Changeset 44993 in webkit

Timestamp:

Jun 23, 2009 8:45:12 AM (15 years ago)

Author:

treat@webkit.org

Message:

2009-06-23 Joe Mason <​joe.mason@torchmobile.com>

Reviewed by Adam Treat.

Authors: Yong Li <​yong.li@torchmobile.com>, Joe Mason <​joe.mason@torchmobile.com>

​https://bugs.webkit.org/show_bug.cgi?id=26611
Implement currentThreadStackBase on WINCE by adding a global,
g_stackBase, which must be set to the address of a local variable
by the caller before calling any WebKit function that invokes JSC.

Location:

trunk/JavaScriptCore

Files:

• ChangeLog (modified) (1 diff)
• runtime/Collector.cpp (modified) (2 diffs)

trunk/JavaScriptCore/ChangeLog

@@ +1 @@
+2009-06-23  Joe Mason  <joe.mason@torchmobile.com>
+
+        Reviewed by Adam Treat.
+
+        Authors: Yong Li <yong.li@torchmobile.com>, Joe Mason <joe.mason@torchmobile.com>
+
+        https://bugs.webkit.org/show_bug.cgi?id=26611
+        Implement currentThreadStackBase on WINCE by adding a global,
+        g_stackBase, which must be set to the address of a local variable
+        by the caller before calling any WebKit function that invokes JSC.
+
+        * runtime/Collector.cpp:
+        (JSC::isPageWritable):
+        (JSC::getStackBase):
+          Starts at the top of the stack and returns the entire range of
+          consecutive writable pages as an estimate of the actual stack.
+          This will be much bigger than the actual stack range, so some
+          dead objects can't be collected, but it guarantees live objects
+          aren't collected prematurely.
+
+        (JSC::currentThreadStackBase):
+          On WinCE, returns g_stackBase if set or call getStackBase as a
+          fallback if not.
+
 2009-06-23  Oliver Hunt  <oliver@apple.com>
 

trunk/JavaScriptCore/runtime/Collector.cpp

@@ -393 +393 @@
     return heapAllocate<NumberHeap>(s);
 }
+
+#if PLATFORM(WINCE)
+void* g_stackBase = 0;
+
+inline bool isPageWritable(void* page)
+{
+    MEMORY_BASIC_INFORMATION memoryInformation;
+    DWORD result = VirtualQuery(page, &memoryInformation, sizeof(memoryInformation));
+
+    // return false on error, including ptr outside memory
+    if (result != sizeof(memoryInformation))
+        return false;
+
+    DWORD protect = memoryInformation.Protect & ~(PAGE_GUARD | PAGE_NOCACHE);
+    return protect == PAGE_READWRITE
+        || protect == PAGE_WRITECOPY
+        || protect == PAGE_EXECUTE_READWRITE
+        || protect == PAGE_EXECUTE_WRITECOPY;
+}
+
+static void* getStackBase(void* previousFrame)
+{
+    // find the address of this stack frame by taking the address of a local variable
+    bool isGrowingDownward;
+    void* thisFrame = (void*)(&isGrowingDownward);
+
+    isGrowingDownward = previousFrame < &thisFrame;
+    static DWORD pageSize = 0;
+    if (!pageSize) {
+        SYSTEM_INFO systemInfo;
+        GetSystemInfo(&systemInfo);
+        pageSize = systemInfo.dwPageSize;
+    }
+
+    // scan all of memory starting from this frame, and return the last writeable page found
+    register char* currentPage = (char*)((DWORD)thisFrame & ~(pageSize - 1));
+    if (isGrowingDownward) {
+        while (currentPage > 0) {
+            // check for underflow
+            if (currentPage >= (char*)pageSize)
+                currentPage -= pageSize;
+            else
+                currentPage = 0;
+            if (!isPageWritable(currentPage))
+                return currentPage + pageSize;
+        }
+        return 0;
+    } else {
+        while (true) {
+            // guaranteed to complete because isPageWritable returns false at end of memory
+            currentPage += pageSize;
+            if (!isPageWritable(currentPage))
+                return currentPage;
+        }
+    }
+}
+#endif
 
 static inline void* currentThreadStackBase()
@@ -459 +516 @@
     }
     return static_cast<char*>(stackBase) + stackSize;
+#elif PLATFORM(WINCE)
+    if (g_stackBase)
+        return g_stackBase;
+    else {
+        int dummy;
+        return getStackBase(&dummy);
+    }
 #else
 #error Need a way to get the stack base on this platform