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android / platform / dalvik.git / android-4.2.2_r1 / . / vm / analysis / DexPrepare.cpp
blob: e8112d543872df1ab3d9f4d712caedc909f70f57 [file] [log] [blame]
/*
* Copyright (C) 2008 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/*
* Prepare a DEX file for use by the VM. Depending upon the VM options
* we will attempt to verify and/or optimize the code, possibly appending
* register maps.
*
* TODO: the format of the optimized header is currently "whatever we
* happen to write", since the VM that writes it is by definition the same
* as the VM that reads it. Still, it should be better documented and
* more rigorously structured.
*/
#include "Dalvik.h"
#include "libdex/OptInvocation.h"
#include "analysis/RegisterMap.h"
#include "analysis/Optimize.h"
#include <string>
#include <libgen.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/file.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <fcntl.h>
#include <errno.h>
#include <unistd.h>
#include <zlib.h>
/* fwd */
static bool rewriteDex(u1* addr, int len, bool doVerify, bool doOpt,
DexClassLookup** ppClassLookup, DvmDex** ppDvmDex);
static bool loadAllClasses(DvmDex* pDvmDex);
static void verifyAndOptimizeClasses(DexFile* pDexFile, bool doVerify,
bool doOpt);
static void verifyAndOptimizeClass(DexFile* pDexFile, ClassObject* clazz,
const DexClassDef* pClassDef, bool doVerify, bool doOpt);
static void updateChecksum(u1* addr, int len, DexHeader* pHeader);
static int writeDependencies(int fd, u4 modWhen, u4 crc);
static bool writeOptData(int fd, const DexClassLookup* pClassLookup,\
const RegisterMapBuilder* pRegMapBuilder);
static bool computeFileChecksum(int fd, off_t start, size_t length, u4* pSum);
/*
* Get just the directory portion of the given path. Equivalent to dirname(3).
*/
static std::string saneDirName(const std::string& path) {
size_t n = path.rfind('/');
if (n == std::string::npos) {
return ".";
}
return path.substr(0, n);
}
/*
* Helper for dvmOpenCacheDexFile() in a known-error case: Check to
* see if the directory part of the given path (all but the last
* component) exists and is writable. Complain to the log if not.
*/
static bool directoryIsValid(const std::string& fileName)
{
std::string dirName(saneDirName(fileName));
struct stat sb;
if (stat(dirName.c_str(), &sb) < 0) {
ALOGE("Could not stat dex cache directory '%s': %s", dirName.c_str(), strerror(errno));
return false;
}
if (!S_ISDIR(sb.st_mode)) {
ALOGE("Dex cache directory isn't a directory: %s", dirName.c_str());
return false;
}
if (access(dirName.c_str(), W_OK) < 0) {
ALOGE("Dex cache directory isn't writable: %s", dirName.c_str());
return false;
}
if (access(dirName.c_str(), R_OK) < 0) {
ALOGE("Dex cache directory isn't readable: %s", dirName.c_str());
return false;
}
return true;
}
/*
* Return the fd of an open file in the DEX file cache area. If the cache
* file doesn't exist or is out of date, this will remove the old entry,
* create a new one (writing only the file header), and return with the
* "new file" flag set.
*
* It's possible to execute from an unoptimized DEX file directly,
* assuming the byte ordering and structure alignment is correct, but
* disadvantageous because some significant optimizations are not possible.
* It's not generally possible to do the same from an uncompressed Jar
* file entry, because we have to guarantee 32-bit alignment in the
* memory-mapped file.
*
* For a Jar/APK file (a zip archive with "classes.dex" inside), "modWhen"
* and "crc32" come from the Zip directory entry. For a stand-alone DEX
* file, it's the modification date of the file and the Adler32 from the
* DEX header (which immediately follows the magic). If these don't
* match what's stored in the opt header, we reject the file immediately.
*
* On success, the file descriptor will be positioned just past the "opt"
* file header, and will be locked with flock. "*pCachedName" will point
* to newly-allocated storage.
*/
int dvmOpenCachedDexFile(const char* fileName, const char* cacheFileName,
u4 modWhen, u4 crc, bool isBootstrap, bool* pNewFile, bool createIfMissing)
{
int fd, cc;
struct stat fdStat, fileStat;
bool readOnly = false;
*pNewFile = false;
retry:
/*
* Try to open the cache file. If we've been asked to,
* create it if it doesn't exist.
*/
fd = createIfMissing ? open(cacheFileName, O_CREAT|O_RDWR, 0644) : -1;
if (fd < 0) {
fd = open(cacheFileName, O_RDONLY, 0);
if (fd < 0) {
if (createIfMissing) {
// TODO: write an equivalent of strerror_r that returns a std::string.
const std::string errnoString(strerror(errno));
if (directoryIsValid(cacheFileName)) {
ALOGE("Can't open dex cache file '%s': %s", cacheFileName, errnoString.c_str());
}
}
return fd;
}
readOnly = true;
} else {
fchmod(fd, 0644);
}
/*
* Grab an exclusive lock on the cache file. If somebody else is
* working on it, we'll block here until they complete. Because
* we're waiting on an external resource, we go into VMWAIT mode.
*/
ALOGV("DexOpt: locking cache file %s (fd=%d, boot=%d)",
cacheFileName, fd, isBootstrap);
ThreadStatus oldStatus = dvmChangeStatus(NULL, THREAD_VMWAIT);
cc = flock(fd, LOCK_EX | LOCK_NB);
if (cc != 0) {
ALOGD("DexOpt: sleeping on flock(%s)", cacheFileName);
cc = flock(fd, LOCK_EX);
}
dvmChangeStatus(NULL, oldStatus);
if (cc != 0) {
ALOGE("Can't lock dex cache '%s': %d", cacheFileName, cc);
close(fd);
return -1;
}
ALOGV("DexOpt: locked cache file");
/*
* Check to see if the fd we opened and locked matches the file in
* the filesystem. If they don't, then somebody else unlinked ours
* and created a new file, and we need to use that one instead. (If
* we caught them between the unlink and the create, we'll get an
* ENOENT from the file stat.)
*/
cc = fstat(fd, &fdStat);
if (cc != 0) {
ALOGE("Can't stat open file '%s'", cacheFileName);
LOGVV("DexOpt: unlocking cache file %s", cacheFileName);
goto close_fail;
}
cc = stat(cacheFileName, &fileStat);
if (cc != 0 ||
fdStat.st_dev != fileStat.st_dev || fdStat.st_ino != fileStat.st_ino)
{
ALOGD("DexOpt: our open cache file is stale; sleeping and retrying");
LOGVV("DexOpt: unlocking cache file %s", cacheFileName);
flock(fd, LOCK_UN);
close(fd);
usleep(250 * 1000); /* if something is hosed, don't peg machine */
goto retry;
}
/*
* We have the correct file open and locked. If the file size is zero,
* then it was just created by us, and we want to fill in some fields
* in the "opt" header and set "*pNewFile". Otherwise, we want to
* verify that the fields in the header match our expectations, and
* reset the file if they don't.
*/
if (fdStat.st_size == 0) {
if (readOnly) {
ALOGW("DexOpt: file has zero length and isn't writable");
goto close_fail;
}
cc = dexOptCreateEmptyHeader(fd);
if (cc != 0)
goto close_fail;
*pNewFile = true;
ALOGV("DexOpt: successfully initialized new cache file");
} else {
bool expectVerify, expectOpt;
if (gDvm.classVerifyMode == VERIFY_MODE_NONE) {
expectVerify = false;
} else if (gDvm.classVerifyMode == VERIFY_MODE_REMOTE) {
expectVerify = !isBootstrap;
} else /*if (gDvm.classVerifyMode == VERIFY_MODE_ALL)*/ {
expectVerify = true;
}
if (gDvm.dexOptMode == OPTIMIZE_MODE_NONE) {
expectOpt = false;
} else if (gDvm.dexOptMode == OPTIMIZE_MODE_VERIFIED ||
gDvm.dexOptMode == OPTIMIZE_MODE_FULL) {
expectOpt = expectVerify;
} else /*if (gDvm.dexOptMode == OPTIMIZE_MODE_ALL)*/ {
expectOpt = true;
}
ALOGV("checking deps, expecting vfy=%d opt=%d",
expectVerify, expectOpt);
if (!dvmCheckOptHeaderAndDependencies(fd, true, modWhen, crc,
expectVerify, expectOpt))
{
if (readOnly) {
/*
* We could unlink and rewrite the file if we own it or
* the "sticky" bit isn't set on the directory. However,
* we're not able to truncate it, which spoils things. So,
* give up now.
*/
if (createIfMissing) {
ALOGW("Cached DEX '%s' (%s) is stale and not writable",
fileName, cacheFileName);
}
goto close_fail;
}
/*
* If we truncate the existing file before unlinking it, any
* process that has it mapped will fail when it tries to touch
* the pages.
*
* This is very important. The zygote process will have the
* boot DEX files (core, framework, etc.) mapped early. If
* (say) core.dex gets updated, and somebody launches an app
* that uses App.dex, then App.dex gets reoptimized because it's
* dependent upon the boot classes. However, dexopt will be
* using the *new* core.dex to do the optimizations, while the
* app will actually be running against the *old* core.dex
* because it starts from zygote.
*
* Even without zygote, it's still possible for a class loader
* to pull in an APK that was optimized against an older set
* of DEX files. We must ensure that everything fails when a
* boot DEX gets updated, and for general "why aren't my
* changes doing anything" purposes its best if we just make
* everything crash when a DEX they're using gets updated.
*/
ALOGD("ODEX file is stale or bad; removing and retrying (%s)",
cacheFileName);
if (ftruncate(fd, 0) != 0) {
ALOGW("Warning: unable to truncate cache file '%s': %s",
cacheFileName, strerror(errno));
/* keep going */
}
if (unlink(cacheFileName) != 0) {
ALOGW("Warning: unable to remove cache file '%s': %d %s",
cacheFileName, errno, strerror(errno));
/* keep going; permission failure should probably be fatal */
}
LOGVV("DexOpt: unlocking cache file %s", cacheFileName);
flock(fd, LOCK_UN);
close(fd);
goto retry;
} else {
ALOGV("DexOpt: good deps in cache file");
}
}
assert(fd >= 0);
return fd;
close_fail:
flock(fd, LOCK_UN);
close(fd);
return -1;
}
/*
* Unlock the file descriptor.
*
* Returns "true" on success.
*/
bool dvmUnlockCachedDexFile(int fd)
{
LOGVV("DexOpt: unlocking cache file fd=%d", fd);
return (flock(fd, LOCK_UN) == 0);
}
/*
* Given a descriptor for a file with DEX data in it, produce an
* optimized version.
*
* The file pointed to by "fd" is expected to be a locked shared resource
* (or private); we make no efforts to enforce multi-process correctness
* here.
*
* "fileName" is only used for debug output. "modWhen" and "crc" are stored
* in the dependency set.
*
* The "isBootstrap" flag determines how the optimizer and verifier handle
* package-scope access checks. When optimizing, we only load the bootstrap
* class DEX files and the target DEX, so the flag determines whether the
* target DEX classes are given a (synthetic) non-NULL classLoader pointer.
* This only really matters if the target DEX contains classes that claim to
* be in the same package as bootstrap classes.
*
* The optimizer will need to load every class in the target DEX file.
* This is generally undesirable, so we start a subprocess to do the
* work and wait for it to complete.
*
* Returns "true" on success. All data will have been written to "fd".
*/
bool dvmOptimizeDexFile(int fd, off_t dexOffset, long dexLength,
const char* fileName, u4 modWhen, u4 crc, bool isBootstrap)
{
const char* lastPart = strrchr(fileName, '/');
if (lastPart != NULL)
lastPart++;
else
lastPart = fileName;
ALOGD("DexOpt: --- BEGIN '%s' (bootstrap=%d) ---", lastPart, isBootstrap);
pid_t pid;
/*
* This could happen if something in our bootclasspath, which we thought
* was all optimized, got rejected.
*/
if (gDvm.optimizing) {
ALOGW("Rejecting recursive optimization attempt on '%s'", fileName);
return false;
}
pid = fork();
if (pid == 0) {
static const int kUseValgrind = 0;
static const char* kDexOptBin = "/bin/dexopt";
static const char* kValgrinder = "/usr/bin/valgrind";
static const int kFixedArgCount = 10;
static const int kValgrindArgCount = 5;
static const int kMaxIntLen = 12; // '-'+10dig+'\0' -OR- 0x+8dig
int bcpSize = dvmGetBootPathSize();
int argc = kFixedArgCount + bcpSize
+ (kValgrindArgCount * kUseValgrind);
const char* argv[argc+1]; // last entry is NULL
char values[argc][kMaxIntLen];
char* execFile;
const char* androidRoot;
int flags;
/* change process groups, so we don't clash with ProcessManager */
setpgid(0, 0);
/* full path to optimizer */
androidRoot = getenv("ANDROID_ROOT");
if (androidRoot == NULL) {
ALOGW("ANDROID_ROOT not set, defaulting to /system");
androidRoot = "/system";
}
execFile = (char*)alloca(strlen(androidRoot) + strlen(kDexOptBin) + 1);
strcpy(execFile, androidRoot);
strcat(execFile, kDexOptBin);
/*
* Create arg vector.
*/
int curArg = 0;
if (kUseValgrind) {
/* probably shouldn't ship the hard-coded path */
argv[curArg++] = (char*)kValgrinder;
argv[curArg++] = "--tool=memcheck";
argv[curArg++] = "--leak-check=yes"; // check for leaks too
argv[curArg++] = "--leak-resolution=med"; // increase from 2 to 4
argv[curArg++] = "--num-callers=16"; // default is 12
assert(curArg == kValgrindArgCount);
}
argv[curArg++] = execFile;
argv[curArg++] = "--dex";
sprintf(values[2], "%d", DALVIK_VM_BUILD);
argv[curArg++] = values[2];
sprintf(values[3], "%d", fd);
argv[curArg++] = values[3];
sprintf(values[4], "%d", (int) dexOffset);
argv[curArg++] = values[4];
sprintf(values[5], "%d", (int) dexLength);
argv[curArg++] = values[5];
argv[curArg++] = (char*)fileName;
sprintf(values[7], "%d", (int) modWhen);
argv[curArg++] = values[7];
sprintf(values[8], "%d", (int) crc);
argv[curArg++] = values[8];
flags = 0;
if (gDvm.dexOptMode != OPTIMIZE_MODE_NONE) {
flags |= DEXOPT_OPT_ENABLED;
if (gDvm.dexOptMode == OPTIMIZE_MODE_ALL)
flags |= DEXOPT_OPT_ALL;
}
if (gDvm.classVerifyMode != VERIFY_MODE_NONE) {
flags |= DEXOPT_VERIFY_ENABLED;
if (gDvm.classVerifyMode == VERIFY_MODE_ALL)
flags |= DEXOPT_VERIFY_ALL;
}
if (isBootstrap)
flags |= DEXOPT_IS_BOOTSTRAP;
if (gDvm.generateRegisterMaps)
flags |= DEXOPT_GEN_REGISTER_MAPS;
sprintf(values[9], "%d", flags);
argv[curArg++] = values[9];
assert(((!kUseValgrind && curArg == kFixedArgCount) ||
((kUseValgrind && curArg == kFixedArgCount+kValgrindArgCount))));
ClassPathEntry* cpe;
for (cpe = gDvm.bootClassPath; cpe->ptr != NULL; cpe++) {
argv[curArg++] = cpe->fileName;
}
assert(curArg == argc);
argv[curArg] = NULL;
if (kUseValgrind)
execv(kValgrinder, const_cast<char**>(argv));
else
execv(execFile, const_cast<char**>(argv));
ALOGE("execv '%s'%s failed: %s", execFile,
kUseValgrind ? " [valgrind]" : "", strerror(errno));
exit(1);
} else {
ALOGV("DexOpt: waiting for verify+opt, pid=%d", (int) pid);
int status;
pid_t gotPid;
/*
* Wait for the optimization process to finish. We go into VMWAIT
* mode here so GC suspension won't have to wait for us.
*/
ThreadStatus oldStatus = dvmChangeStatus(NULL, THREAD_VMWAIT);
while (true) {
gotPid = waitpid(pid, &status, 0);
if (gotPid == -1 && errno == EINTR) {
ALOGD("waitpid interrupted, retrying");
} else {
break;
}
}
dvmChangeStatus(NULL, oldStatus);
if (gotPid != pid) {
ALOGE("waitpid failed: wanted %d, got %d: %s",
(int) pid, (int) gotPid, strerror(errno));
return false;
}
if (WIFEXITED(status) && WEXITSTATUS(status) == 0) {
ALOGD("DexOpt: --- END '%s' (success) ---", lastPart);
return true;
} else {
ALOGW("DexOpt: --- END '%s' --- status=0x%04x, process failed",
lastPart, status);
return false;
}
}
}
/*
* Do the actual optimization. This is executed in the dexopt process.
*
* For best use of disk/memory, we want to extract once and perform
* optimizations in place. If the file has to expand or contract
* to match local structure padding/alignment expectations, we want
* to do the rewrite as part of the extract, rather than extracting
* into a temp file and slurping it back out. (The structure alignment
* is currently correct for all platforms, and this isn't expected to
* change, so we should be okay with having it already extracted.)
*
* Returns "true" on success.
*/
bool dvmContinueOptimization(int fd, off_t dexOffset, long dexLength,
const char* fileName, u4 modWhen, u4 crc, bool isBootstrap)
{
DexClassLookup* pClassLookup = NULL;
RegisterMapBuilder* pRegMapBuilder = NULL;
assert(gDvm.optimizing);
ALOGV("Continuing optimization (%s, isb=%d)", fileName, isBootstrap);
assert(dexOffset >= 0);
/* quick test so we don't blow up on empty file */
if (dexLength < (int) sizeof(DexHeader)) {
ALOGE("too small to be DEX");
return false;
}
if (dexOffset < (int) sizeof(DexOptHeader)) {
ALOGE("not enough room for opt header");
return false;
}
bool result = false;
/*
* Drop this into a global so we don't have to pass it around. We could
* also add a field to DexFile, but since it only pertains to DEX
* creation that probably doesn't make sense.
*/
gDvm.optimizingBootstrapClass = isBootstrap;
{
/*
* Map the entire file (so we don't have to worry about page
* alignment). The expectation is that the output file contains
* our DEX data plus room for a small header.
*/
bool success;
void* mapAddr;
mapAddr = mmap(NULL, dexOffset + dexLength, PROT_READ|PROT_WRITE,
MAP_SHARED, fd, 0);
if (mapAddr == MAP_FAILED) {
ALOGE("unable to mmap DEX cache: %s", strerror(errno));
goto bail;
}
bool doVerify, doOpt;
if (gDvm.classVerifyMode == VERIFY_MODE_NONE) {
doVerify = false;
} else if (gDvm.classVerifyMode == VERIFY_MODE_REMOTE) {
doVerify = !gDvm.optimizingBootstrapClass;
} else /*if (gDvm.classVerifyMode == VERIFY_MODE_ALL)*/ {
doVerify = true;
}
if (gDvm.dexOptMode == OPTIMIZE_MODE_NONE) {
doOpt = false;
} else if (gDvm.dexOptMode == OPTIMIZE_MODE_VERIFIED ||
gDvm.dexOptMode == OPTIMIZE_MODE_FULL) {
doOpt = doVerify;
} else /*if (gDvm.dexOptMode == OPTIMIZE_MODE_ALL)*/ {
doOpt = true;
}
/*
* Rewrite the file. Byte reordering, structure realigning,
* class verification, and bytecode optimization are all performed
* here.
*
* In theory the file could change size and bits could shift around.
* In practice this would be annoying to deal with, so the file
* layout is designed so that it can always be rewritten in place.
*
* This creates the class lookup table as part of doing the processing.
*/
success = rewriteDex(((u1*) mapAddr) + dexOffset, dexLength,
doVerify, doOpt, &pClassLookup, NULL);
if (success) {
DvmDex* pDvmDex = NULL;
u1* dexAddr = ((u1*) mapAddr) + dexOffset;
if (dvmDexFileOpenPartial(dexAddr, dexLength, &pDvmDex) != 0) {
ALOGE("Unable to create DexFile");
success = false;
} else {
/*
* If configured to do so, generate register map output
* for all verified classes. The register maps were
* generated during verification, and will now be serialized.
*/
if (gDvm.generateRegisterMaps) {
pRegMapBuilder = dvmGenerateRegisterMaps(pDvmDex);
if (pRegMapBuilder == NULL) {
ALOGE("Failed generating register maps");
success = false;
}
}
DexHeader* pHeader = (DexHeader*)pDvmDex->pHeader;
updateChecksum(dexAddr, dexLength, pHeader);
dvmDexFileFree(pDvmDex);
}
}
/* unmap the read-write version, forcing writes to disk */
if (msync(mapAddr, dexOffset + dexLength, MS_SYNC) != 0) {
ALOGW("msync failed: %s", strerror(errno));
// weird, but keep going
}
#if 1
/*
* This causes clean shutdown to fail, because we have loaded classes
* that point into it. For the optimizer this isn't a problem,
* because it's more efficient for the process to simply exit.
* Exclude this code when doing clean shutdown for valgrind.
*/
if (munmap(mapAddr, dexOffset + dexLength) != 0) {
ALOGE("munmap failed: %s", strerror(errno));
goto bail;
}
#endif
if (!success)
goto bail;
}
/* get start offset, and adjust deps start for 64-bit alignment */
off_t depsOffset, optOffset, endOffset, adjOffset;
int depsLength, optLength;
u4 optChecksum;
depsOffset = lseek(fd, 0, SEEK_END);
if (depsOffset < 0) {
ALOGE("lseek to EOF failed: %s", strerror(errno));
goto bail;
}
adjOffset = (depsOffset + 7) & ~(0x07);
if (adjOffset != depsOffset) {
ALOGV("Adjusting deps start from %d to %d",
(int) depsOffset, (int) adjOffset);
depsOffset = adjOffset;
lseek(fd, depsOffset, SEEK_SET);
}
/*
* Append the dependency list.
*/
if (writeDependencies(fd, modWhen, crc) != 0) {
ALOGW("Failed writing dependencies");
goto bail;
}
/* compute deps length, then adjust opt start for 64-bit alignment */
optOffset = lseek(fd, 0, SEEK_END);
depsLength = optOffset - depsOffset;
adjOffset = (optOffset + 7) & ~(0x07);
if (adjOffset != optOffset) {
ALOGV("Adjusting opt start from %d to %d",
(int) optOffset, (int) adjOffset);
optOffset = adjOffset;
lseek(fd, optOffset, SEEK_SET);
}
/*
* Append any optimized pre-computed data structures.
*/
if (!writeOptData(fd, pClassLookup, pRegMapBuilder)) {
ALOGW("Failed writing opt data");
goto bail;
}
endOffset = lseek(fd, 0, SEEK_END);
optLength = endOffset - optOffset;
/* compute checksum from start of deps to end of opt area */
if (!computeFileChecksum(fd, depsOffset,
(optOffset+optLength) - depsOffset, &optChecksum))
{
goto bail;
}
/*
* Output the "opt" header with all values filled in and a correct
* magic number.
*/
DexOptHeader optHdr;
memset(&optHdr, 0xff, sizeof(optHdr));
memcpy(optHdr.magic, DEX_OPT_MAGIC, 4);
memcpy(optHdr.magic+4, DEX_OPT_MAGIC_VERS, 4);
optHdr.dexOffset = (u4) dexOffset;
optHdr.dexLength = (u4) dexLength;
optHdr.depsOffset = (u4) depsOffset;
optHdr.depsLength = (u4) depsLength;
optHdr.optOffset = (u4) optOffset;
optHdr.optLength = (u4) optLength;
#if __BYTE_ORDER != __LITTLE_ENDIAN
optHdr.flags = DEX_OPT_FLAG_BIG;
#else
optHdr.flags = 0;
#endif
optHdr.checksum = optChecksum;
fsync(fd); /* ensure previous writes go before header is written */
lseek(fd, 0, SEEK_SET);
if (sysWriteFully(fd, &optHdr, sizeof(optHdr), "DexOpt opt header") != 0)
goto bail;
ALOGV("Successfully wrote DEX header");
result = true;
//dvmRegisterMapDumpStats();
bail:
dvmFreeRegisterMapBuilder(pRegMapBuilder);
free(pClassLookup);
return result;
}
/*
* Prepare an in-memory DEX file.
*
* The data was presented to the VM as a byte array rather than a file.
* We want to do the same basic set of operations, but we can just leave
* them in memory instead of writing them out to a cached optimized DEX file.
*/
bool dvmPrepareDexInMemory(u1* addr, size_t len, DvmDex** ppDvmDex)
{
DexClassLookup* pClassLookup = NULL;
/*
* Byte-swap, realign, verify basic DEX file structure.
*
* We could load + verify + optimize here as well, but that's probably
* not desirable.
*
* (The bulk-verification code is currently only setting the DEX
* file's "verified" flag, not updating the ClassObject. This would
* also need to be changed, or we will try to verify the class twice,
* and possibly reject it when optimized opcodes are encountered.)
*/
if (!rewriteDex(addr, len, false, false, &pClassLookup, ppDvmDex)) {
return false;
}
(*ppDvmDex)->pDexFile->pClassLookup = pClassLookup;
return true;
}
/*
* Perform in-place rewrites on a memory-mapped DEX file.
*
* If this is called from a short-lived child process (dexopt), we can
* go nutty with loading classes and allocating memory. When it's
* called to prepare classes provided in a byte array, we may want to
* be more conservative.
*
* If "ppClassLookup" is non-NULL, a pointer to a newly-allocated
* DexClassLookup will be returned on success.
*
* If "ppDvmDex" is non-NULL, a newly-allocated DvmDex struct will be
* returned on success.
*/
static bool rewriteDex(u1* addr, int len, bool doVerify, bool doOpt,
DexClassLookup** ppClassLookup, DvmDex** ppDvmDex)
{
DexClassLookup* pClassLookup = NULL;
u8 prepWhen, loadWhen, verifyOptWhen;
DvmDex* pDvmDex = NULL;
bool result = false;
const char* msgStr = "???";
/* if the DEX is in the wrong byte order, swap it now */
if (dexSwapAndVerify(addr, len) != 0)
goto bail;
/*
* Now that the DEX file can be read directly, create a DexFile struct
* for it.
*/
if (dvmDexFileOpenPartial(addr, len, &pDvmDex) != 0) {
ALOGE("Unable to create DexFile");
goto bail;
}
/*
* Create the class lookup table. This will eventually be appended
* to the end of the .odex.
*
* We create a temporary link from the DexFile for the benefit of
* class loading, below.
*/
pClassLookup = dexCreateClassLookup(pDvmDex->pDexFile);
if (pClassLookup == NULL)
goto bail;
pDvmDex->pDexFile->pClassLookup = pClassLookup;
/*
* If we're not going to attempt to verify or optimize the classes,
* there's no value in loading them, so bail out early.
*/
if (!doVerify && !doOpt) {
result = true;
goto bail;
}
prepWhen = dvmGetRelativeTimeUsec();
/*
* Load all classes found in this DEX file. If they fail to load for
* some reason, they won't get verified (which is as it should be).
*/
if (!loadAllClasses(pDvmDex))
goto bail;
loadWhen = dvmGetRelativeTimeUsec();
/*
* Create a data structure for use by the bytecode optimizer.
* We need to look up methods in a few classes, so this may cause
* a bit of class loading. We usually do this during VM init, but
* for dexopt on core.jar the order of operations gets a bit tricky,
* so we defer it to here.
*/
if (!dvmCreateInlineSubsTable())
goto bail;
/*
* Verify and optimize all classes in the DEX file (command-line
* options permitting).
*
* This is best-effort, so there's really no way for dexopt to
* fail at this point.
*/
verifyAndOptimizeClasses(pDvmDex->pDexFile, doVerify, doOpt);
verifyOptWhen = dvmGetRelativeTimeUsec();
if (doVerify && doOpt)
msgStr = "verify+opt";
else if (doVerify)
msgStr = "verify";
else if (doOpt)
msgStr = "opt";
ALOGD("DexOpt: load %dms, %s %dms, %d bytes",
(int) (loadWhen - prepWhen) / 1000,
msgStr,
(int) (verifyOptWhen - loadWhen) / 1000,
gDvm.pBootLoaderAlloc->curOffset);
result = true;
bail:
/*
* On success, return the pieces that the caller asked for.
*/
if (pDvmDex != NULL) {
/* break link between the two */
pDvmDex->pDexFile->pClassLookup = NULL;
}
if (ppDvmDex == NULL || !result) {
dvmDexFileFree(pDvmDex);
} else {
*ppDvmDex = pDvmDex;
}
if (ppClassLookup == NULL || !result) {
free(pClassLookup);
} else {
*ppClassLookup = pClassLookup;
}
return result;
}
/*
* Try to load all classes in the specified DEX. If they have some sort
* of broken dependency, e.g. their superclass lives in a different DEX
* that wasn't previously loaded into the bootstrap class path, loading
* will fail. This is the desired behavior.
*
* We have no notion of class loader at this point, so we load all of
* the classes with the bootstrap class loader. It turns out this has
* exactly the behavior we want, and has no ill side effects because we're
* running in a separate process and anything we load here will be forgotten.
*
* We set the CLASS_MULTIPLE_DEFS flag here if we see multiple definitions.
* This works because we only call here as part of optimization / pre-verify,
* not during verification as part of loading a class into a running VM.
*
* This returns "false" if the world is too screwed up to do anything
* useful at all.
*/
static bool loadAllClasses(DvmDex* pDvmDex)
{
u4 count = pDvmDex->pDexFile->pHeader->classDefsSize;
u4 idx;
int loaded = 0;
ALOGV("DexOpt: +++ trying to load %d classes", count);
dvmSetBootPathExtraDex(pDvmDex);
/*
* At this point, it is safe -- and necessary! -- to look up the
* VM's required classes and members, even when what we are in the
* process of processing is the core library that defines these
* classes itself. (The reason it is necessary is that in the act
* of initializing the class Class, below, the system will end up
* referring to many of the class references that got set up by
* this call.)
*/
if (!dvmFindRequiredClassesAndMembers()) {
return false;
}
/*
* We have some circularity issues with Class and Object that are
* most easily avoided by ensuring that Object is never the first
* thing we try to find-and-initialize. The call to
* dvmFindSystemClass() here takes care of that situation. (We
* only need to do this when loading classes from the DEX file
* that contains Object, and only when Object comes first in the
* list, but it costs very little to do it in all cases.)
*/
if (!dvmInitClass(gDvm.classJavaLangClass)) {
ALOGE("ERROR: failed to initialize the class Class!");
return false;
}
for (idx = 0; idx < count; idx++) {
const DexClassDef* pClassDef;
const char* classDescriptor;
ClassObject* newClass;
pClassDef = dexGetClassDef(pDvmDex->pDexFile, idx);
classDescriptor =
dexStringByTypeIdx(pDvmDex->pDexFile, pClassDef->classIdx);
ALOGV("+++ loading '%s'", classDescriptor);
//newClass = dvmDefineClass(pDexFile, classDescriptor,
// NULL);
newClass = dvmFindSystemClassNoInit(classDescriptor);
if (newClass == NULL) {
ALOGV("DexOpt: failed loading '%s'", classDescriptor);
dvmClearOptException(dvmThreadSelf());
} else if (newClass->pDvmDex != pDvmDex) {
/*
* We don't load the new one, and we tag the first one found
* with the "multiple def" flag so the resolver doesn't try
* to make it available.
*/
ALOGD("DexOpt: '%s' has an earlier definition; blocking out",
classDescriptor);
SET_CLASS_FLAG(newClass, CLASS_MULTIPLE_DEFS);
} else {
loaded++;
}
}
ALOGV("DexOpt: +++ successfully loaded %d classes", loaded);
dvmSetBootPathExtraDex(NULL);
return true;
}
/*
* Verify and/or optimize all classes that were successfully loaded from
* this DEX file.
*/
static void verifyAndOptimizeClasses(DexFile* pDexFile, bool doVerify,
bool doOpt)
{
u4 count = pDexFile->pHeader->classDefsSize;
u4 idx;
for (idx = 0; idx < count; idx++) {
const DexClassDef* pClassDef;
const char* classDescriptor;
ClassObject* clazz;
pClassDef = dexGetClassDef(pDexFile, idx);
classDescriptor = dexStringByTypeIdx(pDexFile, pClassDef->classIdx);
/* all classes are loaded into the bootstrap class loader */
clazz = dvmLookupClass(classDescriptor, NULL, false);
if (clazz != NULL) {
verifyAndOptimizeClass(pDexFile, clazz, pClassDef, doVerify, doOpt);
} else {
// TODO: log when in verbose mode
ALOGV("DexOpt: not optimizing unavailable class '%s'",
classDescriptor);
}
}
#ifdef VERIFIER_STATS
ALOGI("Verifier stats:");
ALOGI(" methods examined : %u", gDvm.verifierStats.methodsExamined);
ALOGI(" monitor-enter methods : %u", gDvm.verifierStats.monEnterMethods);
ALOGI(" instructions examined : %u", gDvm.verifierStats.instrsExamined);
ALOGI(" instructions re-examined: %u", gDvm.verifierStats.instrsReexamined);
ALOGI(" copying of register sets: %u", gDvm.verifierStats.copyRegCount);
ALOGI(" merging of register sets: %u", gDvm.verifierStats.mergeRegCount);
ALOGI(" ...that caused changes : %u", gDvm.verifierStats.mergeRegChanged);
ALOGI(" uninit searches : %u", gDvm.verifierStats.uninitSearches);
ALOGI(" max memory required : %u", gDvm.verifierStats.biggestAlloc);
#endif
}
/*
* Verify and/or optimize a specific class.
*/
static void verifyAndOptimizeClass(DexFile* pDexFile, ClassObject* clazz,
const DexClassDef* pClassDef, bool doVerify, bool doOpt)
{
const char* classDescriptor;
bool verified = false;
if (clazz->pDvmDex->pDexFile != pDexFile) {
/*
* The current DEX file defined a class that is also present in the
* bootstrap class path. The class loader favored the bootstrap
* version, which means that we have a pointer to a class that is
* (a) not the one we want to examine, and (b) mapped read-only,
* so we will seg fault if we try to rewrite instructions inside it.
*/
ALOGD("DexOpt: not verifying/optimizing '%s': multiple definitions",
clazz->descriptor);
return;
}
classDescriptor = dexStringByTypeIdx(pDexFile, pClassDef->classIdx);
/*
* First, try to verify it.
*/
if (doVerify) {
if (dvmVerifyClass(clazz)) {
/*
* Set the "is preverified" flag in the DexClassDef. We
* do it here, rather than in the ClassObject structure,
* because the DexClassDef is part of the odex file.
*/
assert((clazz->accessFlags & JAVA_FLAGS_MASK) ==
pClassDef->accessFlags);
((DexClassDef*)pClassDef)->accessFlags |= CLASS_ISPREVERIFIED;
verified = true;
} else {
// TODO: log when in verbose mode
ALOGV("DexOpt: '%s' failed verification", classDescriptor);
}
}
if (doOpt) {
bool needVerify = (gDvm.dexOptMode == OPTIMIZE_MODE_VERIFIED ||
gDvm.dexOptMode == OPTIMIZE_MODE_FULL);
if (!verified && needVerify) {
ALOGV("DexOpt: not optimizing '%s': not verified",
classDescriptor);
} else {
dvmOptimizeClass(clazz, false);
/* set the flag whether or not we actually changed anything */
((DexClassDef*)pClassDef)->accessFlags |= CLASS_ISOPTIMIZED;
}
}
}
/*
* Get the cache file name from a ClassPathEntry.
*/
static const char* getCacheFileName(const ClassPathEntry* cpe)
{
switch (cpe->kind) {
case kCpeJar:
return dvmGetJarFileCacheFileName((JarFile*) cpe->ptr);
case kCpeDex:
return dvmGetRawDexFileCacheFileName((RawDexFile*) cpe->ptr);
default:
ALOGE("DexOpt: unexpected cpe kind %d", cpe->kind);
dvmAbort();
return NULL;
}
}
/*
* Get the SHA-1 signature.
*/
static const u1* getSignature(const ClassPathEntry* cpe)
{
DvmDex* pDvmDex;
switch (cpe->kind) {
case kCpeJar:
pDvmDex = dvmGetJarFileDex((JarFile*) cpe->ptr);
break;
case kCpeDex:
pDvmDex = dvmGetRawDexFileDex((RawDexFile*) cpe->ptr);
break;
default:
ALOGE("unexpected cpe kind %d", cpe->kind);
dvmAbort();
pDvmDex = NULL; // make gcc happy
}
assert(pDvmDex != NULL);
return pDvmDex->pDexFile->pHeader->signature;
}
/*
* Dependency layout:
* 4b Source file modification time, in seconds since 1970 UTC
* 4b CRC-32 from Zip entry, or Adler32 from source DEX header
* 4b Dalvik VM build number
* 4b Number of dependency entries that follow
* Dependency entries:
* 4b Name length (including terminating null)
* var Full path of cache entry (null terminated)
* 20b SHA-1 signature from source DEX file
*
* If this changes, update DEX_OPT_MAGIC_VERS.
*/
static const size_t kMinDepSize = 4 * 4;
static const size_t kMaxDepSize = 4 * 4 + 2048; // sanity check
/*
* Read the "opt" header, verify it, then read the dependencies section
* and verify that data as well.
*
* If "sourceAvail" is "true", this will verify that "modWhen" and "crc"
* match up with what is stored in the header. If they don't, we reject
* the file so that it can be recreated from the updated original. If
* "sourceAvail" isn't set, e.g. for a .odex file, we ignore these arguments.
*
* On successful return, the file will be seeked immediately past the
* "opt" header.
*/
bool dvmCheckOptHeaderAndDependencies(int fd, bool sourceAvail, u4 modWhen,
u4 crc, bool expectVerify, bool expectOpt)
{
DexOptHeader optHdr;
u1* depData = NULL;
const u1* magic;
off_t posn;
int result = false;
ssize_t actual;
/*
* Start at the start. The "opt" header, when present, will always be
* the first thing in the file.
*/
if (lseek(fd, 0, SEEK_SET) != 0) {
ALOGE("DexOpt: failed to seek to start of file: %s", strerror(errno));
goto bail;
}
/*
* Read and do trivial verification on the opt header. The header is
* always in host byte order.
*/
actual = read(fd, &optHdr, sizeof(optHdr));
if (actual < 0) {
ALOGE("DexOpt: failed reading opt header: %s", strerror(errno));
goto bail;
} else if (actual != sizeof(optHdr)) {
ALOGE("DexOpt: failed reading opt header (got %d of %zd)",
(int) actual, sizeof(optHdr));
goto bail;
}
magic = optHdr.magic;
if (memcmp(magic, DEX_MAGIC, 4) == 0) {
/* somebody probably pointed us at the wrong file */
ALOGD("DexOpt: expected optimized DEX, found unoptimized");
goto bail;
} else if (memcmp(magic, DEX_OPT_MAGIC, 4) != 0) {
/* not a DEX file, or previous attempt was interrupted */
ALOGD("DexOpt: incorrect opt magic number (0x%02x %02x %02x %02x)",
magic[0], magic[1], magic[2], magic[3]);
goto bail;
}
if (memcmp(magic+4, DEX_OPT_MAGIC_VERS, 4) != 0) {
ALOGW("DexOpt: stale opt version (0x%02x %02x %02x %02x)",
magic[4], magic[5], magic[6], magic[7]);
goto bail;
}
if (optHdr.depsLength < kMinDepSize || optHdr.depsLength > kMaxDepSize) {
ALOGW("DexOpt: weird deps length %d, bailing", optHdr.depsLength);
goto bail;
}
/*
* Do the header flags match up with what we want?
*
* The only thing we really can't handle is incorrect byte ordering.
*/
{
const u4 matchMask = DEX_OPT_FLAG_BIG;
u4 expectedFlags = 0;
#if __BYTE_ORDER != __LITTLE_ENDIAN
expectedFlags |= DEX_OPT_FLAG_BIG;
#endif
if ((expectedFlags & matchMask) != (optHdr.flags & matchMask)) {
ALOGI("DexOpt: header flag mismatch (0x%02x vs 0x%02x, mask=0x%02x)",
expectedFlags, optHdr.flags, matchMask);
goto bail;
}
}
posn = lseek(fd, optHdr.depsOffset, SEEK_SET);
if (posn < 0) {
ALOGW("DexOpt: seek to deps failed: %s", strerror(errno));
goto bail;
}
/*
* Read all of the dependency stuff into memory.
*/
depData = (u1*) malloc(optHdr.depsLength);
if (depData == NULL) {
ALOGW("DexOpt: unable to allocate %d bytes for deps",
optHdr.depsLength);
goto bail;
}
actual = read(fd, depData, optHdr.depsLength);
if (actual < 0) {
ALOGW("DexOpt: failed reading deps: %s", strerror(errno));
goto bail;
} else if (actual != (ssize_t) optHdr.depsLength) {
ALOGW("DexOpt: failed reading deps: got %d of %d",
(int) actual, optHdr.depsLength);
goto bail;
}
/*
* Verify simple items.
*/
const u1* ptr;
u4 val;
ptr = depData;
val = read4LE(&ptr);
if (sourceAvail && val != modWhen) {
ALOGI("DexOpt: source file mod time mismatch (%08x vs %08x)",
val, modWhen);
goto bail;
}
val = read4LE(&ptr);
if (sourceAvail && val != crc) {
ALOGI("DexOpt: source file CRC mismatch (%08x vs %08x)", val, crc);
goto bail;
}
val = read4LE(&ptr);
if (val != DALVIK_VM_BUILD) {
ALOGD("DexOpt: VM build version mismatch (%d vs %d)",
val, DALVIK_VM_BUILD);
goto bail;
}
/*
* Verify dependencies on other cached DEX files. It must match
* exactly with what is currently defined in the bootclasspath.
*/
ClassPathEntry* cpe;
u4 numDeps;
numDeps = read4LE(&ptr);
ALOGV("+++ DexOpt: numDeps = %d", numDeps);
for (cpe = gDvm.bootClassPath; cpe->ptr != NULL; cpe++) {
const char* cacheFileName =
dvmPathToAbsolutePortion(getCacheFileName(cpe));
assert(cacheFileName != NULL); /* guaranteed by Class.c */
const u1* signature = getSignature(cpe);
size_t len = strlen(cacheFileName) +1;
u4 storedStrLen;
if (numDeps == 0) {
/* more entries in bootclasspath than in deps list */
ALOGI("DexOpt: not all deps represented");
goto bail;
}
storedStrLen = read4LE(&ptr);
if (len != storedStrLen ||
strcmp(cacheFileName, (const char*) ptr) != 0)
{
ALOGI("DexOpt: mismatch dep name: '%s' vs. '%s'",
cacheFileName, ptr);
goto bail;
}
ptr += storedStrLen;
if (memcmp(signature, ptr, kSHA1DigestLen) != 0) {
ALOGI("DexOpt: mismatch dep signature for '%s'", cacheFileName);
goto bail;
}
ptr += kSHA1DigestLen;
ALOGV("DexOpt: dep match on '%s'", cacheFileName);
numDeps--;
}
if (numDeps != 0) {
/* more entries in deps list than in classpath */
ALOGI("DexOpt: Some deps went away");
goto bail;
}
// consumed all data and no more?
if (ptr != depData + optHdr.depsLength) {
ALOGW("DexOpt: Spurious dep data? %d vs %d",
(int) (ptr - depData), optHdr.depsLength);
assert(false);
}
result = true;
bail:
free(depData);
return result;
}
/*
* Write the dependency info to "fd" at the current file position.
*/
static int writeDependencies(int fd, u4 modWhen, u4 crc)
{
u1* buf = NULL;
int result = -1;
ssize_t bufLen;
ClassPathEntry* cpe;
int numDeps;
/*
* Count up the number of completed entries in the bootclasspath.
*/
numDeps = 0;
bufLen = 0;
for (cpe = gDvm.bootClassPath; cpe->ptr != NULL; cpe++) {
const char* cacheFileName =
dvmPathToAbsolutePortion(getCacheFileName(cpe));
assert(cacheFileName != NULL); /* guaranteed by Class.c */
ALOGV("+++ DexOpt: found dep '%s'", cacheFileName);
numDeps++;
bufLen += strlen(cacheFileName) +1;
}
bufLen += 4*4 + numDeps * (4+kSHA1DigestLen);
buf = (u1*)malloc(bufLen);
set4LE(buf+0, modWhen);
set4LE(buf+4, crc);
set4LE(buf+8, DALVIK_VM_BUILD);
set4LE(buf+12, numDeps);
// TODO: do we want to add dvmGetInlineOpsTableLength() here? Won't
// help us if somebody replaces an existing entry, but it'd catch
// additions/removals.
u1* ptr = buf + 4*4;
for (cpe = gDvm.bootClassPath; cpe->ptr != NULL; cpe++) {
const char* cacheFileName =
dvmPathToAbsolutePortion(getCacheFileName(cpe));
assert(cacheFileName != NULL); /* guaranteed by Class.c */
const u1* signature = getSignature(cpe);
int len = strlen(cacheFileName) +1;
if (ptr + 4 + len + kSHA1DigestLen > buf + bufLen) {
ALOGE("DexOpt: overran buffer");
dvmAbort();
}
set4LE(ptr, len);
ptr += 4;
memcpy(ptr, cacheFileName, len);
ptr += len;
memcpy(ptr, signature, kSHA1DigestLen);
ptr += kSHA1DigestLen;
}
assert(ptr == buf + bufLen);
result = sysWriteFully(fd, buf, bufLen, "DexOpt dep info");
free(buf);
return result;
}
/*
* Write a block of data in "chunk" format.
*
* The chunk header fields are always in "native" byte order. If "size"
* is not a multiple of 8 bytes, the data area is padded out.
*/
static bool writeChunk(int fd, u4 type, const void* data, size_t size)
{
union { /* save a syscall by grouping these together */
char raw[8];
struct {
u4 type;
u4 size;
} ts;
} header;
assert(sizeof(header) == 8);
ALOGV("Writing chunk, type=%.4s size=%d", (char*) &type, size);
header.ts.type = type;
header.ts.size = (u4) size;
if (sysWriteFully(fd, &header, sizeof(header),
"DexOpt opt chunk header write") != 0)
{
return false;
}
if (size > 0) {
if (sysWriteFully(fd, data, size, "DexOpt opt chunk write") != 0)
return false;
}
/* if necessary, pad to 64-bit alignment */
if ((size & 7) != 0) {
int padSize = 8 - (size & 7);
ALOGV("size was %d, inserting %d pad bytes", size, padSize);
lseek(fd, padSize, SEEK_CUR);
}
assert( ((int)lseek(fd, 0, SEEK_CUR) & 7) == 0);
return true;
}
/*
* Write opt data.
*
* We have different pieces, some of which may be optional. To make the
* most effective use of space, we use a "chunk" format, with a 4-byte
* type and a 4-byte length. We guarantee 64-bit alignment for the data,
* so it can be used directly when the file is mapped for reading.
*/
static bool writeOptData(int fd, const DexClassLookup* pClassLookup,
const RegisterMapBuilder* pRegMapBuilder)
{
/* pre-computed class lookup hash table */
if (!writeChunk(fd, (u4) kDexChunkClassLookup,
pClassLookup, pClassLookup->size))
{
return false;
}
/* register maps (optional) */
if (pRegMapBuilder != NULL) {
if (!writeChunk(fd, (u4) kDexChunkRegisterMaps,
pRegMapBuilder->data, pRegMapBuilder->size))
{
return false;
}
}
/* write the end marker */
if (!writeChunk(fd, (u4) kDexChunkEnd, NULL, 0)) {
return false;
}
return true;
}
/*
* Compute a checksum on a piece of an open file.
*
* File will be positioned at end of checksummed area.
*
* Returns "true" on success.
*/
static bool computeFileChecksum(int fd, off_t start, size_t length, u4* pSum)
{
unsigned char readBuf[8192];
ssize_t actual;
uLong adler;
if (lseek(fd, start, SEEK_SET) != start) {
ALOGE("Unable to seek to start of checksum area (%ld): %s",
(long) start, strerror(errno));
return false;
}
adler = adler32(0L, Z_NULL, 0);
while (length != 0) {
size_t wanted = (length < sizeof(readBuf)) ? length : sizeof(readBuf);
actual = read(fd, readBuf, wanted);
if (actual <= 0) {
ALOGE("Read failed (%d) while computing checksum (len=%zu): %s",
(int) actual, length, strerror(errno));
return false;
}
adler = adler32(adler, readBuf, actual);
length -= actual;
}
*pSum = adler;
return true;
}
/*
* Update the Adler-32 checksum stored in the DEX file. This covers the
* swapped and optimized DEX data, but does not include the opt header
* or optimized data.
*/
static void updateChecksum(u1* addr, int len, DexHeader* pHeader)
{
/*
* Rewrite the checksum. We leave the SHA-1 signature alone.
*/
uLong adler = adler32(0L, Z_NULL, 0);
const int nonSum = sizeof(pHeader->magic) + sizeof(pHeader->checksum);
adler = adler32(adler, addr + nonSum, len - nonSum);
pHeader->checksum = adler;
}