tor-browser

commit a48c7813a3ef97b25731205732d77e20d269f8b3
parent 09f04022c6f22371a4ad9f46f8b919e55330ae4b
Author: Ryan Hunt <rhunt@eqrion.net>
Date:   Thu, 18 Dec 2025 16:45:29 +0000

Bug 2002625 - wasm: Dynamically switch to main stack in import interp exit. r=yury

Use the infrastructure added for builtin thunks for the import
interp exit.

Differential Revision: https://phabricator.services.mozilla.com/D274194

Diffstat:
M
js/src/wasm/WasmInstance.cpp
 | 
23
+++++------------------
M
js/src/wasm/WasmStubs.cpp
 | 
13
+++----------

2 files changed, 8 insertions(+), 28 deletions(-)
diff --git a/js/src/wasm/WasmInstance.cpp b/js/src/wasm/WasmInstance.cpp
@@ -250,6 +250,11 @@ bool Instance::callImport(JSContext* cx, uint32_t funcImportIndex,
                           unsigned argc, uint64_t* argv) {
   AssertRealmUnchanged aru(cx);
 
+#ifdef ENABLE_WASM_JSPI
+  // We should not be on a suspendable stack.
+  MOZ_ASSERT(!cx->wasm().onSuspendableStack());
+#endif
+
   FuncImportInstanceData& instanceFuncImport =
       funcImportInstanceData(funcImportIndex);
   const FuncType& funcType = codeMeta().getFuncType(funcImportIndex);
@@ -408,24 +413,6 @@ bool Instance::callImport(JSContext* cx, uint32_t funcImportIndex,
 Instance::callImport_general(Instance* instance, int32_t funcImportIndex,
                              int32_t argc, uint64_t* argv) {
   JSContext* cx = instance->cx();
-#ifdef ENABLE_WASM_JSPI
-  if (IsSuspendableStackActive(cx)) {
-    struct ImportCallData {
-      Instance* instance;
-      int32_t funcImportIndex;
-      int32_t argc;
-      uint64_t* argv;
-      static bool Call(ImportCallData* data) {
-        Instance* instance = data->instance;
-        JSContext* cx = instance->cx();
-        return instance->callImport(cx, data->funcImportIndex, data->argc,
-                                    data->argv);
-      }
-    } data = {instance, funcImportIndex, argc, argv};
-    return CallOnMainStack(
-        cx, reinterpret_cast<CallOnMainStackFn>(ImportCallData::Call), &data);
-  }
-#endif
   return instance->callImport(cx, funcImportIndex, argc, argv);
 }
 
diff --git a/js/src/wasm/WasmStubs.cpp b/js/src/wasm/WasmStubs.cpp
@@ -338,13 +338,6 @@ static bool FinishOffsets(MacroAssembler& masm, Offsets* offsets) {
   return !masm.oom();
 }
 
-static void AssertStackAlignment(MacroAssembler& masm, uint32_t alignment,
-                                 uint32_t addBeforeAssert = 0) {
-  MOZ_ASSERT(
-      (sizeof(Frame) + masm.framePushed() + addBeforeAssert) % alignment == 0);
-  masm.assertStackAlignment(alignment, addBeforeAssert);
-}
-
 template <class VectorT>
 static unsigned StackArgBytesHelper(const VectorT& args, ABIKind kind) {
   ABIArgIter<VectorT> iter(args, kind);
@@ -2003,7 +1996,7 @@ static bool GenerateImportInterpExit(MacroAssembler& masm, const FuncImport& fi,
       ComputeByteAlignment(sizeof(Frame), ABIStackAlignment);
   unsigned framePushed = AlignBytes(argOffset + argBytes, ABIStackAlignment);
   GenerateExitPrologue(masm, ExitReason::Fixed::ImportInterp,
-                       /*switchToMainStack*/ false,
+                       /*switchToMainStack*/ true,
                        /*framePushedPreSwitch*/ frameAlignment,
                        /*framePushedPostSwitch*/ framePushed, offsets);
 
@@ -2056,7 +2049,7 @@ static bool GenerateImportInterpExit(MacroAssembler& masm, const FuncImport& fi,
   MOZ_ASSERT(i.done());
 
   // Make the call, test whether it succeeded, and extract the return value.
-  AssertStackAlignment(masm, ABIStackAlignment);
+  masm.assertStackAlignment(ABIStackAlignment);
   masm.call(SymbolicAddress::CallImport_General);
   masm.branchTest32(Assembler::Zero, ReturnReg, ReturnReg, throwLabel);
 
@@ -2125,7 +2118,7 @@ static bool GenerateImportInterpExit(MacroAssembler& masm, const FuncImport& fi,
 #endif
 
   GenerateExitEpilogue(masm, ExitReason::Fixed::ImportInterp,
-                       /*switchToMainStack*/ false, offsets);
+                       /*switchToMainStack*/ true, offsets);
 
   return FinishOffsets(masm, offsets);
 }