/*
* Map a file (from fd's current offset) into a private, read-write memory
* segment that will be marked read-only (a/k/a "writable read-only"). The
* file offset must be a multiple of the system page size.
*
* In some cases the mapping will be fully writable (e.g. for files on
* FAT filesystems).
*
* On success, returns 0 and fills out "pMap". On failure, returns a nonzero
* value and does not disturb "pMap".
*/
int sysMapFileInShmemWritableReadOnly(int fd, MemMapping* pMap)
{
#ifdef HAVE_POSIX_FILEMAP
off_t start;
size_t length;
void* memPtr;
assert(pMap != NULL);
if (getFileStartAndLength(fd, &start, &length) < 0)
return -1;
memPtr = mmap(NULL, length, PROT_READ | PROT_WRITE, MAP_FILE | MAP_PRIVATE,
fd, start);
if (memPtr == MAP_FAILED) {
ALOGW("mmap(%d, R/W, FILE|PRIVATE, %d, %d) failed: %s", (int) length,
fd, (int) start, strerror(errno));
return -1;
}
if (mprotect(memPtr, length, PROT_READ) < 0) {
/* this fails with EACCESS on FAT filesystems, e.g. /sdcard */
int err = errno;
ALOGV("mprotect(%p, %d, PROT_READ) failed: %s",
memPtr, length, strerror(err));
ALOGD("mprotect(RO) failed (%d), file will remain read-write", err);
}
pMap->baseAddr = pMap->addr = memPtr;
pMap->baseLength = pMap->length = length;
return 0;
#else
return sysFakeMapFile(fd, pMap);
#endif
}
/*
* Map a file (from fd's current offset) into a shared, read-only memory
* segment. The file offset must be a multiple of the system page size.
*
* On success, returns 0 and fills out "pMap". On failure, returns a nonzero
* value and does not disturb "pMap".
*/
int sysMapFileInShmemReadOnly(int fd, MemMapping* pMap)
{
#ifdef HAVE_POSIX_FILEMAP
off_t start;
size_t length;
void* memPtr;
assert(pMap != NULL);
if (getFileStartAndLength(fd, &start, &length) < 0)
return -1;
memPtr = mmap(NULL, length, PROT_READ, MAP_FILE | MAP_SHARED, fd, start);
if (memPtr == MAP_FAILED) {
ALOGW("mmap(%d, RO, FILE|SHARED, %d, %d) failed: %s", (int) length,
fd, (int) start, strerror(errno));
return -1;
}
pMap->baseAddr = pMap->addr = memPtr;
pMap->baseLength = pMap->length = length;
return 0;
#else
return sysFakeMapFile(fd, pMap);
#endif
}
