Bug 885336 - Fix various issues with the dl_mmap interface. r=nfroyd

mozglue/linker/CustomElf.cpp

@@ -95,7 +95,7 @@ private:
     mappable->munmap(buf, length);
   }
 
-  Mappable *mappable;
+  mozilla::RefPtr<Mappable> mappable;
 };
 
 
@@ -233,7 +233,6 @@ CustomElf::~CustomElf()
    * Android NDK before r6b doesn't do that. Our wrapped cxa_finalize only
    * calls destructors once, so call it in all cases. */
   ElfLoader::__wrap_cxa_finalize(this);
-  delete mappable;
   ElfLoader::Singleton.Forget(this);
 }
 

mozglue/linker/CustomElf.h

@@ -9,8 +9,6 @@
 #include "Logging.h"
 #include "Elfxx.h"
 
-class Mappable;
-
 /**
  * Library Handle class for ELF libraries we don't let the system linker
  * handle.
@@ -157,7 +155,7 @@ private:
   }
 
   /* Appropriated Mappable */
-  Mappable *mappable;
+  mozilla::RefPtr<Mappable> mappable;
 
   /* Base address where the library is loaded */
   MappedPtr base;

mozglue/linker/ElfLoader.cpp

@@ -182,8 +182,6 @@ LeafName(const char *path)
 LibHandle::~LibHandle()
 {
   free(path);
-  if (mappable && mappable->GetKind() != Mappable::MAPPABLE_EXTRACT_FILE)
-    delete mappable;
 }
 
 const char *
@@ -195,8 +193,7 @@ LibHandle::GetName() const
 size_t
 LibHandle::GetMappableLength() const
 {
-  MOZ_ASSERT(mappable != NULL, "GetMappableLength needs to be called first,"
-                               " and only once");
+  if (!mappable)
     mappable = GetMappable();
   if (!mappable)
     return 0;
@@ -206,8 +203,10 @@ LibHandle::GetMappableLength() const
 void *
 LibHandle::MappableMMap(void *addr, size_t length, off_t offset) const
 {
-  MOZ_ASSERT(mappable == NULL, "MappableMMap must be called after"
-                               " GetMappableLength");
+  if (!mappable)
+    mappable = GetMappable();
+  if (!mappable)
+    return MAP_FAILED;
   void* mapped = mappable->mmap(addr, length, PROT_READ, MAP_PRIVATE, offset);
   if (mapped != MAP_FAILED) {
     /* Ensure the availability of all pages within the mapping */
@@ -221,8 +220,7 @@ LibHandle::MappableMMap(void *addr, size_t length, off_t offset) const
 void
 LibHandle::MappableMUnmap(void *addr, size_t length) const
 {
-  MOZ_ASSERT(mappable == NULL, "MappableMUnmap must be called after"
-                               " MappableMMap and GetMappableLength");
+  if (mappable)
     mappable->munmap(addr, length);
 }
 

mozglue/linker/ElfLoader.h

@@ -11,6 +11,7 @@
 #include "mozilla/RefPtr.h"
 #include "Zip.h"
 #include "Elfxx.h"
+#include "Mappable.h"
 
 /**
  * dlfcn.h replacement functions
@@ -76,9 +77,6 @@ template <> inline RefCounted<LibHandle, AtomicRefCount>::~RefCounted()
 } /* namespace detail */
 } /* namespace mozilla */
 
-/* Forward declaration */
-class Mappable;
-
 /**
  * Abstract class for loaded libraries. Libraries may be loaded through the
  * system linker or this linker, both cases will be derived from this class.
@@ -200,7 +198,7 @@ private:
   char *path;
 
   /* Mappable object keeping the result of GetMappable() */
-  mutable Mappable *mappable;
+  mutable mozilla::RefPtr<Mappable> mappable;
 };
 
 /**

mozglue/linker/Mappable.h

@@ -22,7 +22,7 @@
  * - memory after length and up to the end of the corresponding page is nulled
  *   out.
  */
-class Mappable
+class Mappable: public mozilla::RefCounted<Mappable>
 {
 public:
   virtual ~Mappable() { }
@@ -120,6 +120,9 @@ public:
    */
   static Mappable *Create(const char *name, Zip *zip, Zip::Stream *stream);
 
+  /* Override finalize from MappableFile */
+  virtual void finalize() {}
+
   virtual Kind GetKind() const { return MAPPABLE_EXTRACT_FILE; };
 private:
   MappableExtractFile(int fd, char *path)