Rasmuss

Remote ASeMbler Single Step

Executes machine code instructions on a remote host (possibly a different CPU architecture from your local machine), and outputs a line of JSON containing CPU register values for each step.

Why?

I am using this to create test fixtures for an ARM32 CPU emulator. The emulator's test suite will initialize the emulated CPU's registers from the first line of rasmuss' output. Then it runs the emulation for the opcode in nextInstruction and compares the impact this has on the emulated CPU registers to what the real ARM CPU did running the same code inside a BananaPi connected via Ethernet.

Prerequisits

gcc and gdb need to be installed on the remote machine.

Command Line Usage

Pipe assembler code into rasmus and specify the target machine and (optionally) a username.

HINT set-up passwordless ssh authentication to save keystrokes.

$ npm install -g rasmuss
$ cat demo.s
mov r0, #0x200
$ rasmuss regular@yellowbird < demo.s
{"nextInstruction":"0xe3a00c02","comment":"=> 0x8360 <main>:\tmov\tr0,,512\t; 0x200","registers":["0x1","0xbefffd54","0xbefffd5c","0x8360","0x0","0xbefffc18","0x82e9","0x0","0x0","0x0","0xb6fff000","0x0","0xb6f20dc1","0xbefffc08","0xb6f12cfb","0x8360","0x60000010"]}
{"nextInstruction":"0x43f8e92d","comment":"=> 0x8364 <__libc_csu_init>:\tstmdb\tsp!, {r3, r4, r5, r6, r7, r8, r9, lr}","registers":["0x200","0xbefffd54","0xbefffd5c","0x8360","0x0","0xbefffc18","0x82e9","0x0","0x0","0x0","0xb6fff000","0x0","0xb6f20dc1","0xbefffc08","0xb6f12cfb","0x8364","0x60000010"]}

(notice the first register changing from 0x1 to 0x200)

Programmatic Usage

var rasmuss = require('./');

var target = 'regular@yellowbird';

var asm = [
    'mov r1, #0x320',
    'movs r2, r1, LSL #4'
].join('\n');

var stream = rasmuss(target, asm);
stream.pipe(process.stdout);

License

MIT