Look for ModuleData only in appropriate library

LoaderSymbol calls dlsym with RTLD_DEFAULT pseudo handle making it search in
every loaded library. In addition glibc adds NODELETE flag to the library
containing the symbol.

It's used in doLoadModule to locate <modulename>ModuleData symbol, the
module's library gets the flag and is kept in memory even after it is
unloaded.

This patch adds LoaderSymbolFromModule function that looks for symbol only in
library specified by handle. That way the NODELETE flag isn't added.

This glibc behavior doesn't seem to be documented, but even if other
implementations differ, there is no reason to search ModuleData symbol outside
the module's library.

Signed-off-by: Michal Srb <msrb@suse.com>
Reviewed-by: Daniel Stone <daniel@fooishbar.org>

v2: Switch LoaderSymbolFromModule arguments order.
    Correct description.
Reviewed-by: Adam Jackson <ajax@redhat.com>
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>

hw/xfree86/loader/loader.c

@@ -160,6 +160,12 @@ LoaderSymbol(const char *name)
     return NULL;
 }
 
+void *
+LoaderSymbolFromModule(void *handle, const char *name)
+{
+    return dlsym(handle, name);
+}
+
 void
 LoaderUnload(const char *name, void *handle)
 {

hw/xfree86/loader/loader.h

@@ -72,5 +72,6 @@ extern unsigned long LoaderOptions;
 
 /* Internal Functions */
 void *LoaderOpen(const char *, int *, int *);
+void *LoaderSymbolFromModule(void *, const char *);
 
 #endif                          /* _LOADER_H */

hw/xfree86/loader/loadmod.c

@@ -956,7 +956,7 @@ doLoadModule(const char *module, const char *path, const char **subdirlist,
             *errmin = 0;
         goto LoadModule_fail;
     }
-    initdata = LoaderSymbol(p);
+    initdata = LoaderSymbolFromModule(ret->handle, p);
     if (initdata) {
         ModuleSetupProc setup;
         ModuleTearDownProc teardown;