1 //:: Check that the different operands of an instruction aren't too large for their bitfields.
 2 
 3 :(scenario check_bitfield_sizes)
 4 % Hide_errors = true;
 5 == 0x1
 6 01/add 4/mod 3/rm32 1/r32  # add ECX to EBX
 7 +error: '4/mod' too large to fit in bitfield mod
 8 
 9 :(before "End Globals")
10 map<string, uint32_t> Operand_bound;
11 :(before "End One-time Setup")
12 put_new(Operand_bound, "subop", 1<<3);
13 put_new(Operand_bound, "mod", 1<<2);
14 put_new(Operand_bound, "rm32", 1<<3);
15 put_new(Operand_bound, "base", 1<<3);
16 put_new(Operand_bound, "index", 1<<3);
17 put_new(Operand_bound, "scale", 1<<2);
18 put_new(Operand_bound, "r32", 1<<3);
19 put_new(Operand_bound, "disp8", 1<<8);
20 put_new(Operand_bound, "disp16", 1<<16);
21 // no bound needed for disp32
22 put_new(Operand_bound, "imm8", 1<<8);
23 // no bound needed for imm32
24 
25 :(before "Pack Operands(segment code)")
26 check_operand_bounds(code);
27 if (trace_contains_errors()) return;
28 :(code)
29 void check_operand_bounds(const segment& code) {
30   trace(3, "transform") << "-- check operand bounds" << end();
31   for (int i = 0;  i < SIZE(code.lines);  ++i) {
32     const line& inst = code.lines.at(i);
33     for (int j = first_operand(inst);  j < SIZE(inst.words);  ++j)
34       check_operand_bounds(inst.words.at(j));
35     if (trace_contains_errors()) return;  // stop at the first mal-formed instruction
36   }
37 }
38 
39 void check_operand_bounds(const word& w) {
40   for (map<string, uint32_t>::iterator p = Operand_bound.begin();  p != Operand_bound.end();  ++p) {
41     if (!has_operand_metadata(w, p->first)) continue;
42     if (!looks_like_hex_int(w.data)) continue;  // later transforms are on their own to do their own bounds checking
43     int32_t x = parse_int(w.data);
44     if (x >= 0) {
45       if (static_cast<uint32_t>(x) >= p->second)
46         raise << "'" << w.original << "' too large to fit in bitfield " << p->first << '\n' << end();
47     }
48     else {
49       // hacky? assuming bound is a power of 2
50       if (x < -1*static_cast<int32_t>(p->second/2))
51         raise << "'" << w.original << "' too large to fit in bitfield " << p->first << '\n' << end();
52     }
53   }
54 }