diff options
| -rw-r--r-- | ChangeLog | 16 | ||||
| -rw-r--r-- | resolv/Makefile | 13 | ||||
| -rw-r--r-- | resolv/resolv_conf.c | 71 | ||||
| -rw-r--r-- | resolv/tst-resolv-res_ninit.c | 74 |
4 files changed, 142 insertions, 32 deletions
@@ -1,3 +1,19 @@ +2017-07-03 Florian Weimer <fweimer@redhat.com> + + resolv: Introduce free list for resolv_conf index slosts. + * resolv/resolv_conf.c (struct resolv_conf_array): Change element + type to uintptr_t. + (struct resolv_conf_global): Add free_list_start member. + (resolv_conf_get_1): Check for free list entry. + (decrement_at_index): Put freed slot on the free list. + (__resolv_conf_attach): Obtain new slot from the free list. + * resolv/tst-resolv-res_ninit.c: New file. + * resolv/Makefile (tests-internal): Add tst-resolv-res_ninit. + (tests-special): Add mtrace-tst-resolv-res_ninit.out. + (generated): Add mtrace-tst-resolv-res_ninit.out, + tst-resolv-res_ninit.mtrace. + (mtrace-tst-resolv-res_ninit.out): Add target. + 2017-06-30 Florian Weimer <fweimer@redhat.com> [BZ #984] diff --git a/resolv/Makefile b/resolv/Makefile index d5338f1..5cb2e53 100644 --- a/resolv/Makefile +++ b/resolv/Makefile @@ -63,6 +63,9 @@ tests-internal += \ tst-resolv-res_init \ tst-resolv-res_init-thread \ +# Needs resolv_context. +tests-internal += tst-resolv-res_ninit + endif # This test accesses __inet_ntop_range, an internal libc function. @@ -103,6 +106,7 @@ ifeq ($(run-built-tests),yes) ifneq (no,$(PERL)) tests-special += $(objpfx)mtrace-tst-leaks.out xtests-special += $(objpfx)mtrace-tst-leaks2.out +tests-special += $(objpfx)mtrace-tst-resolv-res_ninit.out endif endif @@ -114,7 +118,8 @@ headers += rpc/netdb.h endif generated += mtrace-tst-leaks.out tst-leaks.mtrace \ - mtrace-tst-leaks2.out tst-leaks2.mtrace + mtrace-tst-leaks2.out tst-leaks2.mtrace \ + mtrace-tst-resolv-res_ninit.out tst-resolv-res_ninit.mtrace \ include ../Rules @@ -142,6 +147,12 @@ $(objpfx)mtrace-tst-leaks2.out: $(objpfx)tst-leaks2.out $(common-objpfx)malloc/mtrace $(objpfx)tst-leaks2.mtrace > $@; \ $(evaluate-test) +tst-resolv-res_ninit-ENV = MALLOC_TRACE=$(objpfx)tst-resolv-res_ninit.mtrace +$(objpfx)mtrace-tst-resolv-res_ninit.out: $(objpfx)tst-resolv-res_ninit.out + $(common-objpfx)malloc/mtrace \ + $(objpfx)tst-resolv-res_ninit.mtrace > $@; \ + $(evaluate-test) + $(objpfx)tst-bug18665-tcp: $(objpfx)libresolv.so $(shared-thread-library) $(objpfx)tst-bug18665: $(objpfx)libresolv.so $(shared-thread-library) $(objpfx)tst-res_use_inet6: $(objpfx)libresolv.so $(shared-thread-library) diff --git a/resolv/resolv_conf.c b/resolv/resolv_conf.c index 9ef5924..b98cf92 100644 --- a/resolv/resolv_conf.c +++ b/resolv/resolv_conf.c @@ -28,9 +28,12 @@ struct resolv_conf_array object. The intent of this construction is to make reasonably sure that even if struct __res_state objects are copied around and patched by applications, we can still detect - accesses to stale extended resolver state. */ + accesses to stale extended resolver state. The array elements are + either struct resolv_conf * pointers (if the LSB is cleared) or + free list entries (if the LSB is set). The free list is used to + speed up finding available entries in the array. */ #define DYNARRAY_STRUCT resolv_conf_array -#define DYNARRAY_ELEMENT struct resolv_conf * +#define DYNARRAY_ELEMENT uintptr_t #define DYNARRAY_PREFIX resolv_conf_array_ #define DYNARRAY_INITIAL_SIZE 0 #include <malloc/dynarray-skeleton.c> @@ -55,6 +58,10 @@ struct resolv_conf_global the array element is overwritten with NULL. */ struct resolv_conf_array array; + /* Start of the free list in the array. The MSB is set if this + field has been initialized. */ + uintptr_t free_list_start; + /* Cached current configuration object for /etc/resolv.conf. */ struct resolv_conf *conf_current; @@ -194,15 +201,17 @@ resolv_conf_get_1 (const struct __res_state *resp) contexts exists, so returning NULL is correct. */ return NULL; size_t index = resp->_u._ext.__glibc_extension_index ^ INDEX_MAGIC; - struct resolv_conf *conf; + struct resolv_conf *conf = NULL; if (index < resolv_conf_array_size (&global_copy->array)) { - conf = *resolv_conf_array_at (&global_copy->array, index); - assert (conf->__refcount > 0); - ++conf->__refcount; + uintptr_t *slot = resolv_conf_array_at (&global_copy->array, index); + if (!(*slot & 1)) + { + conf = (struct resolv_conf *) *slot; + assert (conf->__refcount > 0); + ++conf->__refcount; + } } - else - conf = NULL; put_locked_global (global_copy); return conf; } @@ -550,17 +559,20 @@ decrement_at_index (struct resolv_conf_global *global_copy, size_t index) { if (index < resolv_conf_array_size (&global_copy->array)) { - /* Index found. Deallocate the struct resolv_conf object once - the reference counter reaches. Free the array slot. */ - struct resolv_conf **slot - = resolv_conf_array_at (&global_copy->array, index); - struct resolv_conf *conf = *slot; - if (conf != NULL) + /* Index found. */ + uintptr_t *slot = resolv_conf_array_at (&global_copy->array, index); + /* Check that the slot is not already part of the free list. */ + if (!(*slot & 1)) { + struct resolv_conf *conf = (struct resolv_conf *) *slot; conf_decrement (conf); - /* Clear the slot even if the reference count is positive. - Slots are not shared. */ - *slot = NULL; + /* Put the slot onto the free list. */ + if (global_copy->free_list_start == 0) + /* Not yet initialized. */ + *slot = 1; + else + *slot = global_copy->free_list_start; + global_copy->free_list_start = (index << 1) | 1; } } } @@ -580,24 +592,21 @@ __resolv_conf_attach (struct __res_state *resp, struct resolv_conf *conf) /* Try to find an unused index in the array. */ size_t index; { - size_t size = resolv_conf_array_size (&global_copy->array); - bool found = false; - for (index = 0; index < size; ++index) + if (global_copy->free_list_start & 1) { - struct resolv_conf **p - = resolv_conf_array_at (&global_copy->array, index); - if (*p == NULL) - { - *p = conf; - found = true; - break; - } + /* Unlink from the free list. */ + index = global_copy->free_list_start >> 1; + uintptr_t *slot = resolv_conf_array_at (&global_copy->array, index); + global_copy->free_list_start = *slot; + assert (global_copy->free_list_start & 1); + /* Install the configuration pointer. */ + *slot = (uintptr_t) conf; } - - if (!found) + else { + size_t size = resolv_conf_array_size (&global_copy->array); /* No usable index found. Increase the array size. */ - resolv_conf_array_add (&global_copy->array, conf); + resolv_conf_array_add (&global_copy->array, (uintptr_t) conf); if (resolv_conf_array_has_failed (&global_copy->array)) { put_locked_global (global_copy); diff --git a/resolv/tst-resolv-res_ninit.c b/resolv/tst-resolv-res_ninit.c new file mode 100644 index 0000000..d08153f --- /dev/null +++ b/resolv/tst-resolv-res_ninit.c @@ -0,0 +1,74 @@ +/* Test the creation of many struct __res_state objects. + Copyright (C) 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 <mcheck.h> +#include <resolv.h> +#include <resolv/resolv_context.h> +#include <stdlib.h> +#include <support/check.h> + +/* Order the resolver states by their extended resolver state + index. */ +static int +sort_res_state (const void *a, const void *b) +{ + res_state left = (res_state) a; + res_state right = (res_state) b; + return memcmp (&left->_u._ext.__glibc_extension_index, + &right->_u._ext.__glibc_extension_index, + sizeof (left->_u._ext.__glibc_extension_index)); +} + +static int +do_test (void) +{ + mtrace (); + + enum { count = 100 * 1000 }; + res_state array = calloc (count, sizeof (*array)); + const struct resolv_conf *conf = NULL; + for (size_t i = 0; i < count; ++i) + { + TEST_VERIFY (res_ninit (array + i) == 0); + TEST_VERIFY (array[i].nscount > 0); + struct resolv_context *ctx = __resolv_context_get_override (array + i); + TEST_VERIFY_EXIT (ctx != NULL); + TEST_VERIFY (ctx->resp == array + i); + if (i == 0) + { + conf = ctx->conf; + TEST_VERIFY (conf != NULL); + } + else + /* The underyling configuration should be identical across all + res_state opjects because resolv.conf did not change. */ + TEST_VERIFY (ctx->conf == conf); + } + qsort (array, count, sizeof (*array), sort_res_state); + for (size_t i = 1; i < count; ++i) + /* All extension indices should be different. */ + TEST_VERIFY (sort_res_state (array + i - 1, array + i) < 0); + for (size_t i = 0; i < count; ++i) + res_nclose (array + i); + free (array); + + TEST_VERIFY (res_init () == 0); + return 0; +} + +#include <support/test-driver.c> |