fix/improve shared library ctor/dtor handling, allow recursive dlopen

[musl] / src / ldso / dynlink.c

diff --git a/src/ldso/dynlink.c b/src/ldso/dynlink.c
index 3f9bc14..e07db33 100644 (file)
--- a/src/ldso/dynlink.c
+++ b/src/ldso/dynlink.c
@@ -72,6 +72,7 @@ struct dso {
        void **new_dtv;
        unsigned char *new_tls;
        int new_dtv_idx, new_tls_idx;
+       struct dso *fini_next;
        char *shortname;
        char buf[];
 };
@@ -86,7 +87,7 @@ struct symdef {
 void __init_ssp(size_t *);
 void *__install_initial_tls(void *);
 
-static struct dso *head, *tail, *libc;
+static struct dso *head, *tail, *libc, *fini_head;
 static char *env_path, *sys_path, *r_path;
 static int ssp_used;
 static int runtime;
@@ -97,6 +98,7 @@ static pthread_rwlock_t lock;
 static struct debug debug;
 static size_t *auxv;
 static size_t tls_cnt, tls_size;
+static pthread_mutex_t init_fini_lock = { ._m_type = PTHREAD_MUTEX_RECURSIVE };
 
 struct debug *_dl_debug_addr = &debug;
 
@@ -642,18 +644,37 @@ static void find_map_range(Phdr *ph, size_t cnt, size_t stride, struct dso *p)
        p->map_len = max_addr - min_addr;
 }
 
+static void do_fini()
+{
+       struct dso *p;
+       size_t dyn[DYN_CNT] = {0};
+       for (p=fini_head; p; p=p->fini_next) {
+               if (!p->constructed) continue;
+               decode_vec(p->dynv, dyn, DYN_CNT);
+               ((void (*)(void))(p->base + dyn[DT_FINI]))();
+       }
+}
+
 static void do_init_fini(struct dso *p)
 {
        size_t dyn[DYN_CNT] = {0};
+       int need_locking = __libc.threads_minus_1;
+       /* Allow recursive calls that arise when a library calls
+        * dlopen from one of its constructors, but block any
+        * other threads until all ctors have finished. */
+       if (need_locking) pthread_mutex_lock(&init_fini_lock);
        for (; p; p=p->prev) {
-               if (p->constructed) return;
+               if (p->constructed) continue;
+               p->constructed = 1;
                decode_vec(p->dynv, dyn, DYN_CNT);
-               if (dyn[0] & (1<<DT_FINI))
-                       atexit((void (*)(void))(p->base + dyn[DT_FINI]));
+               if (dyn[0] & (1<<DT_FINI)) {
+                       p->fini_next = fini_head;
+                       fini_head = p;
+               }
                if (dyn[0] & (1<<DT_INIT))
                        ((void (*)(void))(p->base + dyn[DT_INIT]))();
-               p->constructed = 1;
        }
+       if (need_locking) pthread_mutex_unlock(&init_fini_lock);
 }
 
 void _dl_debug_state(void)
@@ -932,6 +953,7 @@ void *__dynlink(int argc, char **argv)
 
        if (ssp_used) __init_ssp(auxv);
 
+       atexit(do_fini);
        do_init_fini(tail);
 
        errno = 0;
@@ -1007,11 +1029,11 @@ void *dlopen(const char *file, int mode)
        if (ssp_used) __init_ssp(auxv);
 
        _dl_debug_state();
-
-       do_init_fini(tail);
+       orig_tail = tail;
 end:
        __release_ptc();
        pthread_rwlock_unlock(&lock);
+       if (p) do_init_fini(orig_tail);
        pthread_setcancelstate(cs, 0);
        return p;
 }