libringbuffer/shm.h

   1 #ifndef _LIBRINGBUFFER_SHM_H
   2 #define _LIBRINGBUFFER_SHM_H
   3
   4 /*
   5  * libringbuffer/shm.h
   6  *
   7  * Copyright (C) 2011-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   8  *
   9  * This library is free software; you can redistribute it and/or
  10  * modify it under the terms of the GNU Lesser General Public
  11  * License as published by the Free Software Foundation; only
  12  * version 2.1 of the License.
  13  *
  14  * This library is distributed in the hope that it will be useful,
  15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  17  * Lesser General Public License for more details.
  18  *
  19  * You should have received a copy of the GNU Lesser General Public
  20  * License along with this library; if not, write to the Free Software
  21  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  22  */
  23
  24 #include <stdint.h>
  25 #include <usterr-signal-safe.h>
  26 #include <urcu/compiler.h>
  27 #include "shm_types.h"
  28
  29 /* channel_handle_create - for UST. */
  30 extern
  31 struct lttng_ust_shm_handle *channel_handle_create(void *data,
  32                                 uint64_t memory_map_size, int wakeup_fd);
  33 /* channel_handle_add_stream - for UST. */
  34 extern
  35 int channel_handle_add_stream(struct lttng_ust_shm_handle *handle,
  36                 int shm_fd, int wakeup_fd, uint32_t stream_nr,
  37                 uint64_t memory_map_size);
  38 unsigned int channel_handle_get_nr_streams(struct lttng_ust_shm_handle *handle);
  39 extern
  40 void channel_destroy(struct channel *chan, struct lttng_ust_shm_handle *handle,
  41                 int consumer);
  42
  43 /*
  44  * Pointer dereferencing. We don't trust the shm_ref, so we validate
  45  * both the index and offset with known boundaries.
  46  *
  47  * "shmp" and "shmp_index" guarantee that it's safe to use the pointer
  48  * target type, even in the occurrence of shm_ref modification by an
  49  * untrusted process having write access to the shm_ref. We return a
  50  * NULL pointer if the ranges are invalid.
  51  */
  52 static inline
  53 char *_shmp_offset(struct shm_object_table *table, struct shm_ref *ref,
  54                    size_t idx, size_t elem_size)
  55 {
  56         struct shm_object *obj;
  57         size_t objindex, ref_offset;
  58
  59         objindex = (size_t) ref->index;
  60         if (caa_unlikely(objindex >= table->allocated_len))
  61                 return NULL;
  62         obj = &table->objects[objindex];
  63         ref_offset = (size_t) ref->offset;
  64         ref_offset += idx * elem_size;
  65         /* Check if part of the element returned would exceed the limits. */
  66         if (caa_unlikely(ref_offset + elem_size > obj->memory_map_size))
  67                 return NULL;
  68         return &obj->memory_map[ref_offset];
  69 }
  70
  71 #define shmp_index(handle, ref, index)                                  \
  72         ({                                                              \
  73                 __typeof__((ref)._type) ____ptr_ret;                    \
  74                 ____ptr_ret = (__typeof__(____ptr_ret)) _shmp_offset((handle)->table, &(ref)._ref, index, sizeof(*____ptr_ret));        \
  75                 ____ptr_ret;                                            \
  76         })
  77
  78 #define shmp(handle, ref)       shmp_index(handle, ref, 0)
  79
  80 static inline
  81 void _set_shmp(struct shm_ref *ref, struct shm_ref src)
  82 {
  83         *ref = src;
  84 }
  85
  86 #define set_shmp(ref, src)      _set_shmp(&(ref)._ref, src)
  87
  88 struct shm_object_table *shm_object_table_create(size_t max_nb_obj);
  89 struct shm_object *shm_object_table_alloc(struct shm_object_table *table,
  90                         size_t memory_map_size,
  91                         enum shm_object_type type);
  92 struct shm_object *shm_object_table_append_shm(struct shm_object_table *table,
  93                         int shm_fd, int wakeup_fd, uint32_t stream_nr,
  94                         size_t memory_map_size);
  95 /* mem ownership is passed to shm_object_table_append_mem(). */
  96 struct shm_object *shm_object_table_append_mem(struct shm_object_table *table,
  97                         void *mem, size_t memory_map_size, int wakeup_fd);
  98 void shm_object_table_destroy(struct shm_object_table *table);
  99
 100 /*
 101  * zalloc_shm - allocate memory within a shm object.
 102  *
 103  * Shared memory is already zeroed by shmget.
 104  * *NOT* multithread-safe (should be protected by mutex).
 105  * Returns a -1, -1 tuple on error.
 106  */
 107 struct shm_ref zalloc_shm(struct shm_object *obj, size_t len);
 108 void align_shm(struct shm_object *obj, size_t align);
 109
 110 static inline
 111 int shm_get_wait_fd(struct lttng_ust_shm_handle *handle, struct shm_ref *ref)
 112 {
 113         struct shm_object_table *table = handle->table;
 114         struct shm_object *obj;
 115         size_t index;
 116
 117         index = (size_t) ref->index;
 118         if (caa_unlikely(index >= table->allocated_len))
 119                 return -EPERM;
 120         obj = &table->objects[index];
 121         return obj->wait_fd[0];
 122 }
 123
 124 static inline
 125 int shm_get_wakeup_fd(struct lttng_ust_shm_handle *handle, struct shm_ref *ref)
 126 {
 127         struct shm_object_table *table = handle->table;
 128         struct shm_object *obj;
 129         size_t index;
 130
 131         index = (size_t) ref->index;
 132         if (caa_unlikely(index >= table->allocated_len))
 133                 return -EPERM;
 134         obj = &table->objects[index];
 135         return obj->wait_fd[1];
 136 }
 137
 138 static inline
 139 int shm_close_wait_fd(struct lttng_ust_shm_handle *handle,
 140                 struct shm_ref *ref)
 141 {
 142         struct shm_object_table *table = handle->table;
 143         struct shm_object *obj;
 144         int wait_fd;
 145         size_t index;
 146         int ret;
 147
 148         index = (size_t) ref->index;
 149         if (caa_unlikely(index >= table->allocated_len))
 150                 return -EPERM;
 151         obj = &table->objects[index];
 152         wait_fd = obj->wait_fd[0];
 153         if (wait_fd < 0)
 154                 return -ENOENT;
 155         obj->wait_fd[0] = -1;
 156         ret = close(wait_fd);
 157         if (ret) {
 158                 ret = -errno;
 159                 return ret;
 160         }
 161         return 0;
 162 }
 163
 164 static inline
 165 int shm_close_wakeup_fd(struct lttng_ust_shm_handle *handle,
 166                 struct shm_ref *ref)
 167 {
 168         struct shm_object_table *table = handle->table;
 169         struct shm_object *obj;
 170         int wakeup_fd;
 171         size_t index;
 172         int ret;
 173
 174         index = (size_t) ref->index;
 175         if (caa_unlikely(index >= table->allocated_len))
 176                 return -EPERM;
 177         obj = &table->objects[index];
 178         wakeup_fd = obj->wait_fd[1];
 179         if (wakeup_fd < 0)
 180                 return -ENOENT;
 181         obj->wait_fd[1] = -1;
 182         ret = close(wakeup_fd);
 183         if (ret) {
 184                 ret = -errno;
 185                 return ret;
 186         }
 187         return 0;
 188 }
 189
 190 static inline
 191 int shm_get_shm_fd(struct lttng_ust_shm_handle *handle, struct shm_ref *ref)
 192 {
 193         struct shm_object_table *table = handle->table;
 194         struct shm_object *obj;
 195         size_t index;
 196
 197         index = (size_t) ref->index;
 198         if (caa_unlikely(index >= table->allocated_len))
 199                 return -EPERM;
 200         obj = &table->objects[index];
 201         return obj->shm_fd;
 202 }
 203
 204
 205 static inline
 206 int shm_get_shm_size(struct lttng_ust_shm_handle *handle, struct shm_ref *ref,
 207                 uint64_t *size)
 208 {
 209         struct shm_object_table *table = handle->table;
 210         struct shm_object *obj;
 211         size_t index;
 212
 213         index = (size_t) ref->index;
 214         if (caa_unlikely(index >= table->allocated_len))
 215                 return -EPERM;
 216         obj = &table->objects[index];
 217         *size = obj->memory_map_size;
 218         return 0;
 219 }
 220
 221 #endif /* _LIBRINGBUFFER_SHM_H */