Restore support for DEX on FAT.
The recent change to mmap(read-write)+mprotect(read-only) doesn't seem
to work on FAT filesystems like /sdcard. This caused problems for the
code that opens Zip files and the code that opens DEX files.
This change splits the "map file" function into "read only" and
"writable read only" versions, using the former for Zip and the latter
for DEX. Further, failure to mprotect(read-only) is now considered a
soft failure and only causes a warning.
The only apps that will be affected by this are those using /sdcard to
hold optimized DEX data for "plugin" APKs.
Also: moved the non-HAVE_POSIX_FILEMAP implementation of file mapping
into a shared function. (Could probably go away entirely.)
Also: fixed the expected output for test 071.
diff --git a/libdex/SysUtil.c b/libdex/SysUtil.c
index 08dc67c..eaa612b 100644
--- a/libdex/SysUtil.c
+++ b/libdex/SysUtil.c
@@ -160,7 +160,7 @@
* On success, returns 0 and fills out "pMap". On failure, returns a nonzero
* value and does not disturb "pMap".
*/
-int sysMapFileInShmem(int fd, MemMapping* pMap)
+int sysMapFileInShmemReadOnly(int fd, MemMapping* pMap)
{
#ifdef HAVE_POSIX_FILEMAP
off_t start;
@@ -172,32 +172,72 @@
if (getFileStartAndLength(fd, &start, &length) < 0)
return -1;
- /*
- * This was originally (PROT_READ, MAP_SHARED), but we want to be able
- * to make local edits for verification errors and debugger breakpoints.
- * So we map it read-write and private, but use mprotect to mark the
- * pages read-only. This should yield identical results so long as the
- * pages are left read-only.
- */
- memPtr = mmap(NULL, length, PROT_READ | PROT_WRITE, MAP_FILE | MAP_PRIVATE,
- fd, start);
+ memPtr = mmap(NULL, length, PROT_READ, MAP_FILE | MAP_SHARED, fd, start);
if (memPtr == MAP_FAILED) {
- LOGW("mmap(%d, R/W, FILE|PRIVATE, %d, %d) failed: %s\n", (int) length,
+ LOGW("mmap(%d, RO, FILE|SHARED, %d, %d) failed: %s\n", (int) length,
fd, (int) start, strerror(errno));
return -1;
}
- if (mprotect(memPtr, length, PROT_READ) < 0) {
- LOGW("mprotect(%p, %d, PROT_READ) failed: %s\n",
- memPtr, length, strerror(errno));
- (void) munmap(memPtr, length);
- return -1;
- }
pMap->baseAddr = pMap->addr = memPtr;
pMap->baseLength = pMap->length = length;
return 0;
#else
+ sysFakeMapFile(fd, pMap);
+#endif
+}
+
+/*
+ * 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) {
+ LOGW("mmap(%d, R/W, FILE|PRIVATE, %d, %d) failed: %s\n", (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;
+ LOGV("mprotect(%p, %d, PROT_READ) failed: %s\n",
+ memPtr, length, strerror(err));
+ LOGD("mprotect(RO) failed (%d), file will remain read-write\n", err);
+ }
+
+ pMap->baseAddr = pMap->addr = memPtr;
+ pMap->baseLength = pMap->length = length;
+
+ return 0;
+#else
+ sysFakeMapFile(fd, pMap);
+#endif
+}
+
+#ifndef HAVE_POSIX_FILEMAP
+int sysFakeMapFile(int fd, MemMapping* pMap)
+{
/* No MMAP, just fake it by copying the bits.
For Win32 we could use MapViewOfFile if really necessary
(see libs/utils/FileMap.cpp).
@@ -222,8 +262,8 @@
pMap->baseLength = pMap->length = length;
return 0;
-#endif
}
+#endif
/*
* Map part of a file (from fd's current offset) into a shared, read-only
@@ -314,7 +354,7 @@
int prot = wantReadWrite ? (PROT_READ|PROT_WRITE) : (PROT_READ);
if (mprotect(alignAddr, alignLength, prot) != 0) {
int err = errno;
- LOGW("mprotect (%p,%zd,%d) failed: %s\n",
+ LOGV("mprotect (%p,%zd,%d) failed: %s\n",
alignAddr, alignLength, prot, strerror(errno));
return (errno != 0) ? errno : -1;
}