Bug 1066760 - Add base address and fall back to system dladdr in __wrap_dladdr; r=froydnj

mozglue/linker/CustomElf.h

@@ -36,6 +36,7 @@ public:
   virtual ~CustomElf();
   virtual void *GetSymbolPtr(const char *symbol) const;
   virtual bool Contains(void *addr) const;
+  virtual void *GetBase() const { return GetPtr(0); }
 
 #ifdef __ARM_EABI__
   virtual const void *FindExidx(int *pcount) const;

mozglue/linker/ElfLoader.cpp

@@ -90,9 +90,11 @@ int
 __wrap_dladdr(void *addr, Dl_info *info)
 {
   RefPtr<LibHandle> handle = ElfLoader::Singleton.GetHandleByPtr(addr);
-  if (!handle)
-    return 0;
+  if (!handle) {
+    return dladdr(addr, info);
+  }
   info->dli_fname = handle->GetPath();
+  info->dli_fbase = handle->GetBase();
   return 1;
 }
 

mozglue/linker/ElfLoader.h

@@ -117,6 +117,11 @@ public:
    */
   virtual bool Contains(void *addr) const = 0;
 
+  /**
+   * Returns the base address of the loaded library.
+   */
+  virtual void *GetBase() const = 0;
+
   /**
    * Returns the file name of the library without the containing directory.
    */
@@ -267,6 +272,7 @@ public:
   virtual ~SystemElf();
   virtual void *GetSymbolPtr(const char *symbol) const;
   virtual bool Contains(void *addr) const { return false; /* UNIMPLEMENTED */ }
+  virtual void *GetBase() const { return nullptr; /* UNIMPLEMENTED */ }
 
 #ifdef __ARM_EABI__
   virtual const void *FindExidx(int *pcount) const;