Bug 1257234 - Detect main thread's stack size at runtime, on Windows. r=ted

js/xpconnect/src/XPCJSRuntime.cpp

@@ -63,6 +63,10 @@
 #include "mozmemory.h"
 #endif
 
+#ifdef XP_WIN
+#include <windows.h>
+#endif
+
 using namespace mozilla;
 using namespace xpc;
 using namespace JS;
@@ -3362,6 +3366,40 @@ XPCJSRuntime::XPCJSRuntime()
 {
 }
 
+#ifdef XP_WIN
+static size_t
+GetWindowsStackSize()
+{
+    // First, get the stack base. Because the stack grows down, this is the top
+    // of the stack.
+    const uint8_t* stackTop;
+#ifdef _WIN64
+    PNT_TIB64 pTib = reinterpret_cast<PNT_TIB64>(NtCurrentTeb());
+    stackTop = reinterpret_cast<const uint8_t*>(pTib->StackBase);
+#else
+    PNT_TIB pTib = reinterpret_cast<PNT_TIB>(NtCurrentTeb());
+    stackTop = reinterpret_cast<const uint8_t*>(pTib->StackBase);
+#endif
+
+    // Now determine the stack bottom. Note that we can't use tib->StackLimit,
+    // because that's the size of the committed area and we're also interested
+    // in the reserved pages below that.
+    MEMORY_BASIC_INFORMATION mbi;
+    if (!VirtualQuery(&mbi, &mbi, sizeof(mbi)))
+        MOZ_CRASH("VirtualQuery failed");
+
+    const uint8_t* stackBottom = reinterpret_cast<const uint8_t*>(mbi.AllocationBase);
+
+    // Do some sanity checks.
+    size_t stackSize = size_t(stackTop - stackBottom);
+    MOZ_RELEASE_ASSERT(stackSize >= 1 * 1024 * 1024);
+    MOZ_RELEASE_ASSERT(stackSize <= 32 * 1024 * 1024);
+
+    // Subtract 20 KB to account for things like the guard page.
+    return stackSize - 20 * 1024;
+}
+#endif
+
 nsresult
 XPCJSRuntime::Initialize()
 {
@@ -3444,9 +3482,9 @@ XPCJSRuntime::Initialize()
     const size_t kStackQuota =  2 * kDefaultStackQuota;
     const size_t kTrustedScriptBuffer = 450 * 1024;
 #elif defined(XP_WIN)
-    // 1MB is the default stack size on Windows, so use 980k.
-    // Windows PGO stack frames have unfortunately gotten pretty large lately. :-(
-    const size_t kStackQuota = 980 * 1024;
+    // 1MB is the default stack size on Windows. We use the /STACK linker flag
+    // to request a larger stack, so we determine the stack size at runtime.
+    const size_t kStackQuota = GetWindowsStackSize();
     const size_t kTrustedScriptBuffer = (sizeof(size_t) == 8) ? 180 * 1024   //win64
                                                               : 120 * 1024;  //win32
     // The following two configurations are linux-only. Given the numbers above,