Memo to build official android emulator

This is a memo to build official android emulator which Android SDK includes. This emulator forked from qemu.

Get source codes

$ cd $WORK
$ git clone git://codeaurora.org/platform/external/qemu.git

Build

$ cd $WORK/qemu
$ git checkout origin/aosp/tools_r13
$ ./android-configure.sh
$ make

Prepare OS images

$ cd $WORK
$ wget http://dl.google.com/android/android-sdk_r13-linux_x86.tgz
$ tar zxf android-sdk_r13-linux_x86.tgz
$ cd android-sdk-linux_x86/
$ ./tools/android
(Install SDK platform packages, then create virtual machine definition named X in GUI. Android 1.6, 2.3.3, and 3.2 will work fine.)

Launch the OS image

$ ANDROID_SDK_ROOT=$WORK/android-sdk-linux_x86 $WORK/qemu/objs/emulator-arm @X
(X is the name you named in preparing OS images.)

Memos

• codeaurora.org is an unofficial mirror repository. If kernel.org come back, you must use the git://android.kernel.org repository.
• If you'd like to build on OS X, you must build in a case-sensitive file system because block.h conflicts with system provided Block.h. Default file system is case-*in*sensitive, so you may prepare a disk image and work in it as follows;
• $ hdiutil create $NAME -size 1024m -fs HFSX -volume $VOLUME; hdiutil attach $NAME; cd /Volumes/$VOLUME; do something...
• If you'd like to build trunk sources, you may want to use prebuilt SDL library in /platform/prebuilt.git. It could be passed via --sdl-config arguments in android-configure.sh. But I guess it miss three functions including SDL_WM_GetPos, etc. Also it will be a pretty tough and boring work to find some stable combinations between versions of SDL, qemu, and OS images.

CPU Emulation using JIT on JavaScript

I'm struck with an idea to implement CPU emulation using JIT like technique on JavaScript. Basically, the emulator generates JavaScript function which emulate a target binary sequence by the basic block, then cache it in hash. The code could be like 'cache[pc] = eval(jit()); cache[pc]();'.

Since I'd like to know how this technique could be effective, I just make a tiny pseudo emulator and estimate its performance. The result show the JavaScript CPU interpretor will be x100 slower than a native code. Modern JavaScript engines become faster and faster. But it seems to be still slow. On the other hand, qemu-arm seems to be quite fast. It's just several times slower than the native one. So how about my emulation using JIT on JavaScript? It's slower than qemu. But not so bad. It might be pretty fast than native CPU interpreter.

As supplements, I must say that this benchmark treats just one simple case and the result will be changed by loop size, count, and JIT overheads in various situations.