4468

1 files changed, 74 insertions, 0 deletions

diff --git a/subx/031check_operand_bounds.cc b/subx/031check_operand_bounds.cc
new file mode 100644
index 00000000..cca4ab24
--- /dev/null
+++ b/subx/031check_operand_bounds.cc
@@ -0,0 +1,74 @@
+//:: Check that the different operands of an instruction aren't too large for their bitfields.
+
+:(scenario check_bitfield_sizes)
+% Hide_errors = true;
+== 0x1
+01/add 4/mod
++error: '4/mod' too large to fit in bitfield mod
+
+:(before "End Globals")
+map<string, uint32_t> Operand_bound;
+:(before "End One-time Setup")
+put(Operand_bound, "subop", 1<<3);
+put(Operand_bound, "mod", 1<<2);
+put(Operand_bound, "rm32", 1<<3);
+put(Operand_bound, "base", 1<<3);
+put(Operand_bound, "index", 1<<3);
+put(Operand_bound, "scale", 1<<2);
+put(Operand_bound, "r32", 1<<3);
+put(Operand_bound, "disp8", 1<<8);
+put(Operand_bound, "disp16", 1<<16);
+// no bound needed for disp32
+put(Operand_bound, "imm8", 1<<8);
+// no bound needed for imm32
+
+:(before "End One-time Setup")
+Transform.push_back(check_operand_bounds);
+:(code)
+void check_operand_bounds(/*const*/ program& p) {
+  trace(99, "transform") << "-- check operand bounds" << end();
+  if (p.segments.empty()) return;
+  const segment& code = p.segments.at(0);
+  for (int i = 0;  i < SIZE(code.lines);  ++i) {
+    const line& inst = code.lines.at(i);
+    for (int j = first_operand(inst);  j < SIZE(inst.words);  ++j)
+      check_operand_bounds(inst.words.at(j));
+    if (trace_contains_errors()) return;  // stop at the first mal-formed instruction
+  }
+}
+
+void check_operand_bounds(const word& w) {
+  for (map<string, uint32_t>::iterator p = Operand_bound.begin();  p != Operand_bound.end();  ++p) {
+    if (!has_metadata(w, p->first)) continue;
+    if (!is_hex_int(w.data)) continue;  // later transforms are on their own to do their own bounds checking
+    int32_t x = parse_int(w.data);
+    if (x >= 0) {
+      if (static_cast<uint32_t>(x) >= p->second)
+        raise << "'" << w.original << "' too large to fit in bitfield " << p->first << '\n' << end();
+    }
+    else {
+      // hacky? assuming bound is a power of 2
+      if (x < -1*static_cast<int32_t>(p->second/2))
+        raise << "'" << w.original << "' too large to fit in bitfield " << p->first << '\n' << end();
+    }
+  }
+}
+
+bool is_hex_int(const string& s) {
+  if (s.empty()) return false;
+  size_t pos = 0;
+  if (s.at(0) == '-' || s.at(0) == '+') pos++;
+  if (s.substr(pos, pos+2) == "0x") pos += 2;
+  return s.find_first_not_of("0123456789abcdefABCDEF", pos) == string::npos;
+}
+
+int32_t parse_int(const string& s) {
+  istringstream in(s);
+  int32_t result = 0;
+  in >> std::hex >> result;
+  if (!in || !in.eof()) {
+    raise << "not a number: " << s << '\n' << end();
+    return 0;
+  }
+  return result;
+}