Changeset 252661 in webkit

Timestamp:

Nov 19, 2019 4:56:39 PM (5 years ago)

Author:

ysuzuki@apple.com

Message:

[JSC] Work-around Leaks' false-positive report about memory leaking
​https://bugs.webkit.org/show_bug.cgi?id=204384
<rdar://problem/56950932>

Reviewed by Mark Lam.

According to the radar, Leaks start reporting false-positive memory leaks about ExecutableAllocator and FixedVMPoolExecutableAllocator,
while they are per-process singleton and reachable through g_jscConfig. I'm guessing this is because Leaks start skipping scan for
readonly memory region. (g_jscConfig is now mprotected to readonly).

To work-around this, we anchor these heap allocated things to global variables to help Leaks scan. Once it is fixed, we should remove it.

• jit/ExecutableAllocator.cpp:

(JSC::ExecutableAllocator::initializeUnderlyingAllocator):
(JSC::ExecutableAllocator::initialize):

Location:

trunk/Source/JavaScriptCore

Files:

• ChangeLog (modified) (1 diff)
• jit/ExecutableAllocator.cpp (modified) (2 diffs)

trunk/Source/JavaScriptCore/ChangeLog

@@ +1 @@
+2019-11-19  Yusuke Suzuki  <ysuzuki@apple.com>
+
+        [JSC] Work-around Leaks' false-positive report about memory leaking
+        https://bugs.webkit.org/show_bug.cgi?id=204384
+        <rdar://problem/56950932>
+
+        Reviewed by Mark Lam.
+
+        According to the radar, Leaks start reporting false-positive memory leaks about ExecutableAllocator and FixedVMPoolExecutableAllocator,
+        while they are per-process singleton and reachable through g_jscConfig. I'm guessing this is because Leaks start skipping scan for
+        readonly memory region. (g_jscConfig is now mprotected to readonly).
+
+        To work-around this, we anchor these heap allocated things to global variables to help Leaks scan. Once it is fixed, we should remove it.
+
+        * jit/ExecutableAllocator.cpp:
+        (JSC::ExecutableAllocator::initializeUnderlyingAllocator):
+        (JSC::ExecutableAllocator::initialize):
+
 2019-11-18  Mark Lam  <mark.lam@apple.com>
 

trunk/Source/JavaScriptCore/jit/ExecutableAllocator.cpp

@@ -415 +415 @@
 }
 
+// Keep this pointer in a mutable global variable to help Leaks find it.
+// But we do not use this pointer.
+static FixedVMPoolExecutableAllocator* globalFixedVMPoolExecutableAllocatorToWorkAroundLeaks = nullptr;
 void ExecutableAllocator::initializeUnderlyingAllocator()
 {
     RELEASE_ASSERT(!g_jscConfig.fixedVMPoolExecutableAllocator);
     g_jscConfig.fixedVMPoolExecutableAllocator = new FixedVMPoolExecutableAllocator();
+    globalFixedVMPoolExecutableAllocatorToWorkAroundLeaks = g_jscConfig.fixedVMPoolExecutableAllocator;
     CodeProfiling::notifyAllocator(g_jscConfig.fixedVMPoolExecutableAllocator);
 }
@@ -643 +647 @@
 namespace JSC {
 
+// Keep this pointer in a mutable global variable to help Leaks find it.
+// But we do not use this pointer.
+static ExecutableAllocator* globalExecutableAllocatorToWorkAroundLeaks = nullptr;
 void ExecutableAllocator::initialize()
 {
     g_jscConfig.executableAllocator = new ExecutableAllocator;
+    globalExecutableAllocatorToWorkAroundLeaks = g_jscConfig.executableAllocator;
 }