diff options
Diffstat (limited to 'elf/dl-lookup.c')
| -rw-r--r-- | elf/dl-lookup.c | 156 |
1 files changed, 108 insertions, 48 deletions
diff --git a/elf/dl-lookup.c b/elf/dl-lookup.c index c529007ca1..92dc7b226a 100644 --- a/elf/dl-lookup.c +++ b/elf/dl-lookup.c @@ -88,20 +88,50 @@ static int internal_function add_dependency (struct link_map *undef_map, struct link_map *map, int flags) { - struct link_map **list; struct link_map *runp; - unsigned int act; unsigned int i; int result = 0; - unsigned long long int serial; /* Avoid self-references and references to objects which cannot be unloaded anyway. */ if (undef_map == map) return 0; + /* Avoid references to objects which cannot be unloaded anyway. */ + assert (map->l_type == lt_loaded); + if ((map->l_flags_1 & DF_1_NODELETE) != 0) + return 0; + + struct link_map_reldeps *l_reldeps + = atomic_forced_read (undef_map->l_reldeps); + + /* Make sure l_reldeps is read before l_initfini. */ + atomic_read_barrier (); + + /* Determine whether UNDEF_MAP already has a reference to MAP. First + look in the normal dependencies. */ + struct link_map **l_initfini = atomic_forced_read (undef_map->l_initfini); + if (l_initfini != NULL) + { + for (i = 0; l_initfini[i] != NULL; ++i) + if (l_initfini[i] == map) + return 0; + } + + /* No normal dependency. See whether we already had to add it + to the special list of dynamic dependencies. */ + unsigned int l_reldepsact = 0; + if (l_reldeps != NULL) + { + struct link_map **list = &l_reldeps->list[0]; + l_reldepsact = l_reldeps->act; + for (i = 0; i < l_reldepsact; ++i) + if (list[i] == map) + return 0; + } + /* Save serial number of the target MAP. */ - serial = map->l_serial; + unsigned long long serial = map->l_serial; /* Make sure nobody can unload the object while we are at it. */ if (__builtin_expect (flags & DL_LOOKUP_GSCOPE_LOCK, 0)) @@ -110,38 +140,52 @@ add_dependency (struct link_map *undef_map, struct link_map *map, int flags) here, that can result in ABBA deadlock. */ THREAD_GSCOPE_RESET_FLAG (); __rtld_lock_lock_recursive (GL(dl_load_lock)); - THREAD_GSCOPE_SET_FLAG (); /* While MAP value won't change, after THREAD_GSCOPE_RESET_FLAG () it can e.g. point to unallocated memory. So avoid the optimizer treating the above read from MAP->l_serial as ensurance it can safely dereference it. */ map = atomic_forced_read (map); - } - else - __rtld_lock_lock_recursive (GL(dl_load_lock)); - /* From this point on it is unsafe to dereference MAP, until it - has been found in one of the lists. */ + /* From this point on it is unsafe to dereference MAP, until it + has been found in one of the lists. */ - /* Determine whether UNDEF_MAP already has a reference to MAP. First - look in the normal dependencies. */ - if (undef_map->l_initfini != NULL) - { - list = undef_map->l_initfini; + /* Redo the l_initfini check in case undef_map's l_initfini + changed in the mean time. */ + if (undef_map->l_initfini != l_initfini + && undef_map->l_initfini != NULL) + { + l_initfini = undef_map->l_initfini; + for (i = 0; l_initfini[i] != NULL; ++i) + if (l_initfini[i] == map) + goto out_check; + } - for (i = 0; list[i] != NULL; ++i) - if (list[i] == map) - goto out_check; + /* Redo the l_reldeps check if undef_map's l_reldeps changed in + the mean time. */ + if (undef_map->l_reldeps != NULL) + { + if (undef_map->l_reldeps != l_reldeps) + { + struct link_map **list = &undef_map->l_reldeps->list[0]; + l_reldepsact = undef_map->l_reldeps->act; + for (i = 0; i < l_reldepsact; ++i) + if (list[i] == map) + goto out_check; + } + else if (undef_map->l_reldeps->act > l_reldepsact) + { + struct link_map **list + = &undef_map->l_reldeps->list[0]; + i = l_reldepsact; + l_reldepsact = undef_map->l_reldeps->act; + for (; i < l_reldepsact; ++i) + if (list[i] == map) + goto out_check; + } + } } - - /* No normal dependency. See whether we already had to add it - to the special list of dynamic dependencies. */ - list = undef_map->l_reldeps; - act = undef_map->l_reldepsact; - - for (i = 0; i < act; ++i) - if (list[i] == map) - goto out_check; + else + __rtld_lock_lock_recursive (GL(dl_load_lock)); /* The object is not yet in the dependency list. Before we add it make sure just one more time the object we are about to @@ -161,8 +205,8 @@ add_dependency (struct link_map *undef_map, struct link_map *map, int flags) if (map->l_serial != serial) goto out_check; - /* Avoid references to objects which cannot be unloaded anyway. */ - assert (map->l_type == lt_loaded); + /* Redo the NODELETE check, as when dl_load_lock wasn't held + yet this could have changed. */ if ((map->l_flags_1 & DF_1_NODELETE) != 0) goto out; @@ -177,33 +221,46 @@ add_dependency (struct link_map *undef_map, struct link_map *map, int flags) } /* Add the reference now. */ - if (__builtin_expect (act >= undef_map->l_reldepsmax, 0)) + if (__builtin_expect (l_reldepsact >= undef_map->l_reldepsmax, 0)) { /* Allocate more memory for the dependency list. Since this can never happen during the startup phase we can use `realloc'. */ - void *newp; - - undef_map->l_reldepsmax += 5; - newp = realloc (undef_map->l_reldeps, - undef_map->l_reldepsmax - * sizeof (struct link_map *)); + struct link_map_reldeps *newp; + unsigned int max + = undef_map->l_reldepsmax ? undef_map->l_reldepsmax * 2 : 10; - if (__builtin_expect (newp != NULL, 1)) - undef_map->l_reldeps = (struct link_map **) newp; + newp = malloc (sizeof (*newp) + max * sizeof (struct link_map *)); + if (newp == NULL) + { + /* If we didn't manage to allocate memory for the list this is + no fatal problem. We simply make sure the referenced object + cannot be unloaded. This is semantically the correct + behavior. */ + map->l_flags_1 |= DF_1_NODELETE; + goto out; + } else - /* Correct the addition. */ - undef_map->l_reldepsmax -= 5; + { + if (l_reldepsact) + memcpy (&newp->list[0], &undef_map->l_reldeps->list[0], + l_reldepsact * sizeof (struct link_map *)); + newp->list[l_reldepsact] = map; + newp->act = l_reldepsact + 1; + atomic_write_barrier (); + void *old = undef_map->l_reldeps; + undef_map->l_reldeps = newp; + undef_map->l_reldepsmax = max; + if (old) + _dl_scope_free (old); + } } - - /* If we didn't manage to allocate memory for the list this is - no fatal mistake. We simply make sure the referenced object - cannot be unloaded. This is semantically the correct - behavior. */ - if (__builtin_expect (act < undef_map->l_reldepsmax, 1)) - undef_map->l_reldeps[undef_map->l_reldepsact++] = map; else - map->l_flags_1 |= DF_1_NODELETE; + { + undef_map->l_reldeps->list[l_reldepsact] = map; + atomic_write_barrier (); + undef_map->l_reldeps->act = l_reldepsact + 1; + } /* Display information if we are debugging. */ if (__builtin_expect (GLRO(dl_debug_mask) & DL_DEBUG_FILES, 0)) @@ -223,6 +280,9 @@ add_dependency (struct link_map *undef_map, struct link_map *map, int flags) /* Release the lock. */ __rtld_lock_unlock_recursive (GL(dl_load_lock)); + if (__builtin_expect (flags & DL_LOOKUP_GSCOPE_LOCK, 0)) + THREAD_GSCOPE_SET_FLAG (); + return result; out_check: |