libringbuffer/shm.h

   1 /*
   2  * SPDX-License-Identifier: LGPL-2.1-only
   3  *
   4  * Copyright (C) 2011-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   5  */
   6
   7 #ifndef _LIBRINGBUFFER_SHM_H
   8 #define _LIBRINGBUFFER_SHM_H
   9
  10 #include <stddef.h>
  11 #include <stdint.h>
  12 #include <unistd.h>
  13 #include <usterr-signal-safe.h>
  14 #include <urcu/compiler.h>
  15 #include "shm_types.h"
  16 #include "ust-helper.h"
  17
  18 /* channel_handle_create - for UST. */
  19 LTTNG_HIDDEN
  20 extern
  21 struct lttng_ust_shm_handle *channel_handle_create(void *data,
  22                                 uint64_t memory_map_size, int wakeup_fd);
  23 /* channel_handle_add_stream - for UST. */
  24 LTTNG_HIDDEN
  25 extern
  26 int channel_handle_add_stream(struct lttng_ust_shm_handle *handle,
  27                 int shm_fd, int wakeup_fd, uint32_t stream_nr,
  28                 uint64_t memory_map_size);
  29 LTTNG_HIDDEN
  30 unsigned int channel_handle_get_nr_streams(struct lttng_ust_shm_handle *handle);
  31 LTTNG_HIDDEN
  32 extern
  33 void channel_destroy(struct channel *chan, struct lttng_ust_shm_handle *handle,
  34                 int consumer);
  35
  36 /*
  37  * Pointer dereferencing. We don't trust the shm_ref, so we validate
  38  * both the index and offset with known boundaries.
  39  *
  40  * "shmp" and "shmp_index" guarantee that it's safe to use the pointer
  41  * target type, even in the occurrence of shm_ref modification by an
  42  * untrusted process having write access to the shm_ref. We return a
  43  * NULL pointer if the ranges are invalid.
  44  */
  45 static inline
  46 char *_shmp_offset(struct shm_object_table *table, struct shm_ref *ref,
  47                    size_t idx, size_t elem_size)
  48 {
  49         struct shm_object *obj;
  50         size_t objindex, ref_offset;
  51
  52         objindex = (size_t) ref->index;
  53         if (caa_unlikely(objindex >= table->allocated_len))
  54                 return NULL;
  55         obj = &table->objects[objindex];
  56         ref_offset = (size_t) ref->offset;
  57         ref_offset += idx * elem_size;
  58         /* Check if part of the element returned would exceed the limits. */
  59         if (caa_unlikely(ref_offset + elem_size > obj->memory_map_size))
  60                 return NULL;
  61         return &obj->memory_map[ref_offset];
  62 }
  63
  64 #define shmp_index(handle, ref, index)                                  \
  65         ({                                                              \
  66                 __typeof__((ref)._type) ____ptr_ret;                    \
  67                 ____ptr_ret = (__typeof__(____ptr_ret)) _shmp_offset((handle)->table, &(ref)._ref, index, sizeof(*____ptr_ret));        \
  68                 ____ptr_ret;                                            \
  69         })
  70
  71 #define shmp(handle, ref)       shmp_index(handle, ref, 0)
  72
  73 static inline
  74 void _set_shmp(struct shm_ref *ref, struct shm_ref src)
  75 {
  76         *ref = src;
  77 }
  78
  79 #define set_shmp(ref, src)      _set_shmp(&(ref)._ref, src)
  80
  81 LTTNG_HIDDEN
  82 struct shm_object_table *shm_object_table_create(size_t max_nb_obj);
  83 LTTNG_HIDDEN
  84 struct shm_object *shm_object_table_alloc(struct shm_object_table *table,
  85                         size_t memory_map_size,
  86                         enum shm_object_type type,
  87                         const int stream_fd,
  88                         int cpu);
  89 LTTNG_HIDDEN
  90 struct shm_object *shm_object_table_append_shm(struct shm_object_table *table,
  91                         int shm_fd, int wakeup_fd, uint32_t stream_nr,
  92                         size_t memory_map_size);
  93 /* mem ownership is passed to shm_object_table_append_mem(). */
  94 LTTNG_HIDDEN
  95 struct shm_object *shm_object_table_append_mem(struct shm_object_table *table,
  96                         void *mem, size_t memory_map_size, int wakeup_fd);
  97 LTTNG_HIDDEN
  98 void shm_object_table_destroy(struct shm_object_table *table, int consumer);
  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 LTTNG_HIDDEN
 108 struct shm_ref zalloc_shm(struct shm_object *obj, size_t len);
 109 LTTNG_HIDDEN
 110 void align_shm(struct shm_object *obj, size_t align);
 111
 112 static inline
 113 int shm_get_wait_fd(struct lttng_ust_shm_handle *handle, struct shm_ref *ref)
 114 {
 115         struct shm_object_table *table = handle->table;
 116         struct shm_object *obj;
 117         size_t index;
 118
 119         index = (size_t) ref->index;
 120         if (caa_unlikely(index >= table->allocated_len))
 121                 return -EPERM;
 122         obj = &table->objects[index];
 123         return obj->wait_fd[0];
 124 }
 125
 126 static inline
 127 int shm_get_wakeup_fd(struct lttng_ust_shm_handle *handle, struct shm_ref *ref)
 128 {
 129         struct shm_object_table *table = handle->table;
 130         struct shm_object *obj;
 131         size_t index;
 132
 133         index = (size_t) ref->index;
 134         if (caa_unlikely(index >= table->allocated_len))
 135                 return -EPERM;
 136         obj = &table->objects[index];
 137         return obj->wait_fd[1];
 138 }
 139
 140 static inline
 141 int shm_close_wait_fd(struct lttng_ust_shm_handle *handle,
 142                 struct shm_ref *ref)
 143 {
 144         struct shm_object_table *table = handle->table;
 145         struct shm_object *obj;
 146         int wait_fd;
 147         size_t index;
 148         int ret;
 149
 150         index = (size_t) ref->index;
 151         if (caa_unlikely(index >= table->allocated_len))
 152                 return -EPERM;
 153         obj = &table->objects[index];
 154         wait_fd = obj->wait_fd[0];
 155         if (wait_fd < 0)
 156                 return -ENOENT;
 157         obj->wait_fd[0] = -1;
 158         ret = close(wait_fd);
 159         if (ret) {
 160                 ret = -errno;
 161                 return ret;
 162         }
 163         return 0;
 164 }
 165
 166 static inline
 167 int shm_close_wakeup_fd(struct lttng_ust_shm_handle *handle,
 168                 struct shm_ref *ref)
 169 {
 170         struct shm_object_table *table = handle->table;
 171         struct shm_object *obj;
 172         int wakeup_fd;
 173         size_t index;
 174         int ret;
 175
 176         index = (size_t) ref->index;
 177         if (caa_unlikely(index >= table->allocated_len))
 178                 return -EPERM;
 179         obj = &table->objects[index];
 180         wakeup_fd = obj->wait_fd[1];
 181         if (wakeup_fd < 0)
 182                 return -ENOENT;
 183         obj->wait_fd[1] = -1;
 184         ret = close(wakeup_fd);
 185         if (ret) {
 186                 ret = -errno;
 187                 return ret;
 188         }
 189         return 0;
 190 }
 191
 192 static inline
 193 int shm_get_shm_fd(struct lttng_ust_shm_handle *handle, struct shm_ref *ref)
 194 {
 195         struct shm_object_table *table = handle->table;
 196         struct shm_object *obj;
 197         size_t index;
 198
 199         index = (size_t) ref->index;
 200         if (caa_unlikely(index >= table->allocated_len))
 201                 return -EPERM;
 202         obj = &table->objects[index];
 203         return obj->shm_fd;
 204 }
 205
 206
 207 static inline
 208 int shm_get_shm_size(struct lttng_ust_shm_handle *handle, struct shm_ref *ref,
 209                 uint64_t *size)
 210 {
 211         struct shm_object_table *table = handle->table;
 212         struct shm_object *obj;
 213         size_t index;
 214
 215         index = (size_t) ref->index;
 216         if (caa_unlikely(index >= table->allocated_len))
 217                 return -EPERM;
 218         obj = &table->objects[index];
 219         *size = obj->memory_map_size;
 220         return 0;
 221 }
 222
 223 #endif /* _LIBRINGBUFFER_SHM_H */