/* SPDX-License-Identifier: GPL-2.0 */
/*
* xloop_file_fmt_qcow_cluster.c
*
* Ported QCOW2 implementation of the QEMU project (GPL-2.0):
* Cluster calculation and lookup for the QCOW2 format.
*
* The copyright (C) 2004-2006 of the original code is owned by Fabrice Bellard.
*
* Copyright (C) 2019 Manuel Bentele <development@manuel-bentele.de>
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/kernel.h>
#include <linux/string.h>
#include "xloop_file_fmt.h"
#include "xloop_file_fmt_qcow_main.h"
#include "xloop_file_fmt_qcow_cache.h"
#include "xloop_file_fmt_qcow_cluster.h"
/*
* __xloop_file_fmt_qcow_cluster_l2_load
*
* @xlo_fmt: QCOW file format
* @offset: A guest offset, used to calculate what slice of the L2
* table to load.
* @l2_offset: Offset to the L2 table in the image file.
* @l2_slice: Location to store the pointer to the L2 slice.
*
* Loads a L2 slice into memory (L2 slices are the parts of L2 tables
* that are loaded by the qcow2 cache). If the slice is in the cache,
* the cache is used; otherwise the L2 slice is loaded from the image
* file.
*/
static int __xloop_file_fmt_qcow_cluster_l2_load(struct xloop_file_fmt *xlo_fmt,
u64 offset, u64 l2_offset, u64 **l2_slice)
{
struct xloop_file_fmt_qcow_data *qcow_data = xlo_fmt->private_data;
int start_of_slice = xloop_file_fmt_qcow_l2_entry_size(qcow_data) * (
xloop_file_fmt_qcow_offset_to_l2_index(qcow_data, offset) -
xloop_file_fmt_qcow_offset_to_l2_slice_index(qcow_data, offset)
);
ASSERT(qcow_data->l2_table_cache != NULL);
return xloop_file_fmt_qcow_cache_get(xlo_fmt, l2_offset + start_of_slice,
(void **) l2_slice);
}
/*
* For a given L2 entry, count the number of contiguous subclusters of
* the same type starting from @sc_from. Compressed clusters are
* treated as if they were divided into subclusters of size
* qcow_data->subcluster_size.
*
* Return the number of contiguous subclusters and set @type to the
* subcluster type.
*
* If the L2 entry is invalid return -errno and set @type to
* QCOW_SUBCLUSTER_INVALID.
*/
static int __xloop_file_fmt_qcow_get_subcluster_range_type(
struct xloop_file_fmt *xlo_fmt, u64 l2_entry, u64 l2_bitmap,
unsigned int sc_from, enum xloop_file_fmt_qcow_subcluster_type *type)
{
struct xloop_file_fmt_qcow_data *qcow_data = xlo_fmt->private_data;
u32 val;
*type = xloop_file_fmt_qcow_get_subcluster_type(xlo_fmt, l2_entry,
l2_bitmap, sc_from);
if (*type == QCOW_SUBCLUSTER_INVALID) {
return -EINVAL;
} else if (!xloop_file_fmt_qcow_has_subclusters(qcow_data) ||
*type == QCOW_SUBCLUSTER_COMPRESSED) {
return qcow_data->subclusters_per_cluster - sc_from;
}
switch (*type) {
case QCOW_SUBCLUSTER_NORMAL:
val = l2_bitmap | QCOW_OFLAG_SUB_ALLOC_RANGE(0, sc_from);
return __builtin_ctz(~val) - sc_from;
case QCOW_SUBCLUSTER_ZERO_PLAIN:
case QCOW_SUBCLUSTER_ZERO_ALLOC:
val = (l2_bitmap | QCOW_OFLAG_SUB_ZERO_RANGE(0, sc_from)) >> 32;
return __builtin_ctz(~val) - sc_from;
case QCOW_SUBCLUSTER_UNALLOCATED_PLAIN:
case QCOW_SUBCLUSTER_UNALLOCATED_ALLOC:
val = ((l2_bitmap >> 32) | l2_bitmap)
& ~QCOW_OFLAG_SUB_ALLOC_RANGE(0, sc_from);
return __builtin_ctz(val) - sc_from;
default:
/* not reachable */
ASSERT(false);
*type = QCOW_SUBCLUSTER_INVALID;
return 0;
}
}
/*
* Return the number of contiguous subclusters of the exact same type
* in a given L2 slice, starting from cluster @l2_index, subcluster
* @sc_index. Allocated subclusters are required to be contiguous in
* the image file.
* At most @nb_clusters are checked (note that this means clusters,
* not subclusters).
* Compressed clusters are always processed one by one but for the
* purpose of this count they are treated as if they were divided into
* subclusters of size qcow_data->subcluster_size.
* On failure return -errno and update @l2_index to point to the
* invalid entry.
*/
static int __xloop_file_fmt_qcow_count_contiguous_subclusters(
struct xloop_file_fmt *xlo_fmt, int nb_clusters, unsigned int sc_index,
u64 *l2_slice, unsigned int *l2_index)
{
struct xloop_file_fmt_qcow_data *qcow_data = xlo_fmt->private_data;
int i, count = 0;
bool check_offset = false;
u64 expected_offset = 0;
enum xloop_file_fmt_qcow_subcluster_type expected_type =
QCOW_SUBCLUSTER_NORMAL;
enum xloop_file_fmt_qcow_subcluster_type type;
ASSERT(*l2_index + nb_clusters <= qcow_data->l2_slice_size);
for (i = 0; i < nb_clusters; i++) {
unsigned int first_sc = (i == 0) ? sc_index : 0;
u64 l2_entry = xloop_file_fmt_qcow_get_l2_entry(qcow_data, l2_slice,
*l2_index + i);
u64 l2_bitmap = xloop_file_fmt_qcow_get_l2_bitmap(qcow_data, l2_slice,
*l2_index + i);
int ret = __xloop_file_fmt_qcow_get_subcluster_range_type(xlo_fmt,
l2_entry, l2_bitmap, first_sc, &type);
if (ret < 0) {
*l2_index += i; /* Point to the invalid entry */
return -EIO;
}
if (i == 0) {
if (type == QCOW_SUBCLUSTER_COMPRESSED) {
/* Compressed clusters are always processed one by one */
return ret;
}
expected_type = type;
expected_offset = l2_entry & QCOW_L2E_OFFSET_MASK;
check_offset = (type == QCOW_SUBCLUSTER_NORMAL ||
type == QCOW_SUBCLUSTER_ZERO_ALLOC ||
type == QCOW_SUBCLUSTER_UNALLOCATED_ALLOC);
} else if (type != expected_type) {
break;
} else if (check_offset) {
expected_offset += qcow_data->cluster_size;
if (expected_offset != (l2_entry & QCOW_L2E_OFFSET_MASK)) {
break;
}
}
count += ret;
/* Stop if there are type changes before the end of the cluster */
if (first_sc + ret < qcow_data->subclusters_per_cluster) {
break;
}
}
return count;
}
/*
* xloop_file_fmt_qcow_get_host_offset
*
* For a given offset of the virtual disk find the equivalent host
* offset in the qcow2 file and store it in *host_offset. Neither
* offset needs to be aligned to a cluster boundary.
*
* If the cluster is unallocated then *host_offset will be 0.
* If the cluster is compressed then *host_offset will contain the
* complete compressed cluster descriptor.
*
* On entry, *bytes is the maximum number of contiguous bytes starting at
* offset that we are interested in.
*
* On exit, *bytes is the number of bytes starting at offset that have the same
* subcluster type and (if applicable) are stored contiguously in the image
* file. The subcluster type is stored in *subcluster_type.
* Compressed clusters are always processed one by one.
*
* Returns 0 on success, -errno in error cases.
*/
int xloop_file_fmt_qcow_get_host_offset(struct xloop_file_fmt *xlo_fmt,
u64 offset, unsigned int *bytes, u64 *host_offset,
enum xloop_file_fmt_qcow_subcluster_type *subcluster_type)
{
struct xloop_file_fmt_qcow_data *qcow_data = xlo_fmt->private_data;
unsigned int l2_index, sc_index;
u64 l1_index, l2_offset, *l2_slice, l2_entry, l2_bitmap;
int sc;
unsigned int offset_in_cluster;
u64 bytes_available, bytes_needed, nb_clusters;
enum xloop_file_fmt_qcow_subcluster_type type;
int ret;
u64 host_cluster_offset;
offset_in_cluster = xloop_file_fmt_qcow_offset_into_cluster(qcow_data,
offset);
bytes_needed = (u64) *bytes + offset_in_cluster;
/* compute how many bytes there are between the start of the cluster
* containing offset and the end of the l2 slice that contains
* the entry pointing to it */
bytes_available = ((u64)(
qcow_data->l2_slice_size -
xloop_file_fmt_qcow_offset_to_l2_slice_index(qcow_data, offset))
) << qcow_data->cluster_bits;
if (bytes_needed > bytes_available) {
bytes_needed = bytes_available;
}
*host_offset = 0;
/* seek to the l2 offset in the l1 table */
l1_index = xloop_file_fmt_qcow_offset_to_l1_index(qcow_data, offset);
if (l1_index >= qcow_data->l1_size) {
type = QCOW_SUBCLUSTER_UNALLOCATED_PLAIN;
goto out;
}
l2_offset = qcow_data->l1_table[l1_index] & QCOW_L1E_OFFSET_MASK;
if (!l2_offset) {
type = QCOW_SUBCLUSTER_UNALLOCATED_PLAIN;
goto out;
}
if (xloop_file_fmt_qcow_offset_into_cluster(qcow_data, l2_offset)) {
dev_err_ratelimited(xloop_file_fmt_to_dev(xlo_fmt), "L2 table offset "
"%llx unaligned (L1 index: %llx)", l2_offset, l1_index);
return -EIO;
}
/* load the l2 slice in memory */
ret = __xloop_file_fmt_qcow_cluster_l2_load(xlo_fmt, offset, l2_offset,
&l2_slice);
if (ret < 0) {
return ret;
}
/* find the cluster offset for the given disk offset */
l2_index = xloop_file_fmt_qcow_offset_to_l2_slice_index(qcow_data,
offset);
sc_index = xloop_file_fmt_qcow_offset_to_sc_index(qcow_data, offset);
l2_entry = xloop_file_fmt_qcow_get_l2_entry(qcow_data, l2_slice,
l2_index);
l2_bitmap = xloop_file_fmt_qcow_get_l2_bitmap(qcow_data, l2_slice,
l2_index);
nb_clusters = xloop_file_fmt_qcow_size_to_clusters(qcow_data,
bytes_needed);
/* bytes_needed <= *bytes + offset_in_cluster, both of which are
* unsigned integers; the minimum cluster size is 512, so this
* assertion is always true */
ASSERT(nb_clusters <= INT_MAX);
type = xloop_file_fmt_qcow_get_subcluster_type(xlo_fmt, l2_entry,
l2_bitmap, sc_index);
if (qcow_data->qcow_version < 3 && (
type == QCOW_SUBCLUSTER_ZERO_PLAIN ||
type == QCOW_SUBCLUSTER_ZERO_ALLOC)) {
dev_err_ratelimited(xloop_file_fmt_to_dev(xlo_fmt), "zero cluster "
"entry found in pre-v3 image (L2 offset: %llx, L2 index: %x)\n",
l2_offset, l2_index);
ret = -EIO;
goto fail;
}
switch (type) {
case QCOW_SUBCLUSTER_INVALID:
break; /* This is handled by count_contiguous_subclusters() below */
case QCOW_SUBCLUSTER_COMPRESSED:
if (xloop_file_fmt_qcow_has_data_file(qcow_data)) {
dev_err_ratelimited(xloop_file_fmt_to_dev(xlo_fmt), "compressed "
"cluster entry found in image with external data file "
"(L2 offset: %llx, L2 index: %x)\n", l2_offset, l2_index);
ret = -EIO;
goto fail;
}
*host_offset = l2_entry & QCOW_L2E_COMPRESSED_OFFSET_SIZE_MASK;
break;
case QCOW_SUBCLUSTER_ZERO_PLAIN:
case QCOW_SUBCLUSTER_UNALLOCATED_PLAIN:
break;
case QCOW_SUBCLUSTER_ZERO_ALLOC:
case QCOW_SUBCLUSTER_NORMAL:
case QCOW_SUBCLUSTER_UNALLOCATED_ALLOC:
host_cluster_offset = l2_entry & QCOW_L2E_OFFSET_MASK;
*host_offset = host_cluster_offset + offset_in_cluster;
if (xloop_file_fmt_qcow_offset_into_cluster(qcow_data,
host_cluster_offset)) {
dev_err_ratelimited(xloop_file_fmt_to_dev(xlo_fmt), "cluster "
"allocation offset %llx unaligned (L2 offset: %llx, "
"L2 index: %x)\n", host_cluster_offset, l2_offset, l2_index);
ret = -EIO;
goto fail;
}
if (xloop_file_fmt_qcow_has_data_file(qcow_data) &&
*host_offset != offset) {
dev_err_ratelimited(xloop_file_fmt_to_dev(xlo_fmt), "external "
"data file host cluster offset %llx does not match guest "
"cluster offset: %llx, L2 index: %x)\n", host_cluster_offset,
offset - offset_in_cluster, l2_index);
ret = -EIO;
goto fail;
}
break;
default:
BUG();
}
sc = __xloop_file_fmt_qcow_count_contiguous_subclusters(xlo_fmt,
nb_clusters, sc_index, l2_slice, &l2_index);
if (sc < 0) {
dev_err_ratelimited(xloop_file_fmt_to_dev(xlo_fmt), "invalid cluster "
"entry found (L2 offset: %#llx, L2 index: %#x)", l2_offset,
l2_index);
ret = -EIO;
goto fail;
}
xloop_file_fmt_qcow_cache_put(xlo_fmt, (void **) &l2_slice);
bytes_available = ((s64) sc + sc_index) << qcow_data->subcluster_bits;
out:
if (bytes_available > bytes_needed) {
bytes_available = bytes_needed;
}
/* bytes_available <= bytes_needed <= *bytes + offset_in_cluster;
* subtracting offset_in_cluster will therefore definitely yield
* something not exceeding UINT_MAX */
ASSERT(bytes_available - offset_in_cluster <= UINT_MAX);
*bytes = bytes_available - offset_in_cluster;
*subcluster_type = type;
return 0;
fail:
xloop_file_fmt_qcow_cache_put(xlo_fmt, (void **) &l2_slice);
return ret;
}
