Add rtld private interface for dso to detect dynamic loading

vs. static linking.

Tested by:	pho, antoine (exp-run)
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week

lib/libc/gen/Symbol.map

@@ -487,6 +487,7 @@ FBSDprivate_1.0 {
 	_rtld_atfork_post;
 	_rtld_error;		/* for private use */
 	_rtld_get_stack_prot;
+	_rtld_is_dlopened;
 	_rtld_thread_init;	/* for private use */
 	__elf_phdr_match_addr;
 	_err;

lib/libc/gen/dlfcn.c

@@ -233,3 +233,10 @@ _rtld_get_stack_prot(void)
 	return (PROT_EXEC | PROT_READ | PROT_WRITE);
 }
 
+#pragma weak _rtld_is_dlopened
+int
+_rtld_is_dlopened(void *arg)
+{
+
+	return (0);
+}

libexec/rtld-elf/Symbol.map

@@ -30,5 +30,6 @@ FBSDprivate_1.0 {
     _rtld_atfork_post;
     _rtld_addr_phdr;
     _rtld_get_stack_prot;
+    _rtld_is_dlopened;
     _r_debug_postinit;
 };

libexec/rtld-elf/rtld.c

@@ -2222,6 +2222,7 @@ do_load_object(int fd, const char *name, char *path, struct stat *sbp,
 	return (NULL);
     }
 
+    obj->dlopened = (flags & RTLD_LO_DLOPEN) != 0;
     *obj_tail = obj;
     obj_tail = &obj->next;
     obj_count++;
@@ -4884,6 +4885,27 @@ _rtld_get_stack_prot(void)
 	return (stack_prot);
 }
 
+int
+_rtld_is_dlopened(void *arg)
+{
+	Obj_Entry *obj;
+	RtldLockState lockstate;
+	int res;
+
+	rlock_acquire(rtld_bind_lock, &lockstate);
+	obj = dlcheck(arg);
+	if (obj == NULL)
+		obj = obj_from_addr(arg);
+	if (obj == NULL) {
+		_rtld_error("No shared object contains address");
+		lock_release(rtld_bind_lock, &lockstate);
+		return (-1);
+	}
+	res = obj->dlopened ? 1 : 0;
+	lock_release(rtld_bind_lock, &lockstate);
+	return (res);
+}
+
 static void
 map_stacks_exec(RtldLockState *lockstate)
 {

libexec/rtld-elf/rtld.h

@@ -275,6 +275,7 @@ typedef struct Struct_Obj_Entry {
     bool crt_no_init : 1;	/* Object' crt does not call _init/_fini */
     bool valid_hash_sysv : 1;	/* A valid System V hash hash tag is available */
     bool valid_hash_gnu : 1;	/* A valid GNU hash tag is available */
+    bool dlopened : 1;		/* dlopen()-ed (vs. load statically) */
 
     struct link_map linkmap;	/* For GDB and dlinfo() */
     Objlist dldags;		/* Object belongs to these dlopened DAGs (%) */

sys/sys/link_elf.h

@@ -94,6 +94,7 @@ typedef int (*__dl_iterate_hdr_callback)(struct dl_phdr_info *, size_t, void *);
 extern int dl_iterate_phdr(__dl_iterate_hdr_callback, void *);
 int _rtld_addr_phdr(const void *, struct dl_phdr_info *);
 int _rtld_get_stack_prot(void);
+int _rtld_is_dlopened(void *);
 
 #ifdef __ARM_EABI__
 void * dl_unwind_find_exidx(const void *, int *);