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authorAlexander Bulekov <alxndr@bu.edu>2021-03-15 10:05:10 -0400
committerPaolo Bonzini <pbonzini@redhat.com>2021-03-16 14:30:30 -0400
commit230376d285b38f5b83882ebdd2e0d0570431dd09 (patch)
treeab179fb04da2c021b4e140879185a612c772db56 /hw/mem
parentd7da0e560128e56f55a2f1f27fa66dd8c5db446c (diff)
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memory: add a sparse memory device for fuzzing
For testing, it can be useful to simulate an enormous amount of memory (e.g. 2^64 RAM). This adds an MMIO device that acts as sparse memory. When something writes a nonzero value to a sparse-mem address, we allocate a block of memory. For now, since the only user of this device is the fuzzer, we do not track and free zeroed blocks. The device has a very low priority (so it can be mapped beneath actual RAM, and virtual device MMIO regions). Signed-off-by: Alexander Bulekov <alxndr@bu.edu> Reviewed-by: Darren Kenny <darren.kenny@oracle.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'hw/mem')
-rw-r--r--hw/mem/meson.build1
-rw-r--r--hw/mem/sparse-mem.c151
2 files changed, 152 insertions, 0 deletions
diff --git a/hw/mem/meson.build b/hw/mem/meson.build
index 0d22f2b..ef79e04 100644
--- a/hw/mem/meson.build
+++ b/hw/mem/meson.build
@@ -1,5 +1,6 @@
mem_ss = ss.source_set()
mem_ss.add(files('memory-device.c'))
+mem_ss.add(when: 'CONFIG_FUZZ', if_true: files('sparse-mem.c'))
mem_ss.add(when: 'CONFIG_DIMM', if_true: files('pc-dimm.c'))
mem_ss.add(when: 'CONFIG_NPCM7XX', if_true: files('npcm7xx_mc.c'))
mem_ss.add(when: 'CONFIG_NVDIMM', if_true: files('nvdimm.c'))
diff --git a/hw/mem/sparse-mem.c b/hw/mem/sparse-mem.c
new file mode 100644
index 0000000..a13ac74
--- /dev/null
+++ b/hw/mem/sparse-mem.c
@@ -0,0 +1,151 @@
+/*
+ * A sparse memory device. Useful for fuzzing
+ *
+ * Copyright Red Hat Inc., 2021
+ *
+ * Authors:
+ * Alexander Bulekov <alxndr@bu.edu>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#include "qemu/osdep.h"
+
+#include "exec/address-spaces.h"
+#include "hw/qdev-properties.h"
+#include "hw/sysbus.h"
+#include "qapi/error.h"
+#include "qemu/units.h"
+#include "sysemu/qtest.h"
+#include "hw/mem/sparse-mem.h"
+
+#define SPARSE_MEM(obj) OBJECT_CHECK(SparseMemState, (obj), TYPE_SPARSE_MEM)
+#define SPARSE_BLOCK_SIZE 0x1000
+
+typedef struct SparseMemState {
+ SysBusDevice parent_obj;
+ MemoryRegion mmio;
+ uint64_t baseaddr;
+ uint64_t length;
+ uint64_t size_used;
+ uint64_t maxsize;
+ GHashTable *mapped;
+} SparseMemState;
+
+typedef struct sparse_mem_block {
+ uint8_t data[SPARSE_BLOCK_SIZE];
+} sparse_mem_block;
+
+static uint64_t sparse_mem_read(void *opaque, hwaddr addr, unsigned int size)
+{
+ SparseMemState *s = opaque;
+ uint64_t ret = 0;
+ size_t pfn = addr / SPARSE_BLOCK_SIZE;
+ size_t offset = addr % SPARSE_BLOCK_SIZE;
+ sparse_mem_block *block;
+
+ block = g_hash_table_lookup(s->mapped, (void *)pfn);
+ if (block) {
+ assert(offset + size <= sizeof(block->data));
+ memcpy(&ret, block->data + offset, size);
+ }
+ return ret;
+}
+
+static void sparse_mem_write(void *opaque, hwaddr addr, uint64_t v,
+ unsigned int size)
+{
+ SparseMemState *s = opaque;
+ size_t pfn = addr / SPARSE_BLOCK_SIZE;
+ size_t offset = addr % SPARSE_BLOCK_SIZE;
+ sparse_mem_block *block;
+
+ if (!g_hash_table_lookup(s->mapped, (void *)pfn) &&
+ s->size_used + SPARSE_BLOCK_SIZE < s->maxsize && v) {
+ g_hash_table_insert(s->mapped, (void *)pfn,
+ g_new0(sparse_mem_block, 1));
+ s->size_used += sizeof(block->data);
+ }
+ block = g_hash_table_lookup(s->mapped, (void *)pfn);
+ if (!block) {
+ return;
+ }
+
+ assert(offset + size <= sizeof(block->data));
+
+ memcpy(block->data + offset, &v, size);
+
+}
+
+static const MemoryRegionOps sparse_mem_ops = {
+ .read = sparse_mem_read,
+ .write = sparse_mem_write,
+ .endianness = DEVICE_LITTLE_ENDIAN,
+ .valid = {
+ .min_access_size = 1,
+ .max_access_size = 8,
+ .unaligned = false,
+ },
+};
+
+static Property sparse_mem_properties[] = {
+ /* The base address of the memory */
+ DEFINE_PROP_UINT64("baseaddr", SparseMemState, baseaddr, 0x0),
+ /* The length of the sparse memory region */
+ DEFINE_PROP_UINT64("length", SparseMemState, length, UINT64_MAX),
+ /* Max amount of actual memory that can be used to back the sparse memory */
+ DEFINE_PROP_UINT64("maxsize", SparseMemState, maxsize, 10 * MiB),
+ DEFINE_PROP_END_OF_LIST(),
+};
+
+MemoryRegion *sparse_mem_init(uint64_t addr, uint64_t length)
+{
+ DeviceState *dev;
+
+ dev = qdev_new(TYPE_SPARSE_MEM);
+ qdev_prop_set_uint64(dev, "baseaddr", addr);
+ qdev_prop_set_uint64(dev, "length", length);
+ sysbus_realize_and_unref(SYS_BUS_DEVICE(dev), &error_fatal);
+ sysbus_mmio_map_overlap(SYS_BUS_DEVICE(dev), 0, addr, -10000);
+ return &SPARSE_MEM(dev)->mmio;
+}
+
+static void sparse_mem_realize(DeviceState *dev, Error **errp)
+{
+ SparseMemState *s = SPARSE_MEM(dev);
+ SysBusDevice *sbd = SYS_BUS_DEVICE(dev);
+
+ if (!qtest_enabled()) {
+ error_setg(errp, "sparse_mem device should only be used "
+ "for testing with QTest");
+ return;
+ }
+
+ assert(s->baseaddr + s->length > s->baseaddr);
+
+ s->mapped = g_hash_table_new(NULL, NULL);
+ memory_region_init_io(&s->mmio, OBJECT(s), &sparse_mem_ops, s,
+ "sparse-mem", s->length);
+ sysbus_init_mmio(sbd, &s->mmio);
+}
+
+static void sparse_mem_class_init(ObjectClass *klass, void *data)
+{
+ DeviceClass *dc = DEVICE_CLASS(klass);
+
+ device_class_set_props(dc, sparse_mem_properties);
+
+ dc->desc = "Sparse Memory Device";
+ dc->realize = sparse_mem_realize;
+}
+
+static const TypeInfo sparse_mem_types[] = {
+ {
+ .name = TYPE_SPARSE_MEM,
+ .parent = TYPE_SYS_BUS_DEVICE,
+ .instance_size = sizeof(SparseMemState),
+ .class_init = sparse_mem_class_init,
+ },
+};
+DEFINE_TYPES(sparse_mem_types);