1 /*
2 * Copyright (C) 2008 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 /*
18 * VM-specific state associated with a DEX file.
19 */
20 #include "Dalvik.h"
21 #include <sys/mman.h>
22
23 /*
24 * Create auxillary data structures.
25 *
26 * We need a 4-byte pointer for every reference to a class, method, field,
27 * or string constant. Summed up over all loaded DEX files (including the
28 * whoppers in the boostrap class path), this adds up to be quite a bit
29 * of native memory.
30 *
31 * For more traditional VMs these values could be stuffed into the loaded
32 * class file constant pool area, but we don't have that luxury since our
33 * classes are memory-mapped read-only.
34 *
35 * The DEX optimizer will remove the need for some of these (e.g. we won't
36 * use the entry for virtual methods that are only called through
37 * invoke-virtual-quick), creating the possibility of some space reduction
38 * at dexopt time.
39 */
40
allocateAuxStructures(DexFile * pDexFile)41 static DvmDex* allocateAuxStructures(DexFile* pDexFile)
42 {
43 DvmDex* pDvmDex;
44 const DexHeader* pHeader;
45 u4 stringSize, classSize, methodSize, fieldSize;
46
47 pHeader = pDexFile->pHeader;
48
49 stringSize = pHeader->stringIdsSize * sizeof(struct StringObject*);
50 classSize = pHeader->typeIdsSize * sizeof(struct ClassObject*);
51 methodSize = pHeader->methodIdsSize * sizeof(struct Method*);
52 fieldSize = pHeader->fieldIdsSize * sizeof(struct Field*);
53
54 u4 totalSize = sizeof(DvmDex) +
55 stringSize + classSize + methodSize + fieldSize;
56
57 u1 *blob = (u1 *)dvmAllocRegion(totalSize,
58 PROT_READ | PROT_WRITE, "dalvik-aux-structure");
59 if ((void *)blob == MAP_FAILED)
60 return NULL;
61
62 pDvmDex = (DvmDex*)blob;
63 blob += sizeof(DvmDex);
64
65 pDvmDex->pDexFile = pDexFile;
66 pDvmDex->pHeader = pHeader;
67
68 pDvmDex->pResStrings = (struct StringObject**)blob;
69 blob += stringSize;
70 pDvmDex->pResClasses = (struct ClassObject**)blob;
71 blob += classSize;
72 pDvmDex->pResMethods = (struct Method**)blob;
73 blob += methodSize;
74 pDvmDex->pResFields = (struct Field**)blob;
75
76 ALOGV("+++ DEX %p: allocateAux (%d+%d+%d+%d)*4 = %d bytes",
77 pDvmDex, stringSize/4, classSize/4, methodSize/4, fieldSize/4,
78 stringSize + classSize + methodSize + fieldSize);
79
80 pDvmDex->pInterfaceCache = dvmAllocAtomicCache(DEX_INTERFACE_CACHE_SIZE);
81
82 dvmInitMutex(&pDvmDex->modLock);
83
84 return pDvmDex;
85 }
86
87 /*
88 * Given an open optimized DEX file, map it into read-only shared memory and
89 * parse the contents.
90 *
91 * Returns nonzero on error.
92 */
dvmDexFileOpenFromFd(int fd,DvmDex ** ppDvmDex)93 int dvmDexFileOpenFromFd(int fd, DvmDex** ppDvmDex)
94 {
95 DvmDex* pDvmDex;
96 DexFile* pDexFile;
97 MemMapping memMap;
98 int parseFlags = kDexParseDefault;
99 int result = -1;
100
101 if (gDvm.verifyDexChecksum)
102 parseFlags |= kDexParseVerifyChecksum;
103
104 if (lseek(fd, 0, SEEK_SET) < 0) {
105 ALOGE("lseek rewind failed");
106 goto bail;
107 }
108
109 if (sysMapFileInShmemWritableReadOnly(fd, &memMap) != 0) {
110 ALOGE("Unable to map file");
111 goto bail;
112 }
113
114 pDexFile = dexFileParse((u1*)memMap.addr, memMap.length, parseFlags);
115 if (pDexFile == NULL) {
116 ALOGE("DEX parse failed");
117 sysReleaseShmem(&memMap);
118 goto bail;
119 }
120
121 pDvmDex = allocateAuxStructures(pDexFile);
122 if (pDvmDex == NULL) {
123 dexFileFree(pDexFile);
124 sysReleaseShmem(&memMap);
125 goto bail;
126 }
127
128 /* tuck this into the DexFile so it gets released later */
129 sysCopyMap(&pDvmDex->memMap, &memMap);
130 pDvmDex->isMappedReadOnly = true;
131 *ppDvmDex = pDvmDex;
132 result = 0;
133
134 bail:
135 return result;
136 }
137
138 /*
139 * Create a DexFile structure for a "partial" DEX. This is one that is in
140 * the process of being optimized. The optimization header isn't finished
141 * and we won't have any of the auxillary data tables, so we have to do
142 * the initialization slightly differently.
143 *
144 * Returns nonzero on error.
145 */
dvmDexFileOpenPartial(const void * addr,int len,DvmDex ** ppDvmDex)146 int dvmDexFileOpenPartial(const void* addr, int len, DvmDex** ppDvmDex)
147 {
148 DvmDex* pDvmDex;
149 DexFile* pDexFile;
150 int parseFlags = kDexParseDefault;
151 int result = -1;
152
153 /* -- file is incomplete, new checksum has not yet been calculated
154 if (gDvm.verifyDexChecksum)
155 parseFlags |= kDexParseVerifyChecksum;
156 */
157
158 pDexFile = dexFileParse((u1*)addr, len, parseFlags);
159 if (pDexFile == NULL) {
160 ALOGE("DEX parse failed");
161 goto bail;
162 }
163 pDvmDex = allocateAuxStructures(pDexFile);
164 if (pDvmDex == NULL) {
165 dexFileFree(pDexFile);
166 goto bail;
167 }
168
169 pDvmDex->isMappedReadOnly = false;
170 *ppDvmDex = pDvmDex;
171 result = 0;
172
173 bail:
174 return result;
175 }
176
177 /*
178 * Free up the DexFile and any associated data structures.
179 *
180 * Note we may be called with a partially-initialized DvmDex.
181 */
dvmDexFileFree(DvmDex * pDvmDex)182 void dvmDexFileFree(DvmDex* pDvmDex)
183 {
184 u4 totalSize;
185
186 if (pDvmDex == NULL)
187 return;
188
189 dvmDestroyMutex(&pDvmDex->modLock);
190
191 totalSize = pDvmDex->pHeader->stringIdsSize * sizeof(struct StringObject*);
192 totalSize += pDvmDex->pHeader->typeIdsSize * sizeof(struct ClassObject*);
193 totalSize += pDvmDex->pHeader->methodIdsSize * sizeof(struct Method*);
194 totalSize += pDvmDex->pHeader->fieldIdsSize * sizeof(struct Field*);
195 totalSize += sizeof(DvmDex);
196
197 dexFileFree(pDvmDex->pDexFile);
198
199 ALOGV("+++ DEX %p: freeing aux structs", pDvmDex);
200 dvmFreeAtomicCache(pDvmDex->pInterfaceCache);
201 sysReleaseShmem(&pDvmDex->memMap);
202 munmap(pDvmDex, totalSize);
203 }
204
205
206 /*
207 * Change the byte at the specified address to a new value. If the location
208 * already has the new value, do nothing.
209 *
210 * This requires changing the access permissions to read-write, updating
211 * the value, and then resetting the permissions.
212 *
213 * We need to ensure mutual exclusion at a page granularity to avoid a race
214 * where one threads sets read-write, another thread sets read-only, and
215 * then the first thread does a write. Since we don't do a lot of updates,
216 * and the window is small, we just use a lock across the entire DvmDex.
217 * We're only trying to make the page state change atomic; it's up to the
218 * caller to ensure that multiple threads aren't stomping on the same
219 * location (e.g. breakpoints and verifier/optimizer changes happening
220 * simultaneously).
221 *
222 * TODO: if we're back to the original state of the page, use
223 * madvise(MADV_DONTNEED) to release the private/dirty copy.
224 *
225 * Returns "true" on success.
226 */
dvmDexChangeDex1(DvmDex * pDvmDex,u1 * addr,u1 newVal)227 bool dvmDexChangeDex1(DvmDex* pDvmDex, u1* addr, u1 newVal)
228 {
229 if (*addr == newVal) {
230 ALOGV("+++ byte at %p is already 0x%02x", addr, newVal);
231 return true;
232 }
233
234 /*
235 * We're not holding this for long, so we don't bother with switching
236 * to VMWAIT.
237 */
238 dvmLockMutex(&pDvmDex->modLock);
239
240 ALOGV("+++ change byte at %p from 0x%02x to 0x%02x", addr, *addr, newVal);
241 if (sysChangeMapAccess(addr, 1, true, &pDvmDex->memMap) != 0) {
242 ALOGD("NOTE: DEX page access change (->RW) failed");
243 /* expected on files mounted from FAT; keep going (may crash) */
244 }
245
246 *addr = newVal;
247
248 if (sysChangeMapAccess(addr, 1, false, &pDvmDex->memMap) != 0) {
249 ALOGD("NOTE: DEX page access change (->RO) failed");
250 /* expected on files mounted from FAT; keep going */
251 }
252
253 dvmUnlockMutex(&pDvmDex->modLock);
254
255 return true;
256 }
257
258 /*
259 * Change the 2-byte value at the specified address to a new value. If the
260 * location already has the new value, do nothing.
261 *
262 * Otherwise works like dvmDexChangeDex1.
263 */
dvmDexChangeDex2(DvmDex * pDvmDex,u2 * addr,u2 newVal)264 bool dvmDexChangeDex2(DvmDex* pDvmDex, u2* addr, u2 newVal)
265 {
266 if (*addr == newVal) {
267 ALOGV("+++ value at %p is already 0x%04x", addr, newVal);
268 return true;
269 }
270
271 /*
272 * We're not holding this for long, so we don't bother with switching
273 * to VMWAIT.
274 */
275 dvmLockMutex(&pDvmDex->modLock);
276
277 ALOGV("+++ change 2byte at %p from 0x%04x to 0x%04x", addr, *addr, newVal);
278 if (sysChangeMapAccess(addr, 2, true, &pDvmDex->memMap) != 0) {
279 ALOGD("NOTE: DEX page access change (->RW) failed");
280 /* expected on files mounted from FAT; keep going (may crash) */
281 }
282
283 *addr = newVal;
284
285 if (sysChangeMapAccess(addr, 2, false, &pDvmDex->memMap) != 0) {
286 ALOGD("NOTE: DEX page access change (->RO) failed");
287 /* expected on files mounted from FAT; keep going */
288 }
289
290 dvmUnlockMutex(&pDvmDex->modLock);
291
292 return true;
293 }
294