Mono on Android - Success At Last!

Last week, I blogged about my attempts to get Mono running on Android. I was running into a nasty Illegal Instruction issue, which I didn't look into further until today. And after implementing a quick hack/fix I got it working!

After running strace on Mono, I was able to determine that the Illegal Instruction was occuring in mini-arm.c in the mono_arch_flush_icache function. I wasn't able to decipher whether the inline assembly was correct or not; but I got the jist of what it was trying to do: it was calling cacheflush, but failing with the Illegal Instruction in there. I looked at the mini-x86.c and saw that the equivalent mono_arch_flush_icache was empty; the comment indicating it was "not needed". I don't know if this is some vestigial code or what, but I figured it would be relatively benign to not flush the instruction cache and just see what happens. And the grand results:

root@localhost:~/Desktop# mono test.exe

Hello World

This would not be possible without the help of my co-worker, Kevin Eustice, and my abhorrence towards Java.

Expect to see some performance comparisons between Mono vs Dalvik shortly! Though I don't expect it to even be a fair competition, because Dalvik does not JIT. Lame.

Mono on Android

It's been a little quiet on my blog lately... too quiet. It's cause I've been bashing my head against a wall trying to get Mono on Android (well, Debian running side by side with Android really). So far, I've gotten the Mono runtime cross compiled for Android, but attempting to run anything results in the following:

localhost:~/Desktop/junk# mono
Usage is: mono [options] program [program-options]

Development:
    --aot                  Compiles the assembly to native code
    --debug[=<options>]    Enable debugging support, use --help-debug for details
    --profile[=profiler]   Runs in profiling mode with the specified profiler module
    --trace[=EXPR]         Enable tracing, use --help-trace for details
    --help-devel           Shows more options available to developers

Runtime:
    --config FILE          Loads FILE as the Mono config
    --verbose, -v          Increases the verbosity level
    --help, -h             Show usage information
    --version, -V          Show version information
    --runtime=VERSION      Use the VERSION runtime, instead of autodetecting
    --optimize=OPT         Turns on or off a specific optimization
                           Use --list-opt to get a list of optimizations
    --security[=mode]      Turns on the unsupported security manager (off by default)
                           mode is one of cas, core-clr, verifiable or validil

localhost:~/Desktop/junk# mono test.exe
Illegal instruction

 

Note that mono works fine, but attempting to run a program fails. So yeah, I'm at a loss. I'm guessing there is a bug in the ARM JIT somewhere. Or maybe my make process went horribly wrong due to user error somewhere. I'll try getting Mono from the trunk and building and installing. Apparently there are some more ARM related fixes in there.

I managed to get this far by:

Install Debian on Android.

Cross Compile Mono and its dependency chain using Scratchbox (there are a lot, which I'll detail in a later post). I also did some of the compilation on the G1 itself rather than Scratchbox.