1 files changed, 133 insertions, 0 deletions

diff --git a/src/lib/libc/stdlib/atexit.c b/src/lib/libc/stdlib/atexit.c
new file mode 100644
index 0000000000..50f8ec9372
--- /dev/null
+++ b/src/lib/libc/stdlib/atexit.c
@@ -0,0 +1,133 @@
+/*      $OpenBSD: atexit.c,v 1.12 2006/02/22 07:16:32 otto Exp $ */
+/*
+ * Copyright (c) 2002 Daniel Hartmeier
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ *    - Redistributions of source code must retain the above copyright
+ *      notice, this list of conditions and the following disclaimer.
+ *    - Redistributions in binary form must reproduce the above
+ *      copyright notice, this list of conditions and the following
+ *      disclaimer in the documentation and/or other materials provided
+ *      with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include <sys/types.h>
+#include <sys/mman.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include "atexit.h"
+#include "thread_private.h"
+
+int __atexit_invalid = 1;
+struct atexit *__atexit;
+
+/*
+ * Function pointers are stored in a linked list of pages. The list
+ * is initially empty, and pages are allocated on demand. The first
+ * 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
+ * to prevent unintentional/malicious corruption.
+ */
+
+/*
+ * Register a function to be performed at exit.
+ */
+int
+atexit(void (*fn)(void))
+{
+        struct atexit *p;
+        int pgsize = getpagesize();
+        int ret = -1;
+
+        if (pgsize < sizeof(*p))
+                return (-1);
+        _ATEXIT_LOCK();
+        p = __atexit;
+        if (p != NULL) {
+                if (p->ind + 1 >= p->max)
+                        p = NULL;
+                else if (mprotect(p, pgsize, PROT_READ | PROT_WRITE))
+                        goto unlock;
+        }
+        if (p == NULL) {
+                p = mmap(NULL, pgsize, PROT_READ | PROT_WRITE,
+                    MAP_ANON | MAP_PRIVATE, -1, 0);
+                if (p == MAP_FAILED)
+                        goto unlock;
+                if (__atexit == NULL) {
+                        p->fns[0] = NULL;
+                        p->ind = 1;
+                } else
+                        p->ind = 0;
+                p->max = (pgsize - ((char *)&p->fns[0] - (char *)p)) /
+                    sizeof(p->fns[0]);
+                p->next = __atexit;
+                __atexit = p;
+                if (__atexit_invalid)
+                        __atexit_invalid = 0;
+        }
+        p->fns[p->ind++] = fn;
+        if (mprotect(p, pgsize, PROT_READ))
+                goto unlock;
+        ret = 0;
+unlock:
+        _ATEXIT_UNLOCK();
+        return (ret);
+}
+
+/*
+ * Register the cleanup function
+ */
+void
+__atexit_register_cleanup(void (*fn)(void))
+{
+        struct atexit *p;
+        int pgsize = getpagesize();
+
+        if (pgsize < sizeof(*p))
+                return;
+        _ATEXIT_LOCK();
+        p = __atexit;
+        while (p != NULL && p->next != NULL)
+                p = p->next;
+        if (p == NULL) {
+                p = mmap(NULL, pgsize, PROT_READ | PROT_WRITE,
+                    MAP_ANON | MAP_PRIVATE, -1, 0);
+                if (p == MAP_FAILED)
+                        goto unlock;
+                p->ind = 1;
+                p->max = (pgsize - ((char *)&p->fns[0] - (char *)p)) /
+                    sizeof(p->fns[0]);
+                p->next = NULL;
+                __atexit = p;
+                if (__atexit_invalid)
+                        __atexit_invalid = 0;
+        } else {
+                if (mprotect(p, pgsize, PROT_READ | PROT_WRITE))
+                        goto unlock;
+        }
+        p->fns[0] = fn;
+        mprotect(p, pgsize, PROT_READ);
+unlock:
+        _ATEXIT_UNLOCK();
+}