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Rethink the way we count module references. Simply following

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DT_NEEDED links is not flexible enough for cases where dynamically
loaded modules form a dependency cycle.

This should fix an infinite recursion problem encountered by Yahoo.

Approved by:	re (jhb)
This commit is contained in:
Alexander Kabaev 2003-05-08 01:31:36 +00:00
parent 108b696afe
commit 3ddc66d863
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=114826
1 changed files with 30 additions and 18 deletions
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48
libexec/rtld-elf/rtld.c
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@ -126,6 +126,7 @@ static void trace_loaded_objects(Obj_Entry *obj);
static void unlink_object(Obj_Entry *);
static void unload_object(Obj_Entry *);
static void unref_dag(Obj_Entry *);
static void ref_dag(Obj_Entry *);
void r_debug_state(struct r_debug*, struct link_map*);
@ -361,7 +362,6 @@ _rtld(Elf_Addr *sp, func_ptr_type *exit_proc, Obj_Entry **objp)
*obj_tail = obj_main;
obj_tail = &obj_main->next;
obj_count++;
obj_main->refcount++;
/* Make sure we don't call the main program's init and fini functions. */
obj_main->init = obj_main->fini = NULL;
@ -383,8 +383,10 @@ _rtld(Elf_Addr *sp, func_ptr_type *exit_proc, Obj_Entry **objp)
die();
/* Make a list of all objects loaded at startup. */
for (obj = obj_list; obj != NULL; obj = obj->next)
for (obj = obj_list; obj != NULL; obj = obj->next) {
objlist_push_tail(&list_main, obj);
obj->refcount++;
}
if (ld_tracing) { /* We're done */
trace_loaded_objects(obj_main);
@ -970,6 +972,8 @@ init_dag1(Obj_Entry *root, Obj_Entry *obj, DoneList *dlp)
if (donelist_check(dlp, obj))
return;
obj->refcount++;
objlist_push_tail(&obj->dldags, root);
objlist_push_tail(&root->dagmembers, obj);
for (needed = obj->needed; needed != NULL; needed = needed->next)
@ -1223,7 +1227,6 @@ load_object(char *path)
} else
free(path);
obj->refcount++;
return obj;
}
@ -1579,6 +1582,7 @@ dlclose(void *handle)
/* Unreference the object and its dependencies. */
root->dl_refcount--;
unref_dag(root);
if (root->refcount == 0) {
@ -1682,8 +1686,14 @@ dlopen(const char *name, int mode)
/* Make list of init functions to call. */
initlist_add_objects(obj, &obj->next, &initlist);
}
} else if (ld_tracing)
goto trace;
} else {
/* Bump the reference counts for objects on this DAG. */
ref_dag(obj);
if (ld_tracing)
goto trace;
}
}
GDB_STATE(RT_CONSISTENT,obj ? &obj->linkmap : NULL);
@ -2405,7 +2415,6 @@ unload_object(Obj_Entry *root)
static void
unlink_object(Obj_Entry *root)
{
const Needed_Entry *needed;
Objlist_Entry *elm;
if (root->refcount == 0) {
@ -2413,25 +2422,28 @@ unlink_object(Obj_Entry *root)
objlist_remove(&list_global, root);
/* Remove the object from all objects' DAG lists. */
STAILQ_FOREACH(elm, &root->dagmembers , link)
STAILQ_FOREACH(elm, &root->dagmembers , link) {
objlist_remove(&elm->obj->dldags, root);
if (elm->obj != root)
unlink_object(elm->obj);
}
}
}
for (needed = root->needed; needed != NULL; needed = needed->next)
if (needed->obj != NULL)
unlink_object(needed->obj);
static void
ref_dag(Obj_Entry *root)
{
Objlist_Entry *elm;
STAILQ_FOREACH(elm, &root->dagmembers , link)
elm->obj->refcount++;
}
static void
unref_dag(Obj_Entry *root)
{
const Needed_Entry *needed;
Objlist_Entry *elm;
if (root->refcount == 0)
return;
root->refcount--;
if (root->refcount == 0)
for (needed = root->needed; needed != NULL; needed = needed->next)
if (needed->obj != NULL)
unref_dag(needed->obj);
STAILQ_FOREACH(elm, &root->dagmembers , link)
elm->obj->refcount--;
}