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                         const char *shm_path);
  93 struct shm_object *shm_object_table_append_shm(struct shm_object_table *table,
  94                         int shm_fd, int wakeup_fd, uint32_t stream_nr,
  95                         size_t memory_map_size);
  96 /* mem ownership is passed to shm_object_table_append_mem(). */
  97 struct shm_object *shm_object_table_append_mem(struct shm_object_table *table,
  98                         void *mem, size_t memory_map_size, int wakeup_fd);
  99 void shm_object_table_destroy(struct shm_object_table *table);
 100
 101 /*
 102  * zalloc_shm - allocate memory within a shm object.
 103  *
 104  * Shared memory is already zeroed by shmget.
 105  * *NOT* multithread-safe (should be protected by mutex).
 106  * Returns a -1, -1 tuple on error.
 107  */
 108 struct shm_ref zalloc_shm(struct shm_object *obj, size_t len);
 109 void align_shm(struct shm_object *obj, size_t align);
 110
 111 static inline
 112 int shm_get_wait_fd(struct lttng_ust_shm_handle *handle, struct shm_ref *ref)
 113 {
 114         struct shm_object_table *table = handle->table;
 115         struct shm_object *obj;
 116         size_t index;
 117
 118         index = (size_t) ref->index;
 119         if (caa_unlikely(index >= table->allocated_len))
 120                 return -EPERM;
 121         obj = &table->objects[index];
 122         return obj->wait_fd[0];
 123 }
 124
 125 static inline
 126 int shm_get_wakeup_fd(struct lttng_ust_shm_handle *handle, struct shm_ref *ref)
 127 {
 128         struct shm_object_table *table = handle->table;
 129         struct shm_object *obj;
 130         size_t index;
 131
 132         index = (size_t) ref->index;
 133         if (caa_unlikely(index >= table->allocated_len))
 134                 return -EPERM;
 135         obj = &table->objects[index];
 136         return obj->wait_fd[1];
 137 }
 138
 139 static inline
 140 int shm_close_wait_fd(struct lttng_ust_shm_handle *handle,
 141                 struct shm_ref *ref)
 142 {
 143         struct shm_object_table *table = handle->table;
 144         struct shm_object *obj;
 145         int wait_fd;
 146         size_t index;
 147         int ret;
 148
 149         index = (size_t) ref->index;
 150         if (caa_unlikely(index >= table->allocated_len))
 151                 return -EPERM;
 152         obj = &table->objects[index];
 153         wait_fd = obj->wait_fd[0];
 154         if (wait_fd < 0)
 155                 return -ENOENT;
 156         obj->wait_fd[0] = -1;
 157         ret = close(wait_fd);
 158         if (ret) {
 159                 ret = -errno;
 160                 return ret;
 161         }
 162         return 0;
 163 }
 164
 165 static inline
 166 int shm_close_wakeup_fd(struct lttng_ust_shm_handle *handle,
 167                 struct shm_ref *ref)
 168 {
 169         struct shm_object_table *table = handle->table;
 170         struct shm_object *obj;
 171         int wakeup_fd;
 172         size_t index;
 173         int ret;
 174
 175         index = (size_t) ref->index;
 176         if (caa_unlikely(index >= table->allocated_len))
 177                 return -EPERM;
 178         obj = &table->objects[index];
 179         wakeup_fd = obj->wait_fd[1];
 180         if (wakeup_fd < 0)
 181                 return -ENOENT;
 182         obj->wait_fd[1] = -1;
 183         ret = close(wakeup_fd);
 184         if (ret) {
 185                 ret = -errno;
 186                 return ret;
 187         }
 188         return 0;
 189 }
 190
 191 static inline
 192 int shm_get_shm_fd(struct lttng_ust_shm_handle *handle, struct shm_ref *ref)
 193 {
 194         struct shm_object_table *table = handle->table;
 195         struct shm_object *obj;
 196         size_t index;
 197
 198         index = (size_t) ref->index;
 199         if (caa_unlikely(index >= table->allocated_len))
 200                 return -EPERM;
 201         obj = &table->objects[index];
 202         return obj->shm_fd;
 203 }
 204
 205
 206 static inline
 207 int shm_get_shm_size(struct lttng_ust_shm_handle *handle, struct shm_ref *ref,
 208                 uint64_t *size)
 209 {
 210         struct shm_object_table *table = handle->table;
 211         struct shm_object *obj;
 212         size_t index;
 213
 214         index = (size_t) ref->index;
 215         if (caa_unlikely(index >= table->allocated_len))
 216                 return -EPERM;
 217         obj = &table->objects[index];
 218         *size = obj->memory_map_size;
 219         return 0;
 220 }
 221
 222 #endif /* _LIBRINGBUFFER_SHM_H */