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 <stddef.h>
  25 #include <stdint.h>
  26 #include <unistd.h>
  27 #include <usterr-signal-safe.h>
  28 #include <urcu/compiler.h>
  29 #include "shm_types.h"
  30
  31 /* channel_handle_create - for UST. */
  32 extern
  33 struct lttng_ust_shm_handle *channel_handle_create(void *data,
  34                                 uint64_t memory_map_size, int wakeup_fd);
  35 /* channel_handle_add_stream - for UST. */
  36 extern
  37 int channel_handle_add_stream(struct lttng_ust_shm_handle *handle,
  38                 int shm_fd, int wakeup_fd, uint32_t stream_nr,
  39                 uint64_t memory_map_size);
  40 unsigned int channel_handle_get_nr_streams(struct lttng_ust_shm_handle *handle);
  41 extern
  42 void channel_destroy(struct channel *chan, struct lttng_ust_shm_handle *handle,
  43                 int consumer);
  44
  45 /*
  46  * Pointer dereferencing. We don't trust the shm_ref, so we validate
  47  * both the index and offset with known boundaries.
  48  *
  49  * "shmp" and "shmp_index" guarantee that it's safe to use the pointer
  50  * target type, even in the occurrence of shm_ref modification by an
  51  * untrusted process having write access to the shm_ref. We return a
  52  * NULL pointer if the ranges are invalid.
  53  */
  54 static inline
  55 char *_shmp_offset(struct shm_object_table *table, struct shm_ref *ref,
  56                    size_t idx, size_t elem_size)
  57 {
  58         struct shm_object *obj;
  59         size_t objindex, ref_offset;
  60
  61         objindex = (size_t) ref->index;
  62         if (caa_unlikely(objindex >= table->allocated_len))
  63                 return NULL;
  64         obj = &table->objects[objindex];
  65         ref_offset = (size_t) ref->offset;
  66         ref_offset += idx * elem_size;
  67         /* Check if part of the element returned would exceed the limits. */
  68         if (caa_unlikely(ref_offset + elem_size > obj->memory_map_size))
  69                 return NULL;
  70         return &obj->memory_map[ref_offset];
  71 }
  72
  73 #define shmp_index(handle, ref, index)                                  \
  74         ({                                                              \
  75                 __typeof__((ref)._type) ____ptr_ret;                    \
  76                 ____ptr_ret = (__typeof__(____ptr_ret)) _shmp_offset((handle)->table, &(ref)._ref, index, sizeof(*____ptr_ret));        \
  77                 ____ptr_ret;                                            \
  78         })
  79
  80 #define shmp(handle, ref)       shmp_index(handle, ref, 0)
  81
  82 static inline
  83 void _set_shmp(struct shm_ref *ref, struct shm_ref src)
  84 {
  85         *ref = src;
  86 }
  87
  88 #define set_shmp(ref, src)      _set_shmp(&(ref)._ref, src)
  89
  90 struct shm_object_table *shm_object_table_create(size_t max_nb_obj);
  91 struct shm_object *shm_object_table_alloc(struct shm_object_table *table,
  92                         size_t memory_map_size,
  93                         enum shm_object_type type,
  94                         const int stream_fd,
  95                         int cpu);
  96 struct shm_object *shm_object_table_append_shm(struct shm_object_table *table,
  97                         int shm_fd, int wakeup_fd, uint32_t stream_nr,
  98                         size_t memory_map_size);
  99 /* mem ownership is passed to shm_object_table_append_mem(). */
 100 struct shm_object *shm_object_table_append_mem(struct shm_object_table *table,
 101                         void *mem, size_t memory_map_size, int wakeup_fd);
 102 void shm_object_table_destroy(struct shm_object_table *table, int consumer);
 103
 104 /*
 105  * zalloc_shm - allocate memory within a shm object.
 106  *
 107  * Shared memory is already zeroed by shmget.
 108  * *NOT* multithread-safe (should be protected by mutex).
 109  * Returns a -1, -1 tuple on error.
 110  */
 111 struct shm_ref zalloc_shm(struct shm_object *obj, size_t len);
 112 void align_shm(struct shm_object *obj, size_t align);
 113
 114 static inline
 115 int shm_get_wait_fd(struct lttng_ust_shm_handle *handle, struct shm_ref *ref)
 116 {
 117         struct shm_object_table *table = handle->table;
 118         struct shm_object *obj;
 119         size_t index;
 120
 121         index = (size_t) ref->index;
 122         if (caa_unlikely(index >= table->allocated_len))
 123                 return -EPERM;
 124         obj = &table->objects[index];
 125         return obj->wait_fd[0];
 126 }
 127
 128 static inline
 129 int shm_get_wakeup_fd(struct lttng_ust_shm_handle *handle, struct shm_ref *ref)
 130 {
 131         struct shm_object_table *table = handle->table;
 132         struct shm_object *obj;
 133         size_t index;
 134
 135         index = (size_t) ref->index;
 136         if (caa_unlikely(index >= table->allocated_len))
 137                 return -EPERM;
 138         obj = &table->objects[index];
 139         return obj->wait_fd[1];
 140 }
 141
 142 static inline
 143 int shm_close_wait_fd(struct lttng_ust_shm_handle *handle,
 144                 struct shm_ref *ref)
 145 {
 146         struct shm_object_table *table = handle->table;
 147         struct shm_object *obj;
 148         int wait_fd;
 149         size_t index;
 150         int ret;
 151
 152         index = (size_t) ref->index;
 153         if (caa_unlikely(index >= table->allocated_len))
 154                 return -EPERM;
 155         obj = &table->objects[index];
 156         wait_fd = obj->wait_fd[0];
 157         if (wait_fd < 0)
 158                 return -ENOENT;
 159         obj->wait_fd[0] = -1;
 160         ret = close(wait_fd);
 161         if (ret) {
 162                 ret = -errno;
 163                 return ret;
 164         }
 165         return 0;
 166 }
 167
 168 static inline
 169 int shm_close_wakeup_fd(struct lttng_ust_shm_handle *handle,
 170                 struct shm_ref *ref)
 171 {
 172         struct shm_object_table *table = handle->table;
 173         struct shm_object *obj;
 174         int wakeup_fd;
 175         size_t index;
 176         int ret;
 177
 178         index = (size_t) ref->index;
 179         if (caa_unlikely(index >= table->allocated_len))
 180                 return -EPERM;
 181         obj = &table->objects[index];
 182         wakeup_fd = obj->wait_fd[1];
 183         if (wakeup_fd < 0)
 184                 return -ENOENT;
 185         obj->wait_fd[1] = -1;
 186         ret = close(wakeup_fd);
 187         if (ret) {
 188                 ret = -errno;
 189                 return ret;
 190         }
 191         return 0;
 192 }
 193
 194 static inline
 195 int shm_get_shm_fd(struct lttng_ust_shm_handle *handle, struct shm_ref *ref)
 196 {
 197         struct shm_object_table *table = handle->table;
 198         struct shm_object *obj;
 199         size_t index;
 200
 201         index = (size_t) ref->index;
 202         if (caa_unlikely(index >= table->allocated_len))
 203                 return -EPERM;
 204         obj = &table->objects[index];
 205         return obj->shm_fd;
 206 }
 207
 208
 209 static inline
 210 int shm_get_shm_size(struct lttng_ust_shm_handle *handle, struct shm_ref *ref,
 211                 uint64_t *size)
 212 {
 213         struct shm_object_table *table = handle->table;
 214         struct shm_object *obj;
 215         size_t index;
 216
 217         index = (size_t) ref->index;
 218         if (caa_unlikely(index >= table->allocated_len))
 219                 return -EPERM;
 220         obj = &table->objects[index];
 221         *size = obj->memory_map_size;
 222         return 0;
 223 }
 224
 225 #endif /* _LIBRINGBUFFER_SHM_H */