diff options
Diffstat (limited to 'elf/dl-reloc.c')
| -rw-r--r-- | elf/dl-reloc.c | 48 |
1 files changed, 43 insertions, 5 deletions
diff --git a/elf/dl-reloc.c b/elf/dl-reloc.c index 1f66fccee2..81ee47eb62 100644 --- a/elf/dl-reloc.c +++ b/elf/dl-reloc.c @@ -16,8 +16,10 @@ License along with the GNU C Library; if not, see <http://www.gnu.org/licenses/>. */ +#include <atomic.h> #include <errno.h> #include <libintl.h> +#include <signal.h> #include <stdlib.h> #include <unistd.h> #include <ldsodefs.h> @@ -70,8 +72,6 @@ _dl_try_allocate_static_tls (struct link_map *map) size_t offset = GL(dl_tls_static_used) + (freebytes - n * map->l_tls_align - map->l_tls_firstbyte_offset); - - map->l_tls_offset = GL(dl_tls_static_used) = offset; #elif TLS_DTV_AT_TP /* dl_tls_static_used includes the TCB at the beginning. */ size_t offset = (((GL(dl_tls_static_used) @@ -83,7 +83,36 @@ _dl_try_allocate_static_tls (struct link_map *map) if (used > GL(dl_tls_static_size)) goto fail; - map->l_tls_offset = offset; +#else +# error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined" +#endif + /* We've computed the new value we want, now try to install it. */ + ptrdiff_t val; + if ((val = map->l_tls_offset) == NO_TLS_OFFSET) + { + /* l_tls_offset starts out at NO_TLS_OFFSET, and all attempts to + change it go from NO_TLS_OFFSET to some other value. We use + compare_and_exchange to ensure only one attempt succeeds. We + don't actually need any memory ordering here, but _acq is the + weakest available. */ + (void ) atomic_compare_and_exchange_bool_acq (&map->l_tls_offset, + offset, + NO_TLS_OFFSET); + val = map->l_tls_offset; + assert (val != NO_TLS_OFFSET); + } + if (val != offset) + { + /* We'd like to set a static offset for this section, but another + thread has already used a dynamic TLS block for it. Since we can + only use static offsets if everyone does (and it's not practical + to move that thread's dynamic block), we have to fail. */ + goto fail; + } + /* We installed the value; now update the globals. */ +#if TLS_TCB_AT_TP + GL(dl_tls_static_used) = offset; +#elif TLS_DTV_AT_TP map->l_tls_firstbyte_offset = GL(dl_tls_static_used); GL(dl_tls_static_used) = used; #else @@ -114,8 +143,17 @@ void internal_function __attribute_noinline__ _dl_allocate_static_tls (struct link_map *map) { - if (map->l_tls_offset == FORCED_DYNAMIC_TLS_OFFSET - || _dl_try_allocate_static_tls (map)) + /* We wrap this in a signal mask because it has to iterate all threads + (including this one) and update this map's TLS entry. A signal handler + accessing TLS would try to do the same update and break. */ + sigset_t old; + _dl_mask_all_signals (&old); + int err = -1; + if (map->l_tls_offset != FORCED_DYNAMIC_TLS_OFFSET) + err = _dl_try_allocate_static_tls (map); + + _dl_unmask_signals (&old); + if (err != 0) { _dl_signal_error (0, map->l_name, NULL, N_("\ cannot allocate memory in static TLS block")); |