev->bdev,
+ 1 << v->data_dev_block_bits,
+ 1, 0, NULL, NULL);
+ if (IS_ERR(f->bufio)) {
+ ti->error = "Cannot initialize FEC bufio client";
+ return PTR_ERR(f->bufio);
+ }
+
+ if (dm_bufio_get_device_size(f->bufio) <
+ ((f->start + f->rounds * f->roots) >> v->data_dev_block_bits)) {
+ ti->error = "FEC device is too small";
+ return -E2BIG;
+ }
+
+ f->data_bufio = dm_bufio_client_create(v->data_dev->bdev,
+ 1 << v->data_dev_block_bits,
+ 1, 0, NULL, NULL);
+ if (IS_ERR(f->data_bufio)) {
+ ti->error = "Cannot initialize FEC data bufio client";
+ return PTR_ERR(f->data_bufio);
+ }
+
+ if (dm_bufio_get_device_size(f->data_bufio) < v->data_blocks) {
+ ti->error = "Data device is too small";
+ return -E2BIG;
+ }
+
+ /* Preallocate an rs_control structure for each worker thread */
+ f->rs_pool = mempool_create(num_online_cpus(), fec_rs_alloc,
+ fec_rs_free, (void *) v);
+ if (!f->rs_pool) {
+ ti->error = "Cannot allocate RS pool";
+ return -ENOMEM;
+ }
+
+ f->cache = kmem_cache_create("dm_verity_fec_buffers",
+ f->rsn << DM_VERITY_FEC_BUF_RS_BITS,
+ 0, 0, NULL);
+ if (!f->cache) {
+ ti->error = "Cannot create FEC buffer cache";
+ return -ENOMEM;
+ }
+
+ /* Preallocate DM_VERITY_FEC_BUF_PREALLOC buffers for each thread */
+ f->prealloc_pool = mempool_create_slab_pool(num_online_cpus() *
+ DM_VERITY_FEC_BUF_PREALLOC,
+ f->cache);
+ if (!f->prealloc_pool) {
+ ti->error = "Cannot allocate FEC buffer prealloc pool";
+ return -ENOMEM;
+ }
+
+ f->extra_pool = mempool_create_slab_pool(0, f->cache);
+ if (!f->extra_pool) {
+ ti->error = "Cannot allocate FEC buffer extra pool";
+ return -ENOMEM;
+ }
+
+ /* Preallocate an output buffer for each thread */
+ f->output_pool = mempool_create_kmalloc_pool(num_online_cpus(),
+ 1 << v->data_dev_block_bits);
+ if (!f->output_pool) {
+ ti->error = "Cannot allocate FEC output pool";
+ return -ENOMEM;
+ }
+
+ /* Reserve space for our per-bio data */
+ ti->per_bio_data_size += sizeof(struct dm_verity_fec_io);
+
+ return 0;
+}
diff --git a/drivers/md/dm-verity-fec.h b/drivers/md/dm-verity-fec.h
new file mode 100644
index 0000000000000000000000000000000000000000..7fa0298b995e9e3f1ac25c2356c758fad8b65d34
--- /dev/null
+++ b/drivers/md/dm-verity-fec.h
@@ -0,0 +1,152 @@
+/*
+ * Copyright (C) 2015 Google, Inc.
+ *
+ * Author: Sami Tolvanen <samitolvanen@google.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 2 of the License, or (at your option)
+ * any later version.
+ */
+
+#ifndef DM_VERITY_FEC_H
+#define DM_VERITY_FEC_H
+
+#include "dm-verity.h"
+#include <linux/rslib.h>
+
+/* Reed-Solomon(M, N) parameters */
+#define DM_VERITY_FEC_RSM 255
+#define DM_VERITY_FEC_MAX_RSN 253
+#define DM_VERITY_FEC_MIN_RSN 231 /* ~10% space overhead */
+
+/* buffers for deinterleaving and decoding */
+#define DM_VERITY_FEC_BUF_PREALLOC 1 /* buffers to preallocate */
+#define DM_VERITY_FEC_BUF_RS_BITS 4 /* 1 << RS blocks per buffer */
+/* we need buffers for at most 1 << block size RS blocks */
+#define DM_VERITY_FEC_BUF_MAX \
+ (1 << (PAGE_SHIFT - DM_VERITY_FEC_BUF_RS_BITS))
+
+#define DM_VERITY_OPT_FEC_DEV "use_fec_from_device"
+#define DM_VERITY_OPT_FEC_BLOCKS "fec_blocks"
+#define DM_VERITY_OPT_FEC_START "fec_start"
+#define DM_VERITY_OPT_FEC_ROOTS "fec_roots"
+
+/* configuration */
+struct dm_verity_fec {
+ struct dm_dev *dev; /* parity data device */
+ struct dm_bufio_client *data_bufio; /* for data dev access */
+ struct dm_bufio_client *bufio; /* for parity data access */
+ sector_t start; /* parity data start in blocks */
+ sector_t blocks; /* number of blocks covered */
+ sector_t rounds; /* number of interleaving rounds */
+ sector_t hash_blocks; /* blocks covered after v->hash_start */
+ unsigned char roots; /* number of parity bytes, M-N of RS(M, N) */
+ unsigned char rsn; /* N of RS(M, N) */
+ mempool_t *rs_pool; /* mempool for fio->rs */
+ mempool_t *prealloc_pool; /* mempool for preallocated buffers */
+ mempool_t *extra_pool; /* mempool for extra buffers */
+ mempool_t *output_pool; /* mempool for output */
+ struct kmem_cache *cache; /* cache for buffers */
+};
+
+/* per-bio data */
+struct dm_verity_fec_io {
+ struct rs_control *rs; /* Reed-Solomon state */
+ int erasures[DM_VERITY_FEC_MAX_RSN]; /* erasures for decode_rs8 */
+ u8 *bufs[DM_VERITY_FEC_BUF_MAX]; /* bufs for deinterleaving */
+ unsigned nbufs; /* number of buffers allocated */
+ u8 *output; /* buffer for corrected output */
+ size_t output_pos;
+};
+
+#ifdef CONFIG_DM_VERITY_FEC
+
+/* each feature parameter requires a value */
+#define DM_VERITY_OPTS_FEC 8
+
+extern bool verity_fec_is_enabled(struct dm_verity *v);
+
+extern int verity_fec_decode(struct dm_verity *v, struct dm_verity_io *io,
+ enum verity_block_type type, sector_t block,
+ u8 *dest, struct bvec_iter *iter);
+
+extern unsigned verity_fec_status_table(struct dm_verity *v, unsigned sz,
+ char *result, unsigned maxlen);
+
+extern void verity_fec_finish_io(struct dm_verity_io *io);
+extern void verity_fec_init_io(struct dm_verity_io *io);
+
+extern bool verity_is_fec_opt_arg(const char *arg_name);
+extern int verity_fec_parse_opt_args(struct dm_arg_set *as,
+ struct dm_verity *v, unsigned *argc,
+ const char *arg_name);
+
+extern void verity_fec_dtr(struct dm_verity *v);
+
+extern int verity_fec_ctr_alloc(struct dm_verity *v);
+extern int verity_fec_ctr(struct dm_verity *v);
+
+#else /* !CONFIG_DM_VERITY_FEC */
+
+#define DM_VERITY_OPTS_FEC 0
+
+static inline bool verity_fec_is_enabled(struct dm_verity *v)
+{
+ return false;
+}
+
+static inline int verity_fec_decode(struct dm_verity *v,
+ struct dm_verity_io *io,
+ enum verity_block_type type,
+ sector_t block, u8 *dest,
+ struct bvec_iter *iter)
+{
+ return -EOPNOTSUPP;
+}
+
+static inline unsigned verity_fec_status_table(struct dm_verity *v,
+ unsigned sz, char *result,
+ unsigned maxlen)
+{
+ return sz;
+}
+
+static inline void verity_fec_finish_io(struct dm_verity_io *io)
+{
+}
+
+static inline void verity_fec_init_io(struct dm_verity_io *io)
+{
+}
+
+static inline bool verity_is_fec_opt_arg(const char *arg_name)
+{
+ return false;
+}
+
+static inline int verity_fec_parse_opt_args(struct dm_arg_set *as,
+ struct dm_verity *v,
+ unsigned *argc,
+ const char *arg_name)
+{
+ return -EINVAL;
+}
+
+static inline void verity_fec_dtr(struct dm_verity *v)
+{
+}
+
+static inline int verity_fec_ctr_alloc(struct dm_verity *v)
+{
+ return 0;
+}
+
+static inline int verity_fec_ctr(struct dm_verity *v)
+{
+ return 0;
+}
+
+#endif /* CONFIG_DM_VERITY_FEC */
+
+#endif /* DM_VERITY_FEC_H */
diff --git a/drivers/md/dm-verity-target.c b/drivers/md/dm-verity-target.c
index 2b0ee52d1ad87294f6b2a830a245c73a4ee43eac..4f90ec2c6b7a6d4878891b8d1e70d793929ebb02 100644
--- a/drivers/md/dm-verity-target.c
+++ b/drivers/md/dm-verity-target.c
@@ -15,6 +15,7 @@
*/
#include "dm-verity.h"
+#include "dm-verity-fec.h"
#include <linux/module.h>
#include <linux/reboot.h>
@@ -31,7 +32,7 @@
#define DM_VERITY_OPT_LOGGING "ignore_corruption"
#define DM_VERITY_OPT_RESTART "restart_on_corruption"
-#define DM_VERITY_OPTS_MAX 1
+#define DM_VERITY_OPTS_MAX (1 + DM_VERITY_OPTS_FEC)
static unsigned dm_verity_prefetch_cluster = DM_VERITY_DEFAULT_PREFETCH_SIZE;
@@ -282,6 +283,10 @@ static int verity_verify_level(struct dm_verity *v, struct dm_verity_io *io,
if (likely(memcmp(verity_io_real_digest(v, io), want_digest,
v->digest_size) == 0))
aux->hash_verified = 1;
+ else if (verity_fec_decode(v, io,
+ DM_VERITY_BLOCK_TYPE_METADATA,
+ hash_block, data, NULL) == 0)
+ aux->hash_verified = 1;
else if (verity_handle_err(v,
DM_VERITY_BLOCK_TYPE_METADATA,
hash_block)) {
@@ -411,8 +416,11 @@ static int verity_verify_io(struct dm_verity_io *io)
if (likely(memcmp(verity_io_real_digest(v, io),
verity_io_want_digest(v, io), v->digest_size) == 0))
continue;
+ else if (verity_fec_decode(v, io, DM_VERITY_BLOCK_TYPE_DATA,
+ io->block + b, NULL, &start) == 0)
+ continue;
else if (verity_handle_err(v, DM_VERITY_BLOCK_TYPE_DATA,
- io->block + b))
+ io->block + b))
return -EIO;
}
@@ -430,6 +438,8 @@ static void verity_finish_io(struct dm_verity_io *io, int error)
bio->bi_end_io = io->orig_bi_end_io;
bio->bi_error = error;
+ verity_fec_finish_io(io);
+
bio_endio(bio);
}
@@ -444,7 +454,7 @@ static void verity_end_io(struct bio *bio)
{
struct dm_verity_io *io = bio->bi_private;
- if (bio->bi_error) {
+ if (bio->bi_error && !verity_fec_is_enabled(io->v)) {
verity_finish_io(io, bio->bi_error);
return;
}
@@ -547,6 +557,8 @@ static int verity_map(struct dm_target *ti, struct bio *bio)
bio->bi_private = io;
io->iter = bio->bi_iter;
+ verity_fec_init_io(io);
+
verity_submit_prefetch(v, io);
generic_make_request(bio);
@@ -561,6 +573,7 @@ static void verity_status(struct dm_target *ti, status_type_t type,
unsigned status_flags, char *result, unsigned maxlen)
{
struct dm_verity *v = ti->private;
+ unsigned args = 0;
unsigned sz = 0;
unsigned x;
@@ -587,8 +600,15 @@ static void verity_status(struct dm_target *ti, status_type_t type,
else
for (x = 0; x < v->salt_size; x++)
DMEMIT("%02x", v->salt[x]);
+ if (v->mode != DM_VERITY_MODE_EIO)
+ args++;
+ if (verity_fec_is_enabled(v))
+ args += DM_VERITY_OPTS_FEC;
+ if (!args)
+ return;
+ DMEMIT(" %u", args);
if (v->mode != DM_VERITY_MODE_EIO) {
- DMEMIT(" 1 ");
+ DMEMIT(" ");
switch (v->mode) {
case DM_VERITY_MODE_LOGGING:
DMEMIT(DM_VERITY_OPT_LOGGING);
@@ -600,6 +620,7 @@ static void verity_status(struct dm_target *ti, status_type_t type,
BUG();
}
}
+ sz = verity_fec_status_table(v, sz, result, maxlen);
break;
}
}
@@ -662,6 +683,8 @@ static void verity_dtr(struct dm_target *ti)
if (v->data_dev)
dm_put_device(ti, v->data_dev);
+ verity_fec_dtr(v);
+
kfree(v);
}
@@ -694,6 +717,12 @@ static int verity_parse_opt_args(struct dm_arg_set *as, struct dm_verity *v)
} else if (!strcasecmp(arg_name, DM_VERITY_OPT_RESTART)) {
v->mode = DM_VERITY_MODE_RESTART;
continue;
+
+ } else if (verity_is_fec_opt_arg(arg_name)) {
+ r = verity_fec_parse_opt_args(as, v, &argc, arg_name);
+ if (r)
+ return r;
+ continue;
}
ti->error = "Unrecognized verity feature request";
@@ -736,6 +765,10 @@ static int verity_ctr(struct dm_target *ti, unsigned argc, char **argv)
ti->private = v;
v->ti = ti;
+ r = verity_fec_ctr_alloc(v);
+ if (r)
+ goto bad;
+
if ((dm_table_get_mode(ti->table) & ~FMODE_READ)) {
ti->error = "Device must be readonly";
r = -EINVAL;
@@ -924,8 +957,6 @@ static int verity_ctr(struct dm_target *ti, unsigned argc, char **argv)
goto bad;
}
- ti->per_bio_data_size = roundup(sizeof(struct dm_verity_io) + v->shash_descsize + v->digest_size * 2, __alignof__(struct dm_verity_io));
-
/* WQ_UNBOUND greatly improves performance when running on ramdisk */
v->verify_wq = alloc_workqueue("kverityd", WQ_CPU_INTENSIVE | WQ_MEM_RECLAIM | WQ_UNBOUND, num_online_cpus());
if (!v->verify_wq) {
@@ -934,6 +965,16 @@ static int verity_ctr(struct dm_target *ti, unsigned argc, char **argv)
goto bad;
}
+ ti->per_bio_data_size = sizeof(struct dm_verity_io) +
+ v->shash_descsize + v->digest_size * 2;
+
+ r = verity_fec_ctr(v);
+ if (r)
+ goto bad;
+
+ ti->per_bio_data_size = roundup(ti->per_bio_data_size,
+ __alignof__(struct dm_verity_io));
+
return 0;
bad:
@@ -944,7 +985,7 @@ bad:
static struct target_type verity_target = {
.name = "verity",
- .version = {1, 2, 0},
+ .version = {1, 3, 0},
.module = THIS_MODULE,
.ctr = verity_ctr,
.dtr = verity_dtr,
diff --git a/drivers/md/dm-verity.h b/drivers/md/dm-verity.h
index f5af52df8e381b9d9e2d3746b8931fd54e00fed1..8e853722f6c6ee9f3c44656bb1f3cb9f7b0145ab 100644
--- a/drivers/md/dm-verity.h
+++ b/drivers/md/dm-verity.h
@@ -29,6 +29,8 @@ enum verity_block_type {
DM_VERITY_BLOCK_TYPE_METADATA
};
+struct dm_verity_fec;
+
struct dm_verity {
struct dm_dev *data_dev;
struct dm_dev *hash_dev;
@@ -58,6 +60,8 @@ struct dm_verity {
/* starting blocks for each tree level. 0 is the lowest level. */
sector_t hash_level_block[DM_VERITY_MAX_LEVELS];
+
+ struct dm_verity_fec *fec; /* forward error correction */
};
struct dm_verity_io {
@@ -103,6 +107,12 @@ static inline u8 *verity_io_want_digest(struct dm_verity *v,
return (u8 *)(io + 1) + v->shash_descsize + v->digest_size;
}
+static inline u8 *verity_io_digest_end(struct dm_verity *v,
+ struct dm_verity_io *io)
+{
+ return verity_io_want_digest(v, io) + v->digest_size;
+}
+
extern int verity_for_bv_block(struct dm_verity *v, struct dm_verity_io *io,
struct bvec_iter *iter,
int (*process)(struct dm_verity *v,