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Diffstat (limited to 'REORG.TODO/elf/tlsdeschtab.h')
| -rw-r--r-- | REORG.TODO/elf/tlsdeschtab.h | 164 |
1 files changed, 164 insertions, 0 deletions
diff --git a/REORG.TODO/elf/tlsdeschtab.h b/REORG.TODO/elf/tlsdeschtab.h new file mode 100644 index 0000000000..3091d8b420 --- /dev/null +++ b/REORG.TODO/elf/tlsdeschtab.h @@ -0,0 +1,164 @@ +/* Hash table for TLS descriptors. + Copyright (C) 2005-2017 Free Software Foundation, Inc. + This file is part of the GNU C Library. + Contributed by Alexandre Oliva <aoliva@redhat.com> + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, see + <http://www.gnu.org/licenses/>. */ + +#ifndef TLSDESCHTAB_H +# define TLSDESCHTAB_H 1 + +#include <atomic.h> + +# ifdef SHARED + +# include <inline-hashtab.h> + +inline static int +hash_tlsdesc (void *p) +{ + struct tlsdesc_dynamic_arg *td = p; + + /* We know all entries are for the same module, so ti_offset is the + only distinguishing entry. */ + return td->tlsinfo.ti_offset; +} + +inline static int +eq_tlsdesc (void *p, void *q) +{ + struct tlsdesc_dynamic_arg *tdp = p, *tdq = q; + + return tdp->tlsinfo.ti_offset == tdq->tlsinfo.ti_offset; +} + +inline static size_t +map_generation (struct link_map *map) +{ + size_t idx = map->l_tls_modid; + struct dtv_slotinfo_list *listp = GL(dl_tls_dtv_slotinfo_list); + + /* Find the place in the dtv slotinfo list. */ + do + { + /* Does it fit in the array of this list element? */ + if (idx < listp->len) + { + /* We should never get here for a module in static TLS, so + we can assume that, if the generation count is zero, we + still haven't determined the generation count for this + module. */ + if (listp->slotinfo[idx].map == map && listp->slotinfo[idx].gen) + return listp->slotinfo[idx].gen; + else + break; + } + idx -= listp->len; + listp = listp->next; + } + while (listp != NULL); + + /* If we get to this point, the module still hasn't been assigned an + entry in the dtv slotinfo data structures, and it will when we're + done with relocations. At that point, the module will get a + generation number that is one past the current generation, so + return exactly that. */ + return GL(dl_tls_generation) + 1; +} + +void * +internal_function +_dl_make_tlsdesc_dynamic (struct link_map *map, size_t ti_offset) +{ + struct hashtab *ht; + void **entry; + struct tlsdesc_dynamic_arg *td, test; + + /* FIXME: We could use a per-map lock here, but is it worth it? */ + __rtld_lock_lock_recursive (GL(dl_load_lock)); + + ht = map->l_mach.tlsdesc_table; + if (! ht) + { + ht = htab_create (); + if (! ht) + { + __rtld_lock_unlock_recursive (GL(dl_load_lock)); + return 0; + } + map->l_mach.tlsdesc_table = ht; + } + + test.tlsinfo.ti_module = map->l_tls_modid; + test.tlsinfo.ti_offset = ti_offset; + entry = htab_find_slot (ht, &test, 1, hash_tlsdesc, eq_tlsdesc); + if (! entry) + { + __rtld_lock_unlock_recursive (GL(dl_load_lock)); + return 0; + } + + if (*entry) + { + td = *entry; + __rtld_lock_unlock_recursive (GL(dl_load_lock)); + return td; + } + + *entry = td = malloc (sizeof (struct tlsdesc_dynamic_arg)); + /* This may be higher than the map's generation, but it doesn't + matter much. Worst case, we'll have one extra DTV update per + thread. */ + td->gen_count = map_generation (map); + td->tlsinfo = test.tlsinfo; + + __rtld_lock_unlock_recursive (GL(dl_load_lock)); + return td; +} + +# endif /* SHARED */ + +/* The idea of the following two functions is to stop multiple threads + from attempting to resolve the same TLS descriptor without busy + waiting. Ideally, we should be able to release the lock right + after changing td->entry, and then using say a condition variable + or a futex wake to wake up any waiting threads, but let's try to + avoid introducing such dependencies. */ + +static int +_dl_tlsdesc_resolve_early_return_p (struct tlsdesc volatile *td, void *caller) +{ + if (caller != atomic_load_relaxed (&td->entry)) + return 1; + + __rtld_lock_lock_recursive (GL(dl_load_lock)); + if (caller != atomic_load_relaxed (&td->entry)) + { + __rtld_lock_unlock_recursive (GL(dl_load_lock)); + return 1; + } + + atomic_store_relaxed (&td->entry, _dl_tlsdesc_resolve_hold); + + return 0; +} + +static void +_dl_tlsdesc_wake_up_held_fixups (void) +{ + __rtld_lock_unlock_recursive (GL(dl_load_lock)); +} + +#endif |