From: John Marino <draco@marino.st>
Date: Sat, 30 Nov 2013 09:47:20 +0000 (+0100)
Subject: rtld: Implement Interpose DSO flag
X-Git-Tag: v3.9.0~1089
X-Git-Url: https://gitweb.dragonflybsd.org/~nant/dragonfly.git/commitdiff_plain/22f5846a17808dfa6cb3d59db7e21c3d8d7b49e5

rtld: Implement Interpose DSO flag

This implementation was sponsored by FreeBSD Foundation.

Taken from:
SVN 256101 (07 OCT 2013)
---

diff --git a/libexec/rtld-elf/rtld.c b/libexec/rtld-elf/rtld.c
index 1a9a47f1d0..968a526d13 100644
--- a/libexec/rtld-elf/rtld.c
+++ b/libexec/rtld-elf/rtld.c
@@ -116,6 +116,7 @@ static Objlist_Entry *objlist_find(Objlist *, const Obj_Entry *);
 static void objlist_init(Objlist *);
 static void objlist_push_head(Objlist *, Obj_Entry *);
 static void objlist_push_tail(Objlist *, Obj_Entry *);
+static void objlist_put_after(Objlist *, Obj_Entry *, Obj_Entry *);
 static void objlist_remove(Objlist *, Obj_Entry *);
 static void *path_enumerate(const char *, path_enum_proc, void *);
 static int relocate_object_dag(Obj_Entry *root, bool bind_now,
@@ -323,6 +324,7 @@ ld_utrace_log(int event, void *handle, void *mapbase, size_t mapsize,
 func_ptr_type
 _rtld(Elf_Addr *sp, func_ptr_type *exit_proc, Obj_Entry **objp)
 {
+    Obj_Entry *last_interposer;
     Elf_Auxinfo *aux_info[AT_COUNT];
     int i;
     int argc;
@@ -566,8 +568,14 @@ _rtld(Elf_Addr *sp, func_ptr_type *exit_proc, Obj_Entry **objp)
 	die();
 
     /* Make a list of all objects loaded at startup. */
+    last_interposer = obj_main;
     for (obj = obj_list;  obj != NULL;  obj = obj->next) {
-	objlist_push_tail(&list_main, obj);
+       if (obj->z_interpose && obj != obj_main) {
+	   objlist_put_after(&list_main, last_interposer, obj);
+	   last_interposer = obj;
+       } else {
+	   objlist_push_tail(&list_main, obj);
+       }
 	obj->refcount++;
     }
 
@@ -1199,6 +1207,8 @@ digest_dynamic1(Obj_Entry *obj, int early, const Elf_Dyn **dyn_rpath,
 		    obj->z_nodelete = true;
 		if (dynp->d_un.d_val & DF_1_LOADFLTR)
 		    obj->z_loadfltr = true;
+               if (dynp->d_un.d_val & DF_1_INTERPOSE)
+                   obj->z_interpose = true;
 		if (dynp->d_un.d_val & DF_1_NODEFLIB)
 		    obj->z_nodeflib = true;
 	    break;
@@ -2031,6 +2041,7 @@ static int
 load_preload_objects(void)
 {
     char *p = ld_preload;
+    Obj_Entry *obj;
     static const char delim[] = " \t:;";
 
     if (p == NULL)
@@ -2040,7 +2051,6 @@ load_preload_objects(void)
     while (*p != '\0') {
 	size_t len = strcspn(p, delim);
 	char savech;
-	Obj_Entry *obj;
 	SymLook req;
 	int res;
 
@@ -2049,6 +2059,7 @@ load_preload_objects(void)
 	obj = load_object(p, -1, NULL, 0);
 	if (obj == NULL)
 	    return -1;	/* XXX - cleanup */
+	obj->z_interpose = true;
 	p[len] = savech;
 	p += len;
 	p += strspn(p, delim);
@@ -2463,6 +2474,23 @@ objlist_push_tail(Objlist *list, Obj_Entry *obj)
     STAILQ_INSERT_TAIL(list, elm, link);
 }
 
+static void
+objlist_put_after(Objlist *list, Obj_Entry *listobj, Obj_Entry *obj)
+{
+       Objlist_Entry *elm, *listelm;
+
+       STAILQ_FOREACH(listelm, list, link) {
+               if (listelm->obj == listobj)
+                       break;
+       }
+       elm = NEW(Objlist_Entry);
+       elm->obj = obj;
+       if (listelm != NULL)
+               STAILQ_INSERT_AFTER(list, listelm, elm, link);
+       else
+               STAILQ_INSERT_TAIL(list, elm, link);
+}
+
 static void
 objlist_remove(Objlist *list, Obj_Entry *obj)
 {
diff --git a/libexec/rtld-elf/rtld.h b/libexec/rtld-elf/rtld.h
index e5e9cb0ab9..58e7aef9fb 100644
--- a/libexec/rtld-elf/rtld.h
+++ b/libexec/rtld-elf/rtld.h
@@ -242,6 +242,7 @@ typedef struct Struct_Obj_Entry {
     bool z_nodelete : 1;	/* Do not unload the object and dependencies */
     bool z_noopen : 1;		/* Do not load on dlopen */
     bool z_loadfltr : 1;	/* Immediately load filtees */
+    bool z_interpose : 1;	/* Interpose all objects but main */
     bool z_nodeflib : 1;	/* Don't search default /usr/lib path */
     bool ref_nodel : 1;		/* Refcount increased to prevent dlclose */
     bool init_scanned: 1;	/* Object is already on init list. */