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//--------------------------------------------------------------------------------------------------
//
// stage 2 of 3
//
// challenge:
// reveal the solution within VM.mem
//
// disclaimer:
// tested in ie 9, firefox 6, chrome 14 and v8 shell (http://code.google.com/apis/v8/build.html),
// other javascript implementations may or may not work.
//
//--------------------------------------------------------------------------------------------------
var VM = {
mem: [
0x31, 0x04, 0x33, 0xaa, 0x40, 0x02, 0x80, 0x03, 0x52, 0x00, 0x72, 0x01, 0x73, 0x01, 0xb2, 0x50,
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0xc9, 0xb8, 0x0e, 0xbd, 0x7d, 0x0f, 0xc0, 0xf1, 0xd9, 0x03, 0xc5, 0x3a, 0xc6, 0xc7, 0xc8, 0xc9,
0xca, 0xcb, 0xcc, 0xcd, 0xce, 0xcf, 0xd0, 0xd1, 0xd2, 0xd3, 0xd4, 0xd5, 0xd6, 0xd7, 0xd8, 0xd9,
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0x7d, 0x1f, 0x15, 0x60, 0x4d, 0x4d, 0x52, 0x7d, 0x0e, 0x27, 0x6d, 0x10, 0x6d, 0x5a, 0x06, 0x56,
0x47, 0x14, 0x42, 0x0e, 0xb6, 0xb2, 0xb2, 0xe6, 0xeb, 0xb4, 0x83, 0x8e, 0xd7, 0xe5, 0xd4, 0xd9,
0xc3, 0xf0, 0x80, 0x95, 0xf1, 0x82, 0x82, 0x9a, 0xbd, 0x95, 0xa4, 0x8d, 0x9a, 0x2b, 0x30, 0x69,
0x4a, 0x69, 0x65, 0x55, 0x1c, 0x7b, 0x69, 0x1c, 0x6e, 0x04, 0x74, 0x35, 0x21, 0x26, 0x2f, 0x60,
0x03, 0x4e, 0x37, 0x1e, 0x33, 0x54, 0x39, 0xe6, 0xba, 0xb4, 0xa2, 0xad, 0xa4, 0xc5, 0x95, 0xc8,
0xc1, 0xe4, 0x8a, 0xec, 0xe7, 0x92, 0x8b, 0xe8, 0x81, 0xf0, 0xad, 0x98, 0xa4, 0xd0, 0xc0, 0x8d,
0xac, 0x22, 0x52, 0x65, 0x7e, 0x27, 0x2b, 0x5a, 0x12, 0x61, 0x0a, 0x01, 0x7a, 0x6b, 0x1d, 0x67,
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0x01, 0x51, 0x59, 0x5f, 0x56, 0x13, 0x10, 0x43, 0x19, 0x18, 0xe5, 0xe0, 0xbe, 0xbf, 0xbd, 0xe9,
0xf0, 0xf1, 0xf9, 0xfa, 0xab, 0x8f, 0xc1, 0xdf, 0xcf, 0x8d, 0xf8, 0xe7, 0xe2, 0xe9, 0x93, 0x8e,
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0x53, 0x30, 0x11, 0x42, 0xf6, 0xf1, 0xb1, 0xe6, 0xc3, 0xcc, 0xf8, 0xc5, 0xe4, 0xcc, 0xc0, 0xd3,
0x85, 0xfd, 0x9a, 0xe3, 0xe6, 0x81, 0xb5, 0xbb, 0xd7, 0xcd, 0x87, 0xa3, 0xd3, 0x6b, 0x36, 0x6f,
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0x02, 0x30, 0x28, 0x35, 0x15, 0x09, 0x15, 0xdd, 0xec, 0xb8, 0xe2, 0xfb, 0xd8, 0xcb, 0xd8, 0xd1,
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0xcf, 0x45, 0x46, 0x67, 0x20, 0x7d, 0x44, 0x14, 0x6b, 0x45, 0x6d, 0x54, 0x03, 0x17, 0x60, 0x62,
0x55, 0x5a, 0x4a, 0x66, 0x61, 0x11, 0x57, 0x68, 0x75, 0x05, 0x62, 0x36, 0x7d, 0x02, 0x10, 0x4b,
0x08, 0x22, 0x42, 0x32, 0xba, 0xe2, 0xb9, 0xe2, 0xd6, 0xb9, 0xff, 0xc3, 0xe9, 0x8a, 0x8f, 0xc1,
0x8f, 0xe1, 0xb8, 0xa4, 0x96, 0xf1, 0x8f, 0x81, 0xb1, 0x8d, 0x89, 0xcc, 0xd4, 0x78, 0x76, 0x61,
0x72, 0x3e, 0x37, 0x23, 0x56, 0x73, 0x71, 0x79, 0x63, 0x7c, 0x08, 0x11, 0x20, 0x69, 0x7a, 0x14,
0x68, 0x05, 0x21, 0x1e, 0x32, 0x27, 0x59, 0xb7, 0xcf, 0xab, 0xdd, 0xd5, 0xcc, 0x97, 0x93, 0xf2,
0xe7, 0xc0, 0xeb, 0xff, 0xe9, 0xa3, 0xbf, 0xa1, 0xab, 0x8b, 0xbb, 0x9e, 0x9e, 0x8c, 0xa0, 0xc1,
0x9b, 0x5a, 0x2f, 0x2f, 0x4e, 0x4e, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
],
s_seg: 2, // segment size
cpu: {
ip: 0x00, // instruction pointer
r0: 0x00,
r1: 0x00,
r2: 0x00,
r3: 0x00,
cs: 0x00,
ds: 0x10,
fl: 0x00,
firmware: [0xd2ab1f05, 0xda13f110],
is_halted: false
},
exec: function()
{
// virtual machine architecture
// ++++++++++++++++++++++++++++
//
// segmented memory model with 16-byte segment size (notation seg:offset)
//
// 4 general-purpose registers (r0-r3)
// 2 segment registers (cs, ds equiv. to r4, r5)
// 1 flags register (fl)
//
// instruction encoding
// ++++++++++++++++++++
//
// byte 1 byte 2 (optional)
// bits [ 7 6 5 4 3 2 1 0 ] [ 7 6 5 4 3 2 1 0 ]
// opcode - - -
// mod -
// operand1 - - - -
// operand2 - - - - - - - -
//
// operand1 is always a register index
// operand2 is optional, depending upon the instruction set specified below
// the value of mod alters the meaning of any operand2
// 0: operand2 = reg ix
// 1: operand2 = fixed immediate value or target segment (depending on instruction)
//
// instruction set
// +++++++++++++++
//
// Notes:
// * r1, r2 => operand 1 is register 1, operand 2 is register 2
// * movr r1, r2 => move contents of register r2 into register r1
//
// opcode | instruction | operands (mod 0) | operands (mod 1)
// -------+-------------+------------------+-----------------
// 0x00 | jmp | r1 | r2:r1
// 0x01 | movr | r1, r2 | rx, imm
// 0x02 | movm | r1, [ds:r2] | [ds:r1], r2
// 0x03 | add | r1, r2 | r1, imm
// 0x04 | xor | r1, r2 | r1, imm
// 0x05 | cmp | r1, r2 | r1, imm
// 0x06 | jmpe | r1 | r2:r1
// 0x07 | hlt | N/A | N/A
//
// flags
// +++++
//
// cmp r1, r2 instruction results in:
// r1 == r2 => fl = 0
// r1 < r2 => fl = 0xff
// r1 > r2 => fl = 1
//
// jmpe r1
// => if (fl == 0) jmp r1
// else nop
while (!this.cpu.is_halted) {
this.cpu.ip = this.dispatch(this.mem.slice(this.cpu.ip, this.cpu.ip+2))
}
},
dispatch: function(segment) {
advance = 0;
ins = this.instruction_set[this.get_opcode(segment[0])];;
mod = this.get_mod(segment[0]);
// print some nice info
this.dump();
print('=>',
('0x0' + ins.code),
ins.name,
'([', ('0x' + segment[0].toString(16)), ',',
('0x' + segment[1].toString(16)),
'])');
// execute the instruction and add
// its return value to the cpu's internal
// pointer
this.cpu.ip += ins.op((segment.length == 2 ? segment : segment[0]), mod, this)
this.dump();
print("\n");
// return the cpu's current pointer
return this.cpu.ip
},
dump: function() {
print('ip:', this.cpu.ip,
', r0:', this.cpu.r0,
', r1:', this.cpu.r1,
', r2:', this.cpu.r2,
', r3:', this.cpu.r3,
', ds:', this.cpu.ds,
', cs:', this.cpu.cs,
', fl:', this.cpu.fl);
},
addr: function(segment_index, offset) {
// 16-byte segments + any offset given
return (this.cpu[segment_index] * 16) + offset;
},
instruction_set: [
{
'code': 0x00,
'name': 'jmp',
'op': function(ins, mod, inst) {
print(' (ip)', inst.cpu.ip, ':', this.name, mod);
op1 = inst.get_register(inst.get_opand1(ins[0]));
if (!mod) {
addr = inst.addr('cs', inst.cpu[op1]);
print(' (!mod)', op1, addr, inst.cpu[op1]);
inst.cpu.ip = addr;
}
else {
op2 = ins[1];
print(' (mod)', op2, ':', op1);
addr = op2 * 0x10 + inst.cpu[op1];
inst.cpu.cs = op2;
inst.cpu.ip = addr;
}
return 0;
},
},
{
'code': 0x01,
'name': 'movr',
'op': function(ins, mod, inst) {
op1 = inst.get_register(inst.get_opand1(ins[0]));
if (!mod) {
// take value from op2
op2 = inst.get_register(ins[1]);
print(' (!mod) (ip)', inst.cpu.ip, ':', this.name, op2, ',', this.cpu[op2]);
inst.cpu[op1] = inst.cpu[op2]
}
else {
// take immediate value
print(' (mod) (ip)', inst.cpu.ip, ':', this.name, op1, ',', ins[1]);
inst.cpu[op1] = ins[1];
print(' ', op1, '=', inst.cpu[op1]);
}
return inst.s_seg; // advance ip by two
}
},
{
'code': 0x02,
'name': 'movm',
'op': function(ins, mod, inst) {
op1 = inst.get_register(inst.get_opand1(ins[0]));
op2 = inst.get_register(ins[1]);
print(' (ip)', inst.cpu.ip, ':', this.name, mod, op1, op2);
if (!mod) {
addr = inst.addr('ds', inst.cpu[op2]);
print(' (!mod)', op1, ',', '[ds:', op2, ']', addr, inst.mem[addr]);
inst.cpu[op1] = inst.mem[addr];
print(' ', op1, '=', inst.cpu[op1]);
}
else {
addr = inst.addr('ds', inst.cpu[op1]);
print(' (mod)', '[ds:', op1, '],', op2, addr, inst.mem[addr]);
inst.mem[addr] = inst.cpu[op2]
print(' mem:', addr, '=', inst.mem[addr]);
}
return inst.s_seg; // done, advance by two
}
},
{
'code': 0x03,
'name': 'add',
'op': function(ins, mod, inst) {
op1 = inst.get_register(inst.get_opand1(ins[0]));
print(' (ip)', inst.cpu.ip, ':', this.name, op1, mod);
// & 0xff to ensure val no larger than 1 byte
if (!mod) {
print(' (!mod)', op1, op2, inst.cpu[op1], inst.cpu[op2]);
op2 = inst.get_register(ins[1]);
// add both registers together
inst.cpu[op1] = (inst.cpu[op1] + inst.cpu[op2]) & 0xff;
print(' ', op1, inst.cpu[op1]);
}
else {
print(' (mod)', ins[1], op2, ',', inst.cpu[op1]);
// add the value in ins[1]
inst.cpu[op1] = (inst.cpu[op1] + ins[1]) & 0xff;
print(' ', op1, '=', inst.cpu[op1]);
}
return inst.s_seg;
}
},
{
'code': 0x04,
'name': 'xor',
'op': function(ins, mod, inst) {
op1 = inst.get_register(inst.get_opand1(ins[0]));
print(' (ip)', inst.cpu.ip, ':', this.name, mod, ',', op1);
if (!mod) {
op2 = inst.get_register(ins[1]);
print(' (!mod)', op1, op2, inst.cpu[op1], inst.cpu[op2]);
inst.cpu[op1] = inst.cpu[op1] ^ inst.cpu[op2];
print(' ', op1, '=', inst.cpu[op1]);
}
else {
print(' (mod)', ins[1]);
inst.cpu[op1] = (inst.cpu[op1] ^ ins[1]);
}
return inst.s_seg;
},
},
{
'code': 0x05,
'name': 'cmp',
'op': function(ins, mod, inst) {
op1_register = inst.get_register(inst.get_opand1(ins[0]));
op1 = inst.cpu[op1_register];
print(' ', inst.cpu.ip, ':', this.name, mod, op1_register, ',');
op2 = ''
if (!mod) {
op2_regiser = inst.get_register(ins[1]);
print(' (!mod)', op2_register);
op2 = inst.cpu[op2_register];
}
else {
op2 = ins[1];
print(' (mod)', op2);
}
d = op1 - op2;
if (d == 0) {
inst.cpu.fl = 0;
}
else if (d > 0) {
inst.cpu.fl = 1;
}
else {
inst.cpu.fl = -1;
}
print(' cpu.fl =', inst.cpu.fl);
return inst.s_seg;
}
},
{
'code': 0x06,
'name': 'jmpe',
'op': function(ins, mod, inst) {
print(' (ip)', inst.cpu.ip, mod);
if (inst.cpu.fl == 0) {
return inst.instruction_set[0].op(ins, mod, ins);
}
print(' [!] Not taken');
return mod+1;
}
},
{
'code': 0x07,
'name': 'hlt',
'op': function(ins, mod, inst) {
inst.cpu.is_halted = true;
print('hlt')
print('[!] Halting.');
return 0;
}
}
],
get_register: function(ins) {
// return a register to use for each opcode.
// note halt (HLT) has no register
return ['r0', 'r1', 'r2', 'r3', 'cs', 'ds'][ins];
},
get_opcode: function(w) {
// shift bits 5 to the right to get the value of the 3 leftmost bits
return (w >> 5) & 0xff;
},
get_mod: function(w) {
// filter by 0x0f to figure out
return (w >> 4) & 0x01;
},
get_opand1: function(w) {
// filter for 4 rightmost bits
return w & ((1 << 4) - 1);
},
get_opand2: function(w) {
// pass-thru
return w;
},
};
//--------------------------------------------------------------------------------------------------
try
{
VM.exec();
}
catch(e)
{
print(e);
}
//--------------------------------------------------------------------------------------------------
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