On shared object unload, in __cxa_finalize, call and clear all installed

atexit and __cxa_atexit handlers that are either installed by unloaded
dso, or points to the functions provided by the dso.

Use _rtld_addr_phdr to locate segment information from the address of
private variable belonging to the dso, supplied by crtstuff.c. Provide
utility function __elf_phdr_match_addr to do the match of address against
dso executable segment.

Call back into libthr from __cxa_finalize using weak
__pthread_cxa_finalize symbol to remove any atfork handler which
function points into unloaded object.

The rtld needs private __pthread_cxa_finalize symbol to not require
resolution of the weak undefined symbol at initialization time. This
cannot work, since rtld is relocated before sym_zero is set up.

Idea by:	kan
Reviewed by:	kan (previous version)
MFC after:	3 weeks

lib/libc/gen/Makefile.inc

@@ -10,7 +10,7 @@ SRCS+=  __getosreldate.c __xuname.c \
 	alarm.c arc4random.c assert.c aux.c basename.c check_utility_compat.c \
 	clock.c closedir.c confstr.c \
 	crypt.c ctermid.c daemon.c devname.c dirname.c disklabel.c \
-	dlfcn.c drand48.c erand48.c err.c errlst.c errno.c \
+	dlfcn.c drand48.c elf_utils.c erand48.c err.c errlst.c errno.c \
 	exec.c fdevname.c feature_present.c fmtcheck.c fmtmsg.c fnmatch.c \
 	fpclassify.c frexp.c fstab.c ftok.c fts.c fts-compat.c ftw.c \
 	getbootfile.c getbsize.c \

lib/libc/gen/Symbol.map

@@ -451,6 +451,7 @@ FBSDprivate_1.0 {
 	_rtld_atfork_post;
 	_rtld_error;		/* for private use */
 	_rtld_thread_init;	/* for private use */
+	__elf_phdr_match_addr;
 	_err;
 	_warn;
 	__fmtcheck;

lib/libc/gen/elf_utils.c

@@ -0,0 +1,47 @@
+/*
+ * Copyright (c) 2010 Konstantin Belousov <kib@freebsd.org>
+ * 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. Neither the name of the author nor the names of any co-contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * 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.
+ *
+ * $FreeBSD$
+ */
+
+#include <link.h>
+
+int
+__elf_phdr_match_addr(struct dl_phdr_info *phdr_info, void *addr)
+{
+	const Elf_Phdr *ph;
+	int i;
+
+	for (i = 0; i < phdr_info->dlpi_phnum; i++) {
+		ph = &phdr_info->dlpi_phdr[i];
+		if (ph->p_type != PT_LOAD || (ph->p_flags & PF_X) == 0)
+			continue;
+		if (phdr_info->dlpi_addr + ph->p_vaddr <= (uintptr_t)addr &&
+		    (uintptr_t)addr + sizeof(addr) < phdr_info->dlpi_addr +
+		    ph->p_vaddr + ph->p_memsz)
+			break;
+	}
+	return (i != phdr_info->dlpi_phnum);
+}

lib/libc/include/libc_private.h

@@ -214,5 +214,7 @@ extern int	__sys_fcntl(int, int, ...);
 int _execvpe(const char *, char * const *, char * const *);
 
 int _elf_aux_info(int aux, void *buf, int buflen);
+struct dl_phdr_info;
+int __elf_phdr_match_addr(struct dl_phdr_info *, void *);
 
 #endif /* _LIBC_PRIVATE_H_ */

lib/libc/stdlib/atexit.c

@@ -37,6 +37,7 @@ static char sccsid[] = "@(#)atexit.c	8.2 (Berkeley) 7/3/94";
 __FBSDID("$FreeBSD$");
 
 #include "namespace.h"
+#include <link.h>
 #include <stddef.h>
 #include <stdlib.h>
 #include <unistd.h>
@@ -147,6 +148,9 @@ __cxa_atexit(void (*func)(void *), void *arg, void *dso)
 	return (error);
 }
 
+#pragma weak __pthread_cxa_finalize
+void __pthread_cxa_finalize(const struct dl_phdr_info *);
+
 /*
  * Call all handlers registered with __cxa_atexit for the shared
  * object owning 'dso'.  Note: if 'dso' is NULL, then all remaining
@@ -155,18 +159,28 @@ __cxa_atexit(void (*func)(void *), void *arg, void *dso)
 void
 __cxa_finalize(void *dso)
 {
+	struct dl_phdr_info phdr_info;
 	struct atexit *p;
 	struct atexit_fn fn;
-	int n;
+	int n, has_phdr;
+
+	if (dso != NULL)
+		has_phdr = _rtld_addr_phdr(dso, &phdr_info);
+	else
+		has_phdr = 0;
 
 	_MUTEX_LOCK(&atexit_mutex);
 	for (p = __atexit; p; p = p->next) {
 		for (n = p->ind; --n >= 0;) {
 			if (p->fns[n].fn_type == ATEXIT_FN_EMPTY)
 				continue; /* already been called */
-			if (dso != NULL && dso != p->fns[n].fn_dso)
-				continue; /* wrong DSO */
 			fn = p->fns[n];
+			if (dso != NULL && dso != fn.fn_dso) {
+				/* wrong DSO ? */
+				if (!has_phdr || !__elf_phdr_match_addr(
+				    &phdr_info, fn.fn_ptr.cxa_func))
+					continue;
+			}
 			/*
 			  Mark entry to indicate that this particular handler
 			  has already been called.
@@ -185,4 +199,7 @@ __cxa_finalize(void *dso)
 	_MUTEX_UNLOCK(&atexit_mutex);
 	if (dso == NULL)
 		_MUTEX_DESTROY(&atexit_mutex);
+
+	if (&__pthread_cxa_finalize != NULL)
+		__pthread_cxa_finalize(&phdr_info);
 }

lib/libthr/pthread.map

@@ -192,6 +192,7 @@ FBSDprivate_1.0 {
 	__poll;
 	__pthread_cond_timedwait;
 	__pthread_cond_wait;
+	__pthread_cxa_finalize;
 	__pthread_mutex_init;
 	__pthread_mutex_lock;
 	__pthread_mutex_timedlock;

lib/libthr/thread/thr_fork.c

@@ -59,6 +59,7 @@
 
 #include "namespace.h"
 #include <errno.h>
+#include <link.h>
 #include <string.h>
 #include <stdlib.h>
 #include <unistd.h>
@@ -94,6 +95,27 @@ _pthread_atfork(void (*prepare)(void), void (*parent)(void),
 	return (0);
 }
 
+void
+__pthread_cxa_finalize(struct dl_phdr_info *phdr_info)
+{
+	struct pthread *curthread;
+	struct pthread_atfork *af, *af1;
+
+	_thr_check_init();
+
+	curthread = _get_curthread();
+	THR_UMUTEX_LOCK(curthread, &_thr_atfork_lock);
+	TAILQ_FOREACH_SAFE(af, &_thr_atfork_list, qe, af1) {
+		if (__elf_phdr_match_addr(phdr_info, af->prepare) ||
+		    __elf_phdr_match_addr(phdr_info, af->parent) ||
+		    __elf_phdr_match_addr(phdr_info, af->child)) {
+			TAILQ_REMOVE(&_thr_atfork_list, af, qe);
+			free(af);
+		}
+	}
+	THR_UMUTEX_UNLOCK(curthread, &_thr_atfork_lock);
+}
+
 __weak_reference(_fork, fork);
 
 pid_t _fork(void);

lib/libthr/thread/thr_private.h

@@ -740,6 +740,9 @@ _thr_check_init(void)
 		_libpthread_init(NULL);
 }
 
+struct dl_phdr_info;
+void __pthread_cxa_finalize(struct dl_phdr_info *phdr_info);
+
 __END_DECLS
 
 #endif  /* !_THR_PRIVATE_H */

libexec/rtld-elf/rtld.c

@@ -3692,6 +3692,10 @@ fetch_ventry(const Obj_Entry *obj, unsigned long symnum)
     return NULL;
 }
 
+/*
+ * Overrides for libc_pic-provided functions.
+ */
+
 int
 __getosreldate(void)
 {
@@ -3711,3 +3715,11 @@ __getosreldate(void)
 		osreldate = osrel;
 	return (osreldate);
 }
+
+/*
+ * No unresolved symbols for rtld.
+ */
+void
+__pthread_cxa_finalize(struct dl_phdr_info *a)
+{
+}