Bug 984101 - Expand SpiderMonkey's use of poisoning for diagnostics; r=jonco

--HG--
extra : rebase_source : 312db74b85c9b40db1ccfc98a96206d2e1381703

js/public/Utility.h

@@ -35,10 +35,18 @@ namespace mozilla {}
 namespace js {}
 
 /*
- * Pattern used to overwrite freed memory. If you are accessing an object with
- * this pattern, you probably have a dangling pointer.
+ * Patterns used by SpiderMonkey to overwrite unused memory. If you are
+ * accessing an object with one of these pattern, you probably have a dangling
+ * pointer.
  */
-#define JS_FREE_PATTERN 0xDA
+#define JS_FRESH_NURSERY_PATTERN 0x2F
+#define JS_SWEPT_NURSERY_PATTERN 0x2B
+#define JS_ALLOCATED_NURSERY_PATTERN 0x2D
+#define JS_FRESH_TENURED_PATTERN 0x4F
+#define JS_SWEPT_TENURED_PATTERN 0x4B
+#define JS_ALLOCATED_TENURED_PATTERN 0x4D
+#define JS_SWEPT_CODE_PATTERN 0x3b
+#define JS_SWEPT_FRAME_PATTERN 0x5b
 
 #define JS_ASSERT(expr)           MOZ_ASSERT(expr)
 #define JS_ASSERT_IF(cond, expr)  MOZ_ASSERT_IF(cond, expr)

js/src/assembler/assembler/MacroAssemblerCodeRef.h

@@ -36,6 +36,8 @@
 
 #if ENABLE_ASSEMBLER
 
+#include "jsutil.h"
+
 // ASSERT_VALID_CODE_POINTER checks that ptr is a non-null pointer, and that it is a valid
 // instruction address on the platform (for example, check any alignment requirements).
 #if WTF_CPU_ARM_THUMB2
@@ -199,7 +201,7 @@ public:
         if (!m_executablePool)
             return;
 
-        memset(m_code.executableAddress(), JS_FREE_PATTERN, m_allocSize);
+        JS_POISON(m_code.executableAddress(), JS_SWEPT_CODE_PATTERN, m_allocSize);
 
         m_code = MacroAssemblerCodePtr();
 

js/src/gc/Heap.h

@@ -288,6 +288,7 @@ struct FreeSpan
             return nullptr;
         }
         checkSpan();
+        JS_POISON(reinterpret_cast<void *>(thing), JS_ALLOCATED_TENURED_PATTERN, thingSize);
         return reinterpret_cast<void *>(thing);
     }
 

js/src/gc/Marking.cpp

@@ -97,17 +97,36 @@ static void MarkChildren(JSTracer *trc, jit::JitCode *code);
 
 /*** Object Marking ***/
 
-#ifdef DEBUG
+#if defined(DEBUG)
 template<typename T>
 static inline bool
 IsThingPoisoned(T *thing)
 {
-    const uint8_t pb = JS_FREE_PATTERN;
+    static_assert(sizeof(T) >= sizeof(FreeSpan) + sizeof(uint32_t),
+                  "Ensure it is well defined to look past any free span that "
+                  "may be embedded in the thing's header when freed.");
+    const uint8_t poisonBytes[] = {
+        JS_FRESH_NURSERY_PATTERN,
+        JS_SWEPT_NURSERY_PATTERN,
+        JS_ALLOCATED_NURSERY_PATTERN,
+        JS_FRESH_TENURED_PATTERN,
+        JS_SWEPT_TENURED_PATTERN,
+        JS_ALLOCATED_TENURED_PATTERN,
+        JS_SWEPT_CODE_PATTERN,
+        JS_SWEPT_FRAME_PATTERN
+    };
+    const int numPoisonBytes = sizeof(poisonBytes) / sizeof(poisonBytes[0]);
+    uint32_t *p = reinterpret_cast<uint32_t *>(reinterpret_cast<FreeSpan *>(thing) + 1);
+    // Note: all free patterns are odd to make the common, not-poisoned case a single test.
+    if ((*p & 1) == 0)
+        return false;
+    for (int i = 0; i < numPoisonBytes; ++i) {
+        const uint8_t pb = poisonBytes[i];
         const uint32_t pw = pb | (pb << 8) | (pb << 16) | (pb << 24);
-    JS_STATIC_ASSERT(sizeof(T) >= sizeof(FreeSpan) + sizeof(uint32_t));
-    uint32_t *p =
-        reinterpret_cast<uint32_t *>(reinterpret_cast<FreeSpan *>(thing) + 1);
-    return *p == pw;
+        if (*p == pw)
+            return true;
+    }
+    return false;
 }
 #endif
 

js/src/gc/Nursery.cpp

@@ -62,9 +62,7 @@ js::Nursery::init()
     currentStart_ = start();
     rt->gcNurseryEnd_ = chunk(LastNurseryChunk).end();
     numActiveChunks_ = 1;
-#ifdef JS_GC_ZEAL
-    JS_POISON(heap, FreshNursery, NurserySize);
-#endif
+    JS_POISON(heap, JS_FRESH_NURSERY_PATTERN, NurserySize);
     setCurrentChunk(0);
     updateDecommittedRegion();
 
@@ -170,9 +168,7 @@ js::Nursery::allocate(size_t size)
     void *thing = (void *)position();
     position_ = position() + size;
 
-#ifdef JS_GC_ZEAL
-    JS_POISON(thing, AllocatedThing, size);
-#endif
+    JS_POISON(thing, JS_ALLOCATED_NURSERY_PATTERN, size);
     return thing;
 }
 
@@ -877,7 +873,7 @@ js::Nursery::sweep(JSRuntime *rt)
 {
 #ifdef JS_GC_ZEAL
     /* Poison the nursery contents so touching a freed object will crash. */
-    JS_POISON((void *)start(), SweptNursery, NurserySize - sizeof(JSRuntime *));
+    JS_POISON((void *)start(), JS_SWEPT_NURSERY_PATTERN, NurserySize);
     for (int i = 0; i < NumNurseryChunks; ++i)
         chunk(i).trailer.runtime = runtime();
 
@@ -890,6 +886,11 @@ js::Nursery::sweep(JSRuntime *rt)
     } else
 #endif
     {
+#ifdef JS_CRASH_DIAGNOSTICS
+        JS_POISON((void *)start(), JS_SWEPT_NURSERY_PATTERN, allocationEnd() - start());
+        for (int i = 0; i < numActiveChunks_; ++i)
+            chunk(i).trailer.runtime = runtime();
+#endif
         setCurrentChunk(0);
     }
 
@@ -900,7 +901,9 @@ js::Nursery::sweep(JSRuntime *rt)
 void
 js::Nursery::growAllocableSpace()
 {
+#ifdef JS_GC_ZEAL
     MOZ_ASSERT_IF(runtime()->gcZeal_ == ZealGenerationalGCValue, numActiveChunks_ == NumNurseryChunks);
+#endif
     numActiveChunks_ = Min(numActiveChunks_ * 2, NumNurseryChunks);
 }
 

js/src/gc/Nursery.h

@@ -293,9 +293,6 @@ class Nursery
      * In debug and zeal builds, these bytes indicate the state of an unused
      * segment of nursery-allocated memory.
      */
-    static const uint8_t FreshNursery = 0x2a;
-    static const uint8_t SweptNursery = 0x2b;
-    static const uint8_t AllocatedThing = 0x2c;
     void enterZealMode() {
         if (isEnabled())
             numActiveChunks_ = NumNurseryChunks;

js/src/jit/Ion.cpp

@@ -742,7 +742,7 @@ JitCode::finalize(FreeOp *fop)
     // Don't do this if the Ion code is protected, as the signal handler will
     // deadlock trying to reacquire the interrupt lock.
     if (fop->runtime()->jitRuntime() && !fop->runtime()->jitRuntime()->ionCodeProtected())
-        memset(code_, JS_FREE_PATTERN, bufferSize_);
+        memset(code_, JS_SWEPT_CODE_PATTERN, bufferSize_);
     code_ = nullptr;
 
     // Code buffers are stored inside JSC pools.

js/src/jsgc.cpp

@@ -484,7 +484,7 @@ Arena::finalize(FreeOp *fop, AllocKind thingKind, size_t thingSize)
                 if (!newFreeSpanStart)
                     newFreeSpanStart = thing;
                 t->finalize(fop);
-                JS_POISON(t, JS_FREE_PATTERN, thingSize);
+                JS_POISON(t, JS_SWEPT_TENURED_PATTERN, thingSize);
             }
         }
     }
@@ -493,6 +493,7 @@ Arena::finalize(FreeOp *fop, AllocKind thingKind, size_t thingSize)
         JS_ASSERT(newListTail == &newListHead);
         JS_ASSERT(!newFreeSpanStart ||
                   newFreeSpanStart == thingsStart(thingKind));
+        JS_POISON(data, JS_SWEPT_TENURED_PATTERN, sizeof(data));
         return true;
     }
 
@@ -781,7 +782,7 @@ Chunk::prepareToBeFreed(JSRuntime *rt)
 void
 Chunk::init(JSRuntime *rt)
 {
-    JS_POISON(this, JS_FREE_PATTERN, ChunkSize);
+    JS_POISON(this, JS_FRESH_TENURED_PATTERN, ChunkSize);
 
     /*
      * We clear the bitmap to guard against xpc_IsGrayGCThing being called on

js/src/jsiter.cpp

@@ -1472,8 +1472,8 @@ FinalizeGenerator(FreeOp *fop, JSObject *obj)
               gen->state == JSGEN_OPEN);
     // If gen->state is JSGEN_CLOSED, gen->fp may be nullptr.
     if (gen->fp)
-        JS_POISON(gen->fp, JS_FREE_PATTERN, sizeof(InterpreterFrame));
-    JS_POISON(gen, JS_FREE_PATTERN, sizeof(JSGenerator));
+        JS_POISON(gen->fp, JS_SWEPT_FRAME_PATTERN, sizeof(InterpreterFrame));
+    JS_POISON(gen, JS_SWEPT_FRAME_PATTERN, sizeof(JSGenerator));
     fop->free_(gen);
 }
 

js/src/jsutil.h

@@ -278,7 +278,7 @@ ClearAllBitArrayElements(size_t *array, size_t length)
 #ifdef DEBUG
 # define JS_CRASH_DIAGNOSTICS 1
 #endif
-#ifdef JS_CRASH_DIAGNOSTICS
+#if defined(JS_CRASH_DIAGNOSTICS) || defined(JS_GC_ZEAL)
 # define JS_POISON(p, val, size) memset((p), (val), (size))
 #else
 # define JS_POISON(p, val, size) ((void) 0)