| 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 | /* |
| 30 | * Pointer dereferencing. We don't trust the shm_ref, so we validate |
| 31 | * both the index and offset with known boundaries. |
| 32 | * |
| 33 | * "shmp" and "shmp_index" guarantee that it's safe to use the pointer |
| 34 | * target type, even in the occurrence of shm_ref modification by an |
| 35 | * untrusted process having write access to the shm_ref. We return a |
| 36 | * NULL pointer if the ranges are invalid. |
| 37 | */ |
| 38 | static inline |
| 39 | char *_shmp_offset(struct shm_object_table *table, struct shm_ref *ref, |
| 40 | size_t idx, size_t elem_size) |
| 41 | { |
| 42 | struct shm_object *obj; |
| 43 | size_t objindex, ref_offset; |
| 44 | |
| 45 | objindex = (size_t) ref->index; |
| 46 | if (caa_unlikely(objindex >= table->allocated_len)) |
| 47 | return NULL; |
| 48 | obj = &table->objects[objindex]; |
| 49 | ref_offset = (size_t) ref->offset; |
| 50 | ref_offset += idx * elem_size; |
| 51 | /* Check if part of the element returned would exceed the limits. */ |
| 52 | if (caa_unlikely(ref_offset + elem_size > obj->memory_map_size)) |
| 53 | return NULL; |
| 54 | return &obj->memory_map[ref_offset]; |
| 55 | } |
| 56 | |
| 57 | #define shmp_index(handle, ref, index) \ |
| 58 | ({ \ |
| 59 | __typeof__((ref)._type) ____ptr_ret; \ |
| 60 | ____ptr_ret = (__typeof__(____ptr_ret)) _shmp_offset((handle)->table, &(ref)._ref, index, sizeof(*____ptr_ret)); \ |
| 61 | ____ptr_ret; \ |
| 62 | }) |
| 63 | |
| 64 | #define shmp(handle, ref) shmp_index(handle, ref, 0) |
| 65 | |
| 66 | static inline |
| 67 | void _set_shmp(struct shm_ref *ref, struct shm_ref src) |
| 68 | { |
| 69 | *ref = src; |
| 70 | } |
| 71 | |
| 72 | #define set_shmp(ref, src) _set_shmp(&(ref)._ref, src) |
| 73 | |
| 74 | struct shm_object_table *shm_object_table_create(size_t max_nb_obj); |
| 75 | struct shm_object *shm_object_table_append_shadow(struct shm_object_table *table, |
| 76 | int shm_fd, int wait_fd, size_t memory_map_size); |
| 77 | void shm_object_table_destroy(struct shm_object_table *table); |
| 78 | struct shm_object *shm_object_table_append(struct shm_object_table *table, |
| 79 | size_t memory_map_size); |
| 80 | |
| 81 | /* |
| 82 | * zalloc_shm - allocate memory within a shm object. |
| 83 | * |
| 84 | * Shared memory is already zeroed by shmget. |
| 85 | * *NOT* multithread-safe (should be protected by mutex). |
| 86 | * Returns a -1, -1 tuple on error. |
| 87 | */ |
| 88 | struct shm_ref zalloc_shm(struct shm_object *obj, size_t len); |
| 89 | void align_shm(struct shm_object *obj, size_t align); |
| 90 | |
| 91 | static inline |
| 92 | int shm_get_wakeup_fd(struct lttng_ust_shm_handle *handle, struct shm_ref *ref) |
| 93 | { |
| 94 | struct shm_object_table *table = handle->table; |
| 95 | struct shm_object *obj; |
| 96 | size_t index; |
| 97 | |
| 98 | index = (size_t) ref->index; |
| 99 | if (caa_unlikely(index >= table->allocated_len)) |
| 100 | return -EPERM; |
| 101 | obj = &table->objects[index]; |
| 102 | return obj->wait_fd[1]; |
| 103 | |
| 104 | } |
| 105 | |
| 106 | static inline |
| 107 | int shm_get_wait_fd(struct lttng_ust_shm_handle *handle, struct shm_ref *ref) |
| 108 | { |
| 109 | struct shm_object_table *table = handle->table; |
| 110 | struct shm_object *obj; |
| 111 | size_t index; |
| 112 | |
| 113 | index = (size_t) ref->index; |
| 114 | if (caa_unlikely(index >= table->allocated_len)) |
| 115 | return -EPERM; |
| 116 | obj = &table->objects[index]; |
| 117 | return obj->wait_fd[0]; |
| 118 | } |
| 119 | |
| 120 | static inline |
| 121 | int shm_get_object_data(struct lttng_ust_shm_handle *handle, struct shm_ref *ref, |
| 122 | int **shm_fd, int **wait_fd, uint64_t **memory_map_size) |
| 123 | { |
| 124 | struct shm_object_table *table = handle->table; |
| 125 | struct shm_object *obj; |
| 126 | size_t index; |
| 127 | |
| 128 | index = (size_t) ref->index; |
| 129 | if (caa_unlikely(index >= table->allocated_len)) |
| 130 | return -EPERM; |
| 131 | obj = &table->objects[index]; |
| 132 | *shm_fd = &obj->shm_fd; |
| 133 | *wait_fd = &obj->wait_fd[0]; |
| 134 | *memory_map_size = &obj->allocated_len; |
| 135 | return 0; |
| 136 | } |
| 137 | |
| 138 | #endif /* _LIBRINGBUFFER_SHM_H */ |