[wasm] Canonicalize function signature indices for matching in indirect calls.

src/wasm/wasm-interpreter.cc

Index: src/wasm/wasm-interpreter.cc
diff --git a/src/wasm/wasm-interpreter.cc b/src/wasm/wasm-interpreter.cc
index 2ac681eff293dbb1a640ebb16bf6c6e1347323a6..1d03852a2cfa33e9692151d653d91c5d854442db 100644
--- a/src/wasm/wasm-interpreter.cc
+++ b/src/wasm/wasm-interpreter.cc
@@ -1419,7 +1419,15 @@ class ThreadImpl : public WasmInterpreter::Thread {
           if (target == nullptr) {
             return DoTrap(kTrapFuncInvalid, pc);
           } else if (target->function->sig_index != operand.index) {
-            return DoTrap(kTrapFuncSigMismatch, pc);
+            // If not an exact match, we have to do a canonical check.
+            const WasmIndirectFunctionTable* table =

[Clemens Hammacher, 2016/10/10 17:35:03]

Maybe place a TODO to think about caching this instead of doing two map lookups
on every call? We could for example patch the code with the canonical index,
which should always be smaller than the present index.

[titzer, 2016/10/10 17:45:21]

Added a TODO here.

+                &module()->function_tables[0];
+            int function_key = table->map_.Find(target->function->sig);
+            if (function_key < 0 ||
+                (function_key !=
+                 table->map_.Find(module()->signatures[operand.index]))) {
+              return DoTrap(kTrapFuncSigMismatch, pc);
+            }
           }
 
           DoCall(target, &pc, pc + 1 + operand.length, &limit);