diff --git a/libc/upstream-openbsd/lib/libc/stdlib/atexit.c b/libc/upstream-openbsd/lib/libc/stdlib/atexit.c
new file mode 100644
index 0000000..6532b38
--- /dev/null
+++ b/libc/upstream-openbsd/lib/libc/stdlib/atexit.c
@@ -0,0 +1,202 @@
+/*	$OpenBSD: atexit.c,v 1.20 2014/07/11 09:51:37 kettenis 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 <string.h>
+#include <unistd.h>
+#include "atexit.h"
+#include "thread_private.h"
+
+struct atexit *__atexit;
+static int restartloop;
+
+/*
+ * 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 functions, all pages are mprotect()'ed
+ * to prevent unintentional/malicious corruption.
+ */
+
+/*
+ * 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
+__cxa_atexit(void (*func)(void *), void *arg, void *dso)
+{
+	struct atexit *p = __atexit;
+	struct atexit_fn *fnp;
+	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) {
+			memset(&p->fns[0], 0, sizeof(p->fns[0]));
+			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;
+	}
+	fnp = &p->fns[p->ind++];
+	fnp->fn_ptr = func;
+	fnp->fn_arg = arg;
+	fnp->fn_dso = dso;
+	if (mprotect(p, pgsize, PROT_READ))
+		goto unlock;
+	restartloop = 1;
+	ret = 0;
+unlock:
+	_ATEXIT_UNLOCK();
+	return (ret);
+}
+
+/*
+ * 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;
+
+	_ATEXIT_LOCK();
+	call_depth++;
+
+restart:
+	restartloop = 0;
+	for (p = __atexit; p != NULL; p = p->next) {
+		for (n = p->ind; --n >= 0;) {
+			if (p->fns[n].fn_ptr == 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 = NULL;
+				mprotect(p, pgsize, PROT_READ);
+			}
+			_ATEXIT_UNLOCK();
+			(*fn.fn_ptr)(fn.fn_arg);
+			_ATEXIT_LOCK();
+			if (restartloop)
+				goto restart;
+		}
+	}
+
+	call_depth--;
+
+	/*
+	 * 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;
+	}
+	_ATEXIT_UNLOCK();
+}
+
+/*
+ * Register the cleanup function
+ */
+void
+__atexit_register_cleanup(void (*func)(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;
+	} else {
+		if (mprotect(p, pgsize, PROT_READ | PROT_WRITE))
+			goto unlock;
+	}
+	p->fns[0].fn_ptr = (void (*)(void *))func;
+	p->fns[0].fn_arg = NULL;
+	p->fns[0].fn_dso = NULL;
+	mprotect(p, pgsize, PROT_READ);
+	restartloop = 1;
+unlock:
+	_ATEXIT_UNLOCK();
+}
diff --git a/libc/upstream-openbsd/lib/libc/stdlib/atexit.h b/libc/upstream-openbsd/lib/libc/stdlib/atexit.h
new file mode 100644
index 0000000..3de2aa3
--- /dev/null
+++ b/libc/upstream-openbsd/lib/libc/stdlib/atexit.h
@@ -0,0 +1,47 @@
+/*	$OpenBSD: atexit.h,v 1.9 2014/06/18 19:01:10 kettenis 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.
+ *
+ */
+
+struct atexit {
+	struct atexit *next;		/* next in list */
+	int ind;			/* next index in this table */
+	int max;			/* max entries >= ATEXIT_SIZE */
+	struct atexit_fn {
+		void (*fn_ptr)(void *);
+		void *fn_arg;		/* argument for CXA callback */
+		void *fn_dso;		/* shared module handle */
+	} fns[1];			/* the table itself */
+};
+
+extern struct atexit *__atexit;		/* points to head of LIFO stack */
+
+int	__cxa_atexit(void (*)(void *), void *, void *);
+void	__cxa_finalize(void *);