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

1 files changed, 47 insertions, 0 deletions

diff --git a/lib/libc/gen/elf_utils.c b/lib/libc/gen/elf_utils.c
new file mode 100644
index 0000000..9ee5f41
--- /dev/null
+++ b/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);
+}