xref: /openbmc/qemu/hw/mem/sparse-mem.c (revision 51e47cf8)
1 /*
2  * A sparse memory device. Useful for fuzzing
3  *
4  * Copyright Red Hat Inc., 2021
5  *
6  * Authors:
7  *  Alexander Bulekov   <alxndr@bu.edu>
8  *
9  * This work is licensed under the terms of the GNU GPL, version 2 or later.
10  * See the COPYING file in the top-level directory.
11  */
12 
13 #include "qemu/osdep.h"
14 #include "qemu/error-report.h"
15 
16 #include "hw/qdev-properties.h"
17 #include "hw/sysbus.h"
18 #include "qapi/error.h"
19 #include "qemu/units.h"
20 #include "sysemu/qtest.h"
21 #include "hw/mem/sparse-mem.h"
22 
23 #define SPARSE_MEM(obj) OBJECT_CHECK(SparseMemState, (obj), TYPE_SPARSE_MEM)
24 #define SPARSE_BLOCK_SIZE 0x1000
25 
26 typedef struct SparseMemState {
27     SysBusDevice parent_obj;
28     MemoryRegion mmio;
29     uint64_t baseaddr;
30     uint64_t length;
31     uint64_t size_used;
32     uint64_t maxsize;
33     GHashTable *mapped;
34 } SparseMemState;
35 
36 typedef struct sparse_mem_block {
37     uint8_t data[SPARSE_BLOCK_SIZE];
38 } sparse_mem_block;
39 
40 static uint64_t sparse_mem_read(void *opaque, hwaddr addr, unsigned int size)
41 {
42     SparseMemState *s = opaque;
43     uint64_t ret = 0;
44     size_t pfn = addr / SPARSE_BLOCK_SIZE;
45     size_t offset = addr % SPARSE_BLOCK_SIZE;
46     sparse_mem_block *block;
47 
48     block = g_hash_table_lookup(s->mapped, (void *)pfn);
49     if (block) {
50         assert(offset + size <= sizeof(block->data));
51         memcpy(&ret, block->data + offset, size);
52     }
53     return ret;
54 }
55 
56 static void sparse_mem_write(void *opaque, hwaddr addr, uint64_t v,
57                              unsigned int size)
58 {
59     SparseMemState *s = opaque;
60     size_t pfn = addr / SPARSE_BLOCK_SIZE;
61     size_t offset = addr % SPARSE_BLOCK_SIZE;
62     sparse_mem_block *block;
63 
64     if (!g_hash_table_lookup(s->mapped, (void *)pfn) &&
65         s->size_used + SPARSE_BLOCK_SIZE < s->maxsize && v) {
66         g_hash_table_insert(s->mapped, (void *)pfn,
67                             g_new0(sparse_mem_block, 1));
68         s->size_used += sizeof(block->data);
69     }
70     block = g_hash_table_lookup(s->mapped, (void *)pfn);
71     if (!block) {
72         return;
73     }
74 
75     assert(offset + size <= sizeof(block->data));
76 
77     memcpy(block->data + offset, &v, size);
78 
79 }
80 
81 static void sparse_mem_enter_reset(Object *obj, ResetType type)
82 {
83     SparseMemState *s = SPARSE_MEM(obj);
84     g_hash_table_remove_all(s->mapped);
85     return;
86 }
87 
88 static const MemoryRegionOps sparse_mem_ops = {
89     .read = sparse_mem_read,
90     .write = sparse_mem_write,
91     .endianness = DEVICE_LITTLE_ENDIAN,
92     .valid = {
93             .min_access_size = 1,
94             .max_access_size = 8,
95             .unaligned = false,
96         },
97 };
98 
99 static Property sparse_mem_properties[] = {
100     /* The base address of the memory */
101     DEFINE_PROP_UINT64("baseaddr", SparseMemState, baseaddr, 0x0),
102     /* The length of the sparse memory region */
103     DEFINE_PROP_UINT64("length", SparseMemState, length, UINT64_MAX),
104     /* Max amount of actual memory that can be used to back the sparse memory */
105     DEFINE_PROP_UINT64("maxsize", SparseMemState, maxsize, 10 * MiB),
106     DEFINE_PROP_END_OF_LIST(),
107 };
108 
109 MemoryRegion *sparse_mem_init(uint64_t addr, uint64_t length)
110 {
111     DeviceState *dev;
112 
113     dev = qdev_new(TYPE_SPARSE_MEM);
114     qdev_prop_set_uint64(dev, "baseaddr", addr);
115     qdev_prop_set_uint64(dev, "length", length);
116     sysbus_realize_and_unref(SYS_BUS_DEVICE(dev), &error_fatal);
117     sysbus_mmio_map_overlap(SYS_BUS_DEVICE(dev), 0, addr, -10000);
118     return &SPARSE_MEM(dev)->mmio;
119 }
120 
121 static void sparse_mem_realize(DeviceState *dev, Error **errp)
122 {
123     SparseMemState *s = SPARSE_MEM(dev);
124     SysBusDevice *sbd = SYS_BUS_DEVICE(dev);
125 
126     if (!qtest_enabled()) {
127         error_setg(errp, "sparse_mem device should only be used "
128                          "for testing with QTest");
129         return;
130     }
131 
132     assert(s->baseaddr + s->length > s->baseaddr);
133 
134     s->mapped = g_hash_table_new_full(NULL, NULL, NULL,
135                                       (GDestroyNotify)g_free);
136     memory_region_init_io(&s->mmio, OBJECT(s), &sparse_mem_ops, s,
137                           "sparse-mem", s->length);
138     sysbus_init_mmio(sbd, &s->mmio);
139 }
140 
141 static void sparse_mem_class_init(ObjectClass *klass, void *data)
142 {
143     ResettableClass *rc = RESETTABLE_CLASS(klass);
144     DeviceClass *dc = DEVICE_CLASS(klass);
145 
146     device_class_set_props(dc, sparse_mem_properties);
147 
148     dc->desc = "Sparse Memory Device";
149     dc->realize = sparse_mem_realize;
150 
151     rc->phases.enter = sparse_mem_enter_reset;
152 }
153 
154 static const TypeInfo sparse_mem_types[] = {
155     {
156         .name = TYPE_SPARSE_MEM,
157         .parent = TYPE_SYS_BUS_DEVICE,
158         .instance_size = sizeof(SparseMemState),
159         .class_init = sparse_mem_class_init,
160     },
161 };
162 DEFINE_TYPES(sparse_mem_types);
163