diff options
| -rw-r--r-- | ChangeLog | 15 | ||||
| -rw-r--r-- | elf/dl-tls.c | 89 | ||||
| -rw-r--r-- | nptl/Makefile | 8 | ||||
| -rw-r--r-- | nptl/tst-tls3-malloc.c | 176 |
4 files changed, 250 insertions, 38 deletions
@@ -1,6 +1,21 @@ 2016-08-03 Florian Weimer <fweimer@redhat.com> [BZ #17730] + Avoid using memalign for TCB allocations. + * elf/dl-tls.c (tcb_to_pointer_to_free_location): New. + (_dl_allocate_tls_storage): Use malloc and manual alignment. + Avoid alignment gap in the TLS_DTV_AT_TP case. + (_dl_deallocate_tls): Use tcb_to_pointer_to_free_location to + determine the pointer to free. + * nptl/tst-tls3-malloc.c: New test. + * nptl/Makefile (tests): Add it. + (tst-tls3-malloc): Link with libdl, libpthread. + (LDFLAGS-tst-tls3-malloc): Set. + (tst-tls3-malloc.out): Depend on DSO used in test. + +2016-08-03 Florian Weimer <fweimer@redhat.com> + + [BZ #17730] Avoid using memalign for TLS allocations. * sysdeps/generic/dl-dtv.h (struct dtv_pointer): New. Replaces is_static member with to_free member. diff --git a/elf/dl-tls.c b/elf/dl-tls.c index be6a3c7..17567ad 100644 --- a/elf/dl-tls.c +++ b/elf/dl-tls.c @@ -347,6 +347,22 @@ _dl_get_tls_static_info (size_t *sizep, size_t *alignp) *alignp = GL(dl_tls_static_align); } +/* Derive the location of the pointer to the start of the original + allocation (before alignment) from the pointer to the TCB. */ +static inline void ** +tcb_to_pointer_to_free_location (void *tcb) +{ +#if TLS_TCB_AT_TP + /* The TCB follows the TLS blocks, and the pointer to the front + follows the TCB. */ + void **original_pointer_location = tcb + TLS_TCB_SIZE; +#elif TLS_DTV_AT_TP + /* The TCB comes first, preceded by the pre-TCB, and the pointer is + before that. */ + void **original_pointer_location = tcb - TLS_PRE_TCB_SIZE - sizeof (void *); +#endif + return original_pointer_location; +} void * internal_function @@ -359,39 +375,50 @@ _dl_allocate_tls_storage (void) /* Memory layout is: [ TLS_PRE_TCB_SIZE ] [ TLS_TCB_SIZE ] [ TLS blocks ] ^ This should be returned. */ - size += (TLS_PRE_TCB_SIZE + GL(dl_tls_static_align) - 1) - & ~(GL(dl_tls_static_align) - 1); + size += TLS_PRE_TCB_SIZE; #endif - /* Allocate a correctly aligned chunk of memory. */ - result = __libc_memalign (GL(dl_tls_static_align), size); - if (__builtin_expect (result != NULL, 1)) - { - /* Allocate the DTV. */ - void *allocated = result; + /* Perform the allocation. Reserve space for the required alignment + and the pointer to the original allocation. */ + size_t alignment = GL(dl_tls_static_align); + void *allocated = malloc (size + alignment + sizeof (void *)); + if (__glibc_unlikely (allocated == NULL)) + return NULL; + /* Perform alignment and allocate the DTV. */ #if TLS_TCB_AT_TP - /* The TCB follows the TLS blocks. */ - result = (char *) result + size - TLS_TCB_SIZE; - - /* Clear the TCB data structure. We can't ask the caller (i.e. - libpthread) to do it, because we will initialize the DTV et al. */ - memset (result, '\0', TLS_TCB_SIZE); + /* The TCB follows the TLS blocks, which determine the alignment. + (TCB alignment requirements have been taken into account when + calculating GL(dl_tls_static_align).) */ + void *aligned = (void *) roundup ((uintptr_t) allocated, alignment); + result = aligned + size - TLS_TCB_SIZE; + + /* Clear the TCB data structure. We can't ask the caller (i.e. + libpthread) to do it, because we will initialize the DTV et al. */ + memset (result, '\0', TLS_TCB_SIZE); #elif TLS_DTV_AT_TP - result = (char *) result + size - GL(dl_tls_static_size); - - /* Clear the TCB data structure and TLS_PRE_TCB_SIZE bytes before it. - We can't ask the caller (i.e. libpthread) to do it, because we will - initialize the DTV et al. */ - memset ((char *) result - TLS_PRE_TCB_SIZE, '\0', - TLS_PRE_TCB_SIZE + TLS_TCB_SIZE); + /* Pre-TCB and TCB come before the TLS blocks. The layout computed + in _dl_determine_tlsoffset assumes that the TCB is aligned to the + TLS block alignment, and not just the TLS blocks after it. This + can leave an unused alignment gap between the TCB and the TLS + blocks. */ + result = (void *) roundup + (sizeof (void *) + TLS_PRE_TCB_SIZE + (uintptr_t) allocated, + alignment); + + /* Clear the TCB data structure and TLS_PRE_TCB_SIZE bytes before + it. We can't ask the caller (i.e. libpthread) to do it, because + we will initialize the DTV et al. */ + memset (result - TLS_PRE_TCB_SIZE, '\0', TLS_PRE_TCB_SIZE + TLS_TCB_SIZE); #endif - result = allocate_dtv (result); - if (result == NULL) - free (allocated); - } + /* Record the value of the original pointer for later + deallocation. */ + *tcb_to_pointer_to_free_location (result) = allocated; + result = allocate_dtv (result); + if (result == NULL) + free (allocated); return result; } @@ -558,17 +585,7 @@ _dl_deallocate_tls (void *tcb, bool dealloc_tcb) free (dtv - 1); if (dealloc_tcb) - { -#if TLS_TCB_AT_TP - /* The TCB follows the TLS blocks. Back up to free the whole block. */ - tcb -= GL(dl_tls_static_size) - TLS_TCB_SIZE; -#elif TLS_DTV_AT_TP - /* Back up the TLS_PRE_TCB_SIZE bytes. */ - tcb -= (TLS_PRE_TCB_SIZE + GL(dl_tls_static_align) - 1) - & ~(GL(dl_tls_static_align) - 1); -#endif - free (tcb); - } + free (*tcb_to_pointer_to_free_location (tcb)); } rtld_hidden_def (_dl_deallocate_tls) diff --git a/nptl/Makefile b/nptl/Makefile index 0d8aade..2ddcd2b 100644 --- a/nptl/Makefile +++ b/nptl/Makefile @@ -321,8 +321,8 @@ tests += tst-cancelx2 tst-cancelx3 tst-cancelx4 tst-cancelx5 \ tst-cleanupx0 tst-cleanupx1 tst-cleanupx2 tst-cleanupx3 tst-cleanupx4 \ tst-oncex3 tst-oncex4 ifeq ($(build-shared),yes) -tests += tst-atfork2 tst-tls3 tst-tls4 tst-tls5 tst-_res1 tst-fini1 \ - tst-stackguard1 +tests += tst-atfork2 tst-tls3 tst-tls3-malloc tst-tls4 tst-tls5 tst-_res1 \ + tst-fini1 tst-stackguard1 tests-nolibpthread += tst-fini1 ifeq ($(have-z-execstack),yes) tests += tst-execstack @@ -529,6 +529,10 @@ LDFLAGS-tst-tls3 = -rdynamic $(objpfx)tst-tls3.out: $(objpfx)tst-tls3mod.so $(objpfx)tst-tls3mod.so: $(shared-thread-library) +$(objpfx)tst-tls3-malloc: $(libdl) $(shared-thread-library) +LDFLAGS-tst-tls3-malloc = -rdynamic +$(objpfx)tst-tls3-malloc.out: $(objpfx)tst-tls3mod.so + $(objpfx)tst-tls4: $(libdl) $(shared-thread-library) $(objpfx)tst-tls4.out: $(objpfx)tst-tls4moda.so $(objpfx)tst-tls4modb.so diff --git a/nptl/tst-tls3-malloc.c b/nptl/tst-tls3-malloc.c new file mode 100644 index 0000000..5eab3cd --- /dev/null +++ b/nptl/tst-tls3-malloc.c @@ -0,0 +1,176 @@ +/* Test TLS allocation with an interposed malloc. + Copyright (C) 2016 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/>. */ + +/* Reuse the test. */ +#include "tst-tls3.c" + +#include <sys/mman.h> + +/* Interpose a minimal malloc implementation. This implementation + deliberately interposes just a restricted set of symbols, to detect + if the TLS code bypasses the interposed malloc. */ + +/* Lock to guard malloc internals. */ +static pthread_mutex_t malloc_lock = PTHREAD_MUTEX_INITIALIZER; + +/* Information about an allocation chunk. */ +struct malloc_chunk +{ + /* Start of the allocation. */ + void *start; + /* Size of the allocation. */ + size_t size; +}; + +enum { malloc_chunk_count = 1000 }; +static struct malloc_chunk chunks[malloc_chunk_count]; + +/* Lock the malloc lock. */ +static void +xlock (void) +{ + int ret = pthread_mutex_lock (&malloc_lock); + if (ret != 0) + { + errno = ret; + printf ("error: pthread_mutex_lock: %m\n"); + _exit (1); + } +} + +/* Unlock the malloc lock. */ +static void +xunlock (void) +{ + int ret = pthread_mutex_unlock (&malloc_lock); + if (ret != 0) + { + errno = ret; + printf ("error: pthread_mutex_unlock: %m\n"); + _exit (1); + } +} + +/* Internal malloc without locking and registration. */ +static void * +malloc_internal (size_t size) +{ + void *result = mmap (NULL, size, PROT_READ | PROT_WRITE, + MAP_ANONYMOUS | MAP_PRIVATE, -1, 0); + if (result == MAP_FAILED) + { + printf ("error: mmap: %m\n"); + _exit (1); + } + return result; +} + +void * +malloc (size_t size) +{ + if (size == 0) + size = 1; + xlock (); + void *result = malloc_internal (size); + for (int i = 0; i < malloc_chunk_count; ++i) + if (chunks[i].start == NULL) + { + chunks[i].start = result; + chunks[i].size = size; + xunlock (); + return result; + } + xunlock (); + printf ("error: no place to store chunk pointer\n"); + _exit (1); +} + +void * +calloc (size_t a, size_t b) +{ + if (b != 0 && a > SIZE_MAX / b) + return NULL; + /* malloc uses mmap, which provides zeroed memory. */ + return malloc (a * b); +} + +static void +xunmap (void *ptr, size_t size) +{ + int ret = munmap (ptr, size); + if (ret < 0) + { + printf ("error: munmap (%p, %zu) failed: %m\n", ptr, size); + _exit (1); + } +} + +void +free (void *ptr) +{ + if (ptr == NULL) + return; + + xlock (); + for (int i = 0; i < malloc_chunk_count; ++i) + if (chunks[i].start == ptr) + { + xunmap (ptr, chunks[i].size); + chunks[i] = (struct malloc_chunk) {}; + xunlock (); + return; + } + xunlock (); + printf ("error: tried to free non-allocated pointer %p\n", ptr); + _exit (1); +} + +void * +realloc (void *old, size_t size) +{ + if (old != NULL) + { + xlock (); + for (int i = 0; i < malloc_chunk_count; ++i) + if (chunks[i].start == old) + { + size_t old_size = chunks[i].size; + void *result; + if (old_size < size) + { + result = malloc_internal (size); + /* Reuse the slot for the new allocation. */ + memcpy (result, old, old_size); + xunmap (old, old_size); + chunks[i].start = result; + chunks[i].size = size; + } + else + /* Old size is not smaller, so reuse the old + allocation. */ + result = old; + xunlock (); + return result; + } + xunlock (); + printf ("error: tried to realloc non-allocated pointer %p\n", old); + _exit (1); + } + else + return malloc (size); +} |