diff options
Diffstat (limited to 'REORG.TODO/sysdeps/aarch64/tlsdesc.c')
| -rw-r--r-- | REORG.TODO/sysdeps/aarch64/tlsdesc.c | 166 |
1 files changed, 166 insertions, 0 deletions
diff --git a/REORG.TODO/sysdeps/aarch64/tlsdesc.c b/REORG.TODO/sysdeps/aarch64/tlsdesc.c new file mode 100644 index 0000000000..0b57031126 --- /dev/null +++ b/REORG.TODO/sysdeps/aarch64/tlsdesc.c @@ -0,0 +1,166 @@ +/* Manage TLS descriptors. AArch64 version. + + Copyright (C) 2011-2017 Free Software Foundation, Inc. + + This file is part of the GNU C Library. + + 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/>. */ + +#include <link.h> +#include <ldsodefs.h> +#include <elf/dynamic-link.h> +#include <tls.h> +#include <dl-tlsdesc.h> +#include <dl-unmap-segments.h> +#include <tlsdeschtab.h> +#include <atomic.h> + +/* The following functions take an entry_check_offset argument. It's + computed by the caller as an offset between its entry point and the + call site, such that by adding the built-in return address that is + implicitly passed to the function with this offset, we can easily + obtain the caller's entry point to compare with the entry point + given in the TLS descriptor. If it's changed, we want to return + immediately. */ + +/* This function is used to lazily resolve TLS_DESC RELA relocations. + The argument location is used to hold a pointer to the relocation. */ + +void +attribute_hidden +_dl_tlsdesc_resolve_rela_fixup (struct tlsdesc *td, struct link_map *l) +{ + const ElfW(Rela) *reloc = atomic_load_relaxed (&td->arg); + + /* After GL(dl_load_lock) is grabbed only one caller can see td->entry in + initial state in _dl_tlsdesc_resolve_early_return_p, other concurrent + callers will return and retry calling td->entry. The updated td->entry + synchronizes with the single writer so all read accesses here can use + relaxed order. */ + if (_dl_tlsdesc_resolve_early_return_p + (td, (void*)(D_PTR (l, l_info[ADDRIDX (DT_TLSDESC_PLT)]) + l->l_addr))) + return; + + /* The code below was borrowed from _dl_fixup(), + except for checking for STB_LOCAL. */ + const ElfW(Sym) *const symtab + = (const void *) D_PTR (l, l_info[DT_SYMTAB]); + const char *strtab = (const void *) D_PTR (l, l_info[DT_STRTAB]); + const ElfW(Sym) *sym = &symtab[ELFW(R_SYM) (reloc->r_info)]; + lookup_t result; + + /* Look up the target symbol. If the normal lookup rules are not + used don't look in the global scope. */ + if (ELFW(ST_BIND) (sym->st_info) != STB_LOCAL + && __builtin_expect (ELFW(ST_VISIBILITY) (sym->st_other), 0) == 0) + { + const struct r_found_version *version = NULL; + + if (l->l_info[VERSYMIDX (DT_VERSYM)] != NULL) + { + const ElfW(Half) *vernum = + (const void *) D_PTR (l, l_info[VERSYMIDX (DT_VERSYM)]); + ElfW(Half) ndx = vernum[ELFW(R_SYM) (reloc->r_info)] & 0x7fff; + version = &l->l_versions[ndx]; + if (version->hash == 0) + version = NULL; + } + + result = _dl_lookup_symbol_x (strtab + sym->st_name, l, &sym, + l->l_scope, version, ELF_RTYPE_CLASS_PLT, + DL_LOOKUP_ADD_DEPENDENCY, NULL); + } + else + { + /* We already found the symbol. The module (and therefore its load + address) is also known. */ + result = l; + } + + if (!sym) + { + atomic_store_relaxed (&td->arg, (void *) reloc->r_addend); + /* This release store synchronizes with the ldar acquire load + instruction in _dl_tlsdesc_undefweak. */ + atomic_store_release (&td->entry, _dl_tlsdesc_undefweak); + } + else + { +# ifndef SHARED + CHECK_STATIC_TLS (l, result); +# else + if (!TRY_STATIC_TLS (l, result)) + { + void *p = _dl_make_tlsdesc_dynamic (result, sym->st_value + + reloc->r_addend); + atomic_store_relaxed (&td->arg, p); + /* This release store synchronizes with the ldar acquire load + instruction in _dl_tlsdesc_dynamic. */ + atomic_store_release (&td->entry, _dl_tlsdesc_dynamic); + } + else +# endif + { + void *p = (void*) (sym->st_value + result->l_tls_offset + + reloc->r_addend); + atomic_store_relaxed (&td->arg, p); + /* This release store synchronizes with the ldar acquire load + instruction in _dl_tlsdesc_return_lazy. */ + atomic_store_release (&td->entry, _dl_tlsdesc_return_lazy); + } + } + + _dl_tlsdesc_wake_up_held_fixups (); +} + +/* This function is used to avoid busy waiting for other threads to + complete the lazy relocation. Once another thread wins the race to + relocate a TLS descriptor, it sets the descriptor up such that this + function is called to wait until the resolver releases the + lock. */ + +void +attribute_hidden +_dl_tlsdesc_resolve_hold_fixup (struct tlsdesc *td, void *caller) +{ + /* Maybe we're lucky and can return early. */ + if (caller != atomic_load_relaxed (&td->entry)) + return; + + /* Locking here will stop execution until the running resolver runs + _dl_tlsdesc_wake_up_held_fixups(), releasing the lock. + + FIXME: We'd be better off waiting on a condition variable, such + that we didn't have to hold the lock throughout the relocation + processing. */ + __rtld_lock_lock_recursive (GL(dl_load_lock)); + __rtld_lock_unlock_recursive (GL(dl_load_lock)); +} + + +/* Unmap the dynamic object, but also release its TLS descriptor table + if there is one. */ + +void +internal_function +_dl_unmap (struct link_map *map) +{ + _dl_unmap_segments (map); + +#ifdef SHARED + if (map->l_mach.tlsdesc_table) + htab_delete (map->l_mach.tlsdesc_table); +#endif +} |