Attachment 341354 Details for Bug 186004 – proposed patch.

[patch] proposed patch.

bug-186004.patch (text/plain), 2.12 KB, created by Mark Lam on 2018-05-25 16:42:01 PDT

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Creator: Mark Lam

Created: 2018-05-25 16:42:01 PDT

Size: 2.12 KB

patch

obsolete

>Index: Source/JavaScriptCore/ChangeLog
>===================================================================
>--- Source/JavaScriptCore/ChangeLog	(revision 232213)
>+++ Source/JavaScriptCore/ChangeLog	(working copy)
>@@ -1,3 +1,28 @@
>+2018-05-25  Mark Lam  <mark.lam@apple.com>
>+
>+        MachineContext's instructionPointer() should handle null PCs correctly.
>+        https://bugs.webkit.org/show_bug.cgi?id=186004
>+
>+        Reviewed by NOBODY (OOPS!).
>+
>+        instructionPointer() returns a MacroAssemblerCodePtr<CFunctionPtrTag>.  However,
>+        MacroAssemblerCodePtr's constructor does not accept a null pointer value and will
>+        assert accordingly with a debug ASSERT.  This is inconsequential for release
>+        builds, but to avoid this assertion failure, we should check for a null PC and
>+        return MacroAssemblerCodePtr<CFunctionPtrTag>(nullptr) instead (which uses the
>+        MacroAssemblerCodePtr(std::nullptr_t) version of the constructor instead).
>+
>+        Alternatively, we can change all of MacroAssemblerCodePtr's constructors to check
>+        for null pointers, but I rather not do that yet.  In general,
>+        MacroAssemblerCodePtrs are constructed with non-null pointers, and I prefer to
>+        leave it that way for now.
>+
>+        Note: this assertion failure only manifests when we have signal traps enabled,
>+        and encounter a null pointer deref.
>+
>+        * runtime/MachineContext.h:
>+        (JSC::MachineContext::instructionPointer):
>+
> 2018-05-25  Mark Lam  <mark.lam@apple.com>
> 
>         Enforce invariant that GetterSetter objects are invariant.
>Index: Source/JavaScriptCore/runtime/MachineContext.h
>===================================================================
>--- Source/JavaScriptCore/runtime/MachineContext.h	(revision 232211)
>+++ Source/JavaScriptCore/runtime/MachineContext.h	(working copy)
>@@ -438,6 +438,8 @@ inline MacroAssemblerCodePtr<CFunctionPt
> #else
>     void* value = instructionPointerImpl(const_cast<PlatformRegisters&>(regs));
> #endif
>+    if (!value)
>+        return MacroAssemblerCodePtr<CFunctionPtrTag>(nullptr);
>     return MacroAssemblerCodePtr<CFunctionPtrTag>(value);
> }
>

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saam: review+

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