block/raw-format.c - qemu - Git at Google

 /* BlockDriver implementation for "raw" format driver
  *
  * Copyright (C) 2010-2016 Red Hat, Inc.
  * Copyright (C) 2010, Blue Swirl <blauwirbel@gmail.com>
  * Copyright (C) 2009, Anthony Liguori <aliguori@us.ibm.com>
  *
  * Author:
  *   Laszlo Ersek <lersek@redhat.com>
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to
  * deal in the Software without restriction, including without limitation the
  * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
  * sell copies of the Software, and to permit persons to whom the Software is
  * furnished to do so, subject to the following conditions:
  *
  * The above copyright notice and this permission notice shall be included in
  * all copies or substantial portions of the Software.
  *
  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  * IN THE SOFTWARE.
  */

 #include "qemu/osdep.h"
 #include "block/block_int.h"
 #include "qapi/error.h"
 #include "qemu/option.h"

 typedef struct BDRVRawState {
     uint64_t offset;
     uint64_t size;
     bool has_size;
 } BDRVRawState;

 static QemuOptsList raw_runtime_opts = {
     .name = "raw",
     .head = QTAILQ_HEAD_INITIALIZER(raw_runtime_opts.head),
     .desc = {
         {
             .name = "offset",
             .type = QEMU_OPT_SIZE,
             .help = "offset in the disk where the image starts",
         },
         {
             .name = "size",
             .type = QEMU_OPT_SIZE,
             .help = "virtual disk size",
         },
         { /* end of list */ }
     },
 };

 static QemuOptsList raw_create_opts = {
     .name = "raw-create-opts",
     .head = QTAILQ_HEAD_INITIALIZER(raw_create_opts.head),
     .desc = {
         {
             .name = BLOCK_OPT_SIZE,
             .type = QEMU_OPT_SIZE,
             .help = "Virtual disk size"
         },
         { /* end of list */ }
     }
 };

 static int raw_read_options(QDict *options, BlockDriverState *bs,
     BDRVRawState *s, Error **errp)
 {
     Error *local_err = NULL;
     QemuOpts *opts = NULL;
     int64_t real_size = 0;
     int ret;

     real_size = bdrv_getlength(bs->file->bs);
     if (real_size < 0) {
         error_setg_errno(errp, -real_size, "Could not get image size");
         return real_size;
     }

     opts = qemu_opts_create(&raw_runtime_opts, NULL, 0, &error_abort);
     qemu_opts_absorb_qdict(opts, options, &local_err);
     if (local_err) {
         error_propagate(errp, local_err);
         ret = -EINVAL;
         goto end;
     }

     s->offset = qemu_opt_get_size(opts, "offset", 0);
     if (s->offset > real_size) {
         error_setg(errp, "Offset (%" PRIu64 ") cannot be greater than "
             "size of the containing file (%" PRId64 ")",
             s->offset, real_size);
         ret = -EINVAL;
         goto end;
     }

     if (qemu_opt_find(opts, "size") != NULL) {
         s->size = qemu_opt_get_size(opts, "size", 0);
         s->has_size = true;
     } else {
         s->has_size = false;
         s->size = real_size - s->offset;
     }

     /* Check size and offset */
     if ((real_size - s->offset) < s->size) {
         error_setg(errp, "The sum of offset (%" PRIu64 ") and size "
             "(%" PRIu64 ") has to be smaller or equal to the "
             " actual size of the containing file (%" PRId64 ")",
             s->offset, s->size, real_size);
         ret = -EINVAL;
         goto end;
     }

     /* Make sure size is multiple of BDRV_SECTOR_SIZE to prevent rounding
      * up and leaking out of the specified area. */
     if (s->has_size && !QEMU_IS_ALIGNED(s->size, BDRV_SECTOR_SIZE)) {
         error_setg(errp, "Specified size is not multiple of %llu",
             BDRV_SECTOR_SIZE);
         ret = -EINVAL;
         goto end;
     }

     ret = 0;

 end:

     qemu_opts_del(opts);

     return ret;
 }

 static int raw_reopen_prepare(BDRVReopenState *reopen_state,
                               BlockReopenQueue *queue, Error **errp)
 {
     assert(reopen_state != NULL);
     assert(reopen_state->bs != NULL);

     reopen_state->opaque = g_new0(BDRVRawState, 1);

     return raw_read_options(
         reopen_state->options,
         reopen_state->bs,
         reopen_state->opaque,
         errp);
 }

 static void raw_reopen_commit(BDRVReopenState *state)
 {
     BDRVRawState *new_s = state->opaque;
     BDRVRawState *s = state->bs->opaque;

     memcpy(s, new_s, sizeof(BDRVRawState));

     g_free(state->opaque);
     state->opaque = NULL;
 }

 static void raw_reopen_abort(BDRVReopenState *state)
 {
     g_free(state->opaque);
     state->opaque = NULL;
 }

 static int coroutine_fn raw_co_preadv(BlockDriverState *bs, uint64_t offset,
                                       uint64_t bytes, QEMUIOVector *qiov,
                                       int flags)
 {
     BDRVRawState *s = bs->opaque;

     if (offset > UINT64_MAX - s->offset) {
         return -EINVAL;
     }
     offset += s->offset;

     BLKDBG_EVENT(bs->file, BLKDBG_READ_AIO);
     return bdrv_co_preadv(bs->file, offset, bytes, qiov, flags);
 }

 static int coroutine_fn raw_co_pwritev(BlockDriverState *bs, uint64_t offset,
                                        uint64_t bytes, QEMUIOVector *qiov,
                                        int flags)
 {
     BDRVRawState *s = bs->opaque;
     void *buf = NULL;
     BlockDriver *drv;
     QEMUIOVector local_qiov;
     int ret;

     if (s->has_size && (offset > s->size || bytes > (s->size - offset))) {
         /* There's not enough space for the data. Don't write anything and just
          * fail to prevent leaking out of the size specified in options. */
         return -ENOSPC;
     }

     if (offset > UINT64_MAX - s->offset) {
         ret = -EINVAL;
         goto fail;
     }

     if (bs->probed && offset < BLOCK_PROBE_BUF_SIZE && bytes) {
         /* Handling partial writes would be a pain - so we just
          * require that guests have 512-byte request alignment if
          * probing occurred */
         QEMU_BUILD_BUG_ON(BLOCK_PROBE_BUF_SIZE != 512);
         QEMU_BUILD_BUG_ON(BDRV_SECTOR_SIZE != 512);
         assert(offset == 0 && bytes >= BLOCK_PROBE_BUF_SIZE);

         buf = qemu_try_blockalign(bs->file->bs, 512);
         if (!buf) {
             ret = -ENOMEM;
             goto fail;
         }

         ret = qemu_iovec_to_buf(qiov, 0, buf, 512);
         if (ret != 512) {
             ret = -EINVAL;
             goto fail;
         }

         drv = bdrv_probe_all(buf, 512, NULL);
         if (drv != bs->drv) {
             ret = -EPERM;
             goto fail;
         }

         /* Use the checked buffer, a malicious guest might be overwriting its
          * original buffer in the background. */
         qemu_iovec_init(&local_qiov, qiov->niov + 1);
         qemu_iovec_add(&local_qiov, buf, 512);
         qemu_iovec_concat(&local_qiov, qiov, 512, qiov->size - 512);
         qiov = &local_qiov;
     }

     offset += s->offset;

     BLKDBG_EVENT(bs->file, BLKDBG_WRITE_AIO);
     ret = bdrv_co_pwritev(bs->file, offset, bytes, qiov, flags);

 fail:
     if (qiov == &local_qiov) {
         qemu_iovec_destroy(&local_qiov);
     }
     qemu_vfree(buf);
     return ret;
 }

 static int64_t coroutine_fn raw_co_get_block_status(BlockDriverState *bs,
                                             int64_t sector_num,
                                             int nb_sectors, int *pnum,
                                             BlockDriverState **file)
 {
     BDRVRawState *s = bs->opaque;
     *pnum = nb_sectors;
     *file = bs->file->bs;
     sector_num += s->offset / BDRV_SECTOR_SIZE;
     return BDRV_BLOCK_RAW | BDRV_BLOCK_OFFSET_VALID |
            (sector_num << BDRV_SECTOR_BITS);
 }

 static int coroutine_fn raw_co_pwrite_zeroes(BlockDriverState *bs,
                                              int64_t offset, int bytes,
                                              BdrvRequestFlags flags)
 {
     BDRVRawState *s = bs->opaque;
     if (offset > UINT64_MAX - s->offset) {
         return -EINVAL;
     }
     offset += s->offset;
     return bdrv_co_pwrite_zeroes(bs->file, offset, bytes, flags);
 }

 static int coroutine_fn raw_co_pdiscard(BlockDriverState *bs,
                                         int64_t offset, int bytes)
 {
     BDRVRawState *s = bs->opaque;
     if (offset > UINT64_MAX - s->offset) {
         return -EINVAL;
     }
     offset += s->offset;
     return bdrv_co_pdiscard(bs->file->bs, offset, bytes);
 }

 static int64_t raw_getlength(BlockDriverState *bs)
 {
     int64_t len;
     BDRVRawState *s = bs->opaque;

     /* Update size. It should not change unless the file was externally
      * modified. */
     len = bdrv_getlength(bs->file->bs);
     if (len < 0) {
         return len;
     }

     if (len < s->offset) {
         s->size = 0;
     } else {
         if (s->has_size) {
             /* Try to honour the size */
             s->size = MIN(s->size, len - s->offset);
         } else {
             s->size = len - s->offset;
         }
     }

     return s->size;
 }

 static BlockMeasureInfo *raw_measure(QemuOpts *opts, BlockDriverState *in_bs,
                                      Error **errp)
 {
     BlockMeasureInfo *info;
     int64_t required;

     if (in_bs) {
         required = bdrv_getlength(in_bs);
         if (required < 0) {
             error_setg_errno(errp, -required, "Unable to get image size");
             return NULL;
         }
     } else {
         required = ROUND_UP(qemu_opt_get_size_del(opts, BLOCK_OPT_SIZE, 0),
                             BDRV_SECTOR_SIZE);
     }

     info = g_new(BlockMeasureInfo, 1);
     info->required = required;

     /* Unallocated sectors count towards the file size in raw images */
     info->fully_allocated = info->required;
     return info;
 }

 static int raw_get_info(BlockDriverState *bs, BlockDriverInfo *bdi)
 {
     return bdrv_get_info(bs->file->bs, bdi);
 }

 static void raw_refresh_limits(BlockDriverState *bs, Error **errp)
 {
     if (bs->probed) {
         /* To make it easier to protect the first sector, any probed
          * image is restricted to read-modify-write on sub-sector
          * operations. */
         bs->bl.request_alignment = BDRV_SECTOR_SIZE;
     }
 }

 static int raw_truncate(BlockDriverState *bs, int64_t offset,
                         PreallocMode prealloc, Error **errp)
 {
     BDRVRawState *s = bs->opaque;

     if (s->has_size) {
         error_setg(errp, "Cannot resize fixed-size raw disks");
         return -ENOTSUP;
     }

     if (INT64_MAX - offset < s->offset) {
         error_setg(errp, "Disk size too large for the chosen offset");
         return -EINVAL;
     }

     s->size = offset;
     offset += s->offset;
     return bdrv_truncate(bs->file, offset, prealloc, errp);
 }

 static int raw_media_changed(BlockDriverState *bs)
 {
     return bdrv_media_changed(bs->file->bs);
 }

 static void raw_eject(BlockDriverState *bs, bool eject_flag)
 {
     bdrv_eject(bs->file->bs, eject_flag);
 }

 static void raw_lock_medium(BlockDriverState *bs, bool locked)
 {
     bdrv_lock_medium(bs->file->bs, locked);
 }

 static int raw_co_ioctl(BlockDriverState *bs, unsigned long int req, void *buf)
 {
     BDRVRawState *s = bs->opaque;
     if (s->offset || s->has_size) {
         return -ENOTSUP;
     }
     return bdrv_co_ioctl(bs->file->bs, req, buf);
 }

 static int raw_has_zero_init(BlockDriverState *bs)
 {
     return bdrv_has_zero_init(bs->file->bs);
 }

 static int raw_create(const char *filename, QemuOpts *opts, Error **errp)
 {
     return bdrv_create_file(filename, opts, errp);
 }

 static int raw_open(BlockDriverState *bs, QDict *options, int flags,
                     Error **errp)
 {
     BDRVRawState *s = bs->opaque;
     int ret;

     bs->file = bdrv_open_child(NULL, options, "file", bs, &child_file,
                                false, errp);
     if (!bs->file) {
         return -EINVAL;
     }

     bs->sg = bs->file->bs->sg;
     bs->supported_write_flags = BDRV_REQ_FUA &
         bs->file->bs->supported_write_flags;
     bs->supported_zero_flags = (BDRV_REQ_FUA | BDRV_REQ_MAY_UNMAP) &
         bs->file->bs->supported_zero_flags;

     if (bs->probed && !bdrv_is_read_only(bs)) {
         fprintf(stderr,
                 "WARNING: Image format was not specified for '%s' and probing "
                 "guessed raw.\n"
                 "         Automatically detecting the format is dangerous for "
                 "raw images, write operations on block 0 will be restricted.\n"
                 "         Specify the 'raw' format explicitly to remove the "
                 "restrictions.\n",
                 bs->file->bs->filename);
     }

     ret = raw_read_options(options, bs, s, errp);
     if (ret < 0) {
         return ret;
     }

     if (bs->sg && (s->offset || s->has_size)) {
         error_setg(errp, "Cannot use offset/size with SCSI generic devices");
         return -EINVAL;
     }

     return 0;
 }

 static void raw_close(BlockDriverState *bs)
 {
 }

 static int raw_probe(const uint8_t *buf, int buf_size, const char *filename)
 {
     /* smallest possible positive score so that raw is used if and only if no
      * other block driver works
      */
     return 1;
 }

 static int raw_probe_blocksizes(BlockDriverState *bs, BlockSizes *bsz)
 {
     BDRVRawState *s = bs->opaque;
     int ret;

     ret = bdrv_probe_blocksizes(bs->file->bs, bsz);
     if (ret < 0) {
         return ret;
     }

     if (!QEMU_IS_ALIGNED(s->offset, MAX(bsz->log, bsz->phys))) {
         return -ENOTSUP;
     }

     return 0;
 }

 static int raw_probe_geometry(BlockDriverState *bs, HDGeometry *geo)
 {
     BDRVRawState *s = bs->opaque;
     if (s->offset || s->has_size) {
         return -ENOTSUP;
     }
     return bdrv_probe_geometry(bs->file->bs, geo);
 }

 BlockDriver bdrv_raw = {
     .format_name          = "raw",
     .instance_size        = sizeof(BDRVRawState),
     .bdrv_probe           = &raw_probe,
     .bdrv_reopen_prepare  = &raw_reopen_prepare,
     .bdrv_reopen_commit   = &raw_reopen_commit,
     .bdrv_reopen_abort    = &raw_reopen_abort,
     .bdrv_open            = &raw_open,
     .bdrv_close           = &raw_close,
     .bdrv_child_perm      = bdrv_filter_default_perms,
     .bdrv_create          = &raw_create,
     .bdrv_co_preadv       = &raw_co_preadv,
     .bdrv_co_pwritev      = &raw_co_pwritev,
     .bdrv_co_pwrite_zeroes = &raw_co_pwrite_zeroes,
     .bdrv_co_pdiscard     = &raw_co_pdiscard,
     .bdrv_co_get_block_status = &raw_co_get_block_status,
     .bdrv_truncate        = &raw_truncate,
     .bdrv_getlength       = &raw_getlength,
     .has_variable_length  = true,
     .bdrv_measure         = &raw_measure,
     .bdrv_get_info        = &raw_get_info,
     .bdrv_refresh_limits  = &raw_refresh_limits,
     .bdrv_probe_blocksizes = &raw_probe_blocksizes,
     .bdrv_probe_geometry  = &raw_probe_geometry,
     .bdrv_media_changed   = &raw_media_changed,
     .bdrv_eject           = &raw_eject,
     .bdrv_lock_medium     = &raw_lock_medium,
     .bdrv_co_ioctl        = &raw_co_ioctl,
     .create_opts          = &raw_create_opts,
     .bdrv_has_zero_init   = &raw_has_zero_init
 };

 static void bdrv_raw_init(void)
 {
     bdrv_register(&bdrv_raw);
 }

 block_init(bdrv_raw_init);
	/* BlockDriver implementation for "raw" format driver
	*
	* Copyright (C) 2010-2016 Red Hat, Inc.
	* Copyright (C) 2010, Blue Swirl <blauwirbel@gmail.com>
	* Copyright (C) 2009, Anthony Liguori <aliguori@us.ibm.com>
	*
	* Author:
	* Laszlo Ersek <lersek@redhat.com>
	*
	* Permission is hereby granted, free of charge, to any person obtaining a copy
	* of this software and associated documentation files (the "Software"), to
	* deal in the Software without restriction, including without limitation the
	* rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
	* sell copies of the Software, and to permit persons to whom the Software is
	* furnished to do so, subject to the following conditions:
	*
	* The above copyright notice and this permission notice shall be included in
	* all copies or substantial portions of the Software.
	*
	* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
	* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
	* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
	* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
	* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
	* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
	* IN THE SOFTWARE.
	*/

	#include "qemu/osdep.h"
	#include "block/block_int.h"
	#include "qapi/error.h"
	#include "qemu/option.h"

	typedef struct BDRVRawState {
	uint64_t offset;
	uint64_t size;
	bool has_size;
	} BDRVRawState;

	static QemuOptsList raw_runtime_opts = {
	.name = "raw",
	.head = QTAILQ_HEAD_INITIALIZER(raw_runtime_opts.head),
	.desc = {
	{
	.name = "offset",
	.type = QEMU_OPT_SIZE,
	.help = "offset in the disk where the image starts",
	},
	{
	.name = "size",
	.type = QEMU_OPT_SIZE,
	.help = "virtual disk size",
	},
	{ /* end of list */ }
	},
	};

	static QemuOptsList raw_create_opts = {
	.name = "raw-create-opts",
	.head = QTAILQ_HEAD_INITIALIZER(raw_create_opts.head),
	.desc = {
	{
	.name = BLOCK_OPT_SIZE,
	.type = QEMU_OPT_SIZE,
	.help = "Virtual disk size"
	},
	{ /* end of list */ }
	}
	};

	static int raw_read_options(QDict options, BlockDriverState bs,
	BDRVRawState s, Error *errp)
	{
	Error *local_err = NULL;
	QemuOpts *opts = NULL;
	int64_t real_size = 0;
	int ret;

	real_size = bdrv_getlength(bs->file->bs);
	if (real_size < 0) {
	error_setg_errno(errp, -real_size, "Could not get image size");
	return real_size;
	}

	opts = qemu_opts_create(&raw_runtime_opts, NULL, 0, &error_abort);
	qemu_opts_absorb_qdict(opts, options, &local_err);
	if (local_err) {
	error_propagate(errp, local_err);
	ret = -EINVAL;
	goto end;
	}

	s->offset = qemu_opt_get_size(opts, "offset", 0);
	if (s->offset > real_size) {
	error_setg(errp, "Offset (%" PRIu64 ") cannot be greater than "
	"size of the containing file (%" PRId64 ")",
	s->offset, real_size);
	ret = -EINVAL;
	goto end;
	}

	if (qemu_opt_find(opts, "size") != NULL) {
	s->size = qemu_opt_get_size(opts, "size", 0);
	s->has_size = true;
	} else {
	s->has_size = false;
	s->size = real_size - s->offset;
	}

	/* Check size and offset */
	if ((real_size - s->offset) < s->size) {
	error_setg(errp, "The sum of offset (%" PRIu64 ") and size "
	"(%" PRIu64 ") has to be smaller or equal to the "
	" actual size of the containing file (%" PRId64 ")",
	s->offset, s->size, real_size);
	ret = -EINVAL;
	goto end;
	}

	/* Make sure size is multiple of BDRV_SECTOR_SIZE to prevent rounding
	* up and leaking out of the specified area. */
	if (s->has_size && !QEMU_IS_ALIGNED(s->size, BDRV_SECTOR_SIZE)) {
	error_setg(errp, "Specified size is not multiple of %llu",
	BDRV_SECTOR_SIZE);
	ret = -EINVAL;
	goto end;
	}

	ret = 0;

	end:

	qemu_opts_del(opts);

	return ret;
	}

	static int raw_reopen_prepare(BDRVReopenState *reopen_state,
	BlockReopenQueue queue, Error *errp)
	{
	assert(reopen_state != NULL);
	assert(reopen_state->bs != NULL);

	reopen_state->opaque = g_new0(BDRVRawState, 1);

	return raw_read_options(
	reopen_state->options,
	reopen_state->bs,
	reopen_state->opaque,
	errp);
	}

	static void raw_reopen_commit(BDRVReopenState *state)
	{
	BDRVRawState *new_s = state->opaque;
	BDRVRawState *s = state->bs->opaque;

	memcpy(s, new_s, sizeof(BDRVRawState));

	g_free(state->opaque);
	state->opaque = NULL;
	}

	static void raw_reopen_abort(BDRVReopenState *state)
	{
	g_free(state->opaque);
	state->opaque = NULL;
	}

	static int coroutine_fn raw_co_preadv(BlockDriverState *bs, uint64_t offset,
	uint64_t bytes, QEMUIOVector *qiov,
	int flags)
	{
	BDRVRawState *s = bs->opaque;

	if (offset > UINT64_MAX - s->offset) {
	return -EINVAL;
	}
	offset += s->offset;

	BLKDBG_EVENT(bs->file, BLKDBG_READ_AIO);
	return bdrv_co_preadv(bs->file, offset, bytes, qiov, flags);
	}

	static int coroutine_fn raw_co_pwritev(BlockDriverState *bs, uint64_t offset,
	uint64_t bytes, QEMUIOVector *qiov,
	int flags)
	{
	BDRVRawState *s = bs->opaque;
	void *buf = NULL;
	BlockDriver *drv;
	QEMUIOVector local_qiov;
	int ret;

	if (s->has_size && (offset > s->size \|\| bytes > (s->size - offset))) {
	/* There's not enough space for the data. Don't write anything and just
	* fail to prevent leaking out of the size specified in options. */
	return -ENOSPC;
	}

	if (offset > UINT64_MAX - s->offset) {
	ret = -EINVAL;
	goto fail;
	}

	if (bs->probed && offset < BLOCK_PROBE_BUF_SIZE && bytes) {
	/* Handling partial writes would be a pain - so we just
	* require that guests have 512-byte request alignment if
	* probing occurred */
	QEMU_BUILD_BUG_ON(BLOCK_PROBE_BUF_SIZE != 512);
	QEMU_BUILD_BUG_ON(BDRV_SECTOR_SIZE != 512);
	assert(offset == 0 && bytes >= BLOCK_PROBE_BUF_SIZE);

	buf = qemu_try_blockalign(bs->file->bs, 512);
	if (!buf) {
	ret = -ENOMEM;
	goto fail;
	}

	ret = qemu_iovec_to_buf(qiov, 0, buf, 512);
	if (ret != 512) {
	ret = -EINVAL;
	goto fail;
	}

	drv = bdrv_probe_all(buf, 512, NULL);
	if (drv != bs->drv) {
	ret = -EPERM;
	goto fail;
	}

	/* Use the checked buffer, a malicious guest might be overwriting its
	* original buffer in the background. */
	qemu_iovec_init(&local_qiov, qiov->niov + 1);
	qemu_iovec_add(&local_qiov, buf, 512);
	qemu_iovec_concat(&local_qiov, qiov, 512, qiov->size - 512);
	qiov = &local_qiov;
	}

	offset += s->offset;

	BLKDBG_EVENT(bs->file, BLKDBG_WRITE_AIO);
	ret = bdrv_co_pwritev(bs->file, offset, bytes, qiov, flags);

	fail:
	if (qiov == &local_qiov) {
	qemu_iovec_destroy(&local_qiov);
	}
	qemu_vfree(buf);
	return ret;
	}

	static int64_t coroutine_fn raw_co_get_block_status(BlockDriverState *bs,
	int64_t sector_num,
	int nb_sectors, int *pnum,
	BlockDriverState **file)
	{
	BDRVRawState *s = bs->opaque;
	*pnum = nb_sectors;
	*file = bs->file->bs;
	sector_num += s->offset / BDRV_SECTOR_SIZE;
	return BDRV_BLOCK_RAW \| BDRV_BLOCK_OFFSET_VALID \|
	(sector_num << BDRV_SECTOR_BITS);
	}

	static int coroutine_fn raw_co_pwrite_zeroes(BlockDriverState *bs,
	int64_t offset, int bytes,
	BdrvRequestFlags flags)
	{
	BDRVRawState *s = bs->opaque;
	if (offset > UINT64_MAX - s->offset) {
	return -EINVAL;
	}
	offset += s->offset;
	return bdrv_co_pwrite_zeroes(bs->file, offset, bytes, flags);
	}

	static int coroutine_fn raw_co_pdiscard(BlockDriverState *bs,
	int64_t offset, int bytes)
	{
	BDRVRawState *s = bs->opaque;
	if (offset > UINT64_MAX - s->offset) {
	return -EINVAL;
	}
	offset += s->offset;
	return bdrv_co_pdiscard(bs->file->bs, offset, bytes);
	}

	static int64_t raw_getlength(BlockDriverState *bs)
	{
	int64_t len;
	BDRVRawState *s = bs->opaque;

	/* Update size. It should not change unless the file was externally
	* modified. */
	len = bdrv_getlength(bs->file->bs);
	if (len < 0) {
	return len;
	}

	if (len < s->offset) {
	s->size = 0;
	} else {
	if (s->has_size) {
	/* Try to honour the size */
	s->size = MIN(s->size, len - s->offset);
	} else {
	s->size = len - s->offset;
	}
	}

	return s->size;
	}

	static BlockMeasureInfo raw_measure(QemuOpts opts, BlockDriverState *in_bs,
	Error **errp)
	{
	BlockMeasureInfo *info;
	int64_t required;

	if (in_bs) {
	required = bdrv_getlength(in_bs);
	if (required < 0) {
	error_setg_errno(errp, -required, "Unable to get image size");
	return NULL;
	}
	} else {
	required = ROUND_UP(qemu_opt_get_size_del(opts, BLOCK_OPT_SIZE, 0),
	BDRV_SECTOR_SIZE);
	}

	info = g_new(BlockMeasureInfo, 1);
	info->required = required;

	/* Unallocated sectors count towards the file size in raw images */
	info->fully_allocated = info->required;
	return info;
	}

	static int raw_get_info(BlockDriverState bs, BlockDriverInfo bdi)
	{
	return bdrv_get_info(bs->file->bs, bdi);
	}

	static void raw_refresh_limits(BlockDriverState bs, Error *errp)
	{
	if (bs->probed) {
	/* To make it easier to protect the first sector, any probed
	* image is restricted to read-modify-write on sub-sector
	* operations. */
	bs->bl.request_alignment = BDRV_SECTOR_SIZE;
	}
	}

	static int raw_truncate(BlockDriverState *bs, int64_t offset,
	PreallocMode prealloc, Error **errp)
	{
	BDRVRawState *s = bs->opaque;

	if (s->has_size) {
	error_setg(errp, "Cannot resize fixed-size raw disks");
	return -ENOTSUP;
	}

	if (INT64_MAX - offset < s->offset) {
	error_setg(errp, "Disk size too large for the chosen offset");
	return -EINVAL;
	}

	s->size = offset;
	offset += s->offset;
	return bdrv_truncate(bs->file, offset, prealloc, errp);
	}

	static int raw_media_changed(BlockDriverState *bs)
	{
	return bdrv_media_changed(bs->file->bs);
	}

	static void raw_eject(BlockDriverState *bs, bool eject_flag)
	{
	bdrv_eject(bs->file->bs, eject_flag);
	}

	static void raw_lock_medium(BlockDriverState *bs, bool locked)
	{
	bdrv_lock_medium(bs->file->bs, locked);
	}

	static int raw_co_ioctl(BlockDriverState bs, unsigned long int req, void buf)
	{
	BDRVRawState *s = bs->opaque;
	if (s->offset \|\| s->has_size) {
	return -ENOTSUP;
	}
	return bdrv_co_ioctl(bs->file->bs, req, buf);
	}

	static int raw_has_zero_init(BlockDriverState *bs)
	{
	return bdrv_has_zero_init(bs->file->bs);
	}

	static int raw_create(const char filename, QemuOpts opts, Error **errp)
	{
	return bdrv_create_file(filename, opts, errp);
	}

	static int raw_open(BlockDriverState bs, QDict options, int flags,
	Error **errp)
	{
	BDRVRawState *s = bs->opaque;
	int ret;

	bs->file = bdrv_open_child(NULL, options, "file", bs, &child_file,
	false, errp);
	if (!bs->file) {
	return -EINVAL;
	}

	bs->sg = bs->file->bs->sg;
	bs->supported_write_flags = BDRV_REQ_FUA &
	bs->file->bs->supported_write_flags;
	bs->supported_zero_flags = (BDRV_REQ_FUA \| BDRV_REQ_MAY_UNMAP) &
	bs->file->bs->supported_zero_flags;

	if (bs->probed && !bdrv_is_read_only(bs)) {
	fprintf(stderr,
	"WARNING: Image format was not specified for '%s' and probing "
	"guessed raw.\n"
	" Automatically detecting the format is dangerous for "
	"raw images, write operations on block 0 will be restricted.\n"
	" Specify the 'raw' format explicitly to remove the "
	"restrictions.\n",
	bs->file->bs->filename);
	}

	ret = raw_read_options(options, bs, s, errp);
	if (ret < 0) {
	return ret;
	}

	if (bs->sg && (s->offset \|\| s->has_size)) {
	error_setg(errp, "Cannot use offset/size with SCSI generic devices");
	return -EINVAL;
	}

	return 0;
	}

	static void raw_close(BlockDriverState *bs)
	{
	}

	static int raw_probe(const uint8_t buf, int buf_size, const char filename)
	{
	/* smallest possible positive score so that raw is used if and only if no
	* other block driver works
	*/
	return 1;
	}

	static int raw_probe_blocksizes(BlockDriverState bs, BlockSizes bsz)
	{
	BDRVRawState *s = bs->opaque;
	int ret;

	ret = bdrv_probe_blocksizes(bs->file->bs, bsz);
	if (ret < 0) {
	return ret;
	}

	if (!QEMU_IS_ALIGNED(s->offset, MAX(bsz->log, bsz->phys))) {
	return -ENOTSUP;
	}

	return 0;
	}

	static int raw_probe_geometry(BlockDriverState bs, HDGeometry geo)
	{
	BDRVRawState *s = bs->opaque;
	if (s->offset \|\| s->has_size) {
	return -ENOTSUP;
	}
	return bdrv_probe_geometry(bs->file->bs, geo);
	}

	BlockDriver bdrv_raw = {
	.format_name = "raw",
	.instance_size = sizeof(BDRVRawState),
	.bdrv_probe = &raw_probe,
	.bdrv_reopen_prepare = &raw_reopen_prepare,
	.bdrv_reopen_commit = &raw_reopen_commit,
	.bdrv_reopen_abort = &raw_reopen_abort,
	.bdrv_open = &raw_open,
	.bdrv_close = &raw_close,
	.bdrv_child_perm = bdrv_filter_default_perms,
	.bdrv_create = &raw_create,
	.bdrv_co_preadv = &raw_co_preadv,
	.bdrv_co_pwritev = &raw_co_pwritev,
	.bdrv_co_pwrite_zeroes = &raw_co_pwrite_zeroes,
	.bdrv_co_pdiscard = &raw_co_pdiscard,
	.bdrv_co_get_block_status = &raw_co_get_block_status,
	.bdrv_truncate = &raw_truncate,
	.bdrv_getlength = &raw_getlength,
	.has_variable_length = true,
	.bdrv_measure = &raw_measure,
	.bdrv_get_info = &raw_get_info,
	.bdrv_refresh_limits = &raw_refresh_limits,
	.bdrv_probe_blocksizes = &raw_probe_blocksizes,
	.bdrv_probe_geometry = &raw_probe_geometry,
	.bdrv_media_changed = &raw_media_changed,
	.bdrv_eject = &raw_eject,
	.bdrv_lock_medium = &raw_lock_medium,
	.bdrv_co_ioctl = &raw_co_ioctl,
	.create_opts = &raw_create_opts,
	.bdrv_has_zero_init = &raw_has_zero_init
	};

	static void bdrv_raw_init(void)
	{
	bdrv_register(&bdrv_raw);
	}

	block_init(bdrv_raw_init);