Bug 1576254 - Add a wasmForTrustedPrinciples bool onto ContextOptions that (currently) behaves the exact same as the wasm bool r=luke

In a future commit we will tie this boolean to its own preference value, but here we
initialize it with the same value as the wasm boolean.

We also update wasm::HasSupport to check the to-be-added isSystemOrAddonPrincipal()
method on JSPrincipals to determine which member (wasm or wasmForTrustedPrinciples)
to consult.

Differential Revision: https://phabricator.services.mozilla.com/D47472

--HG--
extra : moz-landing-system : lando

dom/workers/RuntimeService.cpp

@@ -286,6 +286,8 @@ void LoadContextOptions(const char* aPrefName, void* /* aClosure */) {
   JS::ContextOptions contextOptions;
   contextOptions.setAsmJS(GetWorkerPref<bool>(NS_LITERAL_CSTRING("asmjs")))
       .setWasm(GetWorkerPref<bool>(NS_LITERAL_CSTRING("wasm")))
+      .setWasmForTrustedPrinciples(
+          GetWorkerPref<bool>(NS_LITERAL_CSTRING("wasm")))
       .setWasmBaseline(
           GetWorkerPref<bool>(NS_LITERAL_CSTRING("wasm_baselinejit")))
       .setWasmIon(GetWorkerPref<bool>(NS_LITERAL_CSTRING("wasm_ionjit")))

js/public/ContextOptions.h

@@ -20,6 +20,7 @@ class JS_PUBLIC_API ContextOptions {
   ContextOptions()
       : asmJS_(true),
         wasm_(true),
+        wasmForTrustedPrinciples_(true),
         wasmVerbose_(false),
         wasmBaseline_(true),
         wasmIon_(true),
@@ -64,6 +65,12 @@ class JS_PUBLIC_API ContextOptions {
     return *this;
   }
 
+  bool wasmForTrustedPrinciples() const { return wasmForTrustedPrinciples_; }
+  ContextOptions& setWasmForTrustedPrinciples(bool flag) {
+    wasmForTrustedPrinciples_ = flag;
+    return *this;
+  }
+
   bool wasmVerbose() const { return wasmVerbose_; }
   ContextOptions& setWasmVerbose(bool flag) {
     wasmVerbose_ = flag;
@@ -187,6 +194,7 @@ class JS_PUBLIC_API ContextOptions {
  private:
   bool asmJS_ : 1;
   bool wasm_ : 1;
+  bool wasmForTrustedPrinciples_ : 1;
   bool wasmVerbose_ : 1;
   bool wasmBaseline_ : 1;
   bool wasmIon_ : 1;

js/src/shell/js.cpp

@@ -10327,6 +10327,7 @@ static bool SetContextOptions(JSContext* cx, const OptionParser& op) {
   JS::ContextOptionsRef(cx)
       .setAsmJS(enableAsmJS)
       .setWasm(enableWasm)
+      .setWasmForTrustedPrinciples(enableWasm)
       .setWasmBaseline(enableWasmBaseline)
       .setWasmIon(enableWasmIon)
 #ifdef ENABLE_WASM_CRANELIFT

js/src/wasm/WasmJS.cpp

@@ -151,8 +151,15 @@ static bool HasAvailableCompilerTier(JSContext* cx) {
 }
 
 bool wasm::HasSupport(JSContext* cx) {
-  return cx->options().wasm() && HasCompilerSupport(cx) &&
-         HasAvailableCompilerTier(cx);
+  // If the general wasm pref is on, it's on for everything.
+  bool prefEnabled = cx->options().wasm();
+  // If the general pref is off, check trusted principals.
+  if (MOZ_UNLIKELY(!prefEnabled)) {
+    prefEnabled = cx->options().wasmForTrustedPrinciples() && cx->realm() &&
+                  cx->realm()->principals() &&
+                  cx->realm()->principals()->isSystemOrAddonPrincipal();
+  }
+  return prefEnabled && HasCompilerSupport(cx) && HasAvailableCompilerTier(cx);
 }
 
 bool wasm::HasStreamingSupport(JSContext* cx) {

js/xpconnect/src/XPCJSContext.cpp

@@ -957,6 +957,7 @@ static void ReloadPrefsCallback(const char* pref, XPCJSContext* xpccx) {
   JS::ContextOptionsRef(cx)
       .setAsmJS(useAsmJS)
       .setWasm(useWasm)
+      .setWasmForTrustedPrinciples(useWasm)
       .setWasmIon(useWasmIon)
       .setWasmBaseline(useWasmBaseline)
 #ifdef ENABLE_WASM_CRANELIFT