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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  * System utilities.
     19  */
     20 #include "DexFile.h"
     21 #include "SysUtil.h"
     22 
     23 #include <stdlib.h>
     24 #include <stdio.h>
     25 #include <unistd.h>
     26 #include <string.h>
     27 #ifdef HAVE_POSIX_FILEMAP
     28 # include <sys/mman.h>
     29 #endif
     30 #include <limits.h>
     31 #include <errno.h>
     32 
     33 #include <JNIHelp.h>        // TEMP_FAILURE_RETRY may or may not be in unistd
     34 
     35 
     36 /*
     37  * Create an anonymous shared memory segment large enough to hold "length"
     38  * bytes.  The actual segment may be larger because mmap() operates on
     39  * page boundaries (usually 4K).
     40  */
     41 static void* sysCreateAnonShmem(size_t length)
     42 {
     43 #ifdef HAVE_POSIX_FILEMAP
     44     void* ptr;
     45 
     46     ptr = mmap(NULL, length, PROT_READ | PROT_WRITE,
     47             MAP_SHARED | MAP_ANON, -1, 0);
     48     if (ptr == MAP_FAILED) {
     49         ALOGW("mmap(%d, RW, SHARED|ANON) failed: %s", (int) length,
     50             strerror(errno));
     51         return NULL;
     52     }
     53 
     54     return ptr;
     55 #else
     56     ALOGE("sysCreateAnonShmem not implemented.");
     57     return NULL;
     58 #endif
     59 }
     60 
     61 /*
     62  * Create a private anonymous storage area.
     63  */
     64 int sysCreatePrivateMap(size_t length, MemMapping* pMap)
     65 {
     66     void* memPtr;
     67 
     68     memPtr = sysCreateAnonShmem(length);
     69     if (memPtr == NULL)
     70         return -1;
     71 
     72     pMap->addr = pMap->baseAddr = memPtr;
     73     pMap->length = pMap->baseLength = length;
     74     return 0;
     75 }
     76 
     77 /*
     78  * Determine the current offset and remaining length of the open file.
     79  */
     80 static int getFileStartAndLength(int fd, off_t *start_, size_t *length_)
     81 {
     82     off_t start, end;
     83     size_t length;
     84 
     85     assert(start_ != NULL);
     86     assert(length_ != NULL);
     87 
     88     start = lseek(fd, 0L, SEEK_CUR);
     89     end = lseek(fd, 0L, SEEK_END);
     90     (void) lseek(fd, start, SEEK_SET);
     91 
     92     if (start == (off_t) -1 || end == (off_t) -1) {
     93         ALOGE("could not determine length of file");
     94         return -1;
     95     }
     96 
     97     length = end - start;
     98     if (length == 0) {
     99         ALOGE("file is empty");
    100         return -1;
    101     }
    102 
    103     *start_ = start;
    104     *length_ = length;
    105 
    106     return 0;
    107 }
    108 
    109 #ifndef HAVE_POSIX_FILEMAP
    110 int sysFakeMapFile(int fd, MemMapping* pMap)
    111 {
    112     /* No MMAP, just fake it by copying the bits.
    113        For Win32 we could use MapViewOfFile if really necessary
    114        (see libs/utils/FileMap.cpp).
    115     */
    116     off_t start;
    117     size_t length;
    118     void* memPtr;
    119 
    120     assert(pMap != NULL);
    121 
    122     if (getFileStartAndLength(fd, &start, &length) < 0)
    123         return -1;
    124 
    125     memPtr = malloc(length);
    126     if (read(fd, memPtr, length) < 0) {
    127         ALOGW("read(fd=%d, start=%d, length=%d) failed: %s", (int) length,
    128             fd, (int) start, strerror(errno));
    129         return -1;
    130     }
    131 
    132     pMap->baseAddr = pMap->addr = memPtr;
    133     pMap->baseLength = pMap->length = length;
    134 
    135     return 0;
    136 }
    137 #endif
    138 
    139 /*
    140  * Map a file (from fd's current offset) into a private, read-write memory
    141  * segment that will be marked read-only (a/k/a "writable read-only").  The
    142  * file offset must be a multiple of the system page size.
    143  *
    144  * In some cases the mapping will be fully writable (e.g. for files on
    145  * FAT filesystems).
    146  *
    147  * On success, returns 0 and fills out "pMap".  On failure, returns a nonzero
    148  * value and does not disturb "pMap".
    149  */
    150 int sysMapFileInShmemWritableReadOnly(int fd, MemMapping* pMap)
    151 {
    152 #ifdef HAVE_POSIX_FILEMAP
    153     off_t start;
    154     size_t length;
    155     void* memPtr;
    156 
    157     assert(pMap != NULL);
    158 
    159     if (getFileStartAndLength(fd, &start, &length) < 0)
    160         return -1;
    161 
    162     memPtr = mmap(NULL, length, PROT_READ | PROT_WRITE, MAP_FILE | MAP_PRIVATE,
    163             fd, start);
    164     if (memPtr == MAP_FAILED) {
    165         ALOGW("mmap(%d, R/W, FILE|PRIVATE, %d, %d) failed: %s", (int) length,
    166             fd, (int) start, strerror(errno));
    167         return -1;
    168     }
    169     if (mprotect(memPtr, length, PROT_READ) < 0) {
    170         /* this fails with EACCESS on FAT filesystems, e.g. /sdcard */
    171         int err = errno;
    172         ALOGV("mprotect(%p, %d, PROT_READ) failed: %s",
    173             memPtr, length, strerror(err));
    174         ALOGD("mprotect(RO) failed (%d), file will remain read-write", err);
    175     }
    176 
    177     pMap->baseAddr = pMap->addr = memPtr;
    178     pMap->baseLength = pMap->length = length;
    179 
    180     return 0;
    181 #else
    182     return sysFakeMapFile(fd, pMap);
    183 #endif
    184 }
    185 
    186 /*
    187  * Map part of a file into a shared, read-only memory segment.  The "start"
    188  * offset is absolute, not relative.
    189  *
    190  * On success, returns 0 and fills out "pMap".  On failure, returns a nonzero
    191  * value and does not disturb "pMap".
    192  */
    193 int sysMapFileSegmentInShmem(int fd, off_t start, size_t length,
    194     MemMapping* pMap)
    195 {
    196 #ifdef HAVE_POSIX_FILEMAP
    197     size_t actualLength;
    198     off_t actualStart;
    199     int adjust;
    200     void* memPtr;
    201 
    202     assert(pMap != NULL);
    203 
    204     /* adjust to be page-aligned */
    205     adjust = start % SYSTEM_PAGE_SIZE;
    206     actualStart = start - adjust;
    207     actualLength = length + adjust;
    208 
    209     memPtr = mmap(NULL, actualLength, PROT_READ, MAP_FILE | MAP_SHARED,
    210                 fd, actualStart);
    211     if (memPtr == MAP_FAILED) {
    212         ALOGW("mmap(%d, R, FILE|SHARED, %d, %d) failed: %s",
    213             (int) actualLength, fd, (int) actualStart, strerror(errno));
    214         return -1;
    215     }
    216 
    217     pMap->baseAddr = memPtr;
    218     pMap->baseLength = actualLength;
    219     pMap->addr = (char*)memPtr + adjust;
    220     pMap->length = length;
    221 
    222     LOGVV("mmap seg (st=%d ln=%d): bp=%p bl=%d ad=%p ln=%d",
    223         (int) start, (int) length,
    224         pMap->baseAddr, (int) pMap->baseLength,
    225         pMap->addr, (int) pMap->length);
    226 
    227     return 0;
    228 #else
    229     ALOGE("sysMapFileSegmentInShmem not implemented.");
    230     return -1;
    231 #endif
    232 }
    233 
    234 /*
    235  * Change the access rights on one or more pages to read-only or read-write.
    236  *
    237  * Returns 0 on success.
    238  */
    239 int sysChangeMapAccess(void* addr, size_t length, int wantReadWrite,
    240     MemMapping* pMap)
    241 {
    242 #ifdef HAVE_POSIX_FILEMAP
    243     /*
    244      * Verify that "addr" is part of this mapping file.
    245      */
    246     if (addr < pMap->baseAddr ||
    247         (u1*)addr >= (u1*)pMap->baseAddr + pMap->baseLength)
    248     {
    249         ALOGE("Attempted to change %p; map is %p - %p",
    250             addr, pMap->baseAddr, (u1*)pMap->baseAddr + pMap->baseLength);
    251         return -1;
    252     }
    253 
    254     /*
    255      * Align "addr" to a page boundary and adjust "length" appropriately.
    256      * (The address must be page-aligned, the length doesn't need to be,
    257      * but we do need to ensure we cover the same range.)
    258      */
    259     u1* alignAddr = (u1*) ((uintptr_t) addr & ~(SYSTEM_PAGE_SIZE-1));
    260     size_t alignLength = length + ((u1*) addr - alignAddr);
    261 
    262     //ALOGI("%p/%zd --> %p/%zd", addr, length, alignAddr, alignLength);
    263     int prot = wantReadWrite ? (PROT_READ|PROT_WRITE) : (PROT_READ);
    264     if (mprotect(alignAddr, alignLength, prot) != 0) {
    265         int err = errno;
    266         ALOGV("mprotect (%p,%zd,%d) failed: %s",
    267             alignAddr, alignLength, prot, strerror(errno));
    268         return (errno != 0) ? errno : -1;
    269     }
    270 #endif
    271 
    272     /* for "fake" mapping, no need to do anything */
    273     return 0;
    274 }
    275 
    276 /*
    277  * Release a memory mapping.
    278  */
    279 void sysReleaseShmem(MemMapping* pMap)
    280 {
    281 #ifdef HAVE_POSIX_FILEMAP
    282     if (pMap->baseAddr == NULL && pMap->baseLength == 0)
    283         return;
    284 
    285     if (munmap(pMap->baseAddr, pMap->baseLength) < 0) {
    286         ALOGW("munmap(%p, %d) failed: %s",
    287             pMap->baseAddr, (int)pMap->baseLength, strerror(errno));
    288     } else {
    289         ALOGV("munmap(%p, %d) succeeded", pMap->baseAddr, pMap->baseLength);
    290         pMap->baseAddr = NULL;
    291         pMap->baseLength = 0;
    292     }
    293 #else
    294     /* Free the bits allocated by sysMapFileInShmem. */
    295     if (pMap->baseAddr != NULL) {
    296       free(pMap->baseAddr);
    297       pMap->baseAddr = NULL;
    298     }
    299     pMap->baseLength = 0;
    300 #endif
    301 }
    302 
    303 /*
    304  * Make a copy of a MemMapping.
    305  */
    306 void sysCopyMap(MemMapping* dst, const MemMapping* src)
    307 {
    308     memcpy(dst, src, sizeof(MemMapping));
    309 }
    310 
    311 /*
    312  * Write until all bytes have been written.
    313  *
    314  * Returns 0 on success, or an errno value on failure.
    315  */
    316 int sysWriteFully(int fd, const void* buf, size_t count, const char* logMsg)
    317 {
    318     while (count != 0) {
    319         ssize_t actual = TEMP_FAILURE_RETRY(write(fd, buf, count));
    320         if (actual < 0) {
    321             int err = errno;
    322             ALOGE("%s: write failed: %s", logMsg, strerror(err));
    323             return err;
    324         } else if (actual != (ssize_t) count) {
    325             ALOGD("%s: partial write (will retry): (%d of %zd)",
    326                 logMsg, (int) actual, count);
    327             buf = (const void*) (((const u1*) buf) + actual);
    328         }
    329         count -= actual;
    330     }
    331 
    332     return 0;
    333 }
    334 
    335 /* See documentation comment in header file. */
    336 int sysCopyFileToFile(int outFd, int inFd, size_t count)
    337 {
    338     const size_t kBufSize = 32768;
    339     unsigned char buf[kBufSize];
    340 
    341     while (count != 0) {
    342         size_t getSize = (count > kBufSize) ? kBufSize : count;
    343 
    344         ssize_t actual = TEMP_FAILURE_RETRY(read(inFd, buf, getSize));
    345         if (actual != (ssize_t) getSize) {
    346             ALOGW("sysCopyFileToFile: copy read failed (%d vs %zd)",
    347                 (int) actual, getSize);
    348             return -1;
    349         }
    350 
    351         if (sysWriteFully(outFd, buf, getSize, "sysCopyFileToFile") != 0)
    352             return -1;
    353 
    354         count -= getSize;
    355     }
    356 
    357     return 0;
    358 }
    359