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