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, 12 insertions, 0 deletions

diff --git a/libexec/rtld-elf/rtld.c b/libexec/rtld-elf/rtld.c
index 77eeafb..dc5cdca 100644
--- a/libexec/rtld-elf/rtld.c
+++ b/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)
+{
+}