[wasm] Reserve space for runtime in wasm stacks

Set the JS limit at a 40KB offset from the actual limit, like on the
native stack. This is an estimate of the maximum stack space needed for
runtime calls.

R=ahaas@chromium.org

Bug: v8:12191
Change-Id: I709d5b25c5e47d2474cf4205ebcb8ee7fc8e794c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3312485Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Thibaud Michaud <thibaudm@chromium.org>
Cr-Commit-Position: refs/heads/main@{#78212}

src/wasm/stacks.h

@@ -43,7 +43,7 @@ class StackMemory {
     if (owned_) allocator->DecommitPages(limit_, size_);
   }
 
-  void* limit() { return limit_; }
+  void* jslimit() { return limit_ + kJSLimitOffsetKB; }
   void* base() { return limit_ + size_; }
 
   // Track external memory usage for Managed<StackMemory> objects.
@@ -53,15 +53,18 @@ class StackMemory {
   // This constructor allocates a new stack segment.
   StackMemory() : owned_(true) {
     PageAllocator* allocator = GetPlatformPageAllocator();
-    size_ = allocator->AllocatePageSize();
-    // TODO(thibaudm): Leave space for runtime functions.
-    limit_ = static_cast<byte*>(allocator->AllocatePages(
-        nullptr, size_, size_, PageAllocator::kReadWrite));
+    int kJsStackSizeKB = 4;
+    size_ = (kJsStackSizeKB + kJSLimitOffsetKB) * KB;
+    limit_ = static_cast<byte*>(
+        allocator->AllocatePages(nullptr, size_, allocator->AllocatePageSize(),
+                                 PageAllocator::kReadWrite));
   }
 
   // Overload to represent a view of the libc stack.
   explicit StackMemory(byte* limit) : limit_(limit), size_(0), owned_(false) {}
 
+  static constexpr int kJSLimitOffsetKB = 40;
+
   byte* limit_;
   size_t size_;
   bool owned_;

src/wasm/wasm-objects.cc

@@ -1748,7 +1748,7 @@ Handle<WasmContinuationObject> WasmContinuationObject::New(
   Handle<WasmContinuationObject> result = Handle<WasmContinuationObject>::cast(
       isolate->factory()->NewStruct(WASM_CONTINUATION_OBJECT_TYPE));
   auto jmpbuf = std::make_unique<wasm::JumpBuffer>();
-  jmpbuf->stack_limit = stack->limit();
+  jmpbuf->stack_limit = stack->jslimit();
   jmpbuf->sp = stack->base();
   result->set_jmpbuf(
       *isolate->factory()->NewForeign(reinterpret_cast<Address>(jmpbuf.get())));