Android - failure on loading library

Question

I have a similar problem to this question, but slightly different. I have compiled a .so library to use with JNI. Because it is large (15 MB), I am putting it on the SDCard instead of in the standard application place.

The file is called libSample.so and it's located at /data/library/libSample.so

I load it in a static initialization block:

try {
        File sdcard = Environment.getExternalStorageDirectory();
        File libraryLoc = new File(sdcard.getAbsolutePath() + "/library/libSample.so");
        Log.i("Library", "Does the library exist?" + libraryLoc.exists());

        System.load(libraryLoc.getAbsolutePath());
    }
    catch (UnsatisfiedLinkError e) {
        Log.e("Translator", e.getMessage());
        Log.e("Translator", e.toString());
    }

Here's the relevant logcat output:

09-02 16:42:58.882: DEBUG/dalvikvm(4185): Trying to load lib /data/data/com.example.hellojni/lib/libhello-jni.so 0x434fb6f8
09-02 16:42:58.892: DEBUG/dalvikvm(4185): Added shared lib /data/data/com.example.hellojni/lib/libhello-jni.so 0x434fb6f8
09-02 16:42:58.892: DEBUG/dalvikvm(4185): No JNI_OnLoad found in /data/data/com.example.hellojni/lib/libhello-jni.so 0x434fb6f8
09-02 16:42:58.892: INFO/Library(4185): Library exists: true
09-02 16:42:58.902: INFO/Library(4185): Library can be read: true
09-02 16:42:58.902: DEBUG/dalvikvm(4185): Trying to load lib /sdcard/library/libSample.so 0x434fb6f8
09-02 16:42:58.902: INFO/dalvikvm(4185): Unable to dlopen(/sdcard/library/libSample.so): Cannot find library
09-02 16:42:58.912: ERROR/Translator(4185): Library /sdcard/library/libSample.so not found
09-02 16:42:58.912: ERROR/Translator(4185): java.lang.UnsatisfiedLinkError: Library /sdcard/library/libSample.so not found

Any idea what's wrong?

I read the post about can android load dll's from sdcard in native mode which said that the sdcard cannot be used to load libraries, so I moved the .so into /data/data/com.example.hellojni/lib/libSample.so (the private app data storage location). No change:

09-02 16:53:18.332: DEBUG/dalvikvm(4515): Trying to load lib /data/data/com.example.hellojni/lib/libhello-jni.so 0x434fb6f8
09-02 16:53:18.342: DEBUG/dalvikvm(4515): Added shared lib /data/data/com.example.hellojni/lib/libhello-jni.so 0x434fb6f8
09-02 16:53:18.342: DEBUG/dalvikvm(4515): No JNI_OnLoad found in /data/data/com.example.hellojni/lib/libhello-jni.so 0x434fb6f8
09-02 16:53:18.352: INFO/Library(4515): Library exists: true
09-02 16:53:18.352: INFO/Library(4515): Library can be read: true
09-02 16:53:18.352: DEBUG/dalvikvm(4515): Trying to load lib /data/data/com.example.hellojni/lib/libSample.so 0x434fb6f8
09-02 16:53:18.482: INFO/dalvikvm(4515): Unable to dlopen(/data/data/com.example.hellojni/lib/libSample.so): Cannot find library
09-02 16:53:18.492: ERROR/Translator(4515): Library /data/data/com.example.hellojni/lib/libSample.so not found
09-02 16:53:18.492: ERROR/Translator(4515): java.lang.UnsatisfiedLinkError: Library /data/data/com.example.hellojni/lib/libSample.so not found

What I don't understand is that clearly the library exists, and the OS is trying to load it ... so what would make it fail?

Following the advice of one of the commentors, I tried attaching via strace to get more detailed error information. The log can be found as a github gist.

The error appears to be on lines 47-51:

mprotect(0x4235d000, 4096, PROT_READ)   = 0
ioctl(1, SNDCTL_TMR_TIMEBASE or TCGETS, 0xbeb58080) = -1 ENOTTY (Not a typewriter)
write(1, "bionic/linker/linker.c:1243| ERROR:    34 unknown reloc type 3 @ 0x811a854c (2441)\n", 83) = 83
write(1, "bionic/linker/linker.c:1641| ERROR: failed to link /data/data/com.example.hellojni/lib/libSample.so\n", 100) = 100
munmap(0x81000000, 8839168)             = 0

Here's the readelf of the library:

arm-eabi-readelf -d libSample.so 

Dynamic section at offset 0x80b648 contains 17 entries:
  Tag        Type                         Name/Value
 0x00000019 (INIT_ARRAY)                 0x7ff234
 0x0000001b (INIT_ARRAYSZ)               76 (bytes)
 0x00000004 (HASH)                       0xd4
 0x00000005 (STRTAB)                     0x7f41c
 0x00000006 (SYMTAB)                     0x2650c
 0x0000000a (STRSZ)                      1197287 (bytes)
 0x0000000b (SYMENT)                     16 (bytes)
 0x00000003 (PLTGOT)                     0x80c6f0
 0x00000002 (PLTRELSZ)                   76480 (bytes)
 0x00000014 (PLTREL)                     REL
 0x00000017 (JMPREL)                     0x1ccb84
 0x00000011 (REL)                        0x1a3904
 0x00000012 (RELSZ)                      168576 (bytes)
 0x00000013 (RELENT)                     8 (bytes)
 0x00000016 (TEXTREL)                    0x0
 0x6ffffffa (RELCOUNT)                   2412
 0x00000000 (NULL)                       0x0

Answer 1

I think it may be more likely that a library that your .so depends upon is not being found. But that is only if .so files can be loaded from an SDCard in the first place.

Answer 2

Does libSample.so have any dependencies on other shared libs that you may be building? If so, you'll need to System.loadLibrary or System.load its dependencies first, making sure to load the most "basic" libraries before others, as if they were static libs. At least it seems to be this way with NDK 7b.

For example, if libSample.so depends on libfoo.so you should do something like:

System.loadLibrary("foo");
System.loadLibrary("Sample");