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, 1 insertions, 0 deletions

diff --git a/lib/libc/gen/Symbol.map b/lib/libc/gen/Symbol.map
index c4f21b5..6bd3140 100644
--- a/lib/libc/gen/Symbol.map
+++ b/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;