Here is an update diff that implements __cxa_thread_atexit which is
emitted by clang (and modern gcc) to implement certain aspects of
C++11 thread_local.
Compared to the previous function this now also prevents unloading of
shared libraries that call __cxa_thread_atexit.
As before uou'll need to install header files and build and install
ld.so before installing the new libc. This also needs a libc minor
bump (not included).
ok?
Index: include/dlfcn.h
===================================================================
RCS file: /cvs/src/include/dlfcn.h,v
retrieving revision 1.13
diff -u -p -r1.13 dlfcn.h
--- include/dlfcn.h 24 Mar 2013 01:37:21 -0000 1.13
+++ include/dlfcn.h 19 Nov 2017 20:59:08 -0000
@@ -72,6 +72,7 @@ typedef struct dl_info {
#define DL_GETLOADADDR x
#define DL_SETTHREADLCK 2
#define DL_SETBINDLCK 3
+#define DL_REFERENCE 4
#define DL_LAZY RTLD_LAZY /* Compat */
Index: include/tib.h
===================================================================
RCS file: /cvs/src/include/tib.h,v
retrieving revision 1.5
diff -u -p -r1.5 tib.h
--- include/tib.h 10 Aug 2017 13:35:18 -0000 1.5
+++ include/tib.h 19 Nov 2017 20:59:08 -0000
@@ -135,6 +135,7 @@
*/
struct tib {
+ void *tib_atexit;
int tib_thread_flags; /* internal to libpthread */
pid_t tib_tid;
int tib_cantcancel;
@@ -182,16 +183,12 @@ struct tib {
int tib_cantcancel;
pid_t tib_tid;
int tib_thread_flags; /* internal to libpthread */
-#if !defined(__LP64__) && !defined(__i386)
- int __tib_padding; /* padding for 8byte alignment */
-#endif
+ void *tib_atexit;
};
#if defined(__i386) || defined(__amd64)
# define _TIB_PREP(tib) \
((void)((tib)->__tib_self = (tib)))
-#elif !defined(__LP64__) && !defined(__i386)
-# define _TIB_PREP(tib) ((void)((tib)->__tib_padding = 0))
#endif
#define TIB_EXTRA_ALIGN sizeof(void *)
@@ -207,6 +204,7 @@ struct tib {
#define TIB_INIT(tib, dtv, thread) do { \
(tib)->tib_thread = (thread); \
+ (tib)->tib_atexit = NULL; \
(tib)->tib_locale = NULL; \
(tib)->tib_cantcancel = 0; \
(tib)->tib_cancel_point = 0; \
Index: lib/libc/Symbols.list
===================================================================
RCS file: /cvs/src/lib/libc/Symbols.list,v
retrieving revision 1.61
diff -u -p -r1.61 Symbols.list
--- lib/libc/Symbols.list 4 Nov 2017 22:53:57 -0000 1.61
+++ lib/libc/Symbols.list 19 Nov 2017 20:59:08 -0000
@@ -1466,6 +1466,7 @@ random
/* stdlib */
_Exit
__cxa_atexit
+__cxa_thread_atexit
__cxa_finalize
__isthreaded
a64l
Index: lib/libc/include/thread_private.h
===================================================================
RCS file: /cvs/src/lib/libc/include/thread_private.h,v
retrieving revision 1.32
diff -u -p -r1.32 thread_private.h
--- lib/libc/include/thread_private.h 4 Nov 2017 22:53:57 -0000 1.32
+++ lib/libc/include/thread_private.h 19 Nov 2017 20:59:09 -0000
@@ -394,6 +394,7 @@ void _spinunlock(volatile _atomic_lock_t
void _rthread_debug(int, const char *, ...)
__attribute__((__format__ (printf, 2, 3)));
pid_t _thread_dofork(pid_t (*_sys_fork)(void));
+void _thread_finalize(void);
/*
* Threading syscalls not declared in system headers
Index: lib/libc/stdlib/atexit.c
===================================================================
RCS file: /cvs/src/lib/libc/stdlib/atexit.c,v
retrieving revision 1.24
diff -u -p -r1.24 atexit.c
--- lib/libc/stdlib/atexit.c 10 Nov 2015 04:14:03 -0000 1.24
+++ lib/libc/stdlib/atexit.c 19 Nov 2017 20:59:09 -0000
@@ -31,12 +31,26 @@
#include <sys/types.h>
#include <sys/mman.h>
+#include <dlfcn.h>
+#ifndef NO_PIC
+#include <elf.h>
+#pragma weak _DYNAMIC
+#endif
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include "atexit.h"
#include "atfork.h"
#include "thread_private.h"
+#include "tib.h"
+
+typeof(dlctl) dlctl asm("_dlctl") __attribute__((weak));
+
+struct thread_atexit_fn {
+ void (*func)(void *);
+ void *arg;
+ struct thread_atexit_fn *next;
+};
struct atexit *__atexit;
static int restartloop;
@@ -121,6 +135,43 @@ atexit(void (*fn)(void))
}
DEF_STRONG(atexit);
+int
+__cxa_thread_atexit(void (*func)(void *), void *arg, void *dso)
+{
+ struct thread_atexit_fn *fnp;
+ struct tib *tib = TIB_GET();
+
+ fnp = calloc(1, sizeof(struct thread_atexit_fn));
+ if (fnp == NULL)
+ return -1;
+
+#ifndef NO_PIC
+ if (_DYNAMIC)
+ dlctl(NULL, DL_REFERENCE, dso);
+#endif
+
+ fnp->func = func;
+ fnp->arg = arg;
+ fnp->next = tib->tib_atexit;
+ tib->tib_atexit = fnp;
+
+ return 0;
+}
+DEF_STRONG(__cxa_thread_atexit);
+
+void
+_thread_finalize(void)
+{
+ struct tib *tib = TIB_GET();
+
+ while (tib->tib_atexit) {
+ struct thread_atexit_fn *fnp = tib->tib_atexit;
+ tib->tib_atexit = fnp->next;
+ fnp->func(fnp->arg);
+ free(fnp);
+ }
+}
+
/*
* Call all handlers registered with __cxa_atexit() for the shared
* object owning 'dso'.
@@ -133,6 +184,9 @@ __cxa_finalize(void *dso)
struct atexit_fn fn;
int n, pgsize = getpagesize();
static int call_depth;
+
+ if (dso == NULL)
+ _thread_finalize();
_ATEXIT_LOCK();
call_depth++;
Index: lib/libc/stdlib/atexit.h
===================================================================
RCS file: /cvs/src/lib/libc/stdlib/atexit.h,v
retrieving revision 1.10
diff -u -p -r1.10 atexit.h
--- lib/libc/stdlib/atexit.h 25 Oct 2015 18:01:24 -0000 1.10
+++ lib/libc/stdlib/atexit.h 19 Nov 2017 20:59:09 -0000
@@ -46,7 +46,9 @@ extern struct atexit *__atexit; /* poin
__END_HIDDEN_DECLS
int __cxa_atexit(void (*)(void *), void *, void *);
+int __cxa_thread_atexit(void (*)(void *), void *, void *);
void __cxa_finalize(void *);
PROTO_NORMAL(__cxa_atexit);
+PROTO_STD_DEPRECATED(__cxa_thread_atexit);
PROTO_NORMAL(__cxa_finalize);
Index: lib/libc/thread/rthread.c
===================================================================
RCS file: /cvs/src/lib/libc/thread/rthread.c,v
retrieving revision 1.6
diff -u -p -r1.6 rthread.c
--- lib/libc/thread/rthread.c 4 Nov 2017 22:53:57 -0000 1.6
+++ lib/libc/thread/rthread.c 19 Nov 2017 20:59:09 -0000
@@ -137,6 +137,7 @@ pthread_exit(void *retval)
oclfn->fn(oclfn->arg);
free(oclfn);
}
+ _thread_finalize();
_rthread_tls_destructors(thread);
if (_thread_cb.tc_thread_release != NULL)
