MFC r303795:

Add __cxa_thread_atexit(3) API implementation.

4 files changed, 152 insertions, 1 deletions

diff --git a/lib/libc/stdlib/Makefile.inc b/lib/libc/stdlib/Makefile.inc
index 3c6ba17..beb5316 100644
--- a/lib/libc/stdlib/Makefile.inc
+++ b/lib/libc/stdlib/Makefile.inc
@@ -5,7 +5,7 @@
 .PATH: ${LIBC_SRCTOP}/${LIBC_ARCH}/stdlib ${LIBC_SRCTOP}/stdlib
 
 MISRCS+=_Exit.c a64l.c abort.c abs.c atexit.c atof.c atoi.c atol.c atoll.c \
-	bsearch.c div.c exit.c getenv.c getopt.c getopt_long.c \
+	bsearch.c cxa_thread_atexit.c div.c exit.c getenv.c getopt.c getopt_long.c \
 	getsubopt.c hcreate.c hcreate_r.c hdestroy_r.c heapsort.c heapsort_b.c \
 	hsearch_r.c imaxabs.c imaxdiv.c \
 	insque.c l64a.c labs.c ldiv.c llabs.c lldiv.c lsearch.c \
diff --git a/lib/libc/stdlib/Symbol.map b/lib/libc/stdlib/Symbol.map
index 782023e..6cdc38e8 100644
--- a/lib/libc/stdlib/Symbol.map
+++ b/lib/libc/stdlib/Symbol.map
@@ -116,8 +116,13 @@ FBSD_1.4 {
 	reallocarray;
 };
 
+FBSD_1.5 {
+	__cxa_thread_atexit;
+};
+
 FBSDprivate_1.0 {
 	__system;
 	_system;
 	__libc_system;
+	__cxa_thread_call_dtors;
 };
diff --git a/lib/libc/stdlib/cxa_thread_atexit.c b/lib/libc/stdlib/cxa_thread_atexit.c
new file mode 100644
index 0000000..c966731
--- /dev/null
+++ b/lib/libc/stdlib/cxa_thread_atexit.c
@@ -0,0 +1,140 @@
+/*-
+ * Copyright (c) 2016 Mahdi Mokhtari <mokhi64@gmail.com>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. 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 AUTHOR 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 AUTHOR 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/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <sys/queue.h>
+#include "namespace.h"
+#include <errno.h>
+#include <link.h>
+#include <pthread.h>
+#include <stddef.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include "un-namespace.h"
+#include "libc_private.h"
+
+/*
+ * C++11 introduces the thread_local scope (like __thread with some
+ * additions).  As a key-feature it should support non-trivial
+ * destructors, registered with __cxa_thread_atexit() to be executed
+ * at the thread termination.
+ *
+ * The implemention keeps a _Thread_local list of destructors per each
+ * thread, and calls __cxa_thread_call_dtors() on each thread's exit
+ * to do cleanup.  For a thread calling exit(3), in particular, for
+ * the initial thread returning from main(), we call
+ * __cxa_thread_call_dtors() inside exit().
+ *
+ * It could be possible that a dynamically loaded library, use
+ * thread_local variable but is dlclose()'d before thread exit.  The
+ * destructor of this variable will then try to access the address,
+ * for calling it but it's unloaded, so it'll crash.  We're using
+ * __elf_phdr_match_addr() to detect and prevent such cases and so
+ * prevent the crash.
+ */
+
+#define CXA_DTORS_ITERATIONS 4
+
+struct cxa_thread_dtor {
+	void *obj;
+	void (*func)(void *);
+	void *dso;
+	LIST_ENTRY(cxa_thread_dtor) entry;
+};
+static _Thread_local LIST_HEAD(dtor_list, cxa_thread_dtor) dtors =
+    LIST_HEAD_INITIALIZER(dtors);
+
+int
+__cxa_thread_atexit(void (*dtor_func)(void *), void *obj, void *dso_symbol)
+{
+	struct cxa_thread_dtor *new_dtor;
+
+	new_dtor = malloc(sizeof(*new_dtor));
+	if (new_dtor == NULL) {
+		errno = ENOMEM; /* forcibly override malloc(3) error */
+		return (-1);
+	}
+
+	new_dtor->obj = obj;
+	new_dtor->func = dtor_func;
+	new_dtor->dso = dso_symbol;
+	LIST_INSERT_HEAD(&dtors, new_dtor, entry);
+	return (0);
+}
+
+static void
+walk_cb_call(struct cxa_thread_dtor *dtor)
+{
+	struct dl_phdr_info phdr_info;
+
+	if (_rtld_addr_phdr(dtor->dso, &phdr_info) &&
+	    __elf_phdr_match_addr(&phdr_info, dtor->func))
+		dtor->func(dtor->obj);
+	else
+		fprintf(stderr, "__cxa_thread_call_dtors: dtr %p from "
+		    "unloaded dso, skipping\n", (void *)(dtor->func));
+}
+
+static void
+walk_cb_nocall(struct cxa_thread_dtor *dtor __unused)
+{
+}
+
+static void
+cxa_thread_walk(void (*cb)(struct cxa_thread_dtor *))
+{
+	struct cxa_thread_dtor *dtor, *tdtor;
+
+	LIST_FOREACH_SAFE(dtor, &dtors, entry, tdtor) {
+		LIST_REMOVE(dtor, entry);
+		cb(dtor);
+		free(dtor);
+	}
+}
+
+/*
+ * This is the callback function we use to call destructors, once for
+ * each thread.  It is called in exit(3) in libc/stdlib/exit.c and
+ * before exit_thread() in libthr/thread/thr_exit.c.
+ */
+void
+__cxa_thread_call_dtors(void)
+{
+	int i;
+
+	for (i = 0; i < CXA_DTORS_ITERATIONS && !LIST_EMPTY(&dtors); i++)
+		cxa_thread_walk(walk_cb_call);
+
+	if (!LIST_EMPTY(&dtors)) {
+		fprintf(stderr, "Thread %p is exiting with more "
+		    "thread-specific dtors created after %d iterations "
+		    "of destructor calls\n",
+		    _pthread_self(), i);
+		cxa_thread_walk(walk_cb_nocall);
+	}
+}
diff --git a/lib/libc/stdlib/exit.c b/lib/libc/stdlib/exit.c
index a656e04..521d05a 100644
--- a/lib/libc/stdlib/exit.c
+++ b/lib/libc/stdlib/exit.c
@@ -63,6 +63,12 @@ exit(int status)
 
 	_thread_autoinit_dummy_decl = 1;
 
+	/*
+	 * We're dealing with cleaning up thread_local destructors in the case of
+	 * the process termination through main() exit.
+	 * Other cases are handled elsewhere.
+	 */
+	__cxa_thread_call_dtors();
 	__cxa_finalize(NULL);
 	if (__cleanup)
 		(*__cleanup)();