boehm-gc/gc_dlopen.c

   1 /*
   2  * Copyright (c) 1991-1994 by Xerox Corporation.  All rights reserved.
   3  * Copyright (c) 1997 by Silicon Graphics.  All rights reserved.
   4  * Copyright (c) 2000 by Hewlett-Packard Company.  All rights reserved.
   5  *
   6  * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
   7  * OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.
   8  *
   9  * Permission is hereby granted to use or copy this program
  10  * for any purpose,  provided the above notices are retained on all copies.
  11  * Permission to modify the code and to distribute modified code is granted,
  12  * provided the above notices are retained, and a notice that the code was
  13  * modified is included with the above copyright notice.
  14  */
  15
  16 #include "private/gc_priv.h"
  17
  18 /* This used to be in dyn_load.c.  It was extracted into a separate     */
  19 /* file to avoid having to link against libdl.{a,so} if the client      */
  20 /* doesn't call dlopen.  Of course this fails if the collector is in    */
  21 /* a dynamic library. -HB                                               */
  22 #if defined(GC_PTHREADS) && !defined(GC_NO_DLOPEN)
  23
  24 #undef GC_MUST_RESTORE_REDEFINED_DLOPEN
  25 #if defined(dlopen) && !defined(GC_USE_LD_WRAP)
  26   /* To support various threads pkgs, gc.h interposes on dlopen by      */
  27   /* defining "dlopen" to be "GC_dlopen", which is implemented below.   */
  28   /* However, both GC_FirstDLOpenedLinkMap() and GC_dlopen() use the    */
  29   /* real system dlopen() in their implementation. We first remove      */
  30   /* gc.h's dlopen definition and restore it later, after GC_dlopen().  */
  31 # undef dlopen
  32 # define GC_MUST_RESTORE_REDEFINED_DLOPEN
  33 #endif
  34
  35 /* Make sure we're not in the middle of a collection, and make sure we  */
  36 /* don't start any.  This is invoked prior to a dlopen call to avoid    */
  37 /* synchronization issues.  We can't just acquire the allocation lock,  */
  38 /* since startup code in dlopen may try to allocate.  This solution     */
  39 /* risks heap growth (or, even, heap overflow) in the presence of many  */
  40 /* dlopen calls in either a multi-threaded environment, or if the       */
  41 /* library initialization code allocates substantial amounts of GC'ed   */
  42 /* memory.                                                              */
  43 #ifndef USE_PROC_FOR_LIBRARIES
  44   static void disable_gc_for_dlopen(void)
  45   {
  46     DCL_LOCK_STATE;
  47     LOCK();
  48     while (GC_incremental && GC_collection_in_progress()) {
  49       GC_collect_a_little_inner(1000);
  50     }
  51     ++GC_dont_gc;
  52     UNLOCK();
  53   }
  54 #endif
  55
  56 /* Redefine dlopen to guarantee mutual exclusion with           */
  57 /* GC_register_dynamic_libraries.  Should probably happen for   */
  58 /* other operating systems, too.                                */
  59
  60 /* This is similar to WRAP/REAL_FUNC() in pthread_support.c.    */
  61 #ifdef GC_USE_LD_WRAP
  62 # define WRAP_DLFUNC(f) __wrap_##f
  63 # define REAL_DLFUNC(f) __real_##f
  64   void * REAL_DLFUNC(dlopen)(const char *, int);
  65 #else
  66 # define WRAP_DLFUNC(f) GC_##f
  67 # define REAL_DLFUNC(f) f
  68 #endif
  69
  70 GC_API void * WRAP_DLFUNC(dlopen)(const char *path, int mode)
  71 {
  72   void * result;
  73
  74 # ifndef USE_PROC_FOR_LIBRARIES
  75     /* Disable collections.  This solution risks heap growth (or,       */
  76     /* even, heap overflow) but there seems no better solutions.        */
  77     disable_gc_for_dlopen();
  78 # endif
  79   result = REAL_DLFUNC(dlopen)(path, mode);
  80 # ifndef USE_PROC_FOR_LIBRARIES
  81     GC_enable(); /* undoes disable_gc_for_dlopen */
  82 # endif
  83   return(result);
  84 }
  85
  86 #ifdef GC_USE_LD_WRAP
  87   /* Define GC_ function as an alias for the plain one, which will be   */
  88   /* intercepted.  This allows files which include gc.h, and hence      */
  89   /* generate references to the GC_ symbol, to see the right symbol.    */
  90   GC_API void *GC_dlopen(const char *path, int mode)
  91   {
  92     return dlopen(path, mode);
  93   }
  94 #endif /* GC_USE_LD_WRAP */
  95
  96 #ifdef GC_MUST_RESTORE_REDEFINED_DLOPEN
  97 # define dlopen GC_dlopen
  98 #endif
  99
 100 #endif  /* GC_PTHREADS && !GC_NO_DLOPEN */