diff options
| -rw-r--r-- | ChangeLog | 13 | ||||
| -rw-r--r-- | elf/dl-misc.c | 132 | ||||
| -rw-r--r-- | elf/dl-tls.c | 34 | ||||
| -rw-r--r-- | sysdeps/generic/ldsodefs.h | 6 |
4 files changed, 169 insertions, 16 deletions
diff --git a/ChangeLog b/ChangeLog index fae243e093..fbc1d153fb 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,5 +1,18 @@ 2013-12-18 Andrew Hunter <ahh@google.com> + * sysdeps/generic/ldsodefs.h (__signal_safe_memalign): New prototype. + (__signal_safe_malloc, __signal_safe_free): Likewise. + (__signal_safe_realloc, __signal_safe_calloc): Likewise. + * elf/dl-misc.c (__signal_safe_allocator_header): New struct. + (__signal_safe_memalign, __signal_safe_malloc): New function. + (__signal_safe_free, __signal_safe_realloc): Likewise. + (__signal_safe_calloc): Likewise. + * elf/dl-tls.c (allocate_dtv, _dl_clear_dtv): Call signal-safe + functions. + (_dl_deallocate_tls, _dl_update_slotinfo): Likewise. + +2013-12-18 Andrew Hunter <ahh@google.com> + * elf/Versions (ld): Add _dl_clear_dtv. * sysdeps/generic/ldsodefs.h (_dl_clear_dtv): New prototype. * elf/dl-tls.c (_dl_clear_dtv): New function. diff --git a/elf/dl-misc.c b/elf/dl-misc.c index 5fc13a44a4..cec65d083a 100644 --- a/elf/dl-misc.c +++ b/elf/dl-misc.c @@ -19,6 +19,7 @@ #include <assert.h> #include <fcntl.h> #include <ldsodefs.h> +#include <libc-symbols.h> #include <limits.h> #include <link.h> #include <stdarg.h> @@ -364,3 +365,134 @@ _dl_higher_prime_number (unsigned long int n) return *low; } + +/* To support accessing TLS variables from signal handlers, we need an + async signal safe memory allocator. These routines are never + themselves invoked reentrantly (all calls to them are surrounded by + signal masks) but may be invoked concurrently from many threads. + The current implementation is not particularly performant nor space + efficient, but it will be used rarely (and only in binaries that use + dlopen.) The API matches that of malloc() and friends. */ + +struct __signal_safe_allocator_header +{ + size_t size; + void *start; +}; + +void *weak_function +__signal_safe_memalign (size_t boundary, size_t size) +{ + struct __signal_safe_allocator_header *header; + if (boundary < sizeof (*header)) + boundary = sizeof (*header); + + /* Boundary must be a power of two. */ + if (boundary & (boundary - 1) == 0) + return NULL; + + size_t pg = GLRO (dl_pagesize); + size_t padded_size; + if (boundary <= pg) + { + /* We'll get a pointer certainly aligned to boundary, so just + add one more boundary-sized chunk to hold the header. */ + padded_size = roundup (size, boundary) + boundary; + } + else + { + /* If we want K pages aligned to a J-page boundary, K+J+1 pages + contains at least one such region that isn't directly at the start + (so we can place the header.) This is wasteful, but you're the one + who wanted 64K-aligned TLS. */ + padded_size = roundup (size, pg) + boundary + pg; + } + + + size_t actual_size = roundup (padded_size, pg); + void *actual = mmap (NULL, actual_size, PROT_READ | PROT_WRITE, + MAP_ANONYMOUS | MAP_PRIVATE, -1, 0); + if (actual == MAP_FAILED) + return NULL; + + if (boundary <= pg) + { + header = actual + boundary - sizeof (*header); + } + else + { + intptr_t actual_pg = ((intptr_t) actual) / pg; + intptr_t boundary_pg = boundary / pg; + intptr_t start_pg = actual_pg + boundary_pg; + start_pg -= start_pg % boundary_pg; + if (start_pg > (actual_pg + 1)) + { + int ret = munmap (actual, (start_pg - actual_pg - 1) * pg); + assert (ret == 0); + actual = (void *) ((start_pg - 1) * pg); + } + char *start = (void *) (start_pg * pg); + header = start - sizeof (*header); + + } + header->size = actual_size; + header->start = actual; + void *ptr = header; + ptr += sizeof (*header); + if (((intptr_t) ptr) % boundary != 0) + _dl_fatal_printf ("__signal_safe_memalign produced incorrect alignment\n"); + return ptr; +} + +void * weak_function +__signal_safe_malloc (size_t size) +{ + return __signal_safe_memalign (1, size); +} + +void weak_function +__signal_safe_free (void *ptr) +{ + if (ptr == NULL) + return; + + struct __signal_safe_allocator_header *header = ((char *) ptr) - sizeof (*header); + int ret = munmap (header->start, header->size); + + assert (ret == 0); +} + +void * weak_function +__signal_safe_realloc (void *ptr, size_t size) +{ + if (size == 0) + { + __signal_safe_free (ptr); + return NULL; + } + if (ptr == NULL) + return __signal_safe_malloc (size); + + struct __signal_safe_allocator_header *header = ((char *) ptr) - sizeof (*header); + size_t old_size = header->size; + if (old_size - sizeof (*header) >= size) + return ptr; + + void *new_ptr = __signal_safe_malloc (size); + if (new_ptr == NULL) + return NULL; + + memcpy (new_ptr, ptr, old_size); + __signal_safe_free (ptr); + + return new_ptr; +} + +void * weak_function +__signal_safe_calloc (size_t nmemb, size_t size) +{ + void *ptr = __signal_safe_malloc (nmemb * size); + if (ptr == NULL) + return NULL; + return memset (ptr, 0, nmemb * size); +} diff --git a/elf/dl-tls.c b/elf/dl-tls.c index c60a6b7b80..12e6e8f3e0 100644 --- a/elf/dl-tls.c +++ b/elf/dl-tls.c @@ -293,7 +293,7 @@ allocate_dtv (void *result) initial set of modules. This should avoid in most cases expansions of the dtv. */ dtv_length = GL(dl_tls_max_dtv_idx) + DTV_SURPLUS; - dtv = calloc (dtv_length + 2, sizeof (dtv_t)); + dtv = __signal_safe_calloc (dtv_length + 2, sizeof (dtv_t)); if (dtv != NULL) { /* This is the initial length of the dtv. */ @@ -470,7 +470,7 @@ _dl_clear_dtv (dtv_t *dtv) for (size_t cnt = 0; cnt < dtv[-1].counter; ++cnt) if (! dtv[1 + cnt].pointer.is_static && dtv[1 + cnt].pointer.val != TLS_DTV_UNALLOCATED) - free (dtv[1 + cnt].pointer.val); + __signal_safe_free (dtv[1 + cnt].pointer.val); memset (dtv, '\0', (dtv[-1].counter + 1) * sizeof (dtv_t)); } @@ -491,11 +491,11 @@ _dl_deallocate_tls (void *tcb, bool dealloc_tcb) for (size_t cnt = 0; cnt < dtv[-1].counter; ++cnt) if (! dtv[1 + cnt].pointer.is_static && dtv[1 + cnt].pointer.val != TLS_DTV_UNALLOCATED) - free (dtv[1 + cnt].pointer.val); + __signal_safe_free (dtv[1 + cnt].pointer.val); /* The array starts with dtv[-1]. */ if (dtv != GL(dl_initial_dtv)) - free (dtv - 1); + __signal_safe_free (dtv - 1); if (dealloc_tcb) { @@ -537,8 +537,7 @@ static void * allocate_and_init (struct link_map *map) { void *newp; - - newp = __libc_memalign (map->l_tls_align, map->l_tls_blocksize); + newp = __signal_safe_memalign (map->l_tls_align, map->l_tls_blocksize); if (newp == NULL) oom (); @@ -608,25 +607,27 @@ _dl_update_slotinfo (unsigned long int req_modid) if (gen <= dtv[0].counter) continue; + size_t modid = total + cnt; + /* If there is no map this means the entry is empty. */ struct link_map *map = listp->slotinfo[cnt].map; if (map == NULL) { /* If this modid was used at some point the memory might still be allocated. */ - if (! dtv[total + cnt].pointer.is_static - && dtv[total + cnt].pointer.val != TLS_DTV_UNALLOCATED) + if (dtv[-1].counter >= modid + && !dtv[modid].pointer.is_static + && dtv[modid].pointer.val != TLS_DTV_UNALLOCATED) { - free (dtv[total + cnt].pointer.val); - dtv[total + cnt].pointer.val = TLS_DTV_UNALLOCATED; + __signal_safe_free (dtv[modid].pointer.val); + dtv[modid].pointer.val = TLS_DTV_UNALLOCATED; } continue; } + assert (modid == map->l_tls_modid); /* Check whether the current dtv array is large enough. */ - size_t modid = map->l_tls_modid; - assert (total + cnt == modid); if (dtv[-1].counter < modid) { /* Reallocate the dtv. */ @@ -640,17 +641,18 @@ _dl_update_slotinfo (unsigned long int req_modid) { /* This is the initial dtv that was allocated during rtld startup using the dl-minimal.c - malloc instead of the real malloc. We can't + malloc instead of the real allocator. We can't free it, we have to abandon the old storage. */ - newp = malloc ((2 + newsize) * sizeof (dtv_t)); + newp = __signal_safe_malloc ( + (2 + newsize) * sizeof (dtv_t)); if (newp == NULL) oom (); memcpy (newp, &dtv[-1], (2 + oldsize) * sizeof (dtv_t)); } else { - newp = realloc (&dtv[-1], + newp = __signal_safe_realloc (&dtv[-1], (2 + newsize) * sizeof (dtv_t)); if (newp == NULL) oom (); @@ -680,7 +682,7 @@ _dl_update_slotinfo (unsigned long int req_modid) deallocate even if it is this dtv entry we are supposed to load. The reason is that we call memalign and not malloc. */ - free (dtv[modid].pointer.val); + __signal_safe_free (dtv[modid].pointer.val); /* This module is loaded dynamically- We defer memory allocation. */ diff --git a/sysdeps/generic/ldsodefs.h b/sysdeps/generic/ldsodefs.h index 1bda60c6fa..48bdb6e44b 100644 --- a/sysdeps/generic/ldsodefs.h +++ b/sysdeps/generic/ldsodefs.h @@ -994,6 +994,12 @@ rtld_hidden_proto (_dl_allocate_tls_init) extern void _dl_clear_dtv (dtv_t *dtv) internal_function; rtld_hidden_proto (_dl_clear_dtv) +extern void *__signal_safe_memalign (size_t boundary, size_t size); +extern void *__signal_safe_malloc (size_t size); +extern void __signal_safe_free (void *ptr); +extern void *__signal_safe_realloc (void *ptr, size_t size); +extern void *__signal_safe_calloc (size_t nmemb, size_t size); + /* Deallocate memory allocated with _dl_allocate_tls. */ extern void _dl_deallocate_tls (void *tcb, bool dealloc_tcb) internal_function; rtld_hidden_proto (_dl_deallocate_tls) |