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      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  * Linear memory allocation, tied to class loaders.
     19  */
     20 #include "Dalvik.h"
     21 
     22 #include <sys/mman.h>
     23 #include <limits.h>
     24 #include <errno.h>
     25 
     26 //#define DISABLE_LINEAR_ALLOC
     27 
     28 // Use ashmem to name the LinearAlloc section
     29 #define USE_ASHMEM 1
     30 
     31 #ifdef USE_ASHMEM
     32 #include <cutils/ashmem.h>
     33 #endif /* USE_ASHMEM */
     34 
     35 /*
     36 Overview
     37 
     38 This is intended to be a simple, fast allocator for "write-once" storage.
     39 The expectation is that this will hold small allocations that don't change,
     40 such as parts of classes (vtables, fields, methods, interfaces).  Because
     41 the lifetime of these items is tied to classes, which in turn are tied
     42 to class loaders, we associate the storage with a ClassLoader object.
     43 
     44 [ We don't yet support class unloading, and our ClassLoader implementation
     45 is in flux, so for now we just have a single global region and the
     46 "classLoader" argument is ignored. ]
     47 
     48 By storing the data here, rather than on the system heap, we reduce heap
     49 clutter, speed class loading, reduce the memory footprint (reduced heap
     50 structure overhead), and most importantly we increase the number of pages
     51 that remain shared between processes launched in "Zygote mode".
     52 
     53 The 4 bytes preceding each block contain the block length.  This allows us
     54 to support "free" and "realloc" calls in a limited way.  We don't free
     55 storage once it has been allocated, but in some circumstances it could be
     56 useful to erase storage to garbage values after a "free" or "realloc".
     57 (Bad idea if we're trying to share pages.)  We need to align to 8-byte
     58 boundaries for some architectures, so we have a 50-50 chance of getting
     59 this for free in a given block.
     60 
     61 A NULL value for the "classLoader" argument refers to the bootstrap class
     62 loader, which is never unloaded (until the VM shuts down).
     63 
     64 Because the memory is not expected to be updated, we can use mprotect to
     65 guard the pages on debug builds.  Handy when tracking down corruption.
     66 */
     67 
     68 /* alignment for allocations; must be power of 2, and currently >= hdr_xtra */
     69 #define BLOCK_ALIGN         8
     70 
     71 /* default length of memory segment (worst case is probably "dexopt") */
     72 #define DEFAULT_MAX_LENGTH  (8*1024*1024)
     73 
     74 /* leave enough space for a length word */
     75 #define HEADER_EXTRA        4
     76 
     77 /* overload the length word */
     78 #define LENGTHFLAG_FREE    0x80000000
     79 #define LENGTHFLAG_RW      0x40000000
     80 #define LENGTHFLAG_MASK    (~(LENGTHFLAG_FREE|LENGTHFLAG_RW))
     81 
     82 
     83 /* fwd */
     84 static void checkAllFree(Object* classLoader);
     85 
     86 
     87 /*
     88  * Someday, retrieve the linear alloc struct associated with a particular
     89  * class loader.  For now, always use the boostrap loader's instance.
     90  */
     91 static inline LinearAllocHdr* getHeader(Object* classLoader)
     92 {
     93     return gDvm.pBootLoaderAlloc;
     94 }
     95 
     96 /*
     97  * Convert a pointer to memory to a pointer to the block header (which is
     98  * currently just a length word).
     99  */
    100 static inline u4* getBlockHeader(void* mem)
    101 {
    102     return ((u4*) mem) -1;
    103 }
    104 
    105 /*
    106  * Create a new linear allocation block.
    107  */
    108 LinearAllocHdr* dvmLinearAllocCreate(Object* classLoader)
    109 {
    110 #ifdef DISABLE_LINEAR_ALLOC
    111     return (LinearAllocHdr*) 0x12345;
    112 #endif
    113     LinearAllocHdr* pHdr;
    114 
    115     pHdr = (LinearAllocHdr*) malloc(sizeof(*pHdr));
    116 
    117 
    118     /*
    119      * "curOffset" points to the location of the next pre-block header,
    120      * which means we have to advance to the next BLOCK_ALIGN address and
    121      * back up.
    122      *
    123      * Note we leave the first page empty (see below), and start the
    124      * first entry on the second page at an offset that ensures the next
    125      * chunk of data will be properly aligned.
    126      */
    127     assert(BLOCK_ALIGN >= HEADER_EXTRA);
    128     pHdr->curOffset = pHdr->firstOffset =
    129         (BLOCK_ALIGN-HEADER_EXTRA) + SYSTEM_PAGE_SIZE;
    130     pHdr->mapLength = DEFAULT_MAX_LENGTH;
    131 
    132 #ifdef USE_ASHMEM
    133     int fd;
    134 
    135     fd = ashmem_create_region("dalvik-LinearAlloc", DEFAULT_MAX_LENGTH);
    136     if (fd < 0) {
    137         LOGE("ashmem LinearAlloc failed %s", strerror(errno));
    138         free(pHdr);
    139         return NULL;
    140     }
    141 
    142     pHdr->mapAddr = (char*)mmap(NULL, pHdr->mapLength, PROT_READ | PROT_WRITE,
    143         MAP_PRIVATE, fd, 0);
    144     if (pHdr->mapAddr == MAP_FAILED) {
    145         LOGE("LinearAlloc mmap(%d) failed: %s", pHdr->mapLength,
    146             strerror(errno));
    147         free(pHdr);
    148         close(fd);
    149         return NULL;
    150     }
    151 
    152     close(fd);
    153 #else /*USE_ASHMEM*/
    154     // MAP_ANON is listed as "deprecated" on Linux,
    155     // but MAP_ANONYMOUS is not defined under Mac OS X.
    156     pHdr->mapAddr = mmap(NULL, pHdr->mapLength, PROT_READ | PROT_WRITE,
    157         MAP_PRIVATE | MAP_ANON, -1, 0);
    158     if (pHdr->mapAddr == MAP_FAILED) {
    159         LOGE("LinearAlloc mmap(%d) failed: %s", pHdr->mapLength,
    160             strerror(errno));
    161         free(pHdr);
    162         return NULL;
    163     }
    164 #endif /*USE_ASHMEM*/
    165 
    166     /* region expected to begin on a page boundary */
    167     assert(((int) pHdr->mapAddr & (SYSTEM_PAGE_SIZE-1)) == 0);
    168 
    169     /* the system should initialize newly-mapped memory to zero */
    170     assert(*(u4*) (pHdr->mapAddr + pHdr->curOffset) == 0);
    171 
    172     /*
    173      * Disable access to all except starting page.  We will enable pages
    174      * as we use them.  This helps prevent bad pointers from working.  The
    175      * pages start out PROT_NONE, become read/write while we access them,
    176      * then go to read-only after we finish our changes.
    177      *
    178      * We have to make the first page readable because we have 4 pad bytes,
    179      * followed by 4 length bytes, giving an initial offset of 8.  The
    180      * generic code below assumes that there could have been a previous
    181      * allocation that wrote into those 4 pad bytes, therefore the page
    182      * must have been marked readable by the previous allocation.
    183      *
    184      * We insert an extra page in here to force a break in the memory map
    185      * so we can see ourselves more easily in "showmap".  Otherwise this
    186      * stuff blends into the neighboring pages.  [TODO: do we still need
    187      * the extra page now that we have ashmem?]
    188      */
    189     if (mprotect(pHdr->mapAddr, pHdr->mapLength, PROT_NONE) != 0) {
    190         LOGW("LinearAlloc init mprotect failed: %s", strerror(errno));
    191         free(pHdr);
    192         return NULL;
    193     }
    194     if (mprotect(pHdr->mapAddr + SYSTEM_PAGE_SIZE, SYSTEM_PAGE_SIZE,
    195             ENFORCE_READ_ONLY ? PROT_READ : PROT_READ|PROT_WRITE) != 0)
    196     {
    197         LOGW("LinearAlloc init mprotect #2 failed: %s", strerror(errno));
    198         free(pHdr);
    199         return NULL;
    200     }
    201 
    202     if (ENFORCE_READ_ONLY) {
    203         /* allocate the per-page ref count */
    204         int numPages = (pHdr->mapLength+SYSTEM_PAGE_SIZE-1) / SYSTEM_PAGE_SIZE;
    205         pHdr->writeRefCount = (short*)calloc(numPages, sizeof(short));
    206         if (pHdr->writeRefCount == NULL) {
    207             free(pHdr);
    208             return NULL;
    209         }
    210     }
    211 
    212     dvmInitMutex(&pHdr->lock);
    213 
    214     LOGV("LinearAlloc: created region at %p-%p",
    215         pHdr->mapAddr, pHdr->mapAddr + pHdr->mapLength-1);
    216 
    217     return pHdr;
    218 }
    219 
    220 /*
    221  * Destroy a linear allocation area.
    222  *
    223  * We do a trivial "has everything been freed?" check before unmapping the
    224  * memory and freeing the LinearAllocHdr.
    225  */
    226 void dvmLinearAllocDestroy(Object* classLoader)
    227 {
    228 #ifdef DISABLE_LINEAR_ALLOC
    229     return;
    230 #endif
    231     LinearAllocHdr* pHdr = getHeader(classLoader);
    232     if (pHdr == NULL)
    233         return;
    234 
    235     checkAllFree(classLoader);
    236 
    237     //dvmLinearAllocDump(classLoader);
    238 
    239     if (gDvm.verboseShutdown) {
    240         LOGV("Unmapping linear allocator base=%p", pHdr->mapAddr);
    241         LOGD("LinearAlloc %p used %d of %d (%d%%)",
    242             classLoader, pHdr->curOffset, pHdr->mapLength,
    243             (pHdr->curOffset * 100) / pHdr->mapLength);
    244     }
    245 
    246     if (munmap(pHdr->mapAddr, pHdr->mapLength) != 0) {
    247         LOGW("LinearAlloc munmap(%p, %d) failed: %s",
    248             pHdr->mapAddr, pHdr->mapLength, strerror(errno));
    249     }
    250     free(pHdr);
    251 }
    252 
    253 /*
    254  * Allocate "size" bytes of storage, associated with a particular class
    255  * loader.
    256  *
    257  * It's okay for size to be zero.
    258  *
    259  * We always leave "curOffset" pointing at the next place where we will
    260  * store the header that precedes the returned storage.
    261  *
    262  * This aborts the VM on failure, so it's not necessary to check for a
    263  * NULL return value.
    264  */
    265 void* dvmLinearAlloc(Object* classLoader, size_t size)
    266 {
    267     LinearAllocHdr* pHdr = getHeader(classLoader);
    268     int startOffset, nextOffset;
    269     int lastGoodOff, firstWriteOff, lastWriteOff;
    270 
    271 #ifdef DISABLE_LINEAR_ALLOC
    272     return calloc(1, size);
    273 #endif
    274 
    275     LOGVV("--- LinearAlloc(%p, %d)", classLoader, size);
    276 
    277     /*
    278      * What we'd like to do is just determine the new end-of-alloc size
    279      * and atomic-swap the updated value in.  The trouble is that, the
    280      * first time we reach a new page, we need to call mprotect() to
    281      * make the page available, and we don't want to call mprotect() on
    282      * every allocation.  The troubled situation is:
    283      *  - thread A allocs across a page boundary, but gets preempted
    284      *    before mprotect() completes
    285      *  - thread B allocs within the new page, and doesn't call mprotect()
    286      */
    287     dvmLockMutex(&pHdr->lock);
    288 
    289     startOffset = pHdr->curOffset;
    290     assert(((startOffset + HEADER_EXTRA) & (BLOCK_ALIGN-1)) == 0);
    291 
    292     /*
    293      * Compute the new offset.  The old offset points at the address where
    294      * we will store the hidden block header, so we advance past that,
    295      * add the size of data they want, add another header's worth so we
    296      * know we have room for that, and round up to BLOCK_ALIGN.  That's
    297      * the next location where we'll put user data.  We then subtract the
    298      * chunk header size off so we're back to the header pointer.
    299      *
    300      * Examples:
    301      *   old=12 size=3 new=((12+(4*2)+3+7) & ~7)-4 = 24-4 --> 20
    302      *   old=12 size=5 new=((12+(4*2)+5+7) & ~7)-4 = 32-4 --> 28
    303      */
    304     nextOffset = ((startOffset + HEADER_EXTRA*2 + size + (BLOCK_ALIGN-1))
    305                     & ~(BLOCK_ALIGN-1)) - HEADER_EXTRA;
    306     LOGVV("--- old=%d size=%d new=%d", startOffset, size, nextOffset);
    307 
    308     if (nextOffset > pHdr->mapLength) {
    309         /*
    310          * We don't have to abort here.  We could fall back on the system
    311          * malloc(), and have our "free" call figure out what to do.  Only
    312          * works if the users of these functions actually free everything
    313          * they allocate.
    314          */
    315         LOGE("LinearAlloc exceeded capacity (%d), last=%d",
    316             pHdr->mapLength, (int) size);
    317         dvmAbort();
    318     }
    319 
    320     /*
    321      * Round up "size" to encompass the entire region, including the 0-7
    322      * pad bytes before the next chunk header.  This way we get maximum
    323      * utility out of "realloc", and when we're doing ENFORCE_READ_ONLY
    324      * stuff we always treat the full extent.
    325      */
    326     size = nextOffset - (startOffset + HEADER_EXTRA);
    327     LOGVV("--- (size now %d)", size);
    328 
    329     /*
    330      * See if we are starting on or have crossed into a new page.  If so,
    331      * call mprotect on the page(s) we're about to write to.  We have to
    332      * page-align the start address, but don't have to make the length a
    333      * SYSTEM_PAGE_SIZE multiple (but we do it anyway).
    334      *
    335      * Note that "startOffset" is not the last *allocated* byte, but rather
    336      * the offset of the first *unallocated* byte (which we are about to
    337      * write the chunk header to).  "nextOffset" is similar.
    338      *
    339      * If ENFORCE_READ_ONLY is enabled, we have to call mprotect even if
    340      * we've written to this page before, because it might be read-only.
    341      */
    342     lastGoodOff = (startOffset-1) & ~(SYSTEM_PAGE_SIZE-1);
    343     firstWriteOff = startOffset & ~(SYSTEM_PAGE_SIZE-1);
    344     lastWriteOff = (nextOffset-1) & ~(SYSTEM_PAGE_SIZE-1);
    345     LOGVV("---  lastGood=0x%04x firstWrite=0x%04x lastWrite=0x%04x",
    346         lastGoodOff, firstWriteOff, lastWriteOff);
    347     if (lastGoodOff != lastWriteOff || ENFORCE_READ_ONLY) {
    348         int cc, start, len;
    349 
    350         start = firstWriteOff;
    351         assert(start <= nextOffset);
    352         len = (lastWriteOff - firstWriteOff) + SYSTEM_PAGE_SIZE;
    353 
    354         LOGVV("---    calling mprotect(start=%d len=%d RW)", start, len);
    355         cc = mprotect(pHdr->mapAddr + start, len, PROT_READ | PROT_WRITE);
    356         if (cc != 0) {
    357             LOGE("LinearAlloc mprotect (+%d %d) failed: %s",
    358                 start, len, strerror(errno));
    359             /* we're going to fail soon, might as do it now */
    360             dvmAbort();
    361         }
    362     }
    363 
    364     /* update the ref counts on the now-writable pages */
    365     if (ENFORCE_READ_ONLY) {
    366         int i, start, end;
    367 
    368         start = firstWriteOff / SYSTEM_PAGE_SIZE;
    369         end = lastWriteOff / SYSTEM_PAGE_SIZE;
    370 
    371         LOGVV("---  marking pages %d-%d RW (alloc %d at %p)",
    372             start, end, size, pHdr->mapAddr + startOffset + HEADER_EXTRA);
    373         for (i = start; i <= end; i++)
    374             pHdr->writeRefCount[i]++;
    375     }
    376 
    377     /* stow the size in the header */
    378     if (ENFORCE_READ_ONLY)
    379         *(u4*)(pHdr->mapAddr + startOffset) = size | LENGTHFLAG_RW;
    380     else
    381         *(u4*)(pHdr->mapAddr + startOffset) = size;
    382 
    383     /*
    384      * Update data structure.
    385      */
    386     pHdr->curOffset = nextOffset;
    387 
    388     dvmUnlockMutex(&pHdr->lock);
    389     return pHdr->mapAddr + startOffset + HEADER_EXTRA;
    390 }
    391 
    392 /*
    393  * Helper function, replaces strdup().
    394  */
    395 char* dvmLinearStrdup(Object* classLoader, const char* str)
    396 {
    397 #ifdef DISABLE_LINEAR_ALLOC
    398     return strdup(str);
    399 #endif
    400     int len = strlen(str);
    401     void* mem = dvmLinearAlloc(classLoader, len+1);
    402     memcpy(mem, str, len+1);
    403     if (ENFORCE_READ_ONLY)
    404         dvmLinearSetReadOnly(classLoader, mem);
    405     return (char*) mem;
    406 }
    407 
    408 /*
    409  * "Reallocate" a piece of memory.
    410  *
    411  * If the new size is <= the old size, we return the original pointer
    412  * without doing anything.
    413  *
    414  * If the new size is > the old size, we allocate new storage, copy the
    415  * old stuff over, and mark the new stuff as free.
    416  */
    417 void* dvmLinearRealloc(Object* classLoader, void* mem, size_t newSize)
    418 {
    419 #ifdef DISABLE_LINEAR_ALLOC
    420     return realloc(mem, newSize);
    421 #endif
    422     /* make sure we have the right region (and mem != NULL) */
    423     assert(mem != NULL);
    424     assert(mem >= (void*) getHeader(classLoader)->mapAddr &&
    425            mem < (void*) (getHeader(classLoader)->mapAddr +
    426                           getHeader(classLoader)->curOffset));
    427 
    428     const u4* pLen = getBlockHeader(mem);
    429     LOGV("--- LinearRealloc(%d) old=%d", newSize, *pLen);
    430 
    431     /* handle size reduction case */
    432     if (*pLen >= newSize) {
    433         if (ENFORCE_READ_ONLY)
    434             dvmLinearSetReadWrite(classLoader, mem);
    435         return mem;
    436     }
    437 
    438     void* newMem;
    439 
    440     newMem = dvmLinearAlloc(classLoader, newSize);
    441     assert(newMem != NULL);
    442     memcpy(newMem, mem, *pLen);
    443     dvmLinearFree(classLoader, mem);
    444 
    445     return newMem;
    446 }
    447 
    448 
    449 /*
    450  * Update the read/write status of one or more pages.
    451  */
    452 static void updatePages(Object* classLoader, void* mem, int direction)
    453 {
    454     LinearAllocHdr* pHdr = getHeader(classLoader);
    455     dvmLockMutex(&pHdr->lock);
    456 
    457     /* make sure we have the right region */
    458     assert(mem >= (void*) pHdr->mapAddr &&
    459            mem < (void*) (pHdr->mapAddr + pHdr->curOffset));
    460 
    461     u4* pLen = getBlockHeader(mem);
    462     u4 len = *pLen & LENGTHFLAG_MASK;
    463     int firstPage, lastPage;
    464 
    465     firstPage = ((u1*)pLen - (u1*)pHdr->mapAddr) / SYSTEM_PAGE_SIZE;
    466     lastPage = ((u1*)mem - (u1*)pHdr->mapAddr + (len-1)) / SYSTEM_PAGE_SIZE;
    467     LOGVV("--- updating pages %d-%d (%d)", firstPage, lastPage, direction);
    468 
    469     int i, cc;
    470 
    471     /*
    472      * Update individual pages.  We could do some sort of "lazy update" to
    473      * combine mprotect calls, but that's almost certainly more trouble
    474      * than it's worth.
    475      */
    476     for (i = firstPage; i <= lastPage; i++) {
    477         if (direction < 0) {
    478             /*
    479              * Trying to mark read-only.
    480              */
    481             if (i == firstPage) {
    482                 if ((*pLen & LENGTHFLAG_RW) == 0) {
    483                     LOGW("Double RO on %p", mem);
    484                     dvmAbort();
    485                 } else
    486                     *pLen &= ~LENGTHFLAG_RW;
    487             }
    488 
    489             if (pHdr->writeRefCount[i] == 0) {
    490                 LOGE("Can't make page %d any less writable", i);
    491                 dvmAbort();
    492             }
    493             pHdr->writeRefCount[i]--;
    494             if (pHdr->writeRefCount[i] == 0) {
    495                 LOGVV("---  prot page %d RO", i);
    496                 cc = mprotect(pHdr->mapAddr + SYSTEM_PAGE_SIZE * i,
    497                         SYSTEM_PAGE_SIZE, PROT_READ);
    498                 assert(cc == 0);
    499             }
    500         } else {
    501             /*
    502              * Trying to mark writable.
    503              */
    504             if (pHdr->writeRefCount[i] >= 32767) {
    505                 LOGE("Can't make page %d any more writable", i);
    506                 dvmAbort();
    507             }
    508             if (pHdr->writeRefCount[i] == 0) {
    509                 LOGVV("---  prot page %d RW", i);
    510                 cc = mprotect(pHdr->mapAddr + SYSTEM_PAGE_SIZE * i,
    511                         SYSTEM_PAGE_SIZE, PROT_READ | PROT_WRITE);
    512                 assert(cc == 0);
    513             }
    514             pHdr->writeRefCount[i]++;
    515 
    516             if (i == firstPage) {
    517                 if ((*pLen & LENGTHFLAG_RW) != 0) {
    518                     LOGW("Double RW on %p", mem);
    519                     dvmAbort();
    520                 } else
    521                     *pLen |= LENGTHFLAG_RW;
    522             }
    523         }
    524     }
    525 
    526     dvmUnlockMutex(&pHdr->lock);
    527 }
    528 
    529 /*
    530  * Try to mark the pages in which a chunk of memory lives as read-only.
    531  * Whether or not the pages actually change state depends on how many
    532  * others are trying to access the same pages.
    533  *
    534  * Only call here if ENFORCE_READ_ONLY is true.
    535  */
    536 void dvmLinearSetReadOnly(Object* classLoader, void* mem)
    537 {
    538 #ifdef DISABLE_LINEAR_ALLOC
    539     return;
    540 #endif
    541     updatePages(classLoader, mem, -1);
    542 }
    543 
    544 /*
    545  * Make the pages on which "mem" sits read-write.
    546  *
    547  * This covers the header as well as the data itself.  (We could add a
    548  * "header-only" mode for dvmLinearFree.)
    549  *
    550  * Only call here if ENFORCE_READ_ONLY is true.
    551  */
    552 void dvmLinearSetReadWrite(Object* classLoader, void* mem)
    553 {
    554 #ifdef DISABLE_LINEAR_ALLOC
    555     return;
    556 #endif
    557     updatePages(classLoader, mem, 1);
    558 }
    559 
    560 /*
    561  * Mark an allocation as free.
    562  */
    563 void dvmLinearFree(Object* classLoader, void* mem)
    564 {
    565 #ifdef DISABLE_LINEAR_ALLOC
    566     free(mem);
    567     return;
    568 #endif
    569     if (mem == NULL)
    570         return;
    571 
    572     /* make sure we have the right region */
    573     assert(mem >= (void*) getHeader(classLoader)->mapAddr &&
    574            mem < (void*) (getHeader(classLoader)->mapAddr +
    575                           getHeader(classLoader)->curOffset));
    576 
    577     if (ENFORCE_READ_ONLY)
    578         dvmLinearSetReadWrite(classLoader, mem);
    579 
    580     u4* pLen = getBlockHeader(mem);
    581     *pLen |= LENGTHFLAG_FREE;
    582 
    583     if (ENFORCE_READ_ONLY)
    584         dvmLinearSetReadOnly(classLoader, mem);
    585 }
    586 
    587 /*
    588  * For debugging, dump the contents of a linear alloc area.
    589  *
    590  * We grab the lock so that the header contents and list output are
    591  * consistent.
    592  */
    593 void dvmLinearAllocDump(Object* classLoader)
    594 {
    595 #ifdef DISABLE_LINEAR_ALLOC
    596     return;
    597 #endif
    598     LinearAllocHdr* pHdr = getHeader(classLoader);
    599 
    600     dvmLockMutex(&pHdr->lock);
    601 
    602     LOGI("LinearAlloc classLoader=%p", classLoader);
    603     LOGI("  mapAddr=%p mapLength=%d firstOffset=%d",
    604         pHdr->mapAddr, pHdr->mapLength, pHdr->firstOffset);
    605     LOGI("  curOffset=%d", pHdr->curOffset);
    606 
    607     int off = pHdr->firstOffset;
    608     u4 rawLen, fullLen;
    609 
    610     while (off < pHdr->curOffset) {
    611         rawLen = *(u4*) (pHdr->mapAddr + off);
    612         fullLen = ((HEADER_EXTRA*2 + (rawLen & LENGTHFLAG_MASK))
    613                     & ~(BLOCK_ALIGN-1));
    614 
    615         LOGI("  %p (%3d): %clen=%d%s", pHdr->mapAddr + off + HEADER_EXTRA,
    616             (int) ((off + HEADER_EXTRA) / SYSTEM_PAGE_SIZE),
    617             (rawLen & LENGTHFLAG_FREE) != 0 ? '*' : ' ',
    618             rawLen & LENGTHFLAG_MASK,
    619             (rawLen & LENGTHFLAG_RW) != 0 ? " [RW]" : "");
    620 
    621         off += fullLen;
    622     }
    623 
    624     if (ENFORCE_READ_ONLY) {
    625         LOGI("writeRefCount map:");
    626 
    627         int numPages = (pHdr->mapLength+SYSTEM_PAGE_SIZE-1) / SYSTEM_PAGE_SIZE;
    628         int zstart = 0;
    629         int i;
    630 
    631         for (i = 0; i < numPages; i++) {
    632             int count = pHdr->writeRefCount[i];
    633 
    634             if (count != 0) {
    635                 if (zstart < i-1)
    636                     printf(" %d-%d: zero\n", zstart, i-1);
    637                 else if (zstart == i-1)
    638                     printf(" %d: zero\n", zstart);
    639                 zstart = i+1;
    640                 printf(" %d: %d\n", i, count);
    641             }
    642         }
    643         if (zstart < i)
    644             printf(" %d-%d: zero\n", zstart, i-1);
    645     }
    646 
    647     LOGD("LinearAlloc %p using %d of %d (%d%%)",
    648         classLoader, pHdr->curOffset, pHdr->mapLength,
    649         (pHdr->curOffset * 100) / pHdr->mapLength);
    650 
    651     dvmUnlockMutex(&pHdr->lock);
    652 }
    653 
    654 /*
    655  * Verify that all blocks are freed.
    656  *
    657  * This should only be done as we're shutting down, but there could be a
    658  * daemon thread that's still trying to do something, so we grab the locks.
    659  */
    660 static void checkAllFree(Object* classLoader)
    661 {
    662 #ifdef DISABLE_LINEAR_ALLOC
    663     return;
    664 #endif
    665     LinearAllocHdr* pHdr = getHeader(classLoader);
    666 
    667     dvmLockMutex(&pHdr->lock);
    668 
    669     int off = pHdr->firstOffset;
    670     u4 rawLen, fullLen;
    671 
    672     while (off < pHdr->curOffset) {
    673         rawLen = *(u4*) (pHdr->mapAddr + off);
    674         fullLen = ((HEADER_EXTRA*2 + (rawLen & LENGTHFLAG_MASK))
    675                     & ~(BLOCK_ALIGN-1));
    676 
    677         if ((rawLen & LENGTHFLAG_FREE) == 0) {
    678             LOGW("LinearAlloc %p not freed: %p len=%d", classLoader,
    679                 pHdr->mapAddr + off + HEADER_EXTRA, rawLen & LENGTHFLAG_MASK);
    680         }
    681 
    682         off += fullLen;
    683     }
    684 
    685     dvmUnlockMutex(&pHdr->lock);
    686 }
    687 
    688 /*
    689  * Determine if [start, start+length) is contained in the in-use area of
    690  * a single LinearAlloc.  The full set of linear allocators is scanned.
    691  *
    692  * [ Since we currently only have one region, this is pretty simple.  In
    693  * the future we'll need to traverse a table of class loaders. ]
    694  */
    695 bool dvmLinearAllocContains(const void* start, size_t length)
    696 {
    697     LinearAllocHdr* pHdr = getHeader(NULL);
    698 
    699     if (pHdr == NULL)
    700         return false;
    701 
    702     return (char*) start >= pHdr->mapAddr &&
    703            ((char*)start + length) <= (pHdr->mapAddr + pHdr->curOffset);
    704 }
    705