Add __cxa_atexit() support for gcc3. This provides support for shared object destructors called at dlclose() time. Inspired by similar changes in FreeBSD and NetBSD.

1 files changed, 84 insertions, 9 deletions

diff --git a/src/lib/libc/stdlib/atexit.c b/src/lib/libc/stdlib/atexit.c
index 50f8ec9372..ebf5f8775c 100644
--- a/src/lib/libc/stdlib/atexit.c
+++ b/src/lib/libc/stdlib/atexit.c
@@ -1,4 +1,4 @@
-/*      $OpenBSD: atexit.c,v 1.12 2006/02/22 07:16:32 otto Exp $ */
+/*      $OpenBSD: atexit.c,v 1.13 2007/09/03 14:40:16 millert Exp $ */
 /*
  * Copyright (c) 2002 Daniel Hartmeier
  * All rights reserved.
@@ -45,17 +45,22 @@ struct atexit *__atexit;
  * function pointer in the first allocated page (the last one in
  * the linked list) is reserved for the cleanup function.
  *
- * Outside the following two functions, all pages are mprotect()'ed
+ * Outside the following functions, all pages are mprotect()'ed
  * to prevent unintentional/malicious corruption.
  */
 
 /*
- * Register a function to be performed at exit.
+ * Register a function to be performed at exit or when a shared object
+ * with the given dso handle is unloaded dynamically.  Also used as
+ * the backend for atexit().  For more info on this API, see:
+ *
+ *      http://www.codesourcery.com/cxx-abi/abi.html#dso-dtor
  */
 int
-atexit(void (*fn)(void))
+__cxa_atexit(void (*func)(void *), void *arg, void *dso)
 {
-        struct atexit *p;
+        struct atexit *p = __atexit;
+        struct atexit_fn *fnp;
         int pgsize = getpagesize();
         int ret = -1;
 
@@ -75,7 +80,7 @@ atexit(void (*fn)(void))
                 if (p == MAP_FAILED)
                         goto unlock;
                 if (__atexit == NULL) {
-                        p->fns[0] = NULL;
+                        memset(&p->fns[0], 0, sizeof(p->fns[0]));
                         p->ind = 1;
                 } else
                         p->ind = 0;
@@ -86,7 +91,10 @@ atexit(void (*fn)(void))
                 if (__atexit_invalid)
                         __atexit_invalid = 0;
         }
-        p->fns[p->ind++] = fn;
+        fnp = &p->fns[p->ind++];
+        fnp->fn_ptr.cxa_func = func;
+        fnp->fn_arg = arg;
+        fnp->fn_dso = dso;
         if (mprotect(p, pgsize, PROT_READ))
                 goto unlock;
         ret = 0;
@@ -96,10 +104,75 @@ unlock:
 }
 
 /*
+ * Register a function to be performed at exit.
+ */
+int
+atexit(void (*func)(void))
+{
+        return (__cxa_atexit((void (*)(void *))func, NULL, NULL));
+}
+
+/*
+ * Call all handlers registered with __cxa_atexit() for the shared
+ * object owning 'dso'.
+ * Note: if 'dso' is NULL, then all remaining handlers are called.
+ */
+void
+__cxa_finalize(void *dso)
+{
+        struct atexit *p, *q;
+        struct atexit_fn fn;
+        int n, pgsize = getpagesize();
+        static int call_depth;
+
+        if (__atexit_invalid)
+                return;
+
+        call_depth++;
+
+        for (p = __atexit; p != NULL; p = p->next) {
+                for (n = p->ind; --n >= 0;) {
+                        if (p->fns[n].fn_ptr.cxa_func == NULL)
+                                continue;       /* already called */
+                        if (dso != NULL && dso != p->fns[n].fn_dso)
+                                continue;       /* wrong DSO */
+
+                        /*
+                         * Mark handler as having been already called to avoid
+                         * dupes and loops, then call the appropriate function.
+                         */
+                        fn = p->fns[n];
+                        if (mprotect(p, pgsize, PROT_READ | PROT_WRITE) == 0) {
+                                p->fns[n].fn_ptr.cxa_func = NULL;
+                                mprotect(p, pgsize, PROT_READ);
+                        }
+                        if (dso != NULL)
+                                (*fn.fn_ptr.cxa_func)(fn.fn_arg);
+                        else
+                                (*fn.fn_ptr.std_func)();
+                }
+        }
+
+        /*
+         * If called via exit(), unmap the pages since we have now run
+         * all the handlers.  We defer this until calldepth == 0 so that
+         * we don't unmap things prematurely if called recursively.
+         */
+        if (dso == NULL && --call_depth == 0) {
+                for (p = __atexit; p != NULL; ) {
+                        q = p;
+                        p = p->next;
+                        munmap(q, pgsize);
+                }
+                __atexit = NULL;
+        }
+}
+
+/*
  * Register the cleanup function
  */
 void
-__atexit_register_cleanup(void (*fn)(void))
+__atexit_register_cleanup(void (*func)(void))
 {
         struct atexit *p;
         int pgsize = getpagesize();
@@ -126,7 +199,9 @@ __atexit_register_cleanup(void (*fn)(void))
                 if (mprotect(p, pgsize, PROT_READ | PROT_WRITE))
                         goto unlock;
         }
-        p->fns[0] = fn;
+        p->fns[0].fn_ptr.std_func = func;
+        p->fns[0].fn_arg = NULL;
+        p->fns[0].fn_dso = NULL;
         mprotect(p, pgsize, PROT_READ);
 unlock:
         _ATEXIT_UNLOCK();