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
 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(Operand_bound, "subop", 1<<3);
13 put(Operand_bound, "mod", 1<<2);
14 put(Operand_bound, "rm32", 1<<3);
15 put(Operand_bound, "base", 1<<3);
16 put(Operand_bound, "index", 1<<3);
17 put(Operand_bound, "scale", 1<<2);
18 put(Operand_bound, "r32", 1<<3);
19 put(Operand_bound, "disp8", 1<<8);
20 put(Operand_bound, "disp16", 1<<16);
21 // no bound needed for disp32
22 put(Operand_bound, "imm8", 1<<8);
23 // no bound needed for imm32
24 
25 :(before "End One-time Setup")
26 Transform.push_back(check_operand_bounds);
27 :(code)
28 void check_operand_bounds(/*const*/ program& p) {
29   trace(99, "transform") << "-- check operand bounds" << end();
30   if (p.segments.empty()) return;
31   const segment& code = p.segments.at(0);
32   for (int i = 0;  i < SIZE(code.lines);  ++i) {
33     const line& inst = code.lines.at(i);
34     for (int j = first_operand(inst);  j < SIZE(inst.words);  ++j)
35       check_operand_bounds(inst.words.at(j));
36     if (trace_contains_errors()) return;  // stop at the first mal-formed instruction
37   }
38 }
39 
40 void check_operand_bounds(const word& w) {
41   for (map<string, uint32_t>::iterator p = Operand_bound.begin();  p != Operand_bound.end();  ++p) {
42     if (!has_metadata(w, p->first)) continue;
43     if (!is_hex_int(w.data)) continue;  // later transforms are on their own to do their own bounds checking
44     int32_t x = parse_int(w.data);
45     if (x >= 0) {
46       if (static_cast<uint32_t>(x) >= p->second)
47         raise << "'" << w.original << "' too large to fit in bitfield " << p->first << '\n' << end();
48     }
49     else {
50       // hacky? assuming bound is a power of 2
51       if (x < -1*static_cast<int32_t>(p->second/2))
52         raise << "'" << w.original << "' too large to fit in bitfield " << p->first << '\n' << end();
53     }
54   }
55 }
56 
57 bool is_hex_int(const string& s) {
58   if (s.empty()) return false;
59   size_t pos = 0;
60   if (s.at(0) == '-' || s.at(0) == '+') pos++;
61   if (s.substr(pos, pos+2) == "0x") pos += 2;
62   return s.find_first_not_of("0123456789abcdefABCDEF", pos) == string::npos;
63 }
64 
65 int32_t parse_int(const string& s) {
66   istringstream in(s);
67   int32_t result = 0;
68   in >> std::hex >> result;
69   if (!in || !in.eof()) {
70     raise << "not a number: " << s << '\n' << end();
71     return 0;
72   }
73   return result;
74 }