diff options
| -rw-r--r-- | ChangeLog | 9 | ||||
| -rw-r--r-- | elf/dl-open.c | 5 | ||||
| -rw-r--r-- | elf/dl-reloc.c | 48 | ||||
| -rw-r--r-- | elf/dl-tls.c | 100 | ||||
| -rw-r--r-- | nptl/ChangeLog | 9 | ||||
| -rw-r--r-- | nptl/Makefile | 12 | ||||
| -rw-r--r-- | nptl/allocatestack.c | 13 | ||||
| -rw-r--r-- | nptl/tst-tls7.c | 120 | ||||
| -rw-r--r-- | nptl/tst-tls7mod.c | 43 |
9 files changed, 313 insertions, 46 deletions
@@ -1,3 +1,12 @@ +2014-01-03 Andrew Hunter <ahh@google.com> + + * elf/dl-open.c (): New comment. + * elf/dl-reloc.c (_dl_try_allocate_static_tls): Use + atomic_compare_and_exchange_bool_acq + (_dl_allocate_static_tls): Block signals. + * elf/dl-tls.c (allocate_and_init): Return void. + (_dl_update_slotinfo): Block signals, use atomic update. + 2014-01-03 Joseph Myers <joseph@codesourcery.com> * math/auto-libm-test-in: Mark various tests with diff --git a/elf/dl-open.c b/elf/dl-open.c index a9ca6b3b44..ea222d03e1 100644 --- a/elf/dl-open.c +++ b/elf/dl-open.c @@ -548,7 +548,10 @@ cannot load any more object with static TLS")); generation of the DSO we are allocating data for. */ _dl_update_slotinfo (imap->l_tls_modid); #endif - + /* We do this iteration under a signal mask in dl-reloc; why not + here? Because these symbols are new and dlopen hasn't + returned yet. So we can't possibly be racing with a TLS + access to them from another thread. */ GL(dl_init_static_tls) (imap); assert (imap->l_need_tls_init == 0); } 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")); diff --git a/elf/dl-tls.c b/elf/dl-tls.c index c1802e7d4e..50ec876eae 100644 --- a/elf/dl-tls.c +++ b/elf/dl-tls.c @@ -17,6 +17,7 @@ <http://www.gnu.org/licenses/>. */ #include <assert.h> +#include <atomic.h> #include <errno.h> #include <libintl.h> #include <signal.h> @@ -533,19 +534,21 @@ rtld_hidden_def (_dl_deallocate_tls) # endif -static void * -allocate_and_init (struct link_map *map) +static void +allocate_and_init (dtv_t *dtv, struct link_map *map) { void *newp; newp = __signal_safe_memalign (map->l_tls_align, map->l_tls_blocksize); if (newp == NULL) oom (); - /* Initialize the memory. */ + /* Initialize the memory. Since this is our thread's space, we are + under a signal mask, and no one has touched this section before, + we can safely just overwrite whatever's there. */ memset (__mempcpy (newp, map->l_tls_initimage, map->l_tls_initimage_size), '\0', map->l_tls_blocksize - map->l_tls_initimage_size); - return newp; + dtv->pointer.val = newp; } @@ -587,7 +590,15 @@ _dl_update_slotinfo (unsigned long int req_modid) the entry we need. */ size_t new_gen = listp->slotinfo[idx].gen; size_t total = 0; - + sigset_t old; + + _dl_mask_all_signals (&old); + /* We use the signal mask as a lock against reentrancy here. + Check that a signal taken before the lock didn't already + update us. */ + dtv = THREAD_DTV (); + if (dtv[0].counter >= listp->slotinfo[idx].gen) + goto out; /* We have to look through the entire dtv slotinfo list. */ listp = GL(dl_tls_dtv_slotinfo_list); do @@ -699,6 +710,8 @@ _dl_update_slotinfo (unsigned long int req_modid) /* This will be the new maximum generation counter. */ dtv[0].counter = new_gen; + out: + _dl_unmask_signals (&old); } return the_map; @@ -724,39 +737,60 @@ tls_get_addr_tail (GET_ADDR_ARGS, dtv_t *dtv, struct link_map *the_map) the_map = listp->slotinfo[idx].map; } - - again: - /* Make sure that, if a dlopen running in parallel forces the - variable into static storage, we'll wait until the address in the - static TLS block is set up, and use that. If we're undecided - yet, make sure we make the decision holding the lock as well. */ - if (__builtin_expect (the_map->l_tls_offset - != FORCED_DYNAMIC_TLS_OFFSET, 0)) + sigset_t old; + _dl_mask_all_signals (&old); + + /* As with update_slotinfo, we use the sigmask as a check against + reentrancy. */ + if (dtv[GET_ADDR_MODULE].pointer.val != TLS_DTV_UNALLOCATED) + goto out; + + /* Synchronize against a parallel dlopen() forcing this variable + into static storage. If that happens, we have to be more careful + about initializing the area, as that dlopen() will be iterating + the threads to do so itself. */ + ptrdiff_t offset; + if ((offset = the_map->l_tls_offset) == NO_TLS_OFFSET) { - __rtld_lock_lock_recursive (GL(dl_load_lock)); - if (__builtin_expect (the_map->l_tls_offset == NO_TLS_OFFSET, 1)) - { - the_map->l_tls_offset = FORCED_DYNAMIC_TLS_OFFSET; - __rtld_lock_unlock_recursive (GL(dl_load_lock)); - } - else + /* 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 (&the_map->l_tls_offset, + FORCED_DYNAMIC_TLS_OFFSET, + NO_TLS_OFFSET); + offset = the_map->l_tls_offset; + assert (offset != NO_TLS_OFFSET); + } + if (offset == FORCED_DYNAMIC_TLS_OFFSET) + { + allocate_and_init (&dtv[GET_ADDR_MODULE], the_map); + } + else + { + void **pp = &dtv[GET_ADDR_MODULE].pointer.val; + while (atomic_forced_read (*pp) == TLS_DTV_UNALLOCATED) { - __rtld_lock_unlock_recursive (GL(dl_load_lock)); - if (__builtin_expect (the_map->l_tls_offset - != FORCED_DYNAMIC_TLS_OFFSET, 1)) - { - void *p = dtv[GET_ADDR_MODULE].pointer.val; - if (__builtin_expect (p == TLS_DTV_UNALLOCATED, 0)) - goto again; - - return (char *) p + GET_ADDR_OFFSET; - } + /* for lack of a better (safe) thing to do, just spin. + Someone else (not us; it's done under a signal mask) set + this map to a static TLS offset, and they'll iterate all + threads to initialize it. They'll eventually write + to pointer.val, at which point we know they've fully + completed initialization. */ + atomic_delay (); } + /* Make sure we've picked up their initialization of the actual + block; this pairs against the write barrier in + init_one_static_tls, guaranteeing that we see their write of + the tls_initimage into the static region. */ + atomic_read_barrier (); } - void *p = dtv[GET_ADDR_MODULE].pointer.val = allocate_and_init (the_map); - dtv[GET_ADDR_MODULE].pointer.is_static = false; +out: + assert (dtv[GET_ADDR_MODULE].pointer.val != TLS_DTV_UNALLOCATED); + _dl_unmask_signals (&old); - return (char *) p + GET_ADDR_OFFSET; + return (char *) dtv[GET_ADDR_MODULE].pointer.val + GET_ADDR_OFFSET; } diff --git a/nptl/ChangeLog b/nptl/ChangeLog index c27ace4822..3c7675e591 100644 --- a/nptl/ChangeLog +++ b/nptl/ChangeLog @@ -1,4 +1,11 @@ -2011-12-12 Adhemerval Zanella <azanella@linux.vnet.ibm.com> +2014-01-03 Andrew Hunter <ahh@google.com> + + * nptl/Makefile (tst-tls7): New test. + * nptl/tst-tls7.c: New file. + * nptl/tst-tls7mod.c: New file. + * nptl/allocatestack.c (init_one_static_tls): Use atomic barrier. + +2013-12-12 Adhemerval Zanella <azanella@linux.vnet.ibm.com> * sysdeps/powerpc/tls.h (struct tcbhead_t): Add DSO and TAR fields. * nptl/sysdeps/powerpc/tcb-offsets.sym: Likewise. diff --git a/nptl/Makefile b/nptl/Makefile index 57cc8c69e4..a43e740847 100644 --- a/nptl/Makefile +++ b/nptl/Makefile @@ -293,7 +293,7 @@ tests += tst-cancelx2 tst-cancelx3 tst-cancelx4 tst-cancelx5 \ tst-oncex3 tst-oncex4 endif ifeq ($(build-shared),yes) -tests += tst-atfork2 tst-tls3 tst-tls4 tst-tls5 tst-_res1 tst-fini1 \ +tests += tst-atfork2 tst-tls3 tst-tls4 tst-tls5 tst-tls7 tst-_res1 tst-fini1 \ tst-stackguard1 tests-nolibpthread += tst-fini1 ifeq ($(have-z-execstack),yes) @@ -304,7 +304,8 @@ endif modules-names = tst-atfork2mod tst-tls3mod tst-tls4moda tst-tls4modb \ tst-tls5mod tst-tls5moda tst-tls5modb tst-tls5modc \ tst-tls5modd tst-tls5mode tst-tls5modf \ - tst-_res1mod1 tst-_res1mod2 tst-execstack-mod tst-fini1mod + tst-_res1mod1 tst-_res1mod2 tst-execstack-mod tst-fini1mod \ + tst-tls7mod extra-test-objs += $(addsuffix .os,$(strip $(modules-names))) tst-cleanup4aux.o test-extras += $(modules-names) tst-cleanup4aux test-modules = $(addprefix $(objpfx),$(addsuffix .so,$(modules-names))) @@ -318,6 +319,7 @@ tst-tls5modc.so-no-z-defs = yes tst-tls5modd.so-no-z-defs = yes tst-tls5mode.so-no-z-defs = yes tst-tls5modf.so-no-z-defs = yes +tst-tls7mod.so-no-z-defs = yes ifeq ($(build-shared),yes) # Build all the modules even when not actually running test programs. @@ -480,6 +482,12 @@ $(objpfx)tst-tls5: $(objpfx)tst-tls5mod.so $(shared-thread-library) LDFLAGS-tst-tls5 = $(no-as-needed) LDFLAGS-tst-tls5mod.so = -Wl,-soname,tst-tls5mod.so +# ensure free(malloc()) isn't optimized out +CFLAGS-tst-tls7.c = -fno-builtin-malloc -fno-builtin-free +$(objpfx)tst-tls7: $(libdl) $(shared-thread-library) +$(objpfx)tst-tls7.out: $(objpfx)tst-tls7mod.so +$(objpfx)tst-tls7mod.so: $(shared-thread-library) + ifeq ($(build-shared),yes) ifeq ($(run-built-tests),yes) tests: $(objpfx)tst-tls6.out diff --git a/nptl/allocatestack.c b/nptl/allocatestack.c index 7f6094ebb2..2a5ac22117 100644 --- a/nptl/allocatestack.c +++ b/nptl/allocatestack.c @@ -1173,13 +1173,18 @@ init_one_static_tls (struct pthread *curp, struct link_map *map) # error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined" # endif - /* Fill in the DTV slot so that a later LD/GD access will find it. */ - dtv[map->l_tls_modid].pointer.val = dest; - dtv[map->l_tls_modid].pointer.is_static = true; - /* Initialize the memory. */ memset (__mempcpy (dest, map->l_tls_initimage, map->l_tls_initimage_size), '\0', map->l_tls_blocksize - map->l_tls_initimage_size); + + /* Fill in the DTV slot so that a later LD/GD access will find it. */ + dtv[map->l_tls_modid].pointer.is_static = true; + /* Pairs against the read barrier in tls_get_attr_tail, guaranteeing + any thread waiting for an update to pointer.val sees the + initimage write. */ + atomic_write_barrier (); + dtv[map->l_tls_modid].pointer.val = dest; + } void diff --git a/nptl/tst-tls7.c b/nptl/tst-tls7.c new file mode 100644 index 0000000000..3bb3f7db6b --- /dev/null +++ b/nptl/tst-tls7.c @@ -0,0 +1,120 @@ +/* Copyright (C) 2013 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/>. */ + + +/* This test checks that TLS in a dlopened object works when first accessed + from a signal handler. */ + +#include <dlfcn.h> +#include <pthread.h> +#include <semaphore.h> +#include <signal.h> +#include <stdio.h> +#include <stdlib.h> + +void * +spin (void *ignored) +{ + while (1) + { + /* busywork */ + free (malloc (128)); + } + + /* never reached */ + return NULL; +} + +int +do_test (void) +{ + pthread_t th[10]; + + for (int i = 0; i < 10; ++i) + { + if (pthread_create (&th[i], NULL, spin, NULL)) + { + puts ("pthread_create failed"); + exit (1); + } + } +#define NITERS 75 + + for (int i = 0; i < NITERS; ++i) + { + void *h = dlopen ("tst-tls7mod.so", RTLD_LAZY); + if (h == NULL) + { + puts ("dlopen failed"); + exit (1); + } + + void (*action) (int, siginfo_t *, void *) = dlsym (h, "action"); + if (action == NULL) + { + puts ("dlsym for action failed"); + exit (1); + } + + struct sigaction sa; + sa.sa_sigaction = action; + sigemptyset (&sa.sa_mask); + sa.sa_flags = SA_SIGINFO; + if (sigaction (SIGUSR1, &sa, NULL)) + { + puts ("sigaction failed"); + exit (1); + } + + sem_t sem; + if (sem_init (&sem, 0, 0)) + { + puts ("sem_init failed"); + } + + sigval_t val; + val.sival_ptr = &sem; + for (int i = 0; i < 10; ++i) + { + if (pthread_sigqueue (th[i], SIGUSR1, val)) + { + puts ("pthread_sigqueue failed"); + } + } + + + for (int i = 0; i < 10; ++i) + { + if (sem_wait (&sem)) + { + puts ("sem_wait failed"); + } + } + + if (dlclose (h)) + { + puts ("dlclose failed"); + exit (1); + } + } + return 0; +} + +#define TIMEOUT 4 + +#define TEST_FUNCTION do_test () +#include "../test-skeleton.c" diff --git a/nptl/tst-tls7mod.c b/nptl/tst-tls7mod.c new file mode 100644 index 0000000000..aff29b9d6c --- /dev/null +++ b/nptl/tst-tls7mod.c @@ -0,0 +1,43 @@ +/* Copyright (C) 2013 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/>. */ + +/* Dynamic module with TLS to be accessed by a signal handler to check safety + of that mode. */ + +#include <semaphore.h> +#include <signal.h> +#include <unistd.h> + +/* This is an unlikely value to see in incorrectly initialized TLS + block -- make sure we're initialized properly. */ +static __thread intptr_t tls_data = 0xdeadbeef; + +void +action (int signo, siginfo_t *info, void *ignored) +{ + sem_t *sem = info->si_value.sival_ptr; + if (tls_data != 0xdeadbeef) + { + write (STDOUT_FILENO, "wrong TLS value\n", 17); + _exit (1); + } + + /* arbitrary choice, just write something unique-ish. */ + tls_data = (intptr_t) info; + + sem_post (sem); +} |