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
  17 /* channel_handle_create - for UST. */
  18 __attribute__((visibility("hidden")))
  19 extern
  20 struct lttng_ust_shm_handle *channel_handle_create(void *data,
  21                                 uint64_t memory_map_size, int wakeup_fd);
  22
  23 /* channel_handle_add_stream - for UST. */
  24 __attribute__((visibility("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
  30 __attribute__((visibility("hidden")))
  31 unsigned int channel_handle_get_nr_streams(struct lttng_ust_shm_handle *handle);
  32
  33 __attribute__((visibility("hidden")))
  34 extern
  35 void channel_destroy(struct lttng_ust_lib_ring_buffer_channel *chan,
  36                 struct lttng_ust_shm_handle *handle,
  37                 int consumer);
  38
  39 /*
  40  * Pointer dereferencing. We don't trust the shm_ref, so we validate
  41  * both the index and offset with known boundaries.
  42  *
  43  * "shmp" and "shmp_index" guarantee that it's safe to use the pointer
  44  * target type, even in the occurrence of shm_ref modification by an
  45  * untrusted process having write access to the shm_ref. We return a
  46  * NULL pointer if the ranges are invalid.
  47  */
  48 static inline
  49 char *_shmp_offset(struct shm_object_table *table, struct shm_ref *ref,
  50                    size_t idx, size_t elem_size)
  51 {
  52         struct shm_object *obj;
  53         size_t objindex, ref_offset;
  54
  55         objindex = (size_t) ref->index;
  56         if (caa_unlikely(objindex >= table->allocated_len))
  57                 return NULL;
  58         obj = &table->objects[objindex];
  59         ref_offset = (size_t) ref->offset;
  60         ref_offset += idx * elem_size;
  61         /* Check if part of the element returned would exceed the limits. */
  62         if (caa_unlikely(ref_offset + elem_size > obj->memory_map_size))
  63                 return NULL;
  64         return &obj->memory_map[ref_offset];
  65 }
  66
  67 #define shmp_index(handle, ref, index)                                  \
  68         ({                                                              \
  69                 __typeof__((ref)._type) ____ptr_ret;                    \
  70                 ____ptr_ret = (__typeof__(____ptr_ret)) _shmp_offset((handle)->table, &(ref)._ref, index, sizeof(*____ptr_ret));        \
  71                 ____ptr_ret;                                            \
  72         })
  73
  74 #define shmp(handle, ref)       shmp_index(handle, ref, 0)
  75
  76 static inline
  77 void _set_shmp(struct shm_ref *ref, struct shm_ref src)
  78 {
  79         *ref = src;
  80 }
  81
  82 #define set_shmp(ref, src)      _set_shmp(&(ref)._ref, src)
  83
  84 __attribute__((visibility("hidden")))
  85 struct shm_object_table *shm_object_table_create(size_t max_nb_obj);
  86
  87 __attribute__((visibility("hidden")))
  88 struct shm_object *shm_object_table_alloc(struct shm_object_table *table,
  89                         size_t memory_map_size,
  90                         enum shm_object_type type,
  91                         const int stream_fd,
  92                         int cpu);
  93
  94 __attribute__((visibility("hidden")))
  95 struct shm_object *shm_object_table_append_shm(struct shm_object_table *table,
  96                         int shm_fd, int wakeup_fd, uint32_t stream_nr,
  97                         size_t memory_map_size);
  98
  99 /* mem ownership is passed to shm_object_table_append_mem(). */
 100 __attribute__((visibility("hidden")))
 101 struct shm_object *shm_object_table_append_mem(struct shm_object_table *table,
 102                         void *mem, size_t memory_map_size, int wakeup_fd);
 103
 104 __attribute__((visibility("hidden")))
 105 void shm_object_table_destroy(struct shm_object_table *table, int consumer);
 106
 107 /*
 108  * zalloc_shm - allocate memory within a shm object.
 109  *
 110  * Shared memory is already zeroed by shmget.
 111  * *NOT* multithread-safe (should be protected by mutex).
 112  * Returns a -1, -1 tuple on error.
 113  */
 114 __attribute__((visibility("hidden")))
 115 struct shm_ref zalloc_shm(struct shm_object *obj, size_t len);
 116
 117 __attribute__((visibility("hidden")))
 118 void align_shm(struct shm_object *obj, size_t align);
 119
 120 static inline
 121 int shm_get_wait_fd(struct lttng_ust_shm_handle *handle, struct shm_ref *ref)
 122 {
 123         struct shm_object_table *table = handle->table;
 124         struct shm_object *obj;
 125         size_t index;
 126
 127         index = (size_t) ref->index;
 128         if (caa_unlikely(index >= table->allocated_len))
 129                 return -EPERM;
 130         obj = &table->objects[index];
 131         return obj->wait_fd[0];
 132 }
 133
 134 static inline
 135 int shm_get_wakeup_fd(struct lttng_ust_shm_handle *handle, struct shm_ref *ref)
 136 {
 137         struct shm_object_table *table = handle->table;
 138         struct shm_object *obj;
 139         size_t index;
 140
 141         index = (size_t) ref->index;
 142         if (caa_unlikely(index >= table->allocated_len))
 143                 return -EPERM;
 144         obj = &table->objects[index];
 145         return obj->wait_fd[1];
 146 }
 147
 148 static inline
 149 int shm_close_wait_fd(struct lttng_ust_shm_handle *handle,
 150                 struct shm_ref *ref)
 151 {
 152         struct shm_object_table *table = handle->table;
 153         struct shm_object *obj;
 154         int wait_fd;
 155         size_t index;
 156         int ret;
 157
 158         index = (size_t) ref->index;
 159         if (caa_unlikely(index >= table->allocated_len))
 160                 return -EPERM;
 161         obj = &table->objects[index];
 162         wait_fd = obj->wait_fd[0];
 163         if (wait_fd < 0)
 164                 return -ENOENT;
 165         obj->wait_fd[0] = -1;
 166         ret = close(wait_fd);
 167         if (ret) {
 168                 ret = -errno;
 169                 return ret;
 170         }
 171         return 0;
 172 }
 173
 174 static inline
 175 int shm_close_wakeup_fd(struct lttng_ust_shm_handle *handle,
 176                 struct shm_ref *ref)
 177 {
 178         struct shm_object_table *table = handle->table;
 179         struct shm_object *obj;
 180         int wakeup_fd;
 181         size_t index;
 182         int ret;
 183
 184         index = (size_t) ref->index;
 185         if (caa_unlikely(index >= table->allocated_len))
 186                 return -EPERM;
 187         obj = &table->objects[index];
 188         wakeup_fd = obj->wait_fd[1];
 189         if (wakeup_fd < 0)
 190                 return -ENOENT;
 191         obj->wait_fd[1] = -1;
 192         ret = close(wakeup_fd);
 193         if (ret) {
 194                 ret = -errno;
 195                 return ret;
 196         }
 197         return 0;
 198 }
 199
 200 static inline
 201 int shm_get_shm_fd(struct lttng_ust_shm_handle *handle, struct shm_ref *ref)
 202 {
 203         struct shm_object_table *table = handle->table;
 204         struct shm_object *obj;
 205         size_t index;
 206
 207         index = (size_t) ref->index;
 208         if (caa_unlikely(index >= table->allocated_len))
 209                 return -EPERM;
 210         obj = &table->objects[index];
 211         return obj->shm_fd;
 212 }
 213
 214
 215 static inline
 216 int shm_get_shm_size(struct lttng_ust_shm_handle *handle, struct shm_ref *ref,
 217                 uint64_t *size)
 218 {
 219         struct shm_object_table *table = handle->table;
 220         struct shm_object *obj;
 221         size_t index;
 222
 223         index = (size_t) ref->index;
 224         if (caa_unlikely(index >= table->allocated_len))
 225                 return -EPERM;
 226         obj = &table->objects[index];
 227         *size = obj->memory_map_size;
 228         return 0;
 229 }
 230
 231 #endif /* _LIBRINGBUFFER_SHM_H */